The use of oxygen consumption and delivery as endpoints for resuscitation in critically ill patients

Oxygen consumption (VO2I) and delivery (DO2I) indices have been stated to be superior to conventional parameters as endpoints for resuscitation. However, another interpretation of published data is that inability to increase VO2I/DO2I given adequate volume resuscitation reflects inadequate physiologic reserve and poor outcome. Fifty-eight critically ill patients were randomized to two groups. In group 1 (27 patients) attempts were made to maintain VO2I > or = 150 or DO2I > or = 600 mL/min/m2. If DO2I was > 600, no attempt was made to increase VO2I even if it was < 150. Group 2 (31 patients) was resuscitated based on conventional parameters. Volume resuscitation protocols and goals for pulmonary capillary wedge pressure were the same in both groups. VO2I/DO2I were recorded in group 2, but physicians were blinded to this data. Age, Injury Severity Score, and Acute Physiology and Chronic Health Evaluation (APACHE II) score were not different between groups. Three patients in group 1 and two patients in group 2 died of organ failure (OF). One additional patient in group 2 died of refractory shock within 24 hours. Two of the patients in group 1 who died failed to meet VO2I/DO2I goals within 24 hours despite maximal resuscitation. Mortality was not different between the groups even with exclusion of the group 1 patients who failed to meet VO2I/DO2I goals (p = 0.66). After exclusion of the patient in group 2 who died of refractory shock, OF occurred in 18 of 27 (67%) in group 1 and in 22 of 30 (73%) in group 2 (p = 0.58). Length of ventilator support, intensive care unit stay, and hospital stay were not different between groups. When all patients were assessed, no difference was found in the incidence of OF between patients who attained the VO2I goal and those who did not. OF occurred in 20 of 34 (59%) patients who maintained a mean DO2I > or = 600 during the first 24 hours of the study and in 21 of 24 (88%) of those who did not (p < 0.02). No difference was found in the incidence of OF or death in patients resuscitated based on oxygen transport parameters compared to conventional parameters. These data suggest that given adequate volume resuscitation, oxygen-based parameters are more useful as predictors of outcome than as endpoints for resuscitation.