Effects of blood transfusion on oxygen transport variables in severe sepsis.

OBJECTIVE: To investigate whether increasing oxygen delivery (DO2) by increasing hematocrit results in increases in oxygen uptake (VO2) in septic patients with an abnormal DO2/VO2 relationship.

DESIGN: Prospective, randomized, interventional crossover study.

SETTING: Tertiary care hospital.

PATIENTS: A consecutive sample of 16 patients admitted to the intensive care unit, who were diagnosed as having severe sepsis by defined criteria and who had a hemoglobin concentration of < 10 g/dL.

INTERVENTIONS: Patients received, in random order, an infusion of dobutamine (10 micrograms/kg/min) and a blood transfusion (800 mL of packed red blood cells in 90 mins). Hemodynamic and oxygen transport variables were determined before and after each treatment, allowing at least 20 mins during the infusion of dobutamine to achieve the steady state.

MEASUREMENTS AND MAIN RESULTS: Changes in DO2 and VO2 induced by each intervention were measured. Dobutamine significantly increased DO2 (48.5 +/- 6.9%; p = .0001) and VO2 (21.7 +/- 3.3%; p = .0001). Blood transfusion increased DO2 (21.4 +/- 4.3%; p = .005) but VO2 did not change significantly (2.2 +/- 4.1%). Correlation coefficients for the percent changes of DO2 and VO2 (r2 = .67, p = .001 for dobutamine; and r2 = 21, p = .07 for blood transfusion) were significantly different for each treatment (p = .0001).

CONCLUSIONS: In patients with an abnormal DO2-dependent VO2, as shown by increases in VO2 brought about by an infusion of dobutamine, blood transfusion does not significantly increase VO2, despite significant changes in DO2. The VO2, in some critically ill patients, depends more on blood flow than on global DO2.