Automated sampling of stormwater runoff in an urban watershed, north-central Texas.

Automated samplers were used to collect urban runoff in Pecan Creek, Denton, Texas. Runoff from four storm events was sampled at four stations. Concentrations of some heavy metals (cadmium and arsenic), as well as pesticides (atrazine and diazinon), exceeded maximum contaminant levels for drinking water, but were within ranges typical for urban runoff. Calcium and phosphorous concentrations were high compared to previous studies, which was attributed to soils, building materials, and fertilizer applications in the study area. First flush samples were more concentrated than composite samples for most of the constituents analyzed, but statistically different for only five constituents. Concentrations of four constituents differed significantly among stations, and six differed significantly among storms, due to variations in land use, channel composition, and storm conditions. Overall, the automated samplers were an effective way to sample urban runoff in Pecan Creek.

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.

Prospective, randomized trial of survivor values of cardiac index, oxygen delivery, and oxygen consumption as resuscitation endpoints in severe trauma.

The objective was to test prospectively supranormal values of cardiac index (CI), oxygen delivery index (DO2I), and oxygen consumption index (VO2I) as resuscitation goals to improve outcome in severely traumatized patients. We included patients > or = 16 years of age who had either (1) an estimated blood loss > or = 2000 mL or (2) a pelvic fracture and/or two or more major long bone fractures with > or = four units of packed red cells given within six hours of admission. The protocol resuscitation goals were CI > or = 4.5 L/min/m2, DO2I > or = 670 mL/min/m2, and VO2I > or = 166 mL/min/m2 within 24 hours of admission. The control resuscitation goals were normal vital signs, urine output, and central venous pressure. The 50 protocol patients had a significantly lower mortality (9 of 50, 18% vs. 24 of 65, 37%) and fewer organ failures per patient (0.74 +/- 0.28 vs. 1.62 +/- 0.45) than did the 75 control patients. We conclude that increased CI, DO2I, and VO2I seen in survivors of severe trauma are primary compensations that have survival value; augmentation of these compensations compared to conventional therapy decreases mortality.

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 radiographic infiltration in severely traumatized patients with and without adult respiratory distress syndrome.

We prospectively evaluated the patterns of pulmonary structural and functional changes in 100 consecutive surgical intensive care unit trauma patients who had (1) emergent major surgery, (2) a pelvic fracture, or (3) two or more major long bone fractures. For each patient, arterial blood gas measurements (ABGs), central venous pressure (CVP), pulmonary capillary occlusion pressure (PAOP), thoracic compliance, arterial oxygen tension/fraction of inspired oxygen (PAO2/FIO2), pulmonary venous admixture (Qs/Qt), and portable chest roentgenograms were sequentially tracked. The senior staff radiologist interpreted all chest roentgenograms. Pulmonary infiltration was quantitated in each of six fields using a scale ranging from 0 to 4, with 0 being no infiltration and 4 being the maximum. Adult respiratory distress syndrome (ARDS) was defined as follows: Qs/Qt > or = 20%, PAO2/FIO2 < 250 or both; dependence on mechanical ventilation for life support for > or = 24 hours; PAOP or CVP or both < 20 mm Hg; and thoracic compliance < 50 mL/cm H2O. Time zero (T0) the time of onset of ARDS, was defined as the time these criteria were met. Eighty-three of 100 study group patients had penetrating injuries, and 17 were admitted with blunt trauma. Fifty-one of 100 patients developed ARDS: 36 of 51 died. Only 4 of 49 (8%) patients without ARDS died. The injured lungs of patients with and without ARDS had similar amounts of infiltration over most measured time intervals. The noninjured lungs of the ARDS patients, however, had significantly greater infiltration than those without ARDS at T0 and over subsequent time intervals.(ABSTRACT TRUNCATED AT 250 WORDS)

Sequence of physiologic patterns in surgical septic shock.

OBJECTIVES: Gradual, almost imperceptible transitions occur between localized infection, generalized infection, systemic manifestations of the sepsis syndrome, septic shock, and death. The aim of this study was to describe the sequential pattern of hemodynamic and oxygen transport patterns of survivors and nonsurvivors of septic shock, so as to differentiate primary from secondary and tertiary events, to evaluate possible physiologic mechanisms, and to provide a template to relate the appearance of biochemical mediators to the sequence of physiologic events. DESIGN: Prospective, cohort study. SETTING: University-run county hospital. PATIENTS: A series of 300 consecutive surgical patients with septic shock; 85 survived and 215 died. INTERVENTIONS: We used specific criteria to define stages as: a) early period, the first recorded increase in cardiac output; b) middle period, time of maximal metabolic activity defined as the highest recorded oxygen consumption (VO2); and c) late period, the time of death or recovery. MEASUREMENTS AND MAIN RESULTS: Hemodynamic and oxygen transport variables were measured at frequent intervals throughout the course of septic shock. Beginning with increased cardiac index and oxygen delivery (Do2), which were the earliest observed hemodynamic changes, there were progressive increases in cardiac index, DO2, and VO2. The values of these variables in the survivors were both greater than normal and greater than those values of the nonsurvivors at comparable time periods. These values decreased in the late stage in nonsurvivors. There were early transient reductions in VO2 that preceded the increase in temperature and the decrease in blood pressure in both survivors and nonsurvivors. Although 86% of the septic patients were hyperdynamic, there were transient hypodynamic episodes (defined as cardiac index < 2.5 L/min/m2) in < 10% of the measurements. Transient preterminal hypermetabolic periods occurred in 9% of the nonsurvivors. CONCLUSIONS: Increased cardiac index and DO2 represent compensations for circulatory deficiencies that limit body metabolism, as reflected by inadequate VO2. Survivors have higher cardiac index, DO2, and VO2 values than those values of both the nonsurvivors and normal values. These data suggest that therapy should be directed toward increasing cardiac index to > 5.5 L/min/m2, DO2 to > 1000 mL/min/m2, and VO2 to > 190 mL/min/m2 as therapeutic goals; these supranormal values were empirically determined by the patterns of the survivors. Further studies to describe temporal relationships of biochemical mediators of these physiologic patterns are needed.

Temporal hemodynamic and oxygen transport patterns in medical patients. Septic shock.

STUDY DESIGN: Because of the gradual insidious transitions between localized infection, generalized infection, and septic shock, it is difficult to compare data of patients in various stages and to differentiate primary from secondary and tertiary events. The aim of the present study was to describe the sequential pattern of hemodynamic and oxygen transport patterns of survivors and nonsurvivors of septic shock in order to evaluate possible physiologic mechanisms and to provide a template to relate the sequence of physiologic events to biochemical mediators. PROCEDURE: A previously described defined protocol was used prospectively to study the sequence of physiologic events using specific criteria to define stages as: (a) early period, the first recorded change in cardiac output; (b) middle period, time of maximal metabolic activity defined as the highest recorded oxygen consumption (VO2); and (c) late period, the time of death or recovery. In addition, three time lines were defined as the first time mean arterial pressure fell below 70 mm Hg, the first time temperature rose above 38 degrees C, and the earliest fall in VO2. Physiologic data were aligned in actual time before or after the time these criteria were met. Invasive hemodynamic and oxygen transport variables were measured with systemic and pulmonary artery catheters; intravascular pressures, arterial and mixed venous gas levels, cardiac output, and derived calculations were made at frequent intervals and keyed to the time of the cardiac output; each set of measurements in turn was keyed to the aforementioned time periods to describe the early, middle, and late periods. RESULTS: Beginning with increased cardiac index and oxygen delivery (DO2) as the early physiologic changes, there were progressive increases in cardiac index, DO2, and VO2 throughout the early and middle periods. They were maintained above the normal range in the late stage of survivors, but fell in the last 16 h in nonsurvivors. These values were greater in survivors than in nonsurvivors throughout. There were early transient reductions in VO2 that preceded the rise in temperature and the fall in mean arterial pressure (MAP). Although 84 percent of the septic patients were hyperdynamic, there were transient hypodynamic episodes defined as cardiac index of less than 2.5 L/min.m2 in approximately 10 percent of the measurements. There were also transient preterminal hypermetabolic periods in about 8 percent of the nonsurvivors. CONCLUSION: We conclude that increased cardiac index and DO2 represent compensations for circulatory inadequacies that limit body metabolism as reflected by VO2. Cardiac index, DO2, and VO2 values of survivors were higher than those of nonsurvivors and normal values. Therapy directed toward increasing cardiac index to supranormal values empirically determined by survivors has been reported to improve outcome. Additional studies to describe temporal relationships of biochemical mediators of these physiologic patterns are needed.

Temporal patterns of blood volume, hemodynamics, and oxygen transport in pathogenesis and therapy of postoperative adult respiratory distress syndrome.

Time relationships of physiologic patterns that are relevant to the pathogenesis of adult respiratory distress syndrome (ARDS) have not been well studied. The purpose of this review is to summarize the temporal relationship of blood volume, hemodynamics, and oxygen transport patterns occurring in postoperative patients before and after ARDS in order to develop a more complete mechanistic evaluation of its pathophysiology and to propose more rational therapeutic strategies. The data indicate that hypovolemia, reduced or uneven blood flow, inadequate delivery of oxygen, and insufficient consumption of oxygen precede the appearance of ARDS and are the primary precipitating physiologic events. This is contrary to conventional thinking which emphasizes capillary leak and fluid overload as the primary problems. The conventional approach also ignores events antecedent to ARDS that produce hypoxia of the lung tissue, result in pulmonary vasoconstriction, and increased pulmonary venous admixture (shunt). Therapy to prevent or rapidly treat these antecedent events has been shown to prevent or attenuate postoperative and posttraumatic ARDS. Various mediators such as interleukin (IL)-1, IL-6, and IL-8 and tumor necrosis factor as measured by plasma concentrations do not precede diagnostic criteria of ARDS, but may accelerate and augment the disorder as it is occurring.

Hemodynamic and oxygen transport responses in survivors and nonsurvivors of high-risk surgery.

OBJECTIVES: To describe temporal hemodynamic and oxygen transport patterns in a large series of high-risk surgical patients in order to document physiologic patterns, to develop therapeutic goals for a wide range of surgical conditions, and to propose a mechanistic model for acute postoperative circulatory failure. DESIGN: Prospective, longitudinal study. Patients identified as high risk were studied prospectively. The data were analyzed immediately after they were acquired, again on formal rounds twice daily, and at a formal data review after completion of monitoring. SETTING: A university-run county hospital. PATIENTS: The patient series consisted of 708 consecutively monitored high-risk surgical patients. INTERVENTIONS: Hemodynamic and oxygen transport values and their responses to surgical trauma are known to vary widely with age and prior medical conditions; they may be used to predict outcome with a high degree of accuracy. Temporal hemodynamic and oxygen transport patterns in a large series of high-risk surgical operations were treated by one group, using a well-developed protocol. MEASUREMENTS AND MAIN RESULTS: Hemodynamic and oxygen transport monitored variables were analyzed before, during, and at frequent intervals after surgical operations. We stratified the temporal patterns of survivors and nonsurvivors in each of the following groups: a) patients without evidence of cardiovascular disease whose preoperative baseline cardiac index values were normal; and b) patients with high or low preoperative baseline cardiac index values due to the presence of preoperatively identified medical conditions that affect the circulatory status. In addition, we stratified patients in various age ranges who were without known cardiovascular diseases. The present study analyzed over 20,000 data sets with up to 32 variables in each data set or > 500,000 values. The major findings were intraoperatively reduced circulatory functions, principally cardiac index values, oxygen delivery (DO2), and oxygen consumption (VO2). These reductions in circulatory functions intraoperatively were followed, in the early postoperative period, by increases in these variables. The postoperative increases in cardiac index, DO2, and VO2 values were greater in survivors than in nonsurvivors; these findings were more apparent when the postoperative patterns of each strata were related to their own preoperative control values. CONCLUSIONS: The data indicate that there are increased metabolic requirements after surgical trauma and that the changes in cardiac index and DO2 represent compensatory increases in circulatory functions stimulated by increased metabolic needs. However, these metabolic needs change with age, gender, severity of illness, type of operation, associated medical conditions, duration of shock, complications, organ failure, and outcome.

Hemodynamic and oxygen transport monitoring to titrate therapy in septic shock.

Traditionally, shock has been recognized or diagnosed by subjective signs and symptoms, particularly in septic shock, where transition from localized to systemic infection and then to septic shock may be gradual and subtle. Management has been directed toward normalizing these subjective symptoms as well as BP, heart rate, urine output, hematocrit, central venous pressure, and blood gases. The major problem is that restoration to normal values of these secondary aspects of shock do not correct the underlying tissue perfusion defect. The aim of this review is to describe a physiologic mechanistic model based on the concept that uneven vasoconstriction and maldistribution of flow are directly related to tissue hypoxia, oxygen debt, shock, shock-related organ failure, and death; second, to show that titration of therapy to optimal physiologic end-points using hemodynamic and oxygen transport monitoring is a potentially cost-effective therapeutic approach. This physiologic approach is based on the hypotheses that: a) the physiologic patterns of high-risk postoperative and septic survivors are significantly different from septic nonsurvivors; b) tissue perfusion can be evaluated by the sequential patterns of cardiac index, oxygen delivery (DO2), and oxygen consumption (VO2) measurements; c) the observed increased cardiac index and DO2 in the survivors are compensations that improve tissue oxygenation, which is reflected by the VO2 pattern; and d) the supranormal values that were documented in survivors provide objective physiologic criteria for therapeutic goals. The data suggest that a mechanistic analysis of the pathogenesis of shock may be elucidated by temporal patterns of the nonsurvivors' physiologic variables. That is, the predictive indices calculated for each variable quantitatively reflect the relationship of the early changes leading to death or survival. In essence, early changes in those variables statistically related to death may reflect pathogenic mechanisms, while early changes related to survival may be used as a first approximation to therapeutic goals. The application of this approach in prospective, randomized trials has demonstrated that prompt attainment of optimal goals (empirically defined from survivors' patterns) improved outcome in postoperative shock with and without sepsis, as well as in medical sepsis and accidental trauma. Specifically, when the optimal values of cardiac index, DO2, and VO2 used as therapeutic goals were attained in 8 to 12 hrs, there was marked and significant reduction in mortality and morbidity rates. This finding was also confirmed in 12 prospective, controlled trials, four of which were randomized. We conclude that driving septic shock patients into the survivors' patterns improves outcome, as has been shown in other shock syndromes.(ABSTRACT TRUNCATED AT 400 WORDS)

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.

Relationship between supranormal circulatory values, time delays, and outcome in severely traumatized patients.

OBJECTIVE: To describe the temporal patterns of hemodynamics and oxygen transport in survivors and nonsurvivors of severe trauma in relation to time delays, mortality, and morbidity. DESIGN: Prospective, empiric analysis. SETTING: University-run, inner city county hospital with a Level I trauma center. PATIENTS: A series of 90 consecutively monitored, severely ill trauma patients. METHODS: We followed 90 patients from admission through their hospital course, and divided the study group into patients with estimated blood loss of < or = 3000 mL and those patients with an estimated blood loss of < 3000 mL. For each patient, vital signs were recorded in the Emergency Department, operating room, recovery room, and surgical ICU. Hemodynamic and oxygen transport variables were measured at least every 12 hrs for 96 hrs postadmission. Final outcome and complications were recorded. RESULTS: In the first 24 hrs, the values of 60 survivors were significantly higher than the values of 30 nonsurvivors for mean cardiac index (4.52 +/- 1.45 vs. 3.80 +/- 1.20 L/min/m2; p < .05), oxygen delivery (670 +/- 230 vs. 540 +/- 200 mL/min/m2; p < .01), and oxygen consumption (166 +/- 48 vs. 134 +/- 47 mL/min/m2; p < .01). Thirteen (50%) of 26 patients who never attained mean survivors' values (defined as the mean survivors' values listed above) died. Also, 12 (57%) of 21 patients who took > 24 hrs to attain these values died. In contrast, only five (12%) of 43 patients who reached mean survivors' values in < or = 24 hrs died. Thirty-five of 90 patients lost < 3000 mL of blood; 17 of these 35 patients failed to reach survivors' values within 24 hrs, and 12 (71%) patients died. However, of 18 patients with an estimated blood loss of > 3000 mL, who reached survivors' values in < or = 24 hrs, only two (12%) died. The patients reaching survivors' values in < or = 24 hrs, > 24 hrs, or not at all had similar Injury Severity Scores (28 +/- 13, 26 +/- 13, and 26 +/- 12, respectively) and Trauma Scores (12 +/- 3, 13 +/- 3, and 12 +/- 3, respectively). Only six (12%) of 43 patients reaching survivors' values in < or = 24 hrs developed adult respiratory distress syndrome (ARDS), while 27 (57%) of 47 patients showed these values in > 24 hrs or never developed ARDS. CONCLUSIONS: Reaching supranormal circulatory values, especially within 24 hrs of injury, may improve survival and reduce the frequency of shock-related organ failure in severely traumatized patients.

Hemodynamic and oxygen transport patterns for outcome prediction, therapeutic goals, and clinical algorithms to improve outcome. Feasibility of artificial intelligence to customize algorithms.

A generalized decision tree or clinical algorithm for treatment of high-risk elective surgical patients was developed from a physiologic model based on empirical data. First, a large data bank was used to do the following: (1) describe temporal hemodynamic and oxygen transport patterns that interrelate cardiac, pulmonary, and tissue perfusion functions in survivors and nonsurvivors; (2) define optimal therapeutic goals based on the supranormal oxygen transport values of high-risk postoperative survivors; (3) compare the relative effectiveness of alternative therapies in a wide variety of clinical and physiologic conditions; and (4) to develop criteria for titration of therapy to the endpoints of the supranormal optimal goals using cardiac index (CI), oxygen delivery (DO2), and oxygen consumption (VO2) as proxy outcome measures. Second, a general purpose algorithm was generated from these data and tested in preoperatively randomized clinical trials of high-risk surgical patients. Improved outcome was demonstrated with this generalized algorithm. The concept that the supranormal values represent compensations that have survival value has been corroborated by several other groups. We now propose a unique approach to refine the generalized algorithm to develop customized algorithms and individualized decision analysis for each patient's unique problems. The present article describes a preliminary evaluation of the feasibility of artificial intelligence techniques to accomplish individualized algorithms that may further improve patient care and outcome.

Relationship of oxygen consumption and oxygen delivery in surgical patients with ARDS.

Previous studies have described oxygen delivery (DO2) and oxygen consumption (VO2) relationships in patients with ARDS and other acute diseases that suggest occasions when VO2 may be dependent on the supply of oxygen, ie, DO2. We studied 127 postoperative patients who developed ARDS to evaluate the relationship of DO2 to VO2. We found a weak correlation between DO2 and VO2 in the total series (r = 0.49) as well as in several clinical subgroups of patients with ARDS. Moreover, we observed similar relationships in a concurrent group of 218 postoperative patients who did not develop ARDS. We also examined the DO2/VO2 data of individual patients with ARDS to identify instances where flow-dependent VO2 patterns developed into flow-independent VO2 patterns. We were able to identify an apparent plateau in the DO2/VO2 relationships in 29/50 (58 percent) patients where multiple measurements were obtained over a short period of time. Our data are consistent with the concept that the DO2/VO2 relationship in acutely ill early postoperative patients with and without ARDS is affected by antecedent circulatory problems that may lead to tissue hypoxia and tissue oxygen deficiencies that are manifest by flow dependency.

Role of oxygen debt in the development of organ failure sepsis, and death in high-risk surgical patients.

In a series of 253 high-risk surgical patients, we measured the oxygen consumption (VO2) at frequent intervals before, during, and immediately after surgical operations and calculated the rate of VO2 deficit from the measured VO2 minus the VO2 need estimated from the patient's own resting preoperative control values corrected for both temperature and anesthesia. The calculated oxygen deficit was related to multiple organ failure, complications, and outcome. The 64 patients who died all had organ failure; their cumulative VO2 deficit averaged 33.2 +/- 4.0 L/m2 (+/- SEM) at its maximum, which occurred 17.8 +/- 2.2 h after surgery. In the 31 survivors with organ failure, the cumulative VO2 deficit averaged 21.6 +/- 3.7 L/m2 at its maximum, which occurred 10.1 +/- 2.7 h after surgery (p less than 0.05). In the 158 survivors without organ failure or major complications, the maximum cumulative VO2 deficit averaged 9.2 +/- 1.3 L/m2 at 4.1 +/- 0.6 h after surgery (p less than 0.05). In a prospective randomized clinical trial, a protocol group maintained at supranormal hemodynamic and oxygen transport values had significantly reduced oxygen debt (7.6 +/- 3.4 L/m2 vs 17.3 +/- 6.8 L/m2; p less than 0.05), fewer organ failures, and lower mortality (4 percent vs 33 percent; p less than 0.05) compared with a control group maintained at normal hemodynamic values. The data demonstrate a strong relationship between the magnitude and duration of the VO2 deficit in the intraoperative and early postoperative period and the subsequent appearance of organ failure and death. The latter may be reduced when oxygen debts were prevented or minimized by augmenting naturally occurring compensations that increased oxygen delivery.

The relationship between ARDS, pulmonary infiltration, fluid balance, and hemodynamics in critically ill surgical patients.

Hypervolemia from fluid overload with resultant pulmonary edema is thought to be a frequent cause of Adult Respiratory Distress Syndrome (ARDS). However, ARDS may also occur as a result of the hypovolemic shock of surgery or trauma. To develop an appropriate rationale for fluid therapy in high-risk surgical patients, the relationship between fluid balance, hemodynamics, the onset of ARDS by physiologic criteria (shunt greater than or equal to 20%, and/or PaO2/FiO2 ratio less than 250) and the onset of pulmonary infiltration (PI) associated with ARDS were examined. Fifty patients were prospectively followed from admission throughout their hospitalizations; 38 (76%) had trauma and 12 (24%) were postoperative. Cardiac index, central venous pressure (CVP), wedge pressure (WP), and shunt (Qsp) were measured. All chest x rays were read by one staff radiologist who was blinded to the patients' identities. PI was graded from "0" to "4" (0 = no PI, 4 = maximum PI). The first x ray reading of "2" or greater was used as the time of onset of PI. ARDS by physiologic criteria occurred in 29 of 50 (58%) patients; 27 of these 29 (94%) also developed +2 or greater PI. The mean onset times of ARDS and of +2 PI were 40 +/- 41 hours and 40 +/- 38 hours, respectively. The ARDS patients had a significantly smaller net positive fluid balance than the non-ARDS patients over the first 40 hours after admission (+6,831 ml +/- 4,909 ml vs 12,440 ml +/- 7,817 ml, (P less than 0.01)).(ABSTRACT TRUNCATED AT 250 WORDS)

Hemodynamic and oxygen transport changes following endotracheal suctioning in trauma patients.

Hemodynamic and oxygen transport responses to four preoxygenation techniques prior to endotracheal suctioning (ETS) were evaluated in 24 critically ill trauma patients with no preexisting lung disease. A within-subjects, repeated measures design was used. All patients had functional arterial and pulmonary artery catheters and were ventilated with a Puritan-Bennett 7200 which could immediately deliver a fraction of inspired oxygen (FIO2) of 1.0. Six breaths of maintenance FIO2 and hyperinflation without hyperoxygenation caused a fall in tissue oxygen delivery as measured by continuous transcutaneous oximetry (PtcO2). The largest increases in PtcO2 and arterial oxygen tension were seen with hyperoxygenation alone and a combination of hyperoxygenation and hyperinflation. No significant changes were found in hemodynamic (cardiac index, mean arterial pressure, mean pulmonary artery pressure, pulmonary capillary wedge pressure, systemic vascular resistance, pulmonary vascular resistance) or oxygen transport variables (oxygen delivery, oxygen extraction, oxygen consumption) 5 minutes postsuctioning. During both hyperinflation protocols, patients experienced dyspnea. It was concluded that three hyperoxygenation breaths before ETS, using a clinically feasible protocol, are adequate in preventing postsuction hypoxemia in young, hemodynamically stable trauma patients. Large volumes of hyperinflation, although found to increase PtcO2, are not advocated because of demonstrated patient discomfort and the possibility of barotrauma.

Oxygen transport measurements to evaluate tissue perfusion and titrate therapy: dobutamine and dopamine effects.

BACKGROUND: Increased cardiac index, oxygen delivery (DO2), and oxygen consumption (VO2) patterns were shown to characterize the physiologic status of surviving high-risk surgical patients, and indicate increased metabolic needs; relatively normal DO2 and VO2 values were found to characterize the sequential pattern of nonsurvivors who developed an early oxygen debt followed by lethal organ failure. The cardiac index, DO2, and VO2 values empirically determined from survivors' patterns were shown to improve outcome in prospective randomized trials. The present study considers these criteria to evaluate the tissue perfusion status as well as the effects of therapy on tissue perfusion and oxygenation. OBJECTIVE: To summarize new information on the temporal patterns of DO2, VO2, and oxygen debt on outcome and the effects of fluids and inotropes on these patterns in a wide range of clinical, temporal, and physiologic conditions. DESIGN: Descriptive analysis based on data gathered prospectively using a specified protocol. PATIENTS: High-risk patients with accidental or elective surgical trauma, and patients with or without sepsis or septic shock and organ failure. SETTING: University-run county hospital with a large trauma service. INTERVENTIONS: Fluids, dobutamine, and dopamine at various times and at various doses throughout critical illness of postoperative, posttraumatic, septic, and hypovolemic patients with and without lethal and nonlethal organ failure. MEASUREMENTS AND MAIN RESULTS: The pattern of DO2 plotted against the corresponding VO2 values in 437 consecutive critically ill surgical patients showed a wide variability and poor correlation probably because complex clinical conditions may obscure the supply-dependent and supply-independent VO2 relationships observed in normal dogs bled or given bacterial infusions. However, the use of specific therapy by well-defined protocols was shown to provide objective evidence of efficacy. Significant increases in DO2 and VO2 were previously shown after whole blood, packed red cells, and colloid administration, but not after crystalloid administration. Dobutamine administration in 715 circumstances in postoperative, traumatic, septic patients and patients with adult respiratory distress syndrome, renal failure, and multiple organ failure significantly improved DO2 and VO2. Dopamine under comparable conditions produced less improvement in DO2 and VO2 than that of dobutamine; most of the VO2 changes were not significant. CONCLUSIONS: The monitored patterns of cardiac index, DO2, and VO2 may be used to evaluate the adequacy of tissue perfusion as well as the relative effectiveness of alternative therapies. Second, these physiologic criteria may be used to titrate therapy in order to achieve optimal outcome. Third, after colloids optimally expand the plasma volume, dobutamine may be used to enhance flow and the distribution of flow in order to improve tissue oxygenation. Vasodilators may be used when hypertensive episodes occur or there is an inadequate response to inotropic agents. Vasopressors are used as a last resort, usually in the terminal or preterminal state.

Effects of prostaglandin E1 in postoperative surgical patients with circulatory deficiency.

Hemodynamic and oxygen transport effects of PGE1 were observed in the early postoperative period before development of ARDS in two series of general surgical patients with circulatory deficiencies. The first was a series of 19 studies in 18 patients, the second was a placebo-controlled series of 20 patients (ten received PGE1 and ten received a placebo). In the first series, PGE1 was given as a trial of therapy after fluid therapy to pulmonary wedge pressures greater than 15 mm Hg failed to correct satisfactorily circulatory and metabolic functions. There were two deaths in the placebo group and none in the PGE1 group. Previous studies indicated that PGE1 disaggregates platelets and reduces local vasoconstriction in pulmonary circulation; this study suggests that PGE1 improves tissue perfusion of systemic circulation. After fluid therapy to PAOP greater than 15 mm Hg fails to restore circulatory function to optimal values. PGE1 should be considered as ancillary therapy in critically ill postoperative patients.