Comparison of Heparin-Based Anticoagulation in Patients With and Without High Output Chylothorax: A Pilot Study

In infants and children with chylothorax after cardiac surgery, loss of antithrombin (AT) may impair the therapeutic effect of AT-dependent anticoagulants such as unfractionated heparin (UFH) and low molecular weight heparin (LMWH). This retrospective pilot study included patients 0-18 years receiving a therapeutic course of UFH or enoxaparin, excluding those on mechanical circulatory support or renal replacement. High output chylothorax courses were matched 1:2 to controls by age and anticoagulation duration. Therapeutic attainment and adverse events were compared for each agent. This study included 16 UFH and 17 enoxaparin courses plus matched controls. Among UFH courses, high output chylothorax was associated with a numerically lower percentage of therapeutic anti-Xa levels during the first seven days (55.9% vs. 68.8%, p = 0.06). Though no differences were observed for dose at first therapeutic level, chylothorax courses required numerically more dose adjustments to reach first therapeutic level and a greater proportion received AT repletion. Among enoxaparin courses, no significant difference was observed for time to therapeutic anti-Xa, though chylothorax courses required numerically higher doses and more dose adjustments to reach first therapeutic level. Baseline and minimum AT were lower in the chylothorax group for both agents. No differences were found in the incidence of thrombosis or bleeding. High output chylothorax after cardiac surgery may impair the therapeutic effect of UFH, while the effect on enoxaparin is less clear. Though most differences were nonsignificant, the findings suggest larger studies are needed to assess the impact of chylothorax on hemostatic outcomes.