Dependence of oxygen consumption on cardiac output in sepsis

We studied the relationship between oxygen consumption (V̇O₂) and cardiac output in 17 hemodynamically stable, septic and eight nonseptic ICU patients. Each received 300 ml of fresh-frozen plasma or 25% albumin with up to 500 ml of crystalloids, in addition to regular maintenance fluids; this treatment increased pulmonary wedge pressure (WP) by 3 to 4 mm Hg. Measurements were performed before and after approximately 5 h of volume loading. Because cardiac index (CI) decreased as WP increased in four septic and three nonseptic patients, we grouped the data according to the state of flow instead of the recording time sequence. From low to high flows, mean CI increased in septic patients and nonseptic patients. Oxygen delivery (ḊO₂) increased in septic and nonseptic patients. V̇O₂ remained unchanged in nonseptic patients, while it increased in septic patients. Accordingly, arteriovenous oxygen difference narrowed in nonseptic patients from 4.46 ± 1.62 to 3.59 ± 1.21 ml/dl (p < .05) but did not change in septic patients. In the septic group, the difference in CI between high and low flows was significantly (p < .05) greater in survivors than in nonsurvivors. We conclude that the septic state is accompanied by a peripheral oxygen deficit, which can be partially reversed by maintaining an above-normal CI and ḊO₂.