Outcome prediction of emergency patients by noninvasive hemodynamic monitoring

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/m(2) (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.

Noninvasive hemodynamic monitoring for early warning of adult respiratory distress syndrome in trauma patients

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.

Endpoints of resuscitation of critically injured patients: normal or supranormal? A prospective randomized trial

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.

Invasive and noninvasive haemodynamic monitoring of acutely ill sepsis and septic shock patients in the emergency department

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.

Transcutaneous oxygen and CO2 as early warning of tissue hypoxia and hemodynamic shock in critically ill emergency patients

BACKGROUND

Although cardiac and pulmonary function can be measured precisely, evaluation of tissue perfusion remains elusive because it usually is inferred from subjective symptoms and imprecise signs of shock. The latter are indirect criteria used to assess the overall circulatory status as well as tissue perfusion but are not direct quantitative measures of perfusion. However, noninvasive transcutaneous oxygen (PtcO2) and carbon dioxide (PtcCO2) tensions, which directly measure skin oxygenation and CO2 retention, may be used to objectively evaluate skin oxygenation and perfusion in emergency patients beginning with resuscitation immediately after hospital admission.

OBJECTIVE

This study was a preliminary evaluation of tissue oxygenation and perfusion by objective PtcO2 and PtcCO2 patterns in severely injured surviving and nonsurviving patients; specifically, the aim was to describe time patterns that may be used as early warning signs of circulatory dysfunction and death.

DESIGN

Prospective descriptive study of a consecutive series of severely injured emergency patients.

SETTING

University-affiliated Level I trauma center and intensive care unit.

PATIENTS AND METHODS

Forty-eight consecutive severely injured patients were prospectively monitored by PtcO2 and PtcCO2 sensors immediately after emergency admission.

RESULTS

Compared with survivors, patients who died had significantly lower PtcO2 and higher PtcCO2 values beginning with the early stage of resuscitation. All patients who maintained PtcO2 >150 torr (19.99 kPa) throughout monitoring survived. Periods of PtcO2 <50 torr (6.66 kPa) for >60 mins or PtcCO2 >60 torr (8.00 kPa) for >30 mins were associated with 90% mortality and 100% morbidity.

CONCLUSION

PtcO2 and PtcCO2 monitoring continuously evaluate tissue perfusion and serve as early warning in critically injured patients during resuscitation immediately after hospital admission.

Hemodynamic patterns of survivors and nonsurvivors during high risk elective surgical operations

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.

Invasive and non-invasive physiological monitoring of blunt trauma patients in the early period after emergency admission

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 the invasive thermodilution method, and are easier and safer to use.

Intraoperative evaluation of tissue perfusion in high-risk patients by invasive and noninvasive hemodynamic monitoring

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.

Early continuous noninvasive haemodynamic monitoring after severe blunt trauma

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.

Physiologic monitoring of circulatory dysfunction in patients with severe head injuries

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.

Multicenter study of noninvasive monitoring systems as alternatives to invasive monitoring of acutely ill emergency patients

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.

Circulatory effects of whole blood, packed red cells, albumin, starch, and crystalloids in resuscitation of shock and acute critical illness

Circulatory deficiencies and the effectiveness of transfusion and fluid therapy may be evaluated by invasive and noninvasive monitoring after high risk surgery, hemorrhage, trauma, and sepsis in the ED, OR, and ICU. Earlier recognition and therapy of circulatory problems in emergency and critically ill patients to achieve optimal goals empirically defined by the survivors' patterns is recommended to improve outcome. WB, Prbc, and colloids markedly and statistically significantly improved pressure, flow, and tissue perfusion and best achieved these goals. Noninvasive monitoring may be used in the ED and OR shortly after admission to identify circulatory deficiencies and to titrate therapy, or they may be used initially as the front-end of subsequent invasive monitoring.

Invasive and noninvasive hemodynamic monitoring of patients with cerebrovascular accidents

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.

Continuous intraoperative noninvasive cardiac output monitoring using a new thoracic bioimpedance device

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.

Early physiologic patterns in acute illness and accidents: toward a concept of circulatory dysfunction and shock based on invasive and noninvasive hemodynamic monitoring

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.

Intraoperative maintenance of tissue perfusion prevents ARDS. Adult Respiratory Distress Syndrome

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.

Noninvasive physiologic monitoring of high-risk surgical patients

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.

Noninvasive hemodynamic monitoring of critical patients in the emergency department

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.

Noninvasive cardiac index monitoring in gunshot wound victims

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.

Multicenter trial of a new thoracic electrical bioimpedance device for cardiac output estimation

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.

Temporal patterns of hemodynamics, oxygen transport, cytokine activity, and complement activity in the development of adult respiratory distress syndrome after severe injury

The aim of this study was to search for early inflammatory mediators in severely traumatized patients that could predict the occurrence of adult respiratory distress syndrome (ARDS). We measured sequential plasma levels of tumor necrosis factor (TNF), interleukin 1 (IL-1), interleukin 6 (IL-6), interleukin 8 (IL-8), complement fragment C3a, and endotoxin. In addition, we measured sequentially the values of hemodynamics, oxygen transport, and pulmonary function. The temporal patterns seen in the patients who developed ARDS were compared with those who did not. In the patients who developed ARDS, the first observed findings were low cardiac index (CI) and oxygen delivery (DO2) followed by progressive increases in IL-6, IL-8 and C3a levels, worsening of pulmonary function, and increases in hemodynamic values. The maximum values of IL-6, IL-8, and C3a occurred after the onset of ARDS. In the patients who did not develop ARDS, initial oxygen transport values were not low, the levels of IL-6, IL-8, and C3a decreased rapidly from their initial peaks, and there were no further increases in hemodynamic values. In both ARDS and nonARDS patients, no measurable quantities of TNF, IL-1, or endotoxin were found. We concluded that none of the mediators we measured reached their peaks before the onset of ARDS and none were found to be predictive of posttraumatic ARDS. However, these and other mediators may augment or intensify the development of ARDS.

Unreliability of blood pressure and heart rate to evaluate cardiac output in emergency resuscitation and critical illness

OBJECTIVE

To evaluate the reliability of the vital signs to evaluate circulatory stability as reflected by cardiac index.

DESIGN

Descriptive analysis based on data gathered prospectively, using a predetermined protocol.

SETTING

University-run county hospital, with a large trauma service.

PATIENTS

Sixty-one high-risk trauma patients with accidental injury who were studied immediately after admission to the Emergency Department, and subsequently, 163 critically ill postoperative ICU patients.

INTERVENTIONS

Standard fluid therapy, usually crystalloids, but occasionally packed red cell transfusions and colloids, as indicated by clinical criteria.

MEASUREMENTS AND RESULTS

Arterial BP was measured by pressure transducer and arterial catheter; heart rate (HR) was measured by electrocardiograph signal, and cardiac output was measured by thermodilution. In sudden severe hypovolemic hypotension, the mean arterial pressure (MAP) nadir (lowest) roughly correlated (r2 = .25) with flow, but there was poor correlation (r2 = .0001) when all pressure and flow values were evaluated. The pressure and flow values were obtained throughout the course of the hypotensive episodes during the initial resuscitation in ICU patients and during terminal illnesses.

CONCLUSIONS

Observations at the time of acute severe hypotensive crises that show rough correlation of MAP and cardiac index should not be extrapolated throughout the entire hypotensive period or to other less extreme clinical situations. The stress response to hypovolemia, with endogenous catecholamines and neural mechanisms, tends to maintain arterial pressure in the face of decreasing flow for a variable period of time. However, when these mechanisms are overwhelmed by prolonged hypovolemia, the pressure decreases precipitously, but not synchronously, with flow. We conclude that blood flow cannot reliably be inferred from arterial pressure and heart rate measurements until extreme hypotension occurs.