To determine whether the levels of oxygen consumption (VO2) required to relieve an existing oxygen debt are variable, increases in VO2 produced by increases in oxygen delivery (DO2) were evaluated longitudinally in septic patients with lactic acidosis and related to changes in lactate levels. Interventions were performed in 17 patients and consisted of fluid administration (n = 11), packed red blood cell transfusion (n = 19), or dobutamine infusion (n = 14). Interventions associated with a decreased lactate level or an unchanged/increased lactate level demonstrated similar increases from baseline VO2 (49 +/- 9 and 47 +/- 6 ml/min.m2, respectively) and similar postintervention absolute VO2 values (187 +/- 13 and 189 +/- 10 ml/min.m2, respectively) (both p greater than 0.6). When all interventions were considered, correlations were not observed between changes in lactate levels and changes in VO2 (r = 0.21, p greater than 0.60) or between changes in lactate levels and the postintervention VO2 values (r = 0.08, p greater than 0.45). These observations demonstrate that optimal levels of VO2 are variable and suggest that therapeutic interventions should be tailored to a patient's individual tissue needs and guided by an assessment of an oxygen debt (eg, lactate levels) rather than absolute VO2 measurements.