Unfractionated heparin dosing for therapeutic anticoagulation in critically ill obese adults

Purpose: Research evaluating unfractionated heparin (UFH) dosing in obese critically ill populations is limited. This study aimed to determine optimal weight-based and total therapeutic infusion rates of UFH in this population. Methods: This retrospective cohort study compared adults on UFH infusions in intensive care units from May 2011 through October 2013 across 3 weight strata: 95 to 104 kg (control), 105 to 129 kg (high weight), and greater than or equal to 130 kg (higher weight). Primary outcomes included total and weight-based infusion rates for therapeutic anticoagulation. Results: To achieve therapeutic activated partial thromboplastin times, higher weight patients had higher mean infusion rates compared with control (2017 vs 1582 U/h; P = .002). Mean weight-based therapeutic infusion rate was lower in the higher weight group compared with control (13.1 vs 15.8 U kg^-1 h^-1; P = .008). Post hoc analyses indicated mean weight-based infusion rate to achieve therapeutic anticoagulation was 15 U kg^-1 h^-1 in patients less than 165 kg and 13 U kg^-1 h^-1 in patients greater than 165 kg. Conclusions: Patients greater than or equal to 130 kg have lower weight-based heparin requirements compared with patients 95 to 104 kg. This difference appears to be driven by patients greater than 165 kg. Patients greater than 165 kg have lower weight-based heparin requirements, whereas patients from 105 to 164 kg have weight-based requirements similar to a normal-weight patient population. Initiating heparin at appropriate weight-based doses for obese patients may optimize anticoagulation.