Activated Clotting Time Value as an Independent Predictor of Postoperative Bleeding and Transfusion

Objectives: Activated Clotting Time (ACT) is commonly used to monitor anticoagulation during cardiac surgeries. Final-ACT values may be essential to predict postoperative bleeding and transfusions, although ideal values remain unknown. Our aim was to evaluate the utility of ACT as a predictor of postoperative bleeding and transfusion use.

Methods: Retrospective study (722 patients) submitted to surgery between July 2018-October 2021. We compared patients with Final-ACT<basal-ACT and Final-ACT≥basal-ACT; and Final-ACT < 140s with ≥140 s. Continuous variables were analyzed with Wilcoxon Rank-Sum test; categorical variables using Chi-square or Fisher’s exact test. A Linear Mixed Regression model was used to analyze bleeding in patients with Final-ACT < 140s and ≥140 s.Independent variables were analyzed with Binary Logistic Regression models to investigate their association with bleeding and transfusion.

Results: Patients with Final-ACT ≥ 140s presented higher postoperative bleeding than Final-ACT < 140s at 12 h (P = 0.006) and 24 h (**P = 0.004). CPB time (OR 1.009,1.002-1.015,95% CI) and masculine sex (OR 2.842,1.721-4.821,95% CI) were significant predictors of bleeding. Patients with Final-ACT ≥ 140s had higher risk of UT (OR 1.81, 1.13-2.89, 95% CI; P = 0.0104), compared to Final-ACT < 140s. CPB time (OR 1.019,1.012-1.026,95% CI) and Final-ACT (OR 1.021,1.010-1.032,95% CI) were significant predictors of transfusion. Female sex was a predictor of UT, with a probability for use of 27.23% (21.84-33.39%,95% CI) in elective surgeries, and 60.38% (37.65-79.36%,95% CI) in urgent surgeries, higher than in males.

Conclusions: Final-ACT has a good predictive value for the use of transfusion. Final-ACT ≥ 140s correlate with higher risk of transfusion and increased bleeding. The risk of bleeding and transfusion is higher with longer periods of CPB. Males have a higher risk of bleeding, but females have a higher risk of transfusion.