The present study was designed to investigate the equivalence of two target activated clotting time (ACT) values with regard to packed red blood cell (PRBC) transfusion in patients undergoing cardiac surgery with cardiopulmonary bypass (CPB). Secondary endpoints include postoperative blood loss, transfusion of other blood products, and postoperative laboratory parameters, including renal function, intensive care unit length of stay, postoperative thrombotic events, and other adverse events.

Multicenter, randomized, single-blind, controlled equivalence trial. Patients were randomized to a lower target ACT of ≥400 seconds or a higher target ACT of ≥480 seconds.

Three tertiary and one university medical center in the Netherlands.

1,021 patients ≥18 years of age scheduled for first-time elective cardiac surgery with CPB between November 2019 and December 2023.

PRBC transfusion was equivalent in both ACT groups (19.1% v 17.2% risk difference –0.029; 0.066). In the low ACT group, blood loss at 6 and 24 hours postoperative was significantly lower (median [interquartile range], 260 [245] v 300 [250] mL, p = 0.003 and 480 [363] v 550 [410] mL, p = 0.007) and the hemoglobin level at 6 hours and 1 day after surgery significantly higher (mean [95% confidence interval], 11.8 [11.6-11.9] v 11.6 [11.3-11.8] g/dL, p = 0.017 and 11.4 [11.1-11.6] v 11.1 [11.0-11.4] g/dL, p = 0.045) compared with the high ACT group, but lacking clinical relevance. The frequency of thromboembolic events was similar in both groups.

This study showed that a target ACT of ≥400 seconds is equivalent to a target ACT of ≥480 seconds in terms of intraoperative and postoperative PRBC transfusion rates in the modern cardiac surgery setting. This target range is considered comparable regarding the outcomes of patients undergoing cardiac surgery with CPB.