Blood transfusion and oxygen consumption in surgical sepsis

OBJECTIVETo evaluate the use of serum lactic acid values to predict flow-dependent increases in oxygen consumption ( o2) in response to increasing oxygen delivery (Ḋo2) after blood transfusion in surgical sepsis. DESIGNProspective study. SETTINGTertiary care, trauma center. PATIENTSTwenty-one patients, postsurgical or posttrauma, judged septic by defined criteria. INTERVENTIONSSerum lactic acid concentrations, Ḋo2, and o2 were measured before and after transfusion therapy. MEASUREMENTS AND MAIN RESULTSOverall, the Ḋo2 increased from 532 ± 146 to 634 ± 225 (sd) mL/min.m (p < .001), and the o2 increased from 145 ± 39 to 160 ± 56 mL/min.m (p = .02). These changes occurred with an Hgb increase from 9.3 ± 1.1 to 10.7 ± 1.5 g/dL (p < .001). The patients were grouped by their pretransfusion serum lactic acid values. In those patients with normal (< 1.6 mmol/dL) serum lactic acid (n = 10), Ḋo2 increased from 560 ± 113 to 676 ± 178 mL/min.m (p < .02), and o2 increased from 150 ± 25 to 183 ± 46 mL/min.m (p < .02). However, in the increased serum lactic acid group (n = 17), o2 was not significantly changed after transfusion (143 ± 46 to 146 ± 58 mL/min.m) despite increased o2 (515 ± 163 to 609 Ḋ251 mL/min.m, p < .01). CONCLUSIONSBlood transfusion can be used to augment o2 and Ḋo2 in septic surgical patients. Increased serum lactic acid values do not predict patients who will respond. The absence of lactic acidosis should not be used in this patient population to justify withholding blood transfusions to improve flow-dependent o2. Patients who have increased lactate concentrations may have a peripheral oxygen utilization defect that prevents improvement in o2 with increasing Ḋo2. (Crit Care Med 1991; 19:512)