Oxygen transport variables in the identification and treatment of tissue hypoxia.

Critically ill patients have greater than normal oxygen demands because of enhanced energy requirements placed on them by the stress of acute illness, blood and fluid loss, surgery, wound healing, and hospitalization. Early recognition of major alterations in oxygen transport variables, oxygen delivery, oxygen consumption, and the oxygen extraction ratio, by the critical care team assists in the prevention and treatment of tissue hypoxia in seriously ill and injured patients. Supranormal levels of oxygen delivery are required to meet these increased oxygen demands, to prevent tissue hypoxia, and to correct tissue oxygen debt. The critical care team should promptly determine the patient's oxygen transport variables on admission to the intensive care unit to provide a starting point for patient resuscitation. When deviations from supranormal values of oxygen transport variables in these patients are identified, specific interventions that improve oxygen delivery to peripheral tissues should be implemented and evaluated for their effectiveness in normalizing the oxygen extraction ratio. When serial measurements of oxygen delivery, oxygen consumption, and the oxygen extraction ratio follow each therapeutic intervention that is directed at increasing oxygen delivery, the survival rate of critically ill patients is significantly improved.