Strategies for red blood cell (RBC) transfusion in patients undergoing cardiac surgery have been traditionally anchored to hemoglobin (Hb) targets. A more physiologic approach would consider markers of organ hypoperfusion.

The authors conducted a systematic review and meta-analysis with trial sequential analysis of randomized controlled trials (RCTs).

Cardiac surgery.

Adult patients.

RBC transfusion targeting only Hb levels compared with strategies combining Hb values with markers of organ hypoperfusion.

Primary outcomes were the number of RBC units transfused, the number of patients transfused at least once, and the average number of transfusions. Secondary outcomes were postoperative complications, intensive care (ICU) and hospital lengths of stay, and mortality. Only 2 RCTs were included (n = 257 patients), and both used central venous oxygen saturation (ScvO₂) as a marker of organ hypoperfusion (cut-off: <70% or ≤65%). A transfusion protocol combining Hb and ScvO₂ reduced the overall number of RBC units transfused (risk ratio [RR]: 1.57 [1.33-1.85]; p < 0.0001, I² = 0%), and the number of patients transfused at least once (RR: 1.33 [1.16-1.53]; p < 0.0001, I² = 41%), but not the average number of transfusions (mean difference [MD]: 0.18 [−0.11 to 0.47]; p = 0.24, I² = 66%), with moderate certainty of evidence. Mortality (RR: 1.29, [0.29-5.77]; p = 0.73, I² = 0%), ICU length-of-stay (MD: −0.06 [−0.58 to 0.46]; p = 0.81, I² = 0%), hospital length-of-stay (MD: −0.05 [−1.49 to 1.39];p = 0.95, I² = 0%), and all postoperative complications were not affected.

In adult patients undergoing cardiac surgery, a restrictive protocol integrating Hb values with a marker of organ hypoperfusion (ScvO₂) reduces the number of RBC units transfused and the number of patients transfused at least once without apparent signals of harm. These findings were preliminary and warrant further multicentric research.