Characterizing the Association of Heparin Dose and Activated Clotting Time on Lower Extremity Bypass Outcomes

INTRODUCTION: Anticoagulation is essential for preventing vascular thrombotic complications following vascular occlusive control. The effects of heparin dosing or monitoring activated clotting time (ACT) on postoperative outcomes remain poorly characterized. METHODS: Using data from a statewide collaborative, we investigated rates of postoperative bleeding, arterial/graft thrombosis, major amputation, readmission and death among patients within 30 days after lower extremity bypass with vein (LEB). We used a Bayesian random-effects multivariable logistic regression model to investigate the association between heparin dosing, ACT monitoring, and the interaction effect of the two, allowing for patients to cluster within surgeons and surgeons to cluster within hospitals. RESULTS: A total of 10,040 patients undergoing LEB from 34 hospitals were included, among whom 215 (2.1%) experienced predischarge arterial/graft thrombosis, 167 (1.7%) post-operative bleeding, 950 (9.5%) 30-day amputation, 1,132 (11.3%) 30-day readmission, and 51 (0.5%) 30-day mortality. Rates of ACT monitoring varied substantially across hospitals (12%-100%) with 4921 (49.1%) patients having ACT monitored. Heparin dose was not associated with post-operative thrombosis (OR 0.88, 95% Credible Interval 0.70-0.1.11), 30-day amputation (OR 0.93, 95% Credible Interval 0.81-1.05) or bleeding (OR 0.99, 95% Credible Interval 0.76-1.29). Administration of protamine was associated with reduced post-operative bleeding (OR 0.51, 95% Credible Interval 0.36-0.72). Achieving an ACT>250 was not associated with postoperative bleeding, thrombosis, amputation, readmission, or mortality. ROC curve analysis suggests no ACT value is a reliable cutoff for any of the assessed outcomes. CONCLUSIONS: Heparin dose, intraoperative ACT monitoring, and achieving an ACT >250 were not associated with any of the outcomes assessed. Furthermore, no ACT target reliably predicted any outcome on ROC curve analysis. Administering adequate heparin doses without ACT monitoring may provide equivalent outcomes without the associated costs and logistical challenges.