#1 J Trauma. 2008 Dec;65(6):1364-73.
Noninvasive monitoring of the autonomic nervous system and hemodynamics of patients with blunt and penetrating trauma.
Colombo J, Shoemaker WC, Belzberg H, Hatzakis G, Fathizadeh P, Demetriades D.
BACKGROUND: To describe early effects of sympathetic (SNS) and parasympathetic nervous system (PSNS) activities measured by heart rate (HR) and respiratory rate variabilities simultaneously with noninvasive hemodynamic patterns in patients with blunt and penetrating trauma.
METHODS: Descriptive study of 168 monitored trauma patients in a level I university-run trauma service. We studied HR and respiratory rate variability by spectral analysis as a measure of autonomic nervous system (ANS) activity in severe blunt and penetrating injuries beginning shortly after their admission to the emergency department. The low frequency area is the area under the HR spectral analysis curve within the frequency range of 0.04 Hz to 0.10 Hz. This area primarily reflects the tone of the SNS as mediated by the vagus nerve. The respiratory frequency area, sometimes referred to as the high frequency area, is a 0.12 Hz-wide frequency range centered around the fundamental respiratory frequency defined by the peak mode of the respiratory activity power spectrum. It is indicative of vagal outflow reflecting PSNS activity. The low frequency area/respiratory frequency area, or L/R ratio, reflects the balance of the SNS and the PSNS. ANS was studied simultaneously with noninvasive hemodynamic patterns after blunt and penetrating thoracic or abdominal injury beginning shortly after admission. We measured cardiac index by bioimpedance, HR, and mean arterial pressure (MAP) to evaluate cardiac function, pulse oximetry (SapO2) to reflect changes in respiratory function, and transcutaneous oxygen indexed to fractional inspired oxygen (PtcO2/FIO2) to reflect tissue perfusion.
RESULTS: ANS activity markedly increased especially in the nonsurvivors at 12 hours to 24 hours after admission. Compared with survivors, the nonsurvivors had lower MAP, CI, and PtcO2/FIO2 values associated with increased ANS activity.
CONCLUSIONS: In the nonsurvivors, low flow, low MAP, and reduced tissue perfusion were associated with pronounced increases in PSNS and lesser increases in SNS activity. In the survivors, higher CI, MAP, and PtcO2/FIO2 values were associated
#2 J Trauma. 2007 Nov;63(5):1032-42.
Hemodynamic and oxygen transport patterns after head trauma and brain death: implications for management of the organ donor.
Belzberg H, Shoemaker WC, Wo CC, Nicholls TP, Dang AB, Zelman V, Gruen JP, Berne TV, Demetriades D.
OBJECTIVES: The aims of the present study were to describe the temporal hemodynamic and oxygen transport patterns of patients with head injuries as well as the patterns of those who became brain dead to better understand the role of underlying central regulatory hemodynamic mechanisms and ultimately to improve rates of organ donation.
METHODS: We studied 388 consecutive noninvasively monitored patients with severe head trauma; 79 of these became brain dead. Monitoring was started shortly after admission to the emergency department and was designed to describe the sequence of cardiac, pulmonary, and tissue perfusion functions by cardiac index (CI), mean arterial pressure, heart rate, arterial saturation by pulse oximetry (Sapo2), and transcutaneous oxygen and carbon dioxide (Ptco2/Fio2 and Ptcco2) patterns. The latter were used as markers of tissue perfusion or oxygenation.
RESULTS: Patients with head injuries who subsequently became brain dead initially had low CI with poor tissue perfusion beginning shortly after emergency department admission. This was followed by a prolonged period characterized by high CI (4.43 +/- 1.3 L x min(-1) x m2) and enhanced tissue oxygenation (Ptco2/Fio2 238 +/- 186). In the late or end stage of brain death, hemodynamic deterioration and collapse led rapidly to arrest. In attempts to maintain hemodynamic stability for organ donation, the effects of various therapies on the hemodynamic patterns were preliminarily described.
CONCLUSIONS: The hyperdynamic state with exaggerated peripheral tissue perfusion or oxygenation in brain-dead patients associated with loss of central vasoconstrictive mechanisms of the stress response resulted in unopposed peripheral metabolic vasodilatation producing high CI and tissue perfusion.
#3 J Trauma. 2007 May;62(5):1192-200.
Effects of age and obesity on hemodynamics, tissue oxygenation, and outcome after trauma.
Belzberg H, Wo CC, Demetriades D, Shoemaker WC.
OBJECTIVE: The aims of this study are (1) to describe the early time course of hemodynamic and tissue perfusion/oxygenation patterns in the elderly and in obese patients who survive and those who die after trauma; and (2) to evaluate postinjury hemodynamic patterns for use as guides for resuscitation and subsequent treatment.
METHODS: We noninvasively monitored 625 trauma patients upon arrival in the emergency department to assess the temporal hemodynamic patterns associated with age and obesity. Cardiac index (CI), mean arterial pressure, and heart rate were monitored to assess cardiac function, pulse oximetry (Sapo2) to reflect changes in pulmonary function and transcutaneous oxygen (PtcO2), carbon dioxide (PtcCO2), and oxygen delivery (DO2) to reflect tissue perfusion. We evaluated these hemodynamic data after they were stratified by the patient age and body mass index.
RESULTS: When all trauma patients were considered together, the predominant findings were high CI, transient hypotension, tachycardia, normal pulmonary function, and reduced tissue oxygenation. The elderly and, to a lesser extent the obese, had lower flow and tissue perfusion. The survivors had higher CI and better tissue oxygenation than did the nonsurvivors of each category.
CONCLUSIONS: Elderly and obese nonsurvivors of severe injury had low CI with reduced tissue oxygenation associated with organ failures and death. The study suggests that survivors' CIs and tissue oxygenation may be used as markers of circulatory deterioration and shock as well as resuscitation
#4 J Trauma. 2007 Apr;62(4):928-32.
Hemodynamic patterns preceding circulatory deterioration and death after trauma.
Chien LC, Lu KJ, Wo CC, Shoemaker WC.
OBJECTIVE: To describe the sequence of hemodynamic changes associated with sudden circulatory deterioration compared with those of terminal patients to identify the earliest signs warning of shock and death.
METHODS: This is a prospective observational study of 89 patients with thermodilution cardiac index and continuous noninvasive hemodynamic monitoring who had episodes of circulatory deterioration. These data were compared with the data of a second group of 24 patients in their terminal stage just before death.
RESULTS: The earliest indications of impending collapse were decreased cardiac index, and tissue perfusion reflected by decreased transcutaneous O2 tension (PtcO2). This was followed by reduced blood pressure, tachycardia, reduced arterial hemoglobin saturation, and increased transcutaneous CO2 tension (PtcCO2). This pattern of changes was more pronounced in the nonsurvivors and was seen in exaggerated form in terminal patients.
CONCLUSION: Sequential hemodynamic patterns revealed reduced blood flow and poor tissue perfusion as the earliest warning signs in both circulatory deterioration and death. These were followed by reduced mean arterial pressure, tachycardia, and low values of pulse oximetry. Adequate blood flow and even distribution of flow are needed for tissue perfusion.
#5 J Trauma. 2007 May;62(5):1192-200.
Effects of age and obesity on hemodynamics, tissue oxygenation, and outcome after trauma.
Belzberg H, Wo CC, Demetriades D, Shoemaker WC.
SourceDepartment of Surgery, Los Angeles County/University of Southern California Medical Center, School of Medicine 90033, USA.
OBJECTIVE: The aims of this study are (1) to describe the early time course of hemodynamic and tissue perfusion/oxygenation patterns in the elderly and in obese patients who survive and those who die after trauma; and (2) to evaluate postinjury hemodynamic patterns for use as guides for resuscitation and subsequent treatment.
METHODS: We noninvasively monitored 625 trauma patients upon arrival in the emergency department to assess the temporal hemodynamic patterns associated with age and obesity. Cardiac index (CI), mean arterial pressure, and heart rate were monitored to assess cardiac function, pulse oximetry (Sapo2) to reflect changes in pulmonary function and transcutaneous oxygen (PtcO2), carbon dioxide (PtcCO2), and oxygen delivery (DO2) to reflect tissue perfusion. We evaluated these hemodynamic data after they were stratified by the patient age and body mass index.
RESULTS: When all trauma patients were considered together, the predominant findings were high CI, transient hypotension, tachycardia, normal pulmonary function, and reduced tissue oxygenation. The elderly and, to a lesser extent the obese, had lower flow and tissue perfusion. The survivors had higher CI and better tissue oxygenation than did the nonsurvivors of each category.
CONCLUSIONS: Elderly and obese nonsurvivors of severe injury had low CI with reduced tissue oxygenation associated with organ failures and death. The study suggests that survivors' CIs and tissue oxygenation may be used as markers of circulatory deterioration and shock as well as resuscitation.
#6 Injury. 2007 Mar;38(3):318-28. Epub 2006 Oct 17.
A mathematical program to predict survival and to support initial therapeutic decisions for trauma patients with long-bone and pelvic fractures.
Lu K, Shoemaker WC, Wo CC, Lee J, Demetriades D.
AIM: To test a mathematical program to monitor early haemodynamic patterns of patients with fractures, predict survival and support initial therapeutic decisions.
METHODS: A mathematical search and display program based on non-invasive haemodynamic monitoring was used to study 430 consecutively monitored patients with fractures during the first 48 h after admission to the emergency department of an inner city public hospital. We studied four types of fractures: simple extremity fractures, long-bone fractures, pelvic fractures and fractures incidental to severe trauma. The program continuously displayed haemodynamic patterns and predicted survival probability (SP), which was evaluated by the actual outcome at hospital discharge. The program also assessed the effectiveness of therapies according to haemodynamic responses.
RESULTS: The cardiac index, heart rate, mean arterial pressure, arterial saturation and transcutaneous oxygen tensions at the initial resuscitation were significantly higher in survivors than in non-survivors. After the first 48 h, the haemodynamic patterns were more influenced by fever, sepsis, complications and organ failures. The calculated survival probability averaged 81%+/-18% in the first 48 h for survivors and 72%+/-20% for non-survivors.
CONCLUSION: Early continuous non-invasive haemodynamic monitoring using the proposed information system is helpful in predicting outcome and guiding therapy for patients with fractures.
#9 J Trauma. 2006 Jan;60(1):82-90.
Outcome prediction by a mathematical model based on noninvasive hemodynamic monitoring.
Shoemaker WC, Wo CC, Lu K, Chien LC, Bayard DS, Belzberg H, Demetriades D, Jelliffe RW.
BACKGROUND: The aims are to apply a mathematical search and display model based on noninvasive hemodynamic monitoring, to predict outcome early in a consecutively monitored series of 661 severely injured patients.
METHODS: A prospective observational study by a previously designed protocol in a Level I trauma service in a university-run inner city public hospital was conducted. The survival probabilities were calculated at the initial resuscitation on admission and at subsequent intervals during their hospitalization beginning shortly after admission to the emergency department. Cardiac function was evaluated by cardiac output (CI), heart rate (HR), and mean arterial blood pressure (MAP), pulmonary function by pulse oximetry (SapO2), and tissue perfusion function by transcutaneous oxygen indexed to FiO2, (PtcO2/FiO2), and carbon dioxide (PtcCO2) tension.
RESULTS: The survival probability (SP) averaged 89 +/- 0.4% for survivors and 75.7 +/- 1.6% (p < 0.001) for nonsurvivors in the first 24-hour period of resuscitation. The CI, MAP, SapO2, PtcO2, and PtcO2/FiO2 were significantly higher in survivors than in nonsurvivors in initial resuscitation, whereas HR and PtcCO2 were higher in nonsurvivors.
CONCLUSIONS: During the initial resuscitation period, misclassifications were 102 of 661 or 15%. The SP provided early objective criteria to evaluate hospital outcome and to track changes throughout the hospital course based on a large database of patients with similar clinical-hemodynamic states.
#95 J Am Coll Surg. 2006 Dec;203(6):899-907. Epub 2006 Oct 2.
Hemodynamic patterns of blunt and penetrating injuries.
Lu KJ, Chien LC, Wo CC, Demetriades D, Shoemaker WC.
BACKGROUND: The aims of this prospective observational study were to describe early hemodynamic patterns of blunt and penetrating truncal injury and to evaluate outcomes prediction using noninvasive hemodynamic monitoring with a mathematical model tested against actual in-hospital outcomes. The hypothesis was that traumatic shock is a circulatory disorder that can be monitored by noninvasive hemodynamic parameters that reflect cardiac, pulmonary, and tissue perfusion functions.
STUDY DESIGN: The cardiac index (CI), heart rate (HR), mean arterial pressure (MAP), pulse oximetry (SapO(2)), transcutaneous oxygen tension indexed to FiO(2) (PtcO(2)/FiO(2)), and carbon dioxide (PtcCO(2)) tensions were monitored beginning shortly after emergency department admission in 657 emergency patients with severe blunt and penetrating chest, abdominal, and extremity trauma. Of these, 113 patients had associated head injury, and these patients also were analyzed separately. A search and display mathematical model, with a decision support program, was based on continuous online, real-time, noninvasive hemodynamic monitoring.
RESULTS: There were similar patterns in the blunt and penetrating injuries; the cardiac index, mean arterial pressure, pulse oximetry, transcutaneous oxygen tension indexed to FiO(2), and survival probability values of the survivors were significantly higher (p < 0.01) than the corresponding values of those who died, although heart rate and carbon dioxide tension were higher in the nonsurvivors during the first 24 hours after their emergency department admission. These patterns occurred more rapidly in patients with penetrating injuries. After initial resuscitation in the emergency department, results were correlated with actual outcomes at hospital discharge and found to be 88% correct.
CONCLUSIONS: Early noninvasive hemodynamic monitoring with a computerized information system provided a feasible pattern recognition program for outcomes prediction and therapeutic decision support.
#10 J Trauma. 2006 Oct;61(4):844-53; discussion 853-4.
Evaluation of invasive and noninvasive hemodynamic monitoring in trauma patients.
Shoemaker WC, Wo CC, Chien LC, Lu K, Ahmadpour N, Belzberg H, Demetriades D.
OBJECTIVES: The aim of this study was to compare a recently developed and improved noninvasive hemodynamic monitoring system with the conventional invasive monitoring by pulmonary artery catheterization (PAC) in acute emergency trauma patients.
METHODS: In a large, university-run, inner city public hospital, we monitored 993 trauma patients noninvasively; 262 of these were simultaneously monitored with both noninvasive hemodynamic and invasive PAC monitoring. The noninvasive monitoring was begun shortly after admission to the emergency department and the invasive PAC monitoring was started in the operating room, or as soon as the patient arrived in the intensive care unit. Noninvasive monitoring included cardiac index (CI) by the IQ or Physio Flow bioimpedance device, together with mean arterial blood pressure, heart rate, pulse oximetry (SapO2), transcutaneous oxygen (PtcO2), and carbon dioxide (PtcCO2) tensions. We compared CI by simultaneous measurements with both invasive and noninvasive methods 907 times in 262 patients.
RESULTS: The CI by thermodilution (CItd) correlated well with simultaneous measurements with the bioimpedance (CIbi), r2 = 0.915, r2 = 0.84, p < 0.001. The bias and precision of simultaneous measurements was -0.070 +/- 0.47 L/min/m2; agreement was considered satisfactory. In the initial resuscitation period of both monitoring systems, the CI, mean arterial blood pressure, SapO2, and tissue perfusion (reflected by invasive DO2 and VO2, and by noninvasive PtcO2/FiO2 ratio) were higher in survivors than in nonsurvivors, whereas heart rate values were higher in the nonsurvivors. We concluded that noninvasive hemodynamic monitoring provided a feasible, safe, inexpensive, accurate, continuous, on-line real-time graphic displays that are equivalent to the essential features of invasive pulmonary artery catheter monitoring.
#11 Mil Med. 2006 Sep;171(9):813-20.
Noninvasive hemodynamic monitoring for combat casualties.
Shoemaker WC, Wo CC, Lu K, Chien LC, Rhee P, Bayard D, Demetriades D, Jelliffe RW.
The aims of this study were to develop and to test a noninvasive hemodynamic monitoring system that could be applied to combat casualties to supplement conventional vital signs, to use an advanced information system to predict outcomes, and to evaluate the relative effectiveness of various therapies with instant feedback information during acute emergency conditions. In a university-run inner city public hospital, we evaluated 1,000 consecutively monitored trauma patients in the initial resuscitation period, beginning shortly after admission to the emergency department. In addition to conventional vital signs, we used noninvasive monitoring devices (cardiac index by bioimpedance with blood pressure and heart rate to measure cardiac function, arterial hemoglobin oxygen saturation by pulse oximetry to reflect changes in pulmonary function, and tissue oxygenation by transcutaneous oxygen tension indexed to fractional inspired oxygen concentration and carbon dioxide tension to evaluate tissue perfusion). The cardiac index, mean arterial pressure, pulse oximetry (arterial hemoglobin oxygen saturation), and transcutaneous oxygen tension/fractional inspired oxygen concentration were significantly higher in survivors, whereas the heart rate and carbon dioxide tension were higher in nonsurvivors. The calculated survival probability was a useful outcome predictor that also served as a measure of severity of illness. The rate of misclassification of survival probability was 13.5% in the series as a whole but only 6% for patients without severe head injuries and brain death. Application of noninvasive hemodynamic monitoring to acute emergency trauma patients in the emergency department is feasible, safe, and inexpensive and provides accurate hemodynamic patterns in continuous, on-line, real-time, graphical displays of the status of cardiac, pulmonary, and tissue perfusion functions. Combined with an information system, this approach provided an early outcome predictor and evaluated, with an objective individualized method, the relative efficacy of alternative therapies for specific patients.
#13 J Am Coll Surg. 2006 Jan;202(1):120-30. Epub 2005 Nov 10.
Survival, hemodynamics, and tissue oxygenation after head trauma.
Nicholls TP, Shoemaker WC, Wo CC, Gruen JP, Amar A, Dang AB.
BACKGROUND: The aims of this study were to describe the early time course of hemodynamic and tissue perfusion and oxygenation patterns in survivors and nonsurvivors after head injury; to suggest physiologic mechanisms responsible for the observed patterns; and to evaluate postinjury parameters that might be useful for treatment. The hypothesis was that reduced hemodynamics and tissue oxygenation and reduced arterial oxygen saturation affect outcomes.
STUDY DESIGN: Sixty patients with head trauma were noninvasively monitored on arrival in the emergency department to assess the temporal hemodynamic patterns associated with head injury; patients who were brain dead were excluded because they have very different hemodynamic patterns. Cardiac index, mean arterial pressure, and heart rate were monitored to assess cardiac function, pulse oximetry to reflect changes in pulmonary function, and transcutaneous oxygen and carbon dioxide to reflect tissue perfusion function. Patients were stratified by inhospital survival outcomes, the Glasgow Coma Scale, and the presence or absence of associated somatic injuries.
RESULTS: When all head injured patients were considered together, the predominant findings were high cardiac index, hypertension, mild tachycardia, normal pulmonary function, and reduced tissue oxygenation. The subset of survivors and those with high Glasgow Coma Scale had greater than normal cardiac index responses (4.02 +/- 0.01 (SEM) L/min/m2, p < 0.01 versus normal) and better tissue oxygenation (217 +/- 2 mmHg PtcO2/FiO2) than nonsurvivors (70 +/- 3 mmHg, p < 0.01) and those with low Glasgow Coma Scale (160 +/- 2, p < 0.05). Patterns of patients with associated somatic injuries were similar to those with isolated head injury.
CONCLUSIONS: The study suggested that survivors' cardiac index, tissue oxygenation, and arterial oxygen saturation may be considered as markers of resuscitation. Nonsurvivors of head injury had normal blood flow with reduced tissue oxygenation that might have contributed to unfavorable outcomes.
#14 Chest. 2005 Oct;128(4):2739-48.
Outcome prediction in chest injury by a mathematical search and display program.
Shoemaker WC, Bayard DS, Wo CC, Chan LS, Chien LC, Lu K, Jelliffe RW.
OBJECTIVE: This study applies a stochastic or probability search and display model to prospectively predict outcome and to evaluate therapeutic effects in a consecutively monitored series of 396 patients with severe thoracic and thoracoabdominal injuries. STUDY DESIGN: Prospective observational study of outcome prediction using noninvasive hemodynamic monitoring by previously designed protocols and tested against actual outcome at hospital discharge in a level 1 trauma service of a university-run, inner-city public hospital.
METHODS: Cardiac index (CI), heart rate (HR), mean arterial pressure (MAP), arterial oxygen saturation measured by pulse oximetry (Sp(O2)), transcutaneous oxygen tension (PtC(O2)), and transcutaneous carbon dioxide tension (Ptc(CO2)) were monitored beginning shortly after admission to the emergency department. The stochastic search and display model with a decision support program based on noninvasive hemodynamic monitoring was applied to 396 severely ill patients with major thoracic and thoracoabdominal trauma. The survival probability (SP) was calculated during initial resuscitation continuously until patients were stabilized, and compared with the actual outcome when the patient was discharged from the hospital usually a week or more later.
RESULTS: The CI, Sp(O2), Ptc(O2), and MAP were appreciably higher in survivors than in nonsurvivors. HR and Ptc(CO2) were higher in the nonsurvivors. The calculated SP in the first 24-h observation period of survivors of chest wounds averaged 83 +/- 18% (+/- SD) and 62 +/- 19% for nonsurvivors. Misclassifications were 9.6%. The relative effects of alternative therapies were evaluated before and after therapy, using hemodynamic monitoring and SP as criteria.
CONCLUSIONS: Noninvasive hemodynamic monitoring with an information system provided a feasible approach to early outcome predictions and therapeutic decision support.
#16 J Clin Monit Comput. 2005 Jun;19(3):223-30.
A stochastic control program to predict outcome and to support therapeutic decisions: a preliminary report.
Shoemaker WC, Bayard DS, Wo CC, Botnen A, Ahmedpour N, Gandhi A, Demetriades D, Jelliffe RW.
BACKGROUND AND OBJECTIVES: Early noninvasive hemodynamic monitoring with an outcome predictor and a therapeutic decision support system may be useful to identify and correct hemodynamic deficiencies in emergency patients. The first aim was to apply a stochastic (probability) search and display model to predict outcome as early as possible. The second aim was to explore the usefulness of a therapeutic decision support system to evaluate the relative effectiveness of various therapies.
METHODS: A stochastic control and display program based on noninvasive hemodynamic monitoring was applied in 100 consecutive critically ill patients admitted to the emergency department of an inner city public hospital. The program continuously displayed the noninvasive hemodynamic data and the patient's predicted survival probability (SP) that was based on the patient's diagnosis, covariates, and hemodynamic data. The accuracy of the SP at the initial resuscitation on admission to the emergency department (ED) was evaluated by the actual outcome at hospital discharge. The therapeutic decision support program evaluated the relative effectiveness of various therapies on based on their hemodynamic and SP responses and outcome of patients with similar clinical-hemodynamic states.
RESULTS: The cardiac index, mean arterial pressure, arterial saturation, transcutaneous oxygen and carbon dioxide tensions were appreciably higher in survivors than in nonsurvivors in the initial resuscitation. Heart rate was higher in the nonsurvivors. The calculated Survival Probability (SP) of survivors averaged 81 +/- 1.4% in the first 24-hour observation period. It was 58 +/- 2.2% for nonsurvivors during this period. Misclassifications were 10/100 or 10%.
#17 Am J Surg. 2005 May;189(5):547-50;
The effect of obesity on bioimpedance cardiac index. Brown CV, Martin MJ, Shoemaker WC, Wo CC, Chan L, Azarow K, Demetriades D.
BACKGROUND: Cardiac performance may be assessed noninvasively at the patient's bedside by using thoracic bioimpedance. However, it is unclear if this technique can be used reliably in critically injured obese patients because of increased body habitus and chest wall mass. METHODS: A prospectively maintained database was used to identify all trauma patients admitted to the intensive care unit who underwent simultaneous measurement of cardiac performance by using both thoracic bioimpedance and thermodilution. Patients were divided into 2 groups based on their body mass index (BMI). Patients with a BMI less than 30 kg/m(2) were classified as nonobese, and patients with a BMI of 30 kg/m(2) or greater were categorized as obese. RESULTS: There were 285 patients who underwent 1,138 simultaneous measurements of cardiac index by using both bioimpedance and thermodilution. There were 211 nonobese patients (BMI = 25 +/- 3 kg/m(2)) and 74 obese patients (BMI = 34 +/- 4 kg/m(2)). Bioimpedance correlated well with thermodilution for the entire population (r = .84, P < .0001), and was reliable equally in obese (r = .85, P < .0001) and nonobese (r = .82, P < .0001) patients. There actually was less test bias in the obese group (-.06 +/- .69) than in the nonobese group (-.16 +/- .75, P = .04). CONCLUSIONS: Thoracic bioimpedance technology may be used reliably as a noninvasive alternative to pulmonary artery catheterization for assessment of cardiac performance in critically injured obese patients.
#18 J Trauma. 2005 Jan;58(1):102-7
Is noninvasive hemodynamic monitoring appropriate for the elderly critically injured patient? Brown CV, Shoemaker WC, Wo CC, Chan L, Demetriades D.
BACKGROUND: Noninvasive hemodynamic monitoring in critically ill patients using bioimpedance technology has been shown to be a reliable alternative to invasive thermodilution techniques. However, there have been some concerns that the bioimpedance method may be unreliable in elderly patients with an atherosclerotic and rigid thoracic aorta. The purpose of the present study was to evaluate the effect of age on the reliability of noninvasive bioimpedance technology in measuring cardiac index. METHODS: This is a retrospective analysis of prospectively collected data in critically injured patients admitted to the surgical intensive care unit. All patients had simultaneous measurement using thermodilution cardiac index (TDCI) and bioimpedance cardiac index (BICI). The population was divided into three age groups (<55 years, 55-70 years, and >70 years). The correlation between TDCI and BICI was calculated for each age group. RESULTS: There were 1,138 simultaneous measurements of TDCI and BICI in 285 patients. The BICI correlated well with TDCI in all three age groups (r = 0.82 for group <55 years, r = 0.87 for group 55-70 years, and r = 0.80 for group >70 years). CONCLUSION: Noninvasive cardiac index monitoring in elderly patients is reliable and correlates well with standard thermodilution techniques
#19 Zhongguo Wei Zhong Bing Ji Jiu Yi Xue. 2004 May;16(5):287-91
Value of non-invasive continuous hemodynamic monitoring system in the differential diagnosis of the patients with dyspnea Gu ZL, Cheng CE, Wu G, Zhang BS, Lu ZK, Xu LH..
OBJECTIVE: To evaluate non-invasive continuous hemodynamic (IQ System) monitoring in the differential diagnosis of dyspnea. METHODS: According to the diagnosis on discharge, 48 patients diagnosed as pulmonary dyspnea were enrolled in control group and 38 patients with cardiac dyspnea were in heart failure group. Each patient underwent IQ monitoring on admission and after recovery. The difference in the diagnosis on admission and on discharge, and the difference in IQ index were analyzed. RESULTS: (1) Clinical diagnosis: 7 patients in heart failure group were missed on admission as 5 were diagnosed as pneumonia and 2 were diagnosed as chronic obstructive pulmonary disease (COPD). One patient with pneumothorax in control group was misdiagnosed as heart failure. (2) Indexes of cardiac function: base impedance (Zo), maximum value of dz/dt (dz/dt max) and Heather index (HI) of heart failure group were markedly lower than those of control group (all P<0.001). The respective values were (19.0+/-3.5) Omega vs. (28.8+/-5.5) Omega, (0.76+/-0.42) Omega/s vs. (1.40+/-0.72) Omega/s, and (7.04+/-4.25) Omega/s2 vs. (13.60+/-6.36) Omega/s2. If Zo value of patients with dyspnea was 22 omicron or less, the sensitivity in diagnosing heart failure was 79 percent, and its specificity was 94 percent. If Zo value was 18.0 omicron or less, the sensitivity in diagnosing heart failure was 47 percent, and its specificity was 100 percent. (3) Comparison within groups: Indexes of cardiac function of control group did not change obviously and Zo, dz/dt max, HI, stroke volume (SV) and acceleration contraction index (ACI) values of heart failure group rose significantly after recovery. (4) Pre-ejection period (PEP) and left ventricular ejection time (VET) in both groups had no statistical significance in differences. CONCLUSION: IQ System was valuable in differential diagnosis to judge if dyspnea is caused by heart failure. Zo, dz/dt max and HI, especially Zo, are reliable
#20 Zhongguo Wei Zhong Bing Ji Jiu Yi Xue. 2003 Dec;15(12):730-4.
Application of non-invasive hemodynamic monitoring on high-risk surgical patients in the early stages after emergency admission Lu JQ, Li CS, Yang JY, Zhu J, Wo C, Shoemaker W.
OBJECTIVE: Pulmonary artery (PA) catheterization monitoring (Swan-Ganz) is usually not available to critically high-risk surgical patients before admission to ICU, where action to correct values derived from such monitoring may be too late. To explored the effect of non-invasive monitoring systems that allow hemodynamic monitoring during the early stages after trauma. METHODS: The early temporal hemodynamic patterns after high-risk trauma with non-invasive monitoring systems were evaluated, and compared these to invasive PA monitoring. The study included 156 patients monitored shortly after admission to the emergency department. RESULTS: The non-invasive impedance cardiac output estimations under extenuating emergency conditions were similar to those of the thermodilution method: r=0.69, r(2)=0.87, P<0.001; bias and precision were (0.62+/-0.38)L. min(-1).m(-2). In ICU, these values improved further to: r=0.84, r(2)=0.93, P<0.001; bias and precision were (0.36+/-0.15) L.min(-1).m(-2). Monitoring revealed episodes of hypotension, low cardiac index, arterial hemoglobin desaturation, low transcutaneous oxygen and high transcutaneous carbon dioxide tension, and low oxygen consumption during initial resuscitation. Low flow and poor tissue perfusion were more pronounced in non-survivors by both METHODS. CONCLUSION: Multicomponent non-invasive monitoring systems offer continuous on-line, real-time display of hemodynamic data, they allow early recognition of circulatory dysfunction. Such systems provide information similar to that provided by the invasive thermodilution method, and are more effective and safer.
#21 AACN Clin Issues. 2003 May;14(2):240-50
Outpatient cardiovascular management utilizing impedance cardiography. Lasater M, Von Rueden KT
Over the past decade, noninvasive hemodynamic and thoracic fluid status monitoring via impedance cardiography has provided clinicians practicing in the outpatient setting with a valuable tool for managing a myriad of cardiovascular disorders. This article reviews impedance cardiography technology and the use of impedance cardiography in the home and outpatient clinic settings for the assessment and management of heart failure, resistant hypertension, and dual-chamber pacemaker optimization.
#22 Acad Emerg Med. 2003 Jun;10(6):669-80.
Bench to bedside: electrophysiologic and clinical principles of noninvasive hemodynamic monitoring using impedance cardiography. Summers RL, Shoemaker WC, Peacock WF, Ander DS, Coleman TG. Department of Emergency Medicine, University of Mississippi Medical Center, Jackson 39216, USA
The evaluation of the hemodynamic state of the severely ill patient is a common problem in emergency medicine. While conventional vital signs offer some insight into delineating the circulatory pathophysiology, it is often impossible to determine the true clinical state from an analysis of blood pressure and heart rate alone. Cardiac output measurements by thermodilution have been the criterion standard for the evaluation of hemodynamics. However, this technology is invasive, expensive, time-consuming, and impractical for most emergency department environments. Impedance cardiography (ICG) is a noninvasive method of obtaining continuous measurements of hemodynamic data such as cardiac output that requires little technical expertise. ICG technology was first developed by NASA in the 1960s and is based on the idea that the human thorax is electrically a nonhomogeneous, bulk conductor. Variation in the impedance to flow of a high-frequency, low-magnitude alternating current across the thorax results in the generation of a measured waveform from which stroke volume can be calculated by a modification of the pulse contour method. To adequately judge the possible role of this technology in the practice of emergency medicine, it is important to have a sufficient understanding of the basic scientific principles involved as well as the clinical validity and limitations of the technique.
#26 Crit Care Med. 2002 Aug;30(8):1686-92
Meta-analysis of hemodynamic optimization in high-risk patients. Kern JW, Shoemaker WC. USC School of Pharmacy, Los Angeles, CA, USA.
OBJECTIVE: The aim of this evidence-based report was to review pertinent randomized controlled studies that describe hemodynamic goals in acute, critically ill patients and to evaluate outcome of resuscitation therapy in association with physiologic, clinical, and therapeutic influences. METHODS: MEDLINE was the source of randomized controlled studies written in English. The inclusion criteria were acutely ill, high-risk elective surgery, trauma, and septic patients. The goals of therapy were to resuscitate to either normal or supranormal values; the latter were described as a cardiac index of >4.5 L x min(-1) x m(-2), pulmonary artery occlusion pressure of <18 mm Hg, oxygen delivery of >600 mL x min(-1) x m(-2), and oxygen consumption of >170 mL x min(-1) x m(-2). The outcome criterion was survival or death. We found 21 randomized clinical trials described in 20 articles. The studies were divided into groups based on the time that goals were implemented (i.e., "early," 8 to 12 hrs postoperatively or before organ failure, vs. "late," or after onset of organ failure) and the severity of illness, determined by the control group mortality as >20% (12 studies) or <15% (nine studies). RESULTS: In severely ill patients (control mortalities group >20%), six studies had a 23% mortality difference (p <.05) between the control and protocol groups with early optimization, but seven studies optimized after the development of organ failure did not have significantly improved mortality. Moreover, outcome was not significantly improved in less severely ill patients (control mortalities group <15%) and normal values as goals or when therapy did not improve oxygen delivery. CONCLUSION: Review of 21 randomized controlled trials with various approaches to treatment revealed statistically significant mortality reductions, with hemodynamic optimization, when patients with acute critical illness were treated early to achieve optimal goals before the development of organ failure, when there were control group mortalities of >20% and when therapy produced differences in oxygen delivery between the control and protocol groups.
#27 Surg Clin North Am. 2002 Feb;82(1):245-55.
New approaches to trauma management using severity of illness and outcome prediction based on noninvasive hemodynamic monitoring. Shoemaker WC Department of Anesthesia and Surgery, Los Angeles County and University of Southern California Medical Center, University of Southern California
The mathematical model satisfactorily predicted outcome in acute emergencies based on noninvasively monitored flow, pressure, pulse oximetry, tissue perfusion values, and their cumulative deficits. A decision support system provided information on the relative effectiveness of various therapeutic modalities based on the responses of patients with very similar states. The concept that hypovolemia and oxygen debt is an early primary problem that plays an important role in low flow and poor tissue perfusion states is supported by direct observation of massive hemorrhage, estimated blood loss of hemoperitoneum and hemothorax at the time of surgery, and prior studies in the literature that documented blood volume deficits in posttraumatic and postoperative patients who subsequently developed organ failures and death.
#29 Anesthesiology. 94(4):566-573, April 2001
Modeling Population Pharmacokinetics of Lidocaine: Should Cardiac Output Be Included as a Patient Factor? Kuipers, J A.; Boer, de Roode, A,Olofsen, E; Bovill, JL. Burm, A G
Background: Inclusion of cardiac output and other physiologic parameters, in addition to or instead of, demographic variables might improve the ,Methods: Thirty-one patients were included in a population pharmacokinetic study of lidocaine. After bolus injection of lidocaine (1 mg/kg), 22 or 10 blood samples per patient were taken from a radial artery. During the experiment, cardiac output was measured using a thoracic electrical bioimpedance method. The following four population pharmacokinetic models were constructed and their performances investigated: a model with no covariates, a model with cardiac output as covariate, a model with demographic covariates, and a model with both cardiac output and demographic characteristics as covariates. Model discrimination was performed with the likelihood ratio test.
Results: Inclusion of cardiac output resulted in a significant improvement of the pharmacokinetic model, but inclusion of demographic covariates was even better. However, the best model was obtained by inclusion of both demographic covariates and cardiac output in the pharmacokinetic model.
Conclusions: When population pharmacokinetic models are used for individualization of dosing schedules, physiologic covariates, e.g., cardiac output, can improve their ability to predict the individual kinetics
#30 Journal of Cardiac Failure Vol. 7 No. 3 Suppl. 2 2001
Orthostatic Changes in Bioimpedance Parameters Identify Decompensated Heart Failure in Emergency Department Patients. W. Frank Peacock, Charles E. Emmerman, Brian A. Janz, Vidya Ramanavarapu, Philippine Kies ; Emergency Medicine, The Cleveland Clinic, Cleveland, OH
Introduction: Non-invasive thoracic bioimpedance (BI) monitoring can determine intrathoracic fluid volumes. Body position changes result in intrathoracic fluid shifts. The hemodynamic responses consequent to fluid changes are detectable using BI monitoring. Since acutely decompensated HF patients have abnormal hemodynamics, measuring the fluid shifts resulting from changes in body position may guide early diagnosis of decompensated heart failure (HF). Objective: To compare body position induced changes in the BI parameters of decompensated ED (Emergency Department) HF patients, as compared to non-HF patients. Methods: Prospective convenience sample of dyspneic patients. The final diagnosis was determined by the physician after all ED investigations were completed. Setting: 1,000 bed hospital, 40,000 visit ED. BI parameters were measured with the patient sitting and recumbent, 5 minutes apart, prior to any therapies anticipated to cause intrathoracic fluid shifts. Definitions: Zo=baseline thoracic impedance BI; and varies inversely with total thoracic fluid content. Statistics: Wilcoxson rank sum test. Results: 62 patients were entered, 34 (55%) were male, 12 had decompensated HF, and 50 were diagnosed as non-HF. the median ages for HF and non-HF were 68.2 (IQR 63 to 78), and 43.5 (IQR 30 to 61), respectively (p=0.0002). There were no differences in initial vital signs. Median sitting Zo was lower in HF, 18.7 ohms (IQR 17.6 to 20.6), compared to non-HF, 25.3 ohms (IQR 21.5 to 28.6). In HF, recumbence resulted in a median ZO decrease of 1.2 ohms (IQR 0.1 to 2.1), versus a median decrease of only 0.1 ohms in non-HF (IQR 0.4 to 0.7, p=0.0004). Sitting median cardiac output (CO) was the same in both HF and non-HF, 3.5 L/m (IQR 2.2 to 4.0), versus 3.5 (IQR 3.0 to 4.2), respectively. However, recumbency increased the CO in HF patients by only).18 L/m (IQR 0.1 to 0.5), compared to an increase of 0.5 L/m in the non-HF group (IQR 0.13 to 1.16, p=0.0413). Other BI parameters were unchanged as a function of recumbency, in those with or without HF. Conclusion: Sitting HF patients have an initially lower Zo, and exhibit a greater change in response to recumbence, than non-HF patients. Cardiac output is increased by recumbence, but only to a significantly lesser extent in decompensated ED HF patients. Orthostatically induces changes in BI parameters help identify patients with HF
#32 Chest. 2001;120:528-537.
Outcome Prediction of Emergency Patients by Noninvasive Hemodynamic Monitoring William C. Shoemaker, MD; Charles C. J. Wo, BS; Linda Chan, PhD; Emily Ramicone, MS; Eman S. Kamel, MD; George C. Velmahos, MD, PhD and Howard Belzberg, MD, FCCP * From the Departments of Anesthesia (Dr. Shoemaker) and Surgery (Drs. Shoemaker, Wo, Kamel, Velmahos, and Belzberg), Los Angeles County/USC Medical Center; Division of Biostatistics and Outcome Assessment (Dr. Chan and Ms. Ramicone), University of Southern California, Los Angeles, CA.
Objectives: We used noninvasive hemodynamic monitoring in the initial resuscitation beginning in the emergency department (ED) for the following reasons: (1) to describe early survivor and nonsurvivor patterns of emergency patients in terms of cardiac, pulmonary, and tissue perfusion deficiencies; (2) to measure quantitatively the net cumulative amount of deficit or excess of the monitored functions that correlate with survival or death; and (3) to explore the use of discriminant analysis to predict outcome and evaluate the biological significance of monitored deficits.
Methods: This is a descriptive study of the feasibility of noninvasive monitoring of patients with acute emergency conditions in the ED to evaluate and quantify hemodynamic deficits as early as possible. The noninvasive monitoring systems consisted of a bioimpedance method for estimating cardiac output together with pulse oximetry to reflect pulmonary function, transcutaneous oxygen tension to reflect tissue perfusion, and BP to reflect the overall circulatory status. These continuously monitored noninvasive measurements were used to prospectively evaluate circulatory patterns in 151 consecutively monitored severely injured patients beginning with admission to the ED in a university-run county hospital. The net cumulative deficit or excess of each monitored parameter was calculated as the cumulative difference from the normal value vs the time-integrated monitored curve for each patient. The deficits of cardiac, pulmonary, and tissue perfusion functions were analyzed in relation to outcome by discriminant analysis and were cross-validated. Results: The mean (± SEM) net cumulative excesses (+) or deficits (-) from normal in surviving vs nonsurviving patients, respectively, were as follows: cardiac index (CI), +81 ± 52 vs -232 ± 138 L/m2 (p = 0.037); arterial hemoglobin saturation, -1 ± 0.3 vs -8 ± 2.6%/h (p = 0.006); and tissue perfusion, +313 ± 88 vs -793 ± 175, mm Hg/h (p = 0.001). The cumulative mean arterial BP deficit for survivors was -10 ± 13 mm Hg/h, and for nonsurvivors it was -57 ± 24 mm Hg/h (p = 0.078). Conclusions: Noninvasive monitoring systems provided continuously monitored on-line displays of data in the early postadmission period from the ED to the operating room and to the ICU for early recognition of circulatory dysfunction in short-term emergency conditions. Survival was predicted by discriminant analysis models based on the quantitative assessment of the net cumulative deficits of CI, arterial hypoxemia, and tissue perfusion, which were significantly greater in the nonsurvivors.
#34 IEEE 2001 3/01:233-236
Development of a Hemodynamic Database in Severe Trauma Patients to Define Optimal Goals and Predict Outcome Wc Shoemaker, Ccj Wo, A Botnen, Rw Jelliffe, University of Southern California Ds Bayard, Jet Propulsion Laboratory
Abstract: Noninvasive hemodynamic monitoring systems provide continuously monitored on-line displays of data from emergency department admission to the OR, and to the ICU for early recognition of circulatory dysfunction in acute emergency conditions. The net cumulative deficits of cardiac index are estimated by thoracic electric bioimpedance, arterial hypoxemia is measured by pulse oximetry, and tissue perfusion is reflected by transcutaneous pO2. Based on a large database, survival was satisfactorily predicted by discriminant analysis and by a new stochastic analysis and control program.
#36 Ann Surg 2000 Sep;232(3):409-18
Endpoints of resuscitation of critically injured patients: normal or supranormal? A prospective randomized trial. Velmahos GC, Demetriades D, Shoemaker WC, Chan LS, Tatevossian R, Wo CC, Vassiliu P, Cornwell EE 3rd, Murray JA, Roth B, Belzberg H, Asensio JA, Berne TV. Department of Surgery, Division of Trauma and Critical Care, and the Department of Biostatistics and Outcomes Research, University of Southern California, Los Angeles, California, USA.
OBJECTIVE: To evaluate the effect of early optimization in the survival of severely injured patients. SUMMARY BACKGROUND DATA: It is unclear whether supranormal ("optimal") hemodynamic values should serve as endpoints of resuscitation or simply as markers of the physiologic reserve of critically injured patients. The failure of optimization to produce improved survival in some randomized controlled trials may be associated with delays in starting the attempt to reach optimal goals. There are limited controlled data on trauma patients. METHODS: Seventy-five consecutive severely injured patients with shock resulting from bleeding and without major intracranial or spinal cord trauma were randomized to resuscitation, starting immediately after admission, to either normal values of systolic blood pressure, urine output, base deficit, hemoglobin, and cardiac index (control group, 35 patients) or optimal values (cardiac index >4.5 L/min/m2, ratio of transcutaneous oxygen tension to fractional inspired oxygen >200, oxygen delivery index >600 mL/min/m2, and oxygen consumption index >170 mL/min/m2; optimal group, 40 patients). Initial cardiac output monitoring was done noninvasively by bioimpedance and, subsequently, invasively by thermodilution. Crystalloids, colloids, blood, inotropes, and vasopressors were used by predetermined algorithms. RESULTS: Optimal values were reached intentionally by 70% of the optimal patients and spontaneously by 40% of the control patients. There was no difference in rates of death (15% optimal vs. 11% control), organ failure, sepsis, or the length of intensive care unit or hospital stay between the two groups. Patients from both groups who achieved optimal values had better outcomes than patients who did not. The death rate was 0% among patients who achieved optimal values compared with 30% among patients who did not. Age younger than 40 years was the only independent predictive factor of the ability to reach optimal values. CONCLUSIONS: Severely injured patients who can achieve optimal hemodynamic values are more likely to survive than those who cannot, regardless of the resuscitation technique. In this study, attempts at early optimization did not improve the outcome of the examined subgroup of severely injured patients.
#37 J Crit Care 2000 Dec;15(4):151-9
Noninvasive hemodynamic monitoring for early warning of adult respiratory distress syndrome in trauma patients. Tatevossian RG, Shoemaker WC, Wo CC, Dang AB, Velmahos GC, Demetriades D. Department of Surgery, University of Southern California and the LAC+USC Medical Center, Los Angeles, USA.
PURPOSE: Traditionally hemodynamic patterns after adult respiratory distress syndrome (ARDS) are described after appropriate diagnostic criteria have been met, but studies begun after the diagnosis of ARDS miss the antecedent circulatory influences that may contribute to its development. This study tests the hypothesis that noninvasive monitoring before the appearance of ARDS may reveal early circulatory deficiencies that lead to this disorder. The aims of this study are as follows: (1) to describe the time course of hemodynamic and tissue perfusion patterns in severely traumatized postoperative patients from the period immediately after admission and during surgical repair to the time that ARDS developed or to hospital discharge in patients who did not develop ARDS, (2) to compare the time course of these patterns in survivors and nonsurvivors of ARDS, and (3) to suggest that reduced flow and perfusion may be early warning signs of ARDS. Prospective descriptive study of severely injured trauma patients noninvasively monitored in the emergency department, operating room, and intensive care unit (ICU). Early hemodynamic pattems were described in the surviving and nonsurviving patients who subsequently developed ARDS. The study was performed in a University-affiliated Level I trauma center and ICU. PATIENTS AND METHODS: A consecutively monitored series of 60 severely injured patients were prospectively monitored by cardiac output, pulse oximetry (Sapo2), and transcutaneous O2 and co2 (Ptco2 and Ptc(co2)) sensors immediately after emergency admission. Twenty-nine patients developed ARDS in their ICU course, whereas 31 were discharged from the ICU and the hospital without developing ARDS. RESULTS: Patients who developed ARDS had significantly lower cardiac index and Ptco2 and higher Ptc(co2) values beginning with the early stage compared with those who did not develop ARDS. Nonsurvivors of ARDS had lower Ptco2 values than did the survivors. CONCLUSION: Early noninvasive monitoring in the emergency department, operating room, and ICU showed reduced cardiac and tissue perfusion functions in patients who subsequently developed ARDS. These patterns were more pronounced in the ARDS patients who died; these patterns may serve as early warning of ARDS.
#38 Eur J Emerg Med 2000 Sep;7(3):169-75
Invasive and noninvasive haemodynamic monitoring of acutely ill sepsis and septic shock patients in the emergency department. Shoemaker WC, Wo CC, Yu S, Farjam F, Thangathurai D. Department of Emergency Medicine, King-Drew Medical Center, Los Angeles, CA, USA.
The objective of this study was to describe early circulatory events of patients presenting to the emergency department (ED) with severe sepsis or septic shock. Invasive and noninvasive monitoring were used to evaluate sequential patterns of both central haemodynamics and peripheral tissue perfusion/oxygenation and to test the hypothesis that increased cardiac output is an early compensation to increased body metabolism. This is a prospective observational study of 45 patients who entered the ED with severe sepsis or septic shock in an urban academic ED. Invasive clinical monitoring was performed using a radial artery catheter and a thermodilution pulmonary artery catheter. Noninvasive monitoring consisted of an improved thoracic electrical bioimpedance device to estimate cardiac output; pulse oximetry for arterial saturation to reflect changes in pulmonary function, and transcutaneous oxygen (PtcO2) and carbon dioxide tensions (PtcCO2) as a reflection of tissue perfusion. Survivors had higher cardiac index, mean arterial pressure (MAP), and better tissue perfusion as measured by PtcO2, oxygen delivery, and oxygen consumption. Oxygen extraction ratio was higher in the nonsurvivors (p < 0.05) and there were episodes of high PtcCO2 values in the nonsurvivors. No significant differences were found in the heart rate, PAOP (wedge pressure) and SaO2 by pulse oximetry between the two groups. It is concluded that ED monitoring septic patients provides a unique opportunity to document early physiologic interactions between cardiac, pulmonary, and tissue perfusion functions in surviving and nonsurviving patients with septic shock. The data is consistent with the concept that increased cardiac output is an early compensatory response to increased body metabolism. Real time haemodynamic monitoring of patients in the ED provides early warning of outcome and may be used to guide therapy.
#39 Congest Heart Fail. 2000 Mar;6(2):86-89.
Bioimpedance monitoring: better than chest x-ray for predicting abnormal pulmonary fluid? Peacock WF IV, Albert NM, Kies P, White RD, Emerman CL.Cleveland Clinic, Cleveland, OH.
Bioimpedance monitoring may aid in treating heart failure. Mean thoracic electrical impedance (Zo) is inversely proportional to thoracic fluid volume and may offer greater sensitivity for detecting thoracic fluid. OBJECTIVE. Compare bioimpedance monitoring thoracic fluid detection to that of chest x-ray. METHOD. Prospective convenience sample. SETTING. 1000 bed teaching hospital. PARTICIPANTS. Patients with suspected heart failure and shortness of breath. A single blinded radiologist interpreted chest x-rays as: normal, cardiomegaly, or abnormal pulmonary fluid. STATISTICS. General linear model with post hoc Bon Ferroni pairwise comparisons. RESULTS. 131 patients, mean age 66.8 years, 64.3% male, with an initial mean Zo=18 ohms. There was a significant difference (p<0.0002) between patients with cardiomegaly (Zo=17.5+/-5.5) or abnormal pulmonary fluid on chest x-ray (Zo=17.2+/-4.2) compared to normals (Zo=23.4+/-5.4). There was no difference between cardiomegaly and abnormal pulmonary fluid patients. CONCLUSION. Bioimpedance measurement may detect pulmonary fluid not apparent on chest radiograph
#41 J Toxicol Clin Toxicol. 2000;38(3):283-90.
Cardiac and hemodynamic assessment of patients with cocaine-associated chest pain syndromes. Baumann BM, Perrone J, Hornig SE, Shofer FS, Hollander JE. Hospital of the University of Pennsylvania, Philadelphia 19102, USA.
BACKGROUND: Animal and human experimental studies have yielded conflicted data regarding the effects of cocaine on cardiovascular function. We studied the cardiac and hemodynamic profiles in emergency department chest pain patients following recent cocaine use. METHODS: After obtaining informed consent, emergency department patients who presented with a chief complaint of chest pain and cocaine use within 24 hours of arrival were prospectively enrolled. All patients underwent a structured 40-item history and physical examination and were placed on the IQ Noninvasive Hemodynamic Surveillance System (Renaissance Technology, Inc., Newton, PA), a validated transthoracic cardiac output monitor. The principal measurements obtained included cardiac output, cardiac index, and stroke volume. Data were analyzed with standard descriptive techniques. RESULTS: Twenty-seven patients were enrolled (median age, 37 years [range, 23-54]; 74% male). Patients used a mean of $200 worth of cocaine, usually crack (67%). Patients had a history of tobacco use (82%), prior myocardial infarction (33%), and prior cocaine-associated chest pain (67%). The median (interquartile range; IQR) for the hemodynamic parameters were: mean arterial blood pressure 92 mm H (IQR 85-100); heart rate 83/min (IQR 72-98); cardiac output 6.9 L/min (IQR 5.1-7.2); cardiac index 3.2 L/min/m2 (IQR 2.4-4.0); stroke volume 78 mL/beat (IQR 64-93). CONCLUSION: Most emergency department patients with cocaine-associated chest pain have normal cardiac profiles at the time of presentation. The negative inotropic effects of high doses of cocaine observed in animal models do not appear to be present in patients who develop chest pain after using recreational doses of cocaine.
#42 Acad Emerg Med. 2000 Aug;7(8):878-85.
Randomized, double-blind, placebo-controlled trial of diazepam, nitroglycerin, or both for treatment of patients with potential cocaine-associated acute coronary syndromes. Baumann BM, Perrone J, Hornig SE, Shofer FS, Hollander JE. Department of Emergency Medicine, Hospital of the University of Pennsylvania, Philadelphia 19102, USA.
INTRODUCTION: To the authors' knowledge, treatment of patients with cocaine-associated acute coronary syndromes has not been rigorously investigated in symptomatic patients. OBJECTIVE: To perform a randomized double-blind trial of diazepam, nitroglycerin, or both for treatment of patients with potential cocaine-associated acute coronary syndromes. METHODS: Patients with potential cocaine-associated acute coronary syndromes were randomized to treatment with either diazepam, nitroglycerin, or both every 5 minutes or until symptom resolution. Outcomes were chest pain resolution (measured by visual analog scale), and changes in blood pressure, pulse rate, cardiac output (L/min), cardiac index (L/min/m2), stroke volume (mL/beat), and stroke index (mL/beat/m2) over the 15-minute treatment period. To adjust for seven outcomes using the Bonferroni correction, alpha was set at 0.007. RESULTS: Forty patients were enrolled (diazepam, 12; nitroglycerin, 13; both, 15). Patients had a mean age (+/-SD) of 35.4 (+/-7.5) years; 75% were male. They presented a mean of 5 hours and 37 minutes after cocaine use. Baseline demographics, cocaine use patterns, chest pain characteristics, and initial electrocardiograms were similar for all groups. Chest pain severity improved similarly in the three groups [-33.3 mm (+/-8.0); -30.7 mm (+/-7.1); -33.0 mm (+/-7.9); p = 0.6]. The stroke index decreased during the 15-minute treatment period for all groups (diazepam, -8.7 (+/-3.3); nitroglycerin, -3.1 +/- 2.8; both, -1.8 (+/-3.1) mL/beat/m2; p = 0.03). After adjustment for differences between baseline hemodynamic and cardiac profiles and multiple comparisons, there was no difference in any response to therapy over time for the different treatments. CONCLUSIONS: For treatment of patients with potential cocaine-associated acute coronary syndromes, chest pain resolutions and changes in cardiac performance are not different in patients treated with diazepam or nitroglycerin. In this study, the use of both agents did not offer any advantage over either agent alone
#45 Injury 1999 Apr;30(3):209-14
Early continuous noninvasive hemodynamic monitoring after severe blunt trauma. Velmahos GC; Wo CC; Demetriades D; Shoemaker WC Department of Surgery, University of Southern California School of Medicine, Los Angeles, USA.
BACKGROUND: Invasive haemodynamic parameters obtained by pulmonary artery (PA) catheterization from survivors' patterns were reported to provide criteria for therapeutic goals in high-risk elective surgery and accidental injuries. This approach is limited because PA catheterization requires critical care conditions; however, noninvasive methods can provide early information anywhere in the hospital. OBJECTIVES: To evaluate the feasibility of using noninvasive haemodynamic monitoring of patients with severe blunt trauma immediately after emergency department (ED) admission and to describe the early time course of haemodynamic events in survivors and nonsurvivors of blunt trauma. SETTING: A large, academic, level-I trauma centre. DESIGN: Prospective, descriptive haemodynamic study. PATIENTS AND METHODS: 38 severely injured patients, 22 (58%) survivors and 16 (42%) nonsurvivors, with ISS > 15 were monitored by: (a) an improved thoracic bioelectric impedance device that estimated cardiac output noninvasively and continuously, (b) simultaneous arterial oxygen saturation by pulse oximetry, (c) noninvasive blood pressure measurement and (d) transcutaneous oxygen and carbon dioxide sensors. The patients were monitored as soon as possible upon arrival at the ED and continued during the first 24 h or more after admission. When the patient reached the ICU, monitoring by PA catheterization was undertaken to validate the noninvasive methods and for continued diagnostic evaluations. RESULTS: Cardiac output estimations by thermodilution and bioimpedance were well correlated; r = 0.91. Survivors started with high cardiac index (CI) values that subsequently rose to over 4 L/min/m2; arterial oxygen saturation (SaO2), transcutaneous oxygen tension and transcutaneous-oxygen-tension-to-inspired-fraction-of-oxygen-concentr ati on (PtcO2/FiO2) values were normal in survivors and higher than those of the nonsurvivors. In the 1st h after admission, nonsurvivors' blood pressures were higher than normal and higher than that of the survivors, but in the 2nd and 3rd h, both groups were in the normal range; thereafter, nonsurvivors' values were lower than survivors' and often lower than normal. CONCLUSIONS: The noninvasive haemodynamic monitoring system provides reasonably accurate, continuous, on-line, real-time display of haemodynamic data that show marked differences in the early patterns of survivors and nonsurvivors. The study suggests noninvasive monitoring may be used for early detection and correction of posttraumatic circulatory deficits.
#47 World J Surg 1999 Dec;23(12):1264-70; discussion 1270-1
Hemodynamic patterns of survivors and nonsurvivors during high risk elective surgical operations. Shoemaker WC, Wo CC, Thangathurai D, Velmahos G, Belzberg H, Asensio JA, Demetriades D. Department of Surgery, University of Southern California School of Medicine, 1200 N. State Street, Room 9900, Los Angeles, California 90033, USA.
Postoperative survivors' and nonsurvivors' hemodynamic and oxygen transport patterns have been extensively studied, and the early postoperative circulatory events leading to organ failures and death have been documented. Outcome was improved when potentially lethal circulatory patterns were treated during the early (the first 8-12 hours) postoperative period; but after the appearance of organ failure, reversal of nonsurvival patterns did not improve the outcome. The purpose of this study was to describe prospectively intraoperative circulatory deficiencies that precede shock, organ failures, and death. The ultimate aim was to elucidate nonsurvivor patterns at the earliest possible time to develop more effective preventive strategies for lethal organ failures. This approach is based on the assumption that it is easier and more effective to prevent the initiators of shock, such as hypovolemia, hypoxemia, poor tissue perfusion, and tissue hypoxia, than to treat the mediators of organ failure, such as cytokines, antigens, eicosinoids, and heat shock proteins. We monitored 356 high risk elective surgical patients with preoperative and intraoperative hemodynamic monitoring by the pulmonary artery (PA) thermodilution catheter. The conventionally monitored mean arterial pressure and heart rate remained in the normal range in both groups; the nonsurvivor pattern included decreased cardiac index, stroke index, stroke work, oxygen delivery, and oxygen consumption. Low oxygen consumption was partly compensated by increased oxygen extraction rates, and arterial pressures were maintained by increasing systemic vascular resistance. The early temporal pattern of nonsurvivors' changes were similar to those described during the postoperative period that preceded development of organ failure and death. This suggests that lethal circulatory dysfunctions may begin during the intraoperative period but become more apparent before and after organs fail during later postoperative stages.
#48 Crit Care Med 1999 Oct;27(10):2147-52
Intraoperative evaluation of tissue perfusion in high-risk patients by invasive and noninvasive hemodynamic monitoring Shoemaker WC; Thangathurai D; Wo CC; Kuchta K; Canas M; Sullivan MJ; Farlo J; Roffey P; Zellman V; Katz RL Department of Anesthesiology, University of Southern California School of Medicine, Los Angeles 90033, USA.
OBJECTIVE: Although invasive monitoring has not been effective in late stages after organ failure has occurred, early postoperative monitoring revealed differences in survivor and nonsurvivor patterns and provided goals for improving outcome. We searched for the earliest divergence of survivor and nonsurvivor circulatory changes as an approach to earlier preventive therapy. The aim was to describe the intraoperative time course of circulatory dysfunction in survivors and nonsurvivors among high-risk elective surgery patients using both the thermodilution pulmonary artery catheter (PAC) and multicomponent noninvasive monitoring. DESIGN: Prospective intraoperative description of circulatory dysfunction. SETTING: University-run county hospital. PATIENTS: Two hundred nine consecutively monitored high-risk elective surgery patients. MEASUREMENTS AND MAIN RESULTS: We evaluated the data of high-risk elective surgery patients using both PAC and multicomponent noninvasive monitoring. The latter consisted of the following: a) an improved bioimpedance method for estimating cardiac output; b) the standard pulse oximetry to screen for pulmonary problems; c) transcutaneous oxygen and carbon dioxide tension sensors to evaluate tissue perfusion; and d) routine noninvasive blood pressure and heart rate. The current noninvasive impedance cardiac output estimations closely approximated those of the thermodilution method; r2 = .74, p < .001; the precision and bias was -0.124 +/- 0.75 L/min/m2. Outcome measures included intraoperative description of circulatory patterns of high-risk surgical patients who survived compared with nonsurvivors. Hypotension, low cardiac index, arterial hemoglobin desaturation, low transcutaneous oxygen, high transcutaneous carbon dioxide tensions, low oxygen delivery, and low oxygen consumption developed intraoperatively gradually over time; the abnormalities were more pronounced in the nonsurvivors than in the survivors. CONCLUSIONS: The survivors had slightly higher mean arterial pressure, cardiac index, and mixed venous oxygen saturation, as well as significantly higher oxygen delivery, oxygen consumption, transcutaneous oxygen tension, and transcutaneous oxygen tension/FIO2 ratios, than did the nonsurvivors. The data suggest that blood flow, oxygen delivery, and tissue oxygenation of the nonsurvivors became inadequate toward the end of the operation. Noninvasive monitoring provides similar information to that of the PAC; both approaches revealed low-flow and poor tissue perfusion that were worse in the nonsurvivors. The continuous on-line real-time displays of hemodynamic trends facilitate early recognition of acute circulatory dysfunction.
#49 Crit Care Nurs Clin North Am. 1999 Mar;11(1):63-75.
Advances in continuous, noninvasive hemodynamic surveillance. Impedance cardiography. Von Rueden KT, Turner MA.
In the current climate of shrinking health care reimbursement and increasing importance of patient centered care, impedance cardiography is one method of enhancing quality of patient care and appropriate use of resources. Hemodynamic and thoracic fluid status data may be obtained quickly, accurately, and without risk, providing a global clinical perspective. Patients benefit from the ability to immediately obtain real time hemodynamic data, particularly those patients who otherwise may not be afforded a high level of monitoring or those needing hemodynamic monitoring when assessment and treatment are delayed because of inaccessibility of critical care beds or in the cardiac catheterization laboratory. Application of a technology assessment model to impedance cardiography illustrates the utility of this method of hemodynamic monitoring. Careful review and critique of the literature differentiates the available impedance technologies, supports use in areas not traditionally associated with hemodynamic monitoring, such as the home and emergency department, and validates the use of impedance cardiography in place of, or as an indication for, pulmonary artery catheterization.
#50 Int Surg 1999 Oct-Dec;84(4):354-60
Invasive and non-invasive physiological monitoring of blunt trauma patients in the early period after emergency admission Velmahos GC; Wo CC; Demetriades D; Murray JA; Cornwell EE 3rd; Asensio JA; Belzberg H; Shoemaker WC Department of Surgery, University of Southern California, Los Angeles, USA
Pulmonary artery catheterization is usually not available to critically injured patients before admission to the intensive care unit, where action to correct values derived from such monitoring may be too late. Methods allowing hemodynamic monitoring during the early stages after trauma need to be explored. We used non-invasive monitoring systems (bioimpedance cardiac output monitoring, pulse oximetry and transcutaneous oximetry) to evaluate early temporal hemodynamic patterns after blunt trauma, and compared these to invasive PA monitoring. We included prospectively 134 patients monitored shortly after admission to the emergency department. The non-invasive impedance cardiac output estimations under extenuating emergency conditions approximated those of the thermodilution method: r = 0.83, r2 = 0.69, P<0.001; bias and precision were -0.02+/-0.78 l/min/m2. In the intensive care unit, these values improved further to: r = 0.91, r2 = 0.83, P<0.001; bias and precision = 0.36+/-0.59 l/min/m2. Monitoring revealed episodes of hypotension, low cardiac index, arterial hemoglobin desaturation, low transcutaneous oxygen and high transcutaneous carbon dioxide tensions, and low oxygen consumption during initial resuscitation. Low flow and poor tissue perfusion were more pronounced in non-survivors by both methods. Multicomponent non-invasive monitoring systems give continuous on-line, real-time displays of physiological data that allow early recognition of circulatory dysfunction. Such systems provide information similar to that provided by
#52 World J Surg 1999 Jan;23(1):54-8
Physiologic monitoring of circulatory dysfunction in patients with severe head injuries. Velmahos GC, Shoemaker WC, Wo CC, Demetriades D. Department of Surgery, Division of Trauma and Critical Care, University of Southern California and the Los Angeles County/USC Medical Center, 1200 N. State Street, Room 9900, Los Angeles California 90033, USA.
Secondary brain insults influence outcome significantly in patients with severe head injuries. Inadequate tissue perfusion should be identified and treated early to avoid such insults. Conventional hemodynamic monitoring (blood pressure, heart rate, urine output) is not a reliable method for evaluating circulatory function in such patients. Invasive monitoring by means of pulmonary artery catheters may offer more precise information on early circulatory abnormalities. The objective of this study was to study the hemodynamic patterns of patients with severe closed head trauma by invasive methods and to correlate the derived information with survival. Fifty-nine consecutive patients with blunt trauma, closed head injuries, and Glascow Coma Scale < 8 were studied. Pulmonary artery catheters were placed in all patients shortly after admission, and flow and flow-derived variables were monitored for 96 hours or patient demise. Survivors had higher cardiac index, oxygen delivery, and oxygen consumption values compared to nonsurvivors during the first 24 hours after injury. Following this period increased values were recorded in both groups. These temporal hemodynamic patterns were similar for patients with isolated head trauma and patients with other associated injuries. Thus initial hemodynamic patterns are associated with final outcome in patients with severe head injuries. Aggressive early hemodynamic monitoring may reveal subtle but significant changes. Further studies are warranted to investigate whether treatment guided by such information can improve survival
#59 West J Med 1998 Jul;169(1):17-22
Invasive and noninvasive hemodynamic monitoring of patients with cerebrovascular accidents. Velmahos GC; Wo CC; Demetriades D; Bishop MH; Shoemaker WC Department of Surgery, Los Angeles County-University of Southern California (LAC-USC) Medical Center 90033, USA.
Seventeen patients with hemodynamic instability from acute cerebrovascular accidents were evaluated shortly after arrival at the emergency department of a university-run county hospital with both invasive Swan-Ganz pulmonary artery catheter placement and a new, noninvasive, thoracic electrical bioimpedance device. Values were recorded and temporal patterns of survivors and nonsurvivors were described. Cardiac indices obtained simultaneously by the 2 techniques were compared. Of the 17 patients, 11 (65%) died. Survivors had higher values than nonsurvivors for mean arterial pressure, cardiac index, and oxygen saturation, delivery, and consumption at comparable times. Cardiac index values, as measured by invasive and noninvasive methods, were correlated. We concluded that hemodynamic monitoring in an acute care setting may recognize temporal circulatory patterns associated with outcome. Noninvasive electrical bioimpedance technology offers a new method for early hemodynamic evaluation. Further research in this area is warranted.
#60 Chest 1998 Dec;114(6):1643-52
Multicenter study of noninvasive monitoring systems as alternatives to invasive monitoring of acutely ill emergency patients Shoemaker WC; Belzberg H; Wo CC; Milzman DP; Pasquale MD; Baga L; Fuss MA; Fulda GJ; Yarbrough K; Van De Water JP; Ferraro PJ; Thangathurai D; Roffey P; Velmahos G; Murray JA; Asensio JA; El Tawil K; Dougherty WR; Sullivan MJ; Patil RS; Adibi J; James CB; Demetriades D Department of Surgery, University of Southern California School of Medicine, Los Angeles, USA.
BACKGROUND: Recent reports showed lack of effectiveness of pulmonary artery catheterization in critically ill medical patients and relatively late-stage surgical patients with organ failure. Since invasive monitoring requires critical care environments, the early hemodynamic patterns may have been missed. Ideally, early noninvasive hemodynamic monitoring systems, if reliable, could be used as the "front end" of invasive monitoring to supply more complete descriptions of circulatory pathophysiology. OBJECTIVES: To evaluate the accuracy and reliability of noninvasive hemodynamic monitoring consisting of a new bioimpedance method for estimating cardiac output combined with arterial BP, pulse oximetry, and transcutaneous PO2 and PCO2; we compared this system of noninvasive monitoring with simultaneous invasive measurements to evaluate circulatory deficiencies in acutely ill patients shortly after hospital admission where invasive monitoring was not readily available. We also preliminarily explored early differences in temporal hemodynamic patterns of survivors and nonsurvivors. DESIGN AND SETTING: Prospective comparison of simultaneous invasive and noninvasive measurements of circulatory function with retrospective analysis of data in university-run county hospitals, university hospitals and affiliated teaching hospitals, and a community private hospital. PATIENTS: We studied 680 patients, including 139 severely injured or hemorrhaging patients in the emergency department (ED), 129 medical (nontrauma) patients on admission to the ED, 274 high-risk surgical patients intraoperatively, and 138 patients recently admitted to the ICU. RESULTS: A new noninvasive impedance device provided cardiac output estimations under conditions in which invasive thermodilution measurements were not usually applied. There were 2,192 simultaneous bioimpedance and thermodilution cardiac index measurements; the correlation coefficient, r = 0.85, r2 = 0.73, p < 0.001. The precision and bias was -0.124+/-0.75 L/min/m2. Both invasive and noninvasive monitoring systems provide similar information and identified episodes of hypotension, low cardiac index, arterial hemoglobin desaturation, low transcutaneous O2, high transcutaneous CO2, and low oxygen consumption before and during initial resuscitation. The limitations of noninvasive systems were described. CONCLUSIONS: Noninvasive monitoring systems gave continuous displays of physiologic data that provided information allowing early recognition of low flow and poor tissue perfusion that were more pronounced in the nonsurvivors. Noninvasive systems may be acceptable alternatives where invasive monitoring is not available.
#62 J Cardiothorac Vasc Anesth 1997 Jun;11(4):440-4
Continuous intraoperative noninvasive cardiac output monitoring using a new thoracic bioimpedance device. Thangathurai D; Charbonnet C; Roessler P; Wo CC; Mikhail M; Yoahida R; Shoemaker WC Department of Anesthesiology, University of Southern California School of Medicine, Los Angeles, USA.
OBJECTIVES: To compare a new noninvasive bioimpedance device with the standard thermodilution method during the intraoperative period in high-risk patients undergoing oncological surgery. DESIGN: Prospectively collected data with retrospective analysis. SETTING: The study was undertaken at a university hospital, single institution. PARTICIPANTS: Twenty-three selected adults undergoing extensive, ablative oncological surgery. INTERVENTIONS: Simultaneous measurements of cardiac output by a new bioimpedance method and the standard thermodilution method during the intraoperative and immediate postoperative periods. MEASUREMENTS AND MAIN RESULTS: The correlation coefficient between the two methods was r = 0.89, p < 0.001. Bias and precision analysis between the two techniques showed a mean bias of 0.1 L/min and SD of the bias [precision] of 1.0 L/min [95% level of agreement +2.1 L/min to -1.9 L/min]. After software enhancement, data from the last 11 monitored patients showed improved correlation between the two methods; r = 0.93, mean bias -0.1 L/min, and precision 0.8 L/min. Electrical and motion-induced interference only transiently impaired the performance of the new impedance method. CONCLUSION: This new impedance device is a safe, reliable, clinically acceptable alternative to the invasive thermodilution method in the operating room environment.
#67 Crit Care Clin 1996 Oct;12(4):939-69
Oxygen transport and oxygen metabolism in shock and critical illness. Invasive and noninvasive monitoring of circulatory dysfunction and shock Shoemaker WC Department of Anesthesiology, University of Southern California School of Medicine, Los Angeles, USA.
The common underlying physiologic problem in shock is low flow from hypovolemia or maldistributed microcirculatory flow from uneven vasoconstriction, leading to inadequate tissue perfusion (hypoxia), often in the face of increased metabolic demands. Noninvasive monitoring which was found to provide similar information to that of invasive monitoring, was used in the earliest period of time shortly after admission to the emergency department to provide objective physiologic criteria as therapeutic goals for each of the three major circulatory components: cardiac, pulmonary, and tissue perfusion functions. A clinical algorithm or branch-chain decision tree for high-risk surgical patients was developed from decision rules based on survivor and nonsurvivor patterns, outcome predictors, prospective controlled clinical trials of the oxygen delivery/oxygen consumption (DO2/VO2)
#68 New Horiz 1996 Nov;4(4):466-74
Intraoperative maintenance of tissue perfusion prevents ARDS. Adult Respiratory Distress Syndrome. Thangathurai D, Charbonnet C, Wo CC, Shoemaker WC, Mikhail MS, Roffey P, Roessler P, Kuchta K, Zelman V, DeMeester TR, Katz R.Department of Anesthesiology, University of Southern California School of Medicine, Los Angeles, USA.
Patients undergoing prolonged, complex oncological surgery are at increased risk of developing the adult respiratory distress syndrome (ARDS) and other organ failures. Our hypothesis is that maintaining adequate tissue perfusion and oxygenation may prevent tissue hypoxia and acidosis in pulmonary, peripheral, and splanchnic microcirculations. Experimental evidence suggests that the hypoxic, acidotic endothelium stimulates the release of cytokines, kinins, and other mediators. We developed and tested an intraoperative protocol for surgical patients likely to develop ARDS and organ dysfunction; the protocol focuses on the intraoperative period but is not limited to this time. Nitroglycerin and fluids were used to maintain tissue perfusion and prevent tissue hypoxia as reflected by transcutaneous oxygen tension values. In 155 high-risk patients, none developed ARDS. We conclude that maintenance of tissue perfusion and oxygenation in high-risk surgical patients decreases the incidence of ARDS.
#69 New Horiz 1996 Nov;4(4):395-412
Early physiologic patterns in acute illness and accidents: toward a concept of circulatory dysfunction and shock based on invasive and noninvasive hemodynamic monitoring Shoemaker WC; Wo CC; Demetriades D; Belzberg H; Asensio JA; Cornwell EE; Murray JA; Berne TV; Adibi J; Patil RS Department of Surgery, University of Southern California School of Medicine, Los Angeles 90033, USA.
The aim of the present study was to explore methods, concepts, and techniques that provide recognition of circulatory deficiencies at the earliest possible time in the patient's illness. We used both the standard invasive pulmonary artery thermodilution catheter and noninvasive hemodynamic monitoring systems consisting of a new bioimpedance cardiac output device, pulse oximetry, transcutaneous oxygen (PtCO2) and carbon dioxide tensions as well as the transcutaneous oxygen tension/fraction of inspired oxygen ratio (PtCO2/FIO2). These three noninvasive systems were used to evaluate cardiac function, pulmonary function, and tissue perfusion, respectively. This approach to early noninvasive monitoring is based on recent evidence suggesting that poor tissue perfusion and oxygenation initiate circulatory dysfunction that leads to shock and organ failure. We studied 303 acute episodes of circulatory dysfunction and shock in 261 patients in a university-run county hospital; 75 were acute traumatic injuries and 109 acute nontrauma medical emergencies on admission to the emergency department, and 77 ICU patients with an acute illness or exacerbation of their current illness. The study was a prospective, descriptive study to identify early abnormal circulatory patterns reflecting the cardiac, pulmonary, and perfusion functions associated with death and with survival. We described noninvasively monitored patterns in individual illustrative cases, in common etiologic groups, and in physiologic categories representing various abnormal functional patterns. We found that hypotensive shock usually was preceded by episodes of high flow followed by low flow and inadequate tissue perfusion indicated by reduced PtCO2; this frequent pattern was modified by associated co-morbid conditions, especially hypovolemia, limited cardiac reserve capacity, age, hypertensive states, and increased body metabolism from infection, trauma, stress, exercise, temperature, and endocrine disorders. Reduced pulmonary function occurred in 18% of emergency patients; these were usually patients with thoracic trauma, severe hypovolemia, head injuries, chronic obstructive pulmonary disease, asthma, drug overdose, and central nervous system failure (massive stroke and coma). We concluded that noninvasive measurements identify early circulatory problems reliably and provide objective criteria for physiologic analysis as well as for definition of therapeutic goals and titration of therapy.
#70 New Horiz 1996 May;4(2):300-18
Temporal physiologic patterns of shock and circulatory dysfunction based on early descriptions by invasive and noninvasive monitoring. Shoemaker WC Department of Surgery, University of Southern California School of Medicine, Los Angeles, USA.
In the past, most investigators failed to consider time relationships in their studies of circulatory problems. Because of this, data obtained in middle- or late-stage shock during organ failure are often presented as being characteristic of specific shock syndromes. Even "early" studies are not physiologically early, but instead have often come to mean early after ICU admission or early after life-threatening hypotensive events. The hypotensive episode represents decompensation of protective circulatory mechanisms, not the beginning of circulatory dysfunction. Early monitoring demonstrates that circulatory changes do not start with hypotension, but with the precipitating event, i.e., hemorrhage, trauma, surgery, or sepsis. When monitoring is started after hypotension, the first half of the problem is missed. It is, therefore, appropriate to focus on the earliest period of circulatory dysfunction with noninvasive methods to evaluate pathophysiology, to predict outcome, and to propose therapeutic protocols to improve outcome. Invasive monitoring is generally accepted as the "gold standard" for critically ill patients. The pulmonary artery flotation catheter has translated information to the bedside previously only available in cardiac catheterization laboratories, forever changing the way we treat ICU patients. Newer high-tech hardware and software innovations in the impedance method give more accurate and reliable cardiac index (CI) measurements that now satisfactorily agree with thermodilution in most clinical conditions. Minor disparities are more than made up for by the continuous online display of data. This impedance device, combined with pulse oximetry and transcutaneous oximetry, provides a feasible, noninvasive hemodynamic monitoring system that can be applied in a manner similar to electrocardiogram electrodes in the emergency department, operating room, ICU, hospital floors, and doctor's offices. More importantly, noninvasive monitoring provides a continuous, online, real-time display of hemodynamic data needed to titrate therapy rapidly and expeditiously. This is a major advantage, since therapy is more effective if given prophylactically or early and then titrated to optimal goals. Noninvasive monitoring provides a powerful method for objective evaluation of early, rapidly changing circulatory dynamics beginning with the precipitating event. This gives a new and different view of circulatory failure, exceeding the boundaries of our old concepts of shock based on blood pressure, subjective symptoms, and imprecise signs. Data of survivors revealed increased cardiac function (CI and oxygen delivery) shortly after surgery, trauma, and sepsis; this response is needed to meet the increased metabolic demands defined by the increased oxygen consumption. Nonsurvivors have limited responses to the added metabolic demands of external stressors. Therapy should augment naturally occurring compensations, but it must be given promptly within appropriate time limits.
#71 Acad Emerg Med 1996 Jul;3(7):675-81
Noninvasive hemodynamic monitoring of critical patients in the emergency department Shoemaker WC; Wo CC; Bishop MH; Thangathurai D; Patil RS Department of Emergency Medicine, King-Drew Medical Center, Los Angeles, CA, USA.
OBJECTIVE: To evaluate the feasibility of multicomponent noninvasive hemodynamic monitoring in critical emergency patients and to compare this technique with simultaneous invasive monitoring by the pulmonary artery thermodilution catheter. METHODS: A prospective observational study was done comparing invasive monitoring and noninvasive monitoring in 60 critically ill or injured patients who required hemodynamic monitoring shortly after entering the ED of a university-affiliated country hospital. Cardiac output (CO) values measured by the standard thermo-dilution pulmonary artery catheter technique were compared with simultaneously obtained measurements using a noninvasive bioimpedance method. Concurrent measurements were made of pulse oximetry to screen pulmonary function and transcutaneous oximetry to assess tissue perfusion. RESULTS: The impedance CO values closely approximated those for the thermodilution method; r 0.81, p < 0.001. Significant circulatory abnormalities, including hypotension, reduced cardiac index, arterial hemoglobin desaturation, tissue hypoxia, reduced O2 delivery, and consumption, were found in 54 of the 60 (90%) patients. The cardiac index decreased in 44% of the patients, the transcutaneous O2 decreased in 39%, and the O2 saturation by pulse oximetry fell in 22% during the observation period in the ED (commonly lasting 2-8 hours). CONCLUSIONS: Noninvasive monitoring can provide hemodynamic and perfusion information previously available only by invasive thermodilution catheters. Such noninvasive monitoring can display continuous on-line real-time data, allowing immediate recognition of circulatory abnormalities and providing a means to titrate therapy to appropriate therapeutic goals.
#72 Arch Surg 1996 Jul;131(7):732-7
Noninvasive physiologic monitoring of high-risk surgical patients. Shoemaker WC, Wo CC, Bishop MH, Asensio J, Demetriades D, Appel PL, Thangathurai D, Patil RS.Department of Emergency Medicine, King-Drew Medical Center, University of Southern California School of Medicine, Los Angeles, USA.
OBJECTIVES: To study the feasibility of multicomponent noninvasive monitoring, consisting of a new bioimpedance method for estimating cardiac output together with routine pulse oximetry and transcutaneous oximetry, and to compare physiologic data obtained noninvasively with hemodynamic and oxygen transport data obtained by standard invasive pulmonary artery thermodilution catheter to evaluate circulatory function in high-risk surgical patients. DESIGN: Prospective descriptive analysis of the time course of physiologic patterns in surgical patients. SETTING: University-run county hospital. PATIENTS: Seventy-one consecutively monitored, high-risk critically ill surgical patients in their perioperative period. OUTCOME MEASURES: Simultaneous measurements by invasive and noninvasive methods to describe and compare the temporal physiologic patterns of survivors and nonsurvivors. RESULTS: The new impedance cardiac output estimations closely approximated those of the thermodilution method (r = 0.82, P < .001). Episodes of hypotension, tachycardia, low cardiac index, arterial hemoglobin desaturation, low transcutaneous oximetry, reduced oxygen delivery, and low oxygen consumption occurred with both groups but were more pronounced in the nonsurvivors than in the survivors. Noninvasive monitoring provided information similar to that of the thermodilution method. Both approaches indicated low flow and poor tissue perfusion (oxygenation) that was worse in the nonsurvivors. CONCLUSIONS: The multicomponent noninvasive monitoring provides continuous online, real-time displays of physiologic data that allow immediate recognition of circulatory dysfunction as well as the means to titrate therapy to appropriate predetermined therapeutic goals. The noninvasive systems are easy to apply, safe, inexpensive, reasonably accurate, and cost-effective.
#74 New Horiz 1996 Nov;4(4):541-50
Application of an artificial intelligence program to therapy of high-risk surgical patients. Patil RS, Adibi J, Shoemaker WC. Information Science Institute, University of Southern California School of Medicine, Los Angeles, USA.
We developed an artificial intelligence program from a large computerized database of hemodynamic and oxygen transport measurements together with prior studies defining survivors' values, outcome predictors, and a branched-chain decision tree. The artificial intelligence program was then tested on the data of 100 survivors and 100 nonsurvivors not used for the development of the program or other analyses. Using the predictor as a surrogate outcome measure, the therapy recommended by the program improved the predicted outcome 3.16% per therapeutic intervention while the actual therapy given increased outcome 1.86% in surviving patients; the artificial intelligence-recommended therapy improved outcome 7.9% in nonsurvivors, while the actual therapy given increased predicted outcome -0.29% in nonsurvivors (p < .05). There were fewer patients whose predicted outcome decreased after recommended treatment (14%) than after the actual therapy given (37%). Review of therapy recommended by the program did not reveal instances of inappropriate or potentially harmful recommendations.
#77 Acad Emerg Med 1996 Jul;3(7):682-8
Noninvasive cardiac index monitoring in gunshot wound victims. Bishop MH; Shoemaker WC; Shuleshko J; Wo CCDepartment of Surgery, King-Drew Medical Center, Los Angeles, CA 90059, USA.
OBJECTIVE: To evaluate a bioimpedance device for the noninvasive measurement of cardiac index (CI) against standard thermodilution measurements in patients with gunshot wounds. METHODS: A prospective open-label performance evaluation was done using a convenience sample of gunshot wound victims initially treated in the resuscitation area of a high-volume, urban ED. After initial resuscitation, patients had a flow-directed pulmonary artery catheter placed for thermodilution cardiac output (CO) measurements. The CO measurements were made in triplicate and averaged. Estimates of body surface area were used to convert these measurements to CI estimates. Electrodes for bioimpedance measurements were placed as soon as practical after ED arrival. Simultaneous measurements of CI using the bioimpedance device were made as clinically indicated during each patient's hospital course. RESULTS: There were 54 patients studied, with an overall mean (+/- SEM) age of 32 +/- 3 years, Revised Trauma Score of 6.7 +/- 0.4, and Injury Severity Scale score of 22 +/- 3. There were 42 survivors and 12 nonsurvivors. The CI as estimated by bioimpedance correlated well with that measured by thermodilution (r = 0.79, p < or = 0.02). The precision of the invasive and noninvasive measurements was 1.1 L/min/m2; the bias was -0.011 L/min/m2. In 24 patients with thoracic injuries requiring tube thoracostomy or thoracic surgery, the correlation of the 2 devices was r = 0.71 with precision and bias of 1.4 L/min/m2 and -0.018 L/min/m2, respectively. CONCLUSIONS: Cardiac index can be noninvasively estimated in acutely injured patients with gunshot wounds using a bioimpedance device. Further study of bioimpedance measurements as a guide to volume therapy is warranted.
#78 Surg Clin North Am 1996 Aug;76(4):985-97
Invasive and noninvasive monitoring for early recognition and treatment of shock in high-risk trauma and surgical patients Asensio JA; Demetriades D; Berne TV; Shoemaker WC Department of Surgery, Los Angeles County/University of Southern California Medical Center, USA.
The proposed noninvasive monitoring systems provide the essential hemodynamic and oxygen transport information previously available only by invasive thermodilution catheters. More importantly, the noninvasive systems provide continuous on-line real-time displays of data which allow immediate recognition of circulatory abnormalities and provide a means to titrate therapy to appropriate therapeutic goals. The noninvasive systems are easy to apply, safe, inexpensive, and more cost-effective than invasive monitoring.
#80 Crit Care Med 1996 Feb;24(2 Suppl):S12-23
Resuscitation from severe hemorrhage. Shoemaker WC, Peitzman AB, Bellamy R, Bellomo R, Bruttig SP, Capone A, Dubick M, Kramer GC, McKenzie JE, Pepe PE, Safar P, Schlichtig R, Severinghaus JW, Tisherman SA, Wiklund L.Department of Emergency Medicine, King/Drew Medical Center, Los Angeles, CA 90059, USA.
The potential to be successfully resuscitation from severe traumatic hemorrhagic shock is not only limited by the "golden 1 hr", but also by the "brass (or platinum) 10 mins" for combat casualties and civilian trauma victims with traumatic exsanguination. One research challenge is to determine how best to prevent cardiac arrest during severe hemorrhage, before control of bleeding is possible. Another research challenge is to determine the critical limits of, and optimal treatments for, protracted hemorrhagic hypotension, in order to prevent "delayed" multiple organ failure after hemostasis and all-out resuscitation. Animal research is shifting from the use of unrealistic, pressure-controlled, hemorrhagic shock models and partially realistic, volume-controlled hemorrhagic shock models to more realistic, uncontrolled hemorrhagic shock outcome models. Animal outcome models of combined trauma and shock are needed; a challenge is to find a humane and clinically realistic long-term method for analgesia that does not interfere with cardiovascular responses. Clinical potentials in need of research are shifting from normotensive to hypotensive (limited) fluid resuscitation with plasma substitutes. Topics include optimal temperature, fluid composition, analgesia, and pharmacotherapy. Hypotensive fluid resuscitation in uncontrolled hemorrhagic shock with the addition of moderate resuscitative (28 degrees to 32 degrees C) hypothermia looks promising in the laboratory. Regarding the composition of the resuscitation fluid, despite encouraging results with new preparations of stroma-free hemoglobin and hypertonic salt solutions with colloid, searches for the optimal combination of oxygen-carrying blood substitute, colloid, and electrolyte solution for limited fluid resuscitation with the smallest volume should continue. For titrating treatment of shock, blood lactate concentrations are of questionable value although metabolic acidemia seems helpful for prognostication. Development of devices for early noninvasive monitoring of multiple parameters in the field is indicated. Molecular research applies more to protracted hypovolemic shock followed by the systemic inflammatory response syndrome or septic shock, which were not the major topics of this discussion.
#82 Biomed Instrum Technol 1995 May-Jun;29(3):203-12
Time-frequency distribution technique in biological signal processing. Wang X, Sun HH, Van de Water JM. Department of Electrical and Computer Engineering, Drexel University, Philadelphia, PA 19104.
Time-frequency distribution (TFD) has gained wide acceptance for deterministic non-stationary signal processing, particularly for biological signals, in both basic research and commercial production. This paper presents the results of a comparison of the TFD technique with other methods for determining physiologic parameters, particularly the ventricular ejection time (VET) and (dZ/dtmax), the differentiation of the thoracic-fluid signal Z0 from non-stationary impedence cardiography dZ/dt. The TFD technique was found to be more accurate--in terms of both time and signal magnitude--than traditional methods such as the baseline and ensemble-averaging techniques when compared with phonocardiograms and hand calculations by experts in the field. It is shown that TFD can also reduce ventilatory/respiratory noise, electrical and muscle noise, and patient-motion artifacts. Correlation analysis and regression analysis as well as Bland-Altman studies showed stronger correlational methods tested.
#86 J Surg Res 1995 Oct;59(4):504-10
Impedance cardiography in the measurement of cardiac output: studies in rabbits. Pappas CG, Wang X, Connolly RJ, Schwaitzberg SD.Department of Surgery, New England Medical Center, Boston, Massachusetts 02111, USA.
A thoracic electric bioimpedance device with improved signal processing was used to noninvasively measure cardiac output in eight New Zealand White rabbits (average wt = 4.7 kg). Prospective correlation was performed between aortic thermodilution and impedance cardiography in a closed chest model. Aortic thermodilution was compared to the electromagnetic flowmeter in an open chest model. In four rabbits, the change in the impedance signal (dZ/dt) was quantified after repeated mechanical occlusion of the aorta and pulmonary artery. The mean cardiac output as measured by the impedance device was 0.56 +/- 0.01 liter/min (range 0.29-1.16 liter/min) compared to 0.53 +/- 0.01 liter/min (range 0.25-0.83 liter/min) by aortic thermodilution. For the 116 data pairs, regression analysis revealed a statistically significant agreement (r = 0.82, P < 0.001) between the two techniques. The mean difference between the techniques (bias) was -0.03 liter/min and 81% of the impedance values were within 0.1 liter/min of the individual thermodilution measurements. A statistically significant decline in the mean magnitude of the dZ/dt signal tracing (1.6 +/- 0.10 V-pre, 0.31 +/- 0.4 V-post, P < 0.005, n = 21) was observed upon aortic arch occlusion. conversely, pulmonary artery occlusion did not have a statistical effect on the impedance signal (1.07 +/- 0.09-pre, 0.95 +/- 0.08-post, P > 0.05, n = 20). In conclusion, a significant correlation was observed between impedance cardiography and aortic thermodilution in measurement of cardiac output in sedated, anesthetized rabbits. This simple technique which involves application of skin electrodes may prove useful in measurement of cardiac output in surgical experimental small animal models
#89 IEEE Trans Biomed Eng 1995 Feb;42(2):224-30
An advanced signal processing technique for impedance cardiography. Wang X, Sun HH, Van de Water JM. Department of Electrical and Computer Engineering, Drexel University, Philadelphia, PA 19104
A new design using the latest technique in signal processing, the time-frequency analysis method, was developed to process impedance cardiography signals. This technique, when used to determine the relevant calculation parameters, was found to be more accurate than conventional methods. It was shown to be advantageous in reducing ventilation artifacts and motion noise, resulting in greater accuracy. Its cardiac output values had a much better correlation coefficient when compared in the clinical setting to the standard thermodilution
#92 Crit Care Nurs Clin North Am 1994 Jun;6(2):295-307
Pathophysiology, monitoring, and therapy of acute circulatory problems. Shoemaker WC.
Acute circulatory problems, including shock, traditionally have been recognized and treated by subjective symptoms and vital signs (BP and HR) which represent only superficial aspects of the underlying physiology. Shock, however, is objectively diagnosed, evaluated, and treated using invasive physiologic monitoring to measure cardiac function and output, pulmonary function, and tissue perfusion. Multicomponent noninvasive monitoring systems are now being developed to obtain comparable information and provide continuous display of data on-line, in real time. These monitoring systems may be used to evaluate the effectiveness of alternative therapies, and to titrate therapy to achieve optimal physiologic goals that improve outcome.
#95 Crit Care Med 1994 Dec;22(12):1907-12
Multicenter trial of a new thoracic electrical bioimpedance device for cardiac output estimation Shoemaker WC; Wo CC; Bishop MH; Appel PL; Van de Water JM; Harrington GR; Wang X; Patil RS Department of Emergency Medicine, King/Drew Medical Center, Los Angeles, CA 90059.
OBJECTIVE: To evaluate the capacity of a new thoracic electric bioimpedance system to estimate cardiac output compared with the conventional thermodilution method. DESIGN: Prospective, multicenter study. SETTING: A university-run county hospital, a university-run U.S. Veterans Affairs hospital, and a university-affiliated U.S. military hospital. PATIENTS: A series of 68 critically ill patients whose conditions required pulmonary artery catheter insertion. MEASUREMENTS AND MAIN RESULTS: A total of 842 simultaneous pairs of cardiac output estimations by conventional thermodilution and a new thoracic electric bioimpedance system that uses an improved signal processing technique based on an all-integer-coefficient filtering technology, using a time-frequency distribution that provides a high signal/noise ratio were evaluated. The r value was .86, r2 = .74, and p < .001 by regression analysis; the mean difference between the two methods relative to their average value was 16.6 +/- 12.9 (SD) %; the precision was 1.4 L/min or 0.8 L/min/m2; the bias was -0.013 L/min. The mean difference between successive pairs of thermodilution measurements was 8.6 +/- 0.6 (SD) %, which was about half the difference between simultaneous pairs of measurement by the two methods. The changes in impedance estimations were close to simultaneously measured changes in thermodilution estimates of cardiac output. CONCLUSIONS: The new bioimpedance system satisfactorily estimated cardiac output as measured by the thermodilution technique. The difference between the two estimations is more than made up for by the continuous noninvasive capability of the impedance system.
#99 Surg Gynecol Obstet 1992 Dec;175(6):535-8
Cardiovascular changes during laparoscopic cholecystectomy.Westerband A, Van De Water J, Amzallag M, Lebowitz PW, Nwasokwa ON, Chardavoyne R, Abou-Taleb A, Wang X, Wise L.Department of Surgery, Long Island Jewish Medical Center.
Although the technique of laparoscopic cholecystectomy has increasing appeal, physiologic data to support the safety of this procedure are lacking. We studied the cardiovascular changes in 16 patients undergoing laparoscopic cholecystectomy, using impedance cardiography as a noninvasive means of continuous monitoring of cardiac output. Serial measurements of mean arterial pressure (MAP), heart rate (HR), intraperitoneal pressure and expired carbon dioxide tension (PECO2) were also recorded. Results revealed a decrease of 30 percent (p < 0.001) in cardiac index and 5 percent (p = 0.089) in HR, along with increases of 15 percent (p < 0.001) in MAP and of 79 percent (p < 0.001) in the calculated total peripheral resistance index. This elevation in afterload could lead to both an increase in myocardial oxygen consumption and to the potential risk of myocardial ischemia and possibly infarction or congestive heart failure, or both, in patients who are susceptible. The data suggest that patients with a history of cardiac disease should have preoperative cardiac evaluation and be closely monitored during laparoscopic cholecystectomy, as in any other extensive operation.
#101 Ann Biomed Eng 1989;17(5):535-56
An impedance cardiography system: a new design. Wang XA, Sun HH, Adamson D, Van de Water JM. Department of Electrical and Computer Engineering, Drexel University, Philadelphia, PA 19104
An IBM compatible impedance cardiac output monitoring prototype system has been developed for use at the bedside on patients in the ICU, CCU, ER, Cath. Lab, and OR, etc. This impedance cardiographic (ICG) system, whose operation is completely technician-free, provides a continuous display with digital results and four channel color waveforms on an Enhanced Graphics Display screen. The software is written in C language with several special segments in assembly code where speed is essential. In this prototype system, a real-time algorithm was introduced to modify the ensemble averaging technique so that it averages nonperiodic signals such as: ECG, dZ/dT, delta Z, etc. Also, a real-time algorithm was developed to adaptively detect R spikes from conventional ECG signals. A signal preprocessor was developed to process signals digitally before any further work is done. This procedure reduces muscle noise, 60 Hz interference, and ventilatory movement. A special digital filter was designed to cope with the cases in which pacemakers are used. A special algorithm was also developed to further reduce the ventilation artifacts so that a period of apnea is unnecessary during the performance of the measurements. An anatomically specified electrode configuration has been defined enabling precise and reproducible positioning of the electrodes--hopefully leading to electrode standardization. At the present time, this prototype system has been compared with standard hand calculation and correlated with the clinical "gold standard," the Swan-Ganz thermodilution cardiac output. Using 144 sets of data from 10 healthy volunteers, 4 critically ill patients, and 8 healthy exercising volunteers, calculations of cardiac output were made using our system and the standard hand calculation of stroke volume, based upon Kubicek's equation; there was a relatively high and stable correlation: r = 0.93, p less than 0.005 (healthy); r = 0.94, p less than 0.002 (ill), r = 0.95, p less than 0.002 (exercise). From 20 patients at two different hospitals all with Swan-Ganz catheters in their hearts, 65 correlation studies between our system and the standard thermodilution technique were performed; the results were encouraging in terms of accuracy and consistency (r1 = 0.84, p less than 0.01, n = 10 CCU patients), and (r2 = 0.93, p less than 0.01, n = ICU patients). These results along with a growing body of data from other investigators indicate that this noninvasive and technician-free system for measuring cardiac output could have a significant role in patient care.