Red blood cell transfusion does not increase oxygen consumption in critically ill septic patients

Background Red blood cell (RBC) transfusion is commonly used to increase ox ygen transport in patients with sepsis. However it does not consistently in crease oxygen uptake at either the whole-body level, as calculated by the F ick method, or within individual organs, as assessed by gastric intramucosa l pH. Aim This study evaluates the hemodynamic and oxygen utilization effects of hemoglobin infusion on critically ill septic patients. Methods Fifteen septic patients undergoing mechanical ventilation whose hem oglobin was <10 g% were eligible. Ten patients (APACHE II: 25.5 <plus/minus > 7.6) received an infusion of 1 unit of packed RBC over 1 h while sedated and paralyzed. The remaining five control patients (APACHE II: 24.3 +/- 6.0 ) received a 5% albumin solution (500 ml) over 1 h. Hemodynamic data, gastr ic tonometry and calorimetry were obtained prior to and immediately after R BC transfusion or 5% albumin infusion. Results Transfusion of RBC was associated with an improvement in left ventr icular systolic work index (38.6 +/- 12.6 to 41.1 +/- 13.0 g/min/m(2); P = 0.04). In the control group there was no significant change in the left ven tricular systolic work index (37.2 +/- 14.3 to 42.2 +/- 18.9 g/min/m(2)). A n increase in pulmonary vascular resistance index (203 +/- 58 to 238 +/- 49 dyne/cm(5)/m(2); P = 0.04) was also observed, while no change was produced by colloid infusion (237 +/- 87.8 to 226.4 +/- 57.8 dyne/cm(5)/m(2)). Oxyg en utilization did not increase either by Fick equation or by indirect calo rimetry in either group. Gastric intramucosal pH increased only in the cont rol group but did not reach statistical significance. Conclusion Hemoglobin increase does not improve either global or regional o xygen utilization in anemic septic patients. Furthermore, RBC transfusion m ay hamper right ventricular ejection by increasing the pulmonary vascular r esistance index.