Red blood cell transfusion compared with gelatin solution and no infusion after cardiac surgery: effect on microvascular perfusion, vascular density, hemoglobin, and oxygen saturation.

BACKGROUND: After cardiac surgery, red blood cell (RBC) transfusion may improve systemic hemodynamics and thereby microvascular blood flow and O2 delivery (DO2). STUDY DESIGN AND METHODS: In a nonrandomized prospective observational study on post-cardiac surgery patients, systemic hemodynamics and microvascular blood flow, vascular density (sidestream dark-field imaging), hemoglobin (Hb) content, and saturation (reflectance spectrophotometry) were measured before and 1 hour after start of transfusion of 1 to 2 units of leukoreduced RBCs (270±203 mL), 500 mL of gelatin solution, or control (no infusion), when patients were considered clinically hypovolemic with (RBC group, n=12) or without (gelatin group, n=14) anemia (Hb<10 g/dL) or not (n=13), respectively.
RESULTS: Systemic Hb was lower and increased in the RBC transfusion but not in gelatin and control groups. There were no differences in changes in systemic DO2, O2 uptake, and extraction between groups. RBC transfusion, compared with gelatin or control, increased medium-sized vascular density, Hb content, and saturation in the microcirculation, while blood flow remained unchanged. Changes of microvascular Hb and saturation paralleled changes in systemic Hb.
CONCLUSION: The data argue in favor of efficacy of RBC transfusion after cardiac surgery. RBC transfusion increases systemic Hb and this in turn increases medium-sized vascular density and DO2 in the sublingual microcirculation, independently of systemic hemodynamics and volume status.