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

OBJECTIVE: 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. DESIGN: 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. MAIN RESULTS: 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). CONCLUSIONS: 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.

Right ventricular end-diastolic volume as a measure of preload.

Right ventricular (RV) end-diastolic volume index (RVEDVI) measured by a modified thermodilution pulmonary artery catheter has been proposed as an improved measure of cardiac preload, compared with pulmonary capillary wedge pressure (PCWP). This study compared the correlation of RVEDVI and PCWP with cardiac index (CI) to determine which parameter better reflected ventricular preload. Modified thermodilution catheters were placed in 38 critically ill patients. Hemodynamic parameters were recorded in these patients at 2- to 4-hour intervals for 1 to 7 days. Complete data sets (1,008) were obtained. Regression analysis was performed comparing PCWP, RVEDVI, RV ejection fraction (RVEF) to CI in the entire group and in individual patients. Because mathematical coupling may exist between RVEDVI and CI, the correlation between these variables was corrected for mathematical coupling using the method described by Stratton. Simple regression analysis of data from all patients, uncorrected for mathematical coupling, yielded a significant correlation between CI and RVEDVI (r = 0.60, p < 0.0001), RVEF (r = 0.37, p < 0.0001), and PCWP (r = 0.01, p < 0.001). Correction for mathematical coupling between RVEDVI and CI resulted in a minor changes of the correlation coefficient to 0.56. In individual patients, a significant, uncorrected correlation (p < 0.05) was found between RVEDVI and CI in 27 of the 38 patients, whereas 11 patients had a significant correlation between PCWP and CI. RVEDVI correlated more closely with CI than did PCWP, even after correlation for mathematical coupling. In both the group as a whole and in individual patients, RVEDVI was a better indicator of cardiac preload.