Oxygen transport in adult respiratory distress syndrome and other acute circulatory problems: relationship of oxygen delivery and oxygen consumption

OBJECTIVE: To evaluate the evidence that oxygen consumption (VO2) is pathologically dependent on oxygen delivery (DO2). DATA SOURCES: Studies published since 1972 with their relevant bibliographies and computerized search of MEDLINE. STUDY SELECTION: All clinical papers reporting the relationship of: VO2 to DO2 in the adult respiratory distress syndrome (ARDS), sepsis, other critically ill patients, and normal individuals; cardiac output determined by measured VO2 to calculated VO2 from the arterial-mixed venous oxygen difference; blood lactate to DO2; and selected basic science studies. DATA EXTRACTION: Study quality was assessed and all pertinent data were summarized. RESULTS OF DATA EXTRACTION: Normal individuals display physiologic dependence of VO2 at very low levels of DO2 (330 mL/min.m2). Pathologic dependence of VO2 on DO2 entails two concepts: a) VO2 varies directly with DO2 over a wide range of DO2 and b) of particular import, tissue oxygen extraction is compromised. This pathologic supply dependence was initially identified in patients with ARDS; subsequently, it has been demonstrated in patients with sepsis and in a variety of other critically ill individuals. There are substantial, but not uniform, data documenting this dependence of VO2 on DO2 in ARDS. In some studies, this relationship correlates best with increased lactate concentrations. However, increased blood lactate concentrations do not accurately track other evidence of tissue hypoxia. Some researchers have attributed the finding of this supply dependency to artifact, when VO2 is determined by the arterial-mixed venous oxygen difference. However, when these methods are compared, the correlation is excellent. Others have raised the concern that appreciable changes in VO2, even over short periods of time, may result in physiologic increases in DO2. However, when "control" groups have been contemporaneously compared with patients with ARDS using the same methodology, they have not shown supply dependency. Interwoven throughout the studies reviewed is overwhelming and uniform evidence that both mixed venous oxygen tension (PVO2) and mixed venous oxygen content (CVO2) correlate poorly with cardiac output, DO2, or VO2. The inconsistencies in identifying pathologic DO2 dependency may well reflect the unknown variables that exist in patients with ARDS, perhaps better labeled, multiple organ system failure. CONCLUSIONS: Pathologic dependence of VO2 on DO2, especially the inability to increase tissue oxygen extraction, is present in most patients with ARDS and many other critically ill individuals. PVO2 and CVO2 are both unreliable indicators of cardiac output, DO2, or VO2.     

Hemodynamic and metabolic effects of dobutamine in 18 patients after open heart surgery

Low cardiac output syndrome frequently follows cardiopulmonary bypass (CPB) surgery. In the present study, we used dobutamine to increase cardiac index (CI) and oxygen delivery (DO2) in 18 patients after open heart surgery. Using increasing doses of dobutamine up to 10 micrograms/kg.min-1, we observed statistically significant (p less than .01) increases in mean CI (2.50 +/- 0.10 to 3.56 +/- 0.18 L/min.m2) and in mean heart rate (HR) (83 +/- 3 to 105 +/- 3 beat/min). Mean systemic vascular resistance index decreased significantly (p less than .01) in all patients (2271 +/- 101 to 1648 +/- 83 dyne.sec/cm5.m2). Pulmonary vascular resistance index did not change in the ten coronary artery bypass graft patients, but decreased significantly (p less than .01) in the eight valve replacement patients (561 +/- 98 to 421 +/- 79 dyne.sec/cm5.m2). Mean DO2 increased in all patients, although there was no concomitant increase in oxygen consumption (VO2) in four patients. We observed a significant (p less than .01) increase in mean VO2 in the remaining 14 patients (110 +/- 6 to 148 +/- 12 ml/min.m2), in spite of significant decreases in PaO2 and increases in right-to-left intrapulmonary shunting. Although increases in HR and ventricular arrhythmias may limit its use, dobutamine increases CI and DO2 in patients after CPB. In the present study, dobutamine's varying metabolic effect exemplifies the need for close monitoring of hemodynamic and metabolic variables when using vasoactive drugs in the postoperative period.     

Oxygen delivery-consumption relationship in adult respiratory distress syndrome patients: The effects of sepsis

The oxygen consumption-delivery relationship (VO2/ O₂) was studied in 15 sedated paralyzed patients with the adult respiratory distress syndrome (ARDS) due to multiple trauma and in whom sepsis was absent. Different levels (0 to 15 cm H2O) of positive end-expiratory pressure (PEEP) were applied. Oxygen delivery was calculated from cardiac index (thermodilution technique) and arterial oxygen content measurements. Oxygen consumption was calculated using Fick's equation. Regression lines were obtained for each patient. Oxygen supply dependency was defined as a significant (P < .05) relationship between changes in O2 and O₂ with PEEP. Results were compared with those obtained in 18 ARDS patients in whom ARDS was due to sepsis. In nonseptic ARDS patients no significant relationship between changes in VO2 and O₂ with PEEP was found within the experimental range of O₂ on zero end-expiratory pressure (ZEEP) (347 to 845 mL/min/m²). None of these patients had multiple organ system failure (MOSF), and 73% survived. In ARDS patients in whom sepsis was present, supply dependency was present only when O₂ on ZEEP ranged between 330 and 640 mL/min/m². All these patients developed MOSF and died. When O₂ on ZEEP ranged between 686 and 951 mL/min/m² in septic ARDS patients, the supply dependency phenomenon was absent and only three patients developed MOSF and died (70% survivors). In almost all patients PEEP reduced O₂ and therefore worsened OZ balance by either increasing OZ extraction ratio and approaching the critical threshold for supply dependency or dismissing O₂ from the range of non-supply dependency.     

高频振动通气在急性呼吸窘迫综合征治疗中的作用

目的　评估高频振动通气 (high frequencypercussiveventilation ,HFPV)在成人ARDS治疗中的有效性和安全性 ,探索ARDS治疗的新途径。方法　临床观察 93例ICU条件下使用HFPV的ARDS病人 ,对常规通气 (conventionalventilation ,CV)和HFPV下的PaO2 /FiO2 、PaCO2 、DO2 、VO2 、Qs/Qt、PEEP/CPAP、PAWP等氧代谢、血流动力学指标和呼吸参数的变化进行统计分析。结果　 93例病人中 ,存活 6 6例 ,死亡2 7例 ,死亡率为 2 9 0 % (除外 7例未死于ICU者 ,实际死亡率为 2 1 5 % )。使用HFPV前后PaO2 /FiO2 、PaC O2 、DO2 、VO2 、Qs/Qt的变化为 (77 6± 2 0 0 )和 (2 0 8 7± 70 8)、 (471 2± 114 7)和 (6 0 1 3± 14 0 9)、(10 7 6± 34 3)和 (14 6 4± 2 3 3)、 (35 7± 2 0 5 )和 (2 4 5± 6 5 ) (P <0 0 5 )。X ray胸片双肺阴影减轻或消失 ,同时可看到病人鼻腔口腔有不等量的混浊液体从呼吸道溢出。结论　HFPV在ARDS治疗中是有效和安全的。临床应用HFPV能明显改善氧代谢 ,提高PaO2 /FIO2 。早期应用和合理化管理能明显降低ARDS的病死率     

The impact of respiratory variables on mortality in non-ARDS and ARDS patients requiring mechanical ventilation

Objectives: Primarily, to determine if respiratory variables, assessed on a daily basis on days 1–6 after ICU admission, were associated with mortality in non-ARDS and ARDS patients with respiratory failure requiring mechanical ventilation. Secondarily, to determine non-respiratory factors associated with mortality in ARDS and non-ARDS patients. Design: Prospective multicentre clinical study. Setting: Seventy-eight intensive care units in Sweden and Iceland. Patients: Five hundred twenty non-ARDS and 95 ARDS patients. Measurements and results: Potentially prognostic factors present at inclusion were tested against 90-day mortality using a Cox regression model. Respiratory variables (PaO₂/FIO₂, PEEP, mean airway pressure (MAP) and base excess (BE)) were tested against mortality using the model. Primary aim: in non-ARDS a low PaO₂/FIO₂ on day 1, RR (risk ratio) = 1.17, CI (95 % confidence interval) (1.00; 1.36), day 4, 1.24 (1.02; 1.50), day 5, 1.25 (1.02; 1.53) and a low MAP at baseline, 1.18 (1.00; 1.39), day 2, 1.24 (1.02; 1.52), day 3, 1.33 (1.06; 1.67), day 6, 2.38 (1.11; 5.73) were significantly associated with 90-day death. Secondary aim: in non-ARDS a low age, RR = 0.77 (0.67; 0.89), female gender, 0.85 (0.74; 0.98), and low APS (acute physiologic score), 0.85 (0.73; 0.99), were associated with survival; chronic disease, 1.31 (1.12; 1.52), and non-pulmonary origin to the respiratory failure, 1.27 (1.10; 1.47), with death. In ARDS low age, RR = 0.65 CI (0.46; 0.91), and low APS, 0.65 (0.46; 0.90), were associated with survival. Conclusions: No independent significant association was seen between 90-day mortality and degree of hypoxaemia, PEEP, MAP or BE for the first full week of ICU care in either ARDS or non-ARDS. In a sub-group of non-ARDS a lower PaO₂/FIO₂ and MAP tended to influence mortality where a significant association was seen for 3 of 7 study days. Age, gender, APS, presence of a chronic disease and a pulmonary/non-pulmonary reason for the respiratory failure were associated with mortality in non-ARDS, while only age and APS showed a similar association in ARDS. Received: 16 February 1999 Final revision received: 4 October 1999 Accepted: 24 February 2000     

Blood transfusion and oxygen consumption in surgical sepsis

OBJECTIVE: To evaluate the use of serum lactic acid values to predict flow-dependent increases in oxygen consumption (VO2) in response to increasing oxygen delivery (DO2) after blood transfusion in surgical sepsis. DESIGN: Prospective study. SETTING: Tertiary care, trauma center. PATIENTS: Twenty-one patients, postsurgical or posttrauma, judged septic by defined criteria. INTERVENTIONS: Serum lactic acid concentrations, DO2, and VO2 were measured before and after transfusion therapy. MEASUREMENTS AND MAIN RESULTS: Overall, the DO2 increased from 532 +/- 146 to 634 +/- 225 (SD) mL/min.m2 (p less than .001), and the VO2 increased from 145 +/- 39 to 160 +/- 56 mL/min.m2 (p = .02). These changes occurred with an Hgb increase from 9.3 +/- 1.1 to 10.7 +/- 1.5 g/dL (p less than .001). The patients were grouped by their pretransfusion serum lactic acid values. In those patients with normal (less than 1.6 mmol/dL) serum lactic acid (n = 10), DO2 increased from 560 +/- 113 to 676 +/- 178 mL/min.m2 (p less than .02), and VO2 increased from 150 +/- 25 to 183 +/- 46 mL/min.m2 (p less than .02). However, in the increased serum lactic acid group (n = 17), VO2 was not significantly changed after transfusion (143 +/- 46 to 146 +/- 58 mL/min.m2) despite increased DO2 (515 +/- 163 to 609 +/- 251 mL/min.m2, p less than .01). CONCLUSIONS: Blood transfusion can be used to augment DO2 and VO2 in septic surgical patients. Increased serum lactic acid values do not predict patients who will respond. The absence of lactic acidosis should not be used in this patient population to justify withholding blood transfusions to improve flow-dependent VO2. Patients who have increased lactate concentrations may have a peripheral oxygen utilization defect that prevents improvement in VO2 with increasing DO2.     

Acute lung injury and acute respiratory distress syndrome at the intensive care unit of a general university hospital in Brazil. An epidemiological study using the American-European Consensus Criteria

OBJECTIVES: To determine: (1) the frequency of acute lung injury (ALI)/acute respiratory distress syndrome (ARDS); (2) the mortality associated with these syndromes and (3) the influence of risk factors, comorbidities and organ system dysfunction in the mortality of ALI patients. DESIGN: Prospective cohort study. SETTING: Intensive care unit (ICU) of a general university hospital in Brazil. PATIENTS AND PARTICIPANTS: All patients that remained in the ICU for more than 24 h were evaluated regarding the presence/development of ALI/ARDS according to the 1994 American-European Consensus Conference. INTERVENTIONS: None. MEASUREMENTS AND RESULTS: One thousand three hundred and one patients were studied and analyzed regarding mortality, risk factors, comorbidities and organ system dysfunction(s). The frequency of ALI was 3.8% (50), of which ARDS was 2.3% (30) and ALI/non-ARDS 1.5% (20) (p=0.15). The ICU mortality of patients with ALI was 44.0%; in ALI/non-ARDS and ARDS patients it was 40.0% and 46.7%, respectively (p=0.43). The hospital mortality of ALI patients was 48.0%; in ALI/non-ARDS and ARDS patients it was 50.0% and 46.7%, respectively (p=0.21). A multivariate analysis demonstrated that renal (ICU and hospital: p=0.002) and hematological dysfunction (ICU: p=0.008; hospital: p=0.02) were independently associated with ICU and hospital mortality in ALI patients. CONCLUSIONS: (1) The frequency of ALI was 3.8%, of which the frequency of ARDS was 2.3% and of ALI/non-ARDS 1.5%; (2) The ICU and hospital mortality of ALI patients was 44.0% and 48.0%, respectively; mortality rates of ARDS and ALI/non-ARDS did not differ significantly; (3) Renal and hematological dysfunction were associated with mortality in ALI patients.     

Respiratory index/pulmonary shunt relationship: quantification of severity and prognosis in the post-traumatic adult respiratory distress syndrome

The relationship between the respiratory index (RI = alveolar-arterial oxygen gradient [P(A-a)O2] normalized by PaO2) and the pulmonary shunt (Qsp/Qt) has been examined in 929 studies from 240 critically ill post-traumatic patients. Of these, 88 patients (443 studies) were individuals who developed post-traumatic adult respiratory distress syndrome (ARDS) and 152 were patients (486 studies) who did not develop ARDS. This study demonstrates that the RI to Qsp/Qt [RI/(Qsp/Qt)] relationship was significantly (p less than .0001) increased in patients who developed fatal ARDS compared with those who did not develop ARDS, or with those whose ARDS resolved. Because of the increased oxygen consumption (VO2) in ARDS patients in association with their severe limitations in gas exchange (RI) and increased Qsp/Qt, surviving ARDS patients had a significant increase in the cardiac index which resulted in a higher oxygen delivery to VO2 ratio. ARDS patients showed significant (p less than .0001) evidence of increased pulmonary vascular tone, correlated with the increase in the RI/(Qsp/Qt) relationship. In addition, those patients with high RI/(Qsp/Qt) also had increased right ventricular (RVSW) to left ventricular work (LVSW) ratios which were shown to be a direct function of the rise in RI. This increase in both RVSW/LVSW and RI/(Qsp/Qt) ratios was significantly (p less than .0001) correlated with an increased mortality. Thus, the RI/(Qsp/Qt) relationship, which can be obtained from arterial and mixed venous blood gases and saturations only, can be used to predict the severity of the ARDS process as well as important pulmonary vascular and right ventricular overload consequences.     

Alterations in regional blood flow during positive end-expiratory pressure ventilation

PEEP improves the gas-exchange abnormalities that accompany adult respiratory distress syndrome (ARDS). However, since PEEP decreases cardiac output, it may also alter regional blood flow and therefore, substrate delivery to specific organs. To test this hypothesis, radiolabeled 15-mu microspheres were used to directly quantify the effects of mechanical ventilation with PEEP on regional blood flow to individual organs in animals. Mechanical ventilation alone produced a -21.2 +/- 3.6% and a -28.1 +/- 5.2% decrease in cardiac output at 30 and 60 min, respectively. The addition of 14 cm H2O PEEP resulted in little further reduction in cardiac output at 30 and 60 min (-28 +/- 2.3% and -36.4 +/- 4.9%, respectively). However, 25 cm H2O PEEP reduced markedly (p less than .01) cardiac output (-59.2 +/- 6.1% at 30 min and -55.1 +/- 4.0% at 60 min). Although blood flows to the kidney and brain were maintained, decreases in cardiac output were invariably accompanied by proportional decreases in blood flow to the heart. Intravascular volume expansion with saline (20 ml/kg) during 14 cm H2O PEEP significantly improved cardiac output (3.23 +/- 0.34 to 4.22 +/- 0.13 L/min; p less than .01) and proportionately increased blood flow to several regional vascular beds, including the heart. These data suggest that PEEP decreases cardiac output to produce reversible alterations in blood flow to a number of regional vascular beds. These PEEP-induced alterations in regional blood flow may have important implications for the development of multiple-organ failure in ARDS patients.     

A clinical study of the adult respiratory distress syndrome

The adult respiratory distress syndrome (ARDS) is a syndrome of diffuse lung injury with a high mortality rate. We evaluated retrospectively 35 adult patients with ARDS. Their overall mortality rate was 69% and was related to their age (32 +/- 14 yr in survivors and 54 +/- 15 yr in nonsurvivors; p less than .001) and to the number of complications during their illness (1.4 complications in survivors, 2.6 in nonsurvivors; p less than .005). The ARDS patients, due to an infectious etiology, incurred a 75% mortality rate, while those with a noninfectious etiology of ARDS had a 55% mortality rate (nonsignificant). Neither a simplified acute physiology score nor a respiratory failure severity index was significantly different between survivors and nonsurvivors on admission. The mean PEEP level on admission in survivors was 8.1 +/- 4.6 cm H2O and in nonsurvivors 3.7 +/- 3.9 cm H2O (p less than .025). We conclude that the age of the patients and superimposed multiple system organ failure are probably related with the still high mortality rate of this syndrome.     

Effects of recruitment maneuvers in patients with acute lung injury and acute respiratory distress syndrome ventilated with high positive end-expiratory pressure

Objective: Positive end-expiratory pressure (PEEP) and recruitment maneuvers (RMs) may partially reverse atelectasis and reduce ventilation-associated lung injury. The purposes of this study were to assess a) magnitude and duration of RM effects on arterial oxygenation and on requirements for oxygenation support (Fio2/PEEP) in patients with acute lung injury and acute respiratory distress syndrome (ALI/ARDS) receiving ventilation with low tidal volumes and high levels of PEEP; and b) frequency of adverse respiratory and circulatory events attributable to RMs. Design: Prospective, randomized, crossover study. Setting: Thirty-four intensive care units at 19 hospitals. Patients: Seventy-two patients with early ALI/ARDS. Baseline PEEP and Fio2 were 13.8 +/- 3.0 cm H2O and 0.39 +/- 0.10, respectively (mean +/- sd). Interventions: We conducted RMs by applying continuous positive airway pressure of 35-40 cm H2O for 30 secs. We conducted sham RMs on alternate days. We monitored oxyhemoglobin saturation by pulse oximetry (SpO2), Fio2/PEEP, blood pressure, and heart rate for 8 hrs after RMs and sham RMs. We examined chest radiographs for barotrauma. Measurements and Main Results: Responses to RMs were variable. Greatest increments from baseline SpO2 within 10 mins after RMs were larger than after sham RMs (1.7 +/- 0.2 vs. 0.6 +/- 0.3 %, mean +/- SEM, p < .01). Systolic blood pressure decreased more +/- 1.1 mm Hg, p < .01). Changes in Fio2/PEEP requirements were not significantly different at any time after RMs vs. sham RMs. Barotrauma was apparent on first radiographs after one RM and one sham RM.Conclusions: In ALI/ARDS patients receiving mechanical ventilation with low tidal volumes and high PEEP, short-term effects of RMs as conducted in this study are variable. Beneficial effects on gas exchange in responders appear to be of brief duration. More information is needed to determine the role of recruitment maneuvers in the management of ALI/ARDS.     

Effect of dobutamine on oxygen consumption and fluid and protein losses after endotoxemia

OBJECTIVE: To determine the effect of a dobutamine infusion on the relationship between oxygen consumption (VO2) and oxygen delivery (DO2) after endotoxin administration, as well as the rate of fluid and protein loss from permeability-injured tissue. METHODS: Unanesthetized adult sheep with lung and soft-tissue lymph fistulas were given 5 micrograms/kg Escherichia coli endotoxin alone, or E. coli endotoxin plus a continuous infusion of dobutamine (10 to 15 micrograms/kg.min) beginning at 3 hrs. Lymph flow reflected the vascular permeability and surface area perfused. Data were compared with dobutamine alone and with controls. Filling pressures were maintained at baseline. RESULTS: Dobutamine alone produced a 75% increase in DO2, a transient 10 +/- 4% increase in VO2, but no increase in lung or soft-tissue lymph flow. Beginning at 3 hrs after endotoxin alone, a significant increase in protein-rich lung and soft-tissue lymph flow was noted, but only a transient 14 +/- 5% increase in VO2. Plasma proteins were slightly decreased. With the addition of dobutamine at 3 hrs postendotoxin, DO2 increased by greater than 50% for the 3-hr infusion period, while VO2 increased for a 30-min period by 25 +/- 8%, which was not different than endotoxin alone. Lung and soft-tissue lymph flow did not increase further, but plasma proteins did decrease significantly compared with controls and with endotoxin alone. CONCLUSION: Increasing DO2 with dobutamine postendotoxin does not increase the surface area perfused or the edema process, at least in lung and soft tissue. Therefore, no microvessels in these tissues are reopened with dobutamine when normal filling pressures are present. Dobutamine administration does not increase VO2 more than the increase seen with endotoxin alone.     

Keratinocyte growth factor and hepatocyte growth factor in bronchoalveolar lavage fluid in acute respiratory distress syndrome patients

OBJECTIVES: To determine bronchoalveolar lavage (BAL) fluid concentrations of keratinocyte growth factor (KGF) and hepatocyte growth factor (HGF), two potent growth factors for alveolar type II epithelial cells, in patients with acute respiratory distress syndrome (ARDS). DESIGN: Prospective study. SETTING: An adult trauma/surgical intensive care unit in an urban teaching hospital. PATIENTS: A total of 32 ventilated patients with pulmonary infiltrates prospectively identified with ARDS (n = 17) or without ARDS (n = 15), including eight patients with hydrostatic edema (HE), and ten nonventilated patients serving as controls. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: BAL was performed 2.88 days +/- 2.4, 3.5 days +/- 2.4, and 2.3 days +/- 2.2 after the lung insult in ARDS, HE, and other non-ARDS patients respectively (p = .32). KGF was detected in BAL fluid in 13 of the 17 ARDS patients (median, 31.6 pg/mL), in one patient with HE, and in none of other non-ARDS patients. In ARDS patients, detection of KGF in BAL was associated in BAL fluid with the detection of type III procollagen peptide (PIIIP), a biological marker of fibroproliferation. In ARDS patients, detection of KGF in BAL was associated with death (p = .02). HGF was detected in 15 ARDS patients (median, 855 pg/mL), in seven patients with HE (median, 294 pg/mL; p = .05 for the comparison with ARDS group), in six of other non-ARDS patients (median, 849 pg/mL; p = .32 with ARDS group). HGF concentrations were higher in nonsurvivors than in survivors (p = .01). None of the ten BAL of controls contained either KGF or HGF. CONCLUSION: KGF was detected almost exclusively in BAL fluid from ARDS patients and correlated with a poor prognosis in this group. In contrast, HGF was detected in the BAL fluid from a majority of patients with or without ARDS. Elevated HGF concentrations were associated with a poor prognosis in the overall group.     

Different dosages of dobutamine in septic shock patients: determining oxygen consumption with a metabolic monitor integrated in a ventilator

OBJECTIVE: Oxygen consumption (VO2) obtained from respiratory gases by indirect calorimetry (VO2,IC) with a metabolic monitor integrated in a ventilator were to be compared to VO2 obtained by the Fick principle (VO2,Fick) in septic patients following an increase in oxygen delivery (DO2) induced by positive inotropic support. DESIGN: Prospective clinical study. SETTING: University Hospital, Surgical Intensive Care Unit (ICU). PATIENTS: Thirty patients suffering from sepsis. INTERVENTIONS: DO2 was increased by dobutamine infusion, starting with an initial dosage of 5 microg x kg x min, increased to a maximum of 10 microg x kg x min. MEASUREMENTS AND MAIN RESULTS: Dobutamine infusion induced a dosage-related increase in DO2 (from 577 +/- 192 to 752 +/- 202 ml x min x m2, p < 0.01), which was associated with a statistically significant increase in VO2,IC (from 173 +/- 30 to 188 +/- 28 ml x min x m2, p < 0.01) and in VO2,Fick (from 140 +/- 25 to 156 +/- 24 ml x min x m2, p < 0.01). The comparison between VO2,IC and VO2,Fick revealed differences (bias and precision--33 +/- 32 ml x min x m2). CONCLUSIONS: With a metabolic monitor integrated in a ventilator it was possible to carry out continuous monitoring of calorimetric data under clinical conditions. In contrast to previous studies using indirect calorimetry, this study showed a moderate correlation between VO2 and DO2 in septic patients using either method. The clinical relevance of this finding requires further investigation. Different factors (e. g. injectant temperature, pulmonary VO2) produced substantial differences between VO2,IC and VO2,Fick as previously shown.     

Cell metabolism in patients undergoing major valvular heart surgery: relationship with intra and postoperative hemodynamics, oxygen transport, and oxygen utilization patterns

The relationships between cell metabolism and both hemodynamics and oxygen transport/utilization (VO2/DO2) pattern were evaluated intra and postoperatively in eight patients undergoing major valvular heart surgery with the aid of moderately hypothermic cardiopulmonary bypass (CPB). Quadriceps femoris specimens were obtained by the needle biopsy technique for muscle ATP, ADP, AMP, phosphocreatine (PCr), creatine and lactate determination at anesthesia induction, after CPB, as well as in the ICU 18 h after surgery. Moreover, hemodynamic variables, oxygen transport and utilization indices, and plasma lactate were measured at the same intervals and throughout the CPB period. After CPB, muscle ATP and PCr contents were reduced (p less than .05) as compared to those of both pre-CPB patients and healthy control subjects; muscle and plasma lactate levels were increased (p less than .05). Mean VO2 and DO2 values measured during CPB significantly decreased (p less than .05), but VO2 reduction was proportionally greater than that of DO2 (-62% vs. -41%). No correlation was found between VO2 and DO2 at that time, but a significant relationship (p less than .05) was found at the end of CPB. A further decrease in muscle ATP and PCr levels was measured in the ICU, as muscle and plasma lactate levels were still elevated. At that time, VO2 and DO2 were not significantly different from pre-CPB values, but were significantly (p less than .05) correlated with each other.(ABSTRACT TRUNCATED AT 250 WORDS)     

Respiratory failure in patients with acquired immunodeficiency syndrome and Pneumocystis carinii pneumonia

Seven patients with acquired immunodeficiency syndrome (AIDS) and Pneumocystis carinii pneumonia were studied to define the pathophysiology of their respiratory failure. The patients had fever, cough, dyspnea, hypoxemia, and diffuse infiltrates on chest x-ray. Biopsies revealed a spectrum of alveolar filling, interstitial edema and infiltration, and fibrosis. The patients were studied on mechanical ventilation to assess the effect of positive end-expiratory pressure (PEEP) and supplemental oxygen on shunt fraction. Mean anatomic shunt (measured on 100% oxygen) was 34 +/- 8%, which increased significantly (p less than .001) to 43 +/- 9% when the FIO2 was decreased to 40% to 60% (physiologic shunt), indicating ventilation/perfusion (V/Q) imbalance or impaired diffusion. Increasing PEEP by 9 +/- 2 cm H2O reduced the anatomic shunt to 30 +/- 7% (p less than .01) and the physiologic shunt to 37 +/- 7% (p less than .02). There was a similar decrease in anatomic and physiologic shunts in five studies, a greater decrease in physiologic shunt in four, and a greater decrease in anatomic shunt in two. Evidence of alveolar recruitment with PEEP, measured by an increase in static thoracic compliance, was found in only one study. There was no correlation between the effect of PEEP on compliance and its effect on shunt. The data suggest that in patients with AIDS and P. carinii pneumonia, PEEP can decrease shunt by reducing the anatomic shunt, improving V/Q imbalance, and converting areas of anatomic shunt to areas of low V/Q. P. carinii pneumonia in patients with AIDS can produce a clinical and pathophysiologic pattern similar to that described in the adult respiratory distress syndrome.     

Effect of blood transfusion on oxygen consumption in pediatric septic shock

Treatment plans for pediatric septic shock advocate increasing oxygen consumption (VO2). Recent studies in septic shock indicate that improving oxygen delivery (DO2) by increasing blood flow will increase VO2. We prospectively examined the effect on VO2 of improving DO2 by increasing oxygen content (CO2) with blood transfusion in eight hemodynamically stable septic shock patients. Transfusion consisted of 8 to 10 ml/kg of packed RBC over 1 to 2 h. Hemodynamic and oxygen transport measurements were obtained before and after blood transfusion. Transfusion significantly (p less than .05) increased Hgb and Hct from 10.2 +/- 0.8 g/dl and 30 +/- 2% to 13.2 +/- 1.4 g/dl and 39 +/- 4%, respectively (mean +/- SD). DO2 significantly (p less than .05) increased after transfusion (599 +/- 65 to 818 +/- 189 ml/min.m2), but VO2 did not change (166 +/- 68 to 176 +/- 74 ml/min.m2; NS). In pediatric septic shock patients, increasing CO2 by blood transfusion may not increase VO2.     

Persistence of supply dependency of oxygen uptake at high levels of delivery in adult respiratory distress syndrome

OBJECTIVE: To identify any plateau in oxygen consumption (VO2) when oxygen delivery (DO2) is increased in patients with the adult respiratory distress syndrome (ARDS). DESIGN: Clinical prospective study; multiple regression analysis was done to assess the relationship between VO2 and DO2 for pooled data and for each individual patient. SETTING: University hospital ICU. PATIENTS: Twenty consecutive patients aged 18 to 78 yrs (mean 43.5) in whom ARDS was present during their ICU stay. INTERVENTIONS: Multiple measurements were obtained in individual patients (mean number of measurements 40, range 20 to 83) and mathematical models were fitted to both pooled and individual patient data. DO2 ranged from 212 to 1550 mL/min.m2 with a maximum of 758 to 1550 mL/min.m2 (mean 1136). Because of the large variations between patients, it was not justifiable to describe a relationship for the pooled data and each case was analyzed individually. MEASUREMENTS AND MAIN RESULTS: We found the optimal regression model to be linear in 13 patients, cubic in four, and either cubic or linear in one. Two patients demonstrated no significant relationship. The relationship for the group was determined from each patient's data and was best described by linear regression. CONCLUSIONS: In no patient was there evidence of a plateau, despite high levels of DO2 being achieved in all patients.