Measurement of tissue perfusion by oxygen transport patterns in experimental shock and in high-risk surgical patients

Survivors of high-risk general (noncardiac) surgery were observed to have cardiac index (CI) values averaging 4.5 l/min·m², oxygen delivery ( $\dot D$ O₂) of >600 ml/min·m², and oxygen consumption ( $\dot V$ O₂) of 170 ml/min·m². In contrast, these values were relatively normal in patients who subsequently died. A very early predictive index based on these observations was found to predict outcome in 94% of high-risk patients. The hypotheses that increased- $\dot D$ O₂ and $\dot V$ O₂ in the survivors represent compensatory physiologic responses and that these values were appropriate therapeutic goals were tested in prospective randomized clinical trials and found to reduce mortality and morbidity significantly. The optimal goals were more easily attained with colloids, red cells, dobutamine, and vasodilators, according to their capacity to improve tissue perfusion, as reflected by increased flow and oxygen transport. The extremely complex interactions between- $\dot D$ O₂ and $\dot V$ O₂ are reviewed.