Supranormal oxygen transport variables for the treatment of the critically ill. Still an appropriate resuscitation goal?

Objective. To review the theoretical bases for the recommendation to increase oxygen delivery (D(̇)O 2), to supranormal values in the hemodynamic resuscitation of critically ill patients, and whether there are evidences that prove that this intervention improves survival. Data source. Relevant studies published in the medical literature and, occasionally, experts' review articles and book chapters on this topic. If possible, we have reviewed prospective, randomized, controlled studies. Results. It is not well proven that oxygen consumption (V(̇)O 2) depends pathologically on D(̇)O 2 in critically ill patients. Nevertheless, there is increasing evidence suggesting that some regional perfusion deficits along with a normal cardiac output and normal D(̇)O 2 values can exist, particularly in the intestinal mucosa. However, whether increasing cardiac output and D(̇)O 2 values to supranormal values reverses this hypoxic state and improves outcome in critically ill patients is not proven. Some studies have reproduced the results that show a higher survival when cardiac output and D(̇)O 2 are increased during the perioperative period. This, as well as other evidences, suggests the possibility of preventing tissue hypoxia. Conclusions. There are reasonable arguments to believe that high cardiac output and D(̇)O 2 values are desirable during the resuscitation of critically ill patients, particularly in the early phases. However, this is not true for the contention that pursuing specific and standard cardiac output, D(̇)O 2 and V(̇)O 2 values will benefit all critically ill patients.