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Timing of resumption of antithrombotic agents following surgical evacuation of chronic subdural hematomas: a retrospective cohort study

Background: Antithrombosis (AT), with antiplatelets or anticoagulants, is a significant risk factor for the development of chronic subdural hematomas (cSDH). Resumption of AT following hematoma evacuation is variable, with scant evidence for guidance. Methods: We retrospectively analyzed 479 patients with surgically-evacuated cSDH at St. Michael’s Hospital from 2007-2012. Collected variables included type of AT, indication for AT, timing and type of postoperative complications, and restart intervals for AT agents. Postoperative complications were classified as major or minor hemorrhages, or thromboembolism. Results: Among all patients, 14.8% experienced major hemorrhage, 23.0% minor hemorrhage, and 1.67% thromboembolism. Patients on any preoperative AT were at higher risk of major hemorrhage (OR=1.93, p=0.014), experienced earlier major hemorrhage (mean 16.2 versus 26.5d, p=0.052) and earlier thromboembolism (mean 2.7 versus 51.5d, p=0.036). The type of agent did not affect complication frequency or timing. Patients restarted on any AT postoperatively were at decreased risk of major rebleed following resumption, than those not restarted (OR=0.06, p<0.01). Conclusions: Patients on preoperative AT experienced thromboembolism significantly earlier, at 3d postoperatively, with no increase in rebleed risk following AT resumption. We provide cursory evidence that resuming AT early, at 3d postoperatively, may be safe. Larger prospective studies are required for definitive recommendations.