Critical care medicine
-
Critical care medicine · May 1991
ReviewExperimental models of pathologic oxygen supply dependency.
Pathologic oxygen supply dependency is an abnormal situation in which oxygen uptake (Vo2) varies directly with oxygen delivery. Its presence in patients with adult respiratory distress syndrome and/or sepsis has been associated with particularly high mortality rates that may be the result of tissue hypoxia that causes multiple organ failure. The evidence for this association has been indirect because we cannot use invasive methods that would be necessary to verify or disprove the hypothesis. ⋯ Regional measurements have shown that gut Vo2 decreases before other areas, particularly skeletal muscle. Lactate measurements alone were shown not to be sufficient proof of tissue hypoxia. More direct measurements of actual energy states and tissue Po2 are indicated for future research efforts.
-
This review article examines the pathophysiology of septic shock, with special attention to the concept of supply-dependent consumption and the implications this concept has for therapy. Patients with septic shock require higher levels of oxygen delivery (DO2) to maintain aerobic metabolism. When DO2 is inadequate, peripheral tissues switch to anaerobic metabolism and oxygen consumption decreases. ⋯ Maximizing DO2 is an important part of the hemodynamic resuscitation of patients with septic shock. To achieve this goal, intravascular volume must be restored and the myocardial depression associated with sepsis must be treated to optimize cardiac output. The normalization of arterial lactate concentration is a reasonable goal of resuscitative efforts.
-
Critical care medicine · May 1991
ReviewOxygen transport in adult respiratory distress syndrome and other acute circulatory problems: relationship of oxygen delivery and oxygen consumption.
To evaluate the evidence that oxygen consumption (VO2) is pathologically dependent on oxygen delivery (DO2). ⋯ 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.
-
To review clinical studies of oxygen transport in cardiogenic and septic shock. ⋯ There are widely differing oxygen transport patterns in cardiogenic and septic shock that may have implications for therapy.
-
Critical care medicine · May 1991
Cardiovascular adjustments and gas exchange during extreme hemodilution in humans.
To examine the cardiovascular adjustments and pattern of gas exchange that occur during hemodilution. ⋯ The data suggest that, during hemodilution, tissue autoregulation of VO2 and utilization are not impaired, but gas exchange function (Qsp/Qt) is impaired.