Journal of critical care
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Journal of critical care · Mar 1993
Comparative StudyOxygen delivery-consumption relationship in adult respiratory distress syndrome patients: the effects of sepsis.
The oxygen consumption-delivery relationship (VO2/DO2) 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. ⋯ All these patients developed MOSF and died. When DO2 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 DO2 and therefore worsened O2 balance by either increasing O2 extraction ratio and approaching the critical threshold for supply dependency or dismissing DO2 from the range of non-supply dependency.
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Journal of critical care · Mar 1993
Does alveolar recruitment occur with positive end-expiratory pressure in adult respiratory distress syndrome patients?
We studied the effects of positive end-expiratory pressure (PEEP) (2 to 14 cm H2O) on alveolar recruitment (Vrec), static respiratory compliance, and end-expiratory lung volume (EELV) in nine sedated, paralyzed, mechanically ventilated adult respiratory distress syndrome patients. Positive end-expiratory pressure was applied in increasing and decreasing steps of 2 cm H2O. Flow, tidal volume, and airway pressure were measured. ⋯ The changes in EELV were measured with respiratory inductive plethysmography. Alveolar recruitment was estimated as the difference in lung volume between PEEP and zero end-expiratory pressure (ZEEP) for the same end-inspiratory Pst, rs (20 cm H2O). We found that (1) Vrec with PEEP up to 14 cm H2O was in general rather small and was absent in two patients; (2) all patients exhibited PEEPi at ZEEP (5.6 +/- 1.0 cm H2O) and little change in EELV and Vrec was achieved until the external PEEP exceeded PEEPi; (3) if end-inspiratory Pst, rs is high at ZEEP, there is little or no alveolar recruitment with PEEP; and (4) Vrec and EELV were slightly higher during stepwise deflation than stepwise inflation with PEEP, except at ZEEP where EELV did not change after inflation-deflation runs with PEEP.
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Journal of critical care · Mar 1993
Oxygen kinetics during liver transplantation: the relationship between delivery and consumption.
In anesthetized humans, oxygen consumption is independent of oxygen delivery above a critical threshold. Below this critical level, lactic acid is a marker of anaerobic metabolism and tissue oxygen debt, and heralds a supply dependency of oxygen consumption. The goal of this study was to determine whether a threshold value for oxygen delivery below which oxygen consumption becomes supply dependent can be identified in patients with normal, impaired, or absent liver function. ⋯ Lactate increased in both groups during surgery, but was significantly higher in nonsurvivors (6.6 +/- 0.4 mmol/L) than in survivors (4.6 +/- 0.1 mmol/L) (P < .05). With similar changes for oxygen delivery and oxygen consumption during increased lactate levels we could not identify a clear supply dependency of oxygen consumption in survivors and nonsurvivors during liver transplantation. We conclude that the interpretation of blood lactate levels during circulatory shock can be biased due to a reduced lactate clearance in patients with impaired liver function, unrelated to the status of the relationship between oxygen delivery and consumption.(ABSTRACT TRUNCATED AT 250 WORDS)
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Journal of critical care · Mar 1993
Oxygen uptake-oxygen delivery alterations in the isolated liver after hydrogen peroxide challenge.
Acute, diffuse lung injury is frequently complicated by systemic organ injury and alterations in the relationship between oxygen uptake (VO2) and oxygen delivery (QO2). In this regard, systemic organ neutrophil accumulation and morphologic alterations consistent with systemic organ injury often occur in nonpulmonary organs in these settings. However, whether VO2-QO2 matching is also altered in these injured systemic organs remains unproven. ⋯ In addition, VO2 was lower for any given level of QO2 in the H2O2-injured livers compared with the control livers (P < .01). Finally, liver extravascular water content was increased in H2O2-injured livers compared with the control livers (0.79 +/- 0.02 v 0.71 +/- 0.05; P < .05). These observations indicate that H2O2, a product of neutrophil oxidative metabolism, is capable of producing both morphologic changes as well as gas exchange alterations in the isolated, perfused liver.