title: Timing of the resumption of antithrombotic agents following surgical evacuation of chronic subdural hematomas: a retrospective cohort study.
abstract: OBJECTIVE
  Antithrombosis (AT), defined here as either antiplatelets or anticoagulants, is a significant risk factor for the development of chronic subdural hematomas (cSDHs). Resuming AT following the evacuation of cSDH is a highly variable practice, with scant evidence in the literature for guidance. Here, a retrospective analysis of a cohort of patients from a single institution undergoing surgical drainage of cSDH was performed to evaluate postoperative complications and determine the optimal timing of the resumption of common antithrombotic agents.
  
  
  METHODS
  This retrospective analysis was performed on 479 patients undergoing surgical evacuation of cSDH at St. Michael's Hospital over a 5-year period (2007-2012). The collected variables included the type of AT agent, indications for AT, timing and type of postoperative complications, and the restart intervals for the AT agents, when available. Postoperative complications were classified as major hemorrhages, minor hemorrhages, or thromboembolic events.
  
  
  RESULTS
  Among all 479 study patients, 71 experienced major hemorrhage (14.8%), 110 experienced minor hemorrhage (23.0%), and 8 experienced thromboembolism (1.67%) postoperatively. Patients on any type of preoperative AT regimen were at a higher risk of major hemorrhage (19.0% vs 10.9%; OR 1.93; 95% CI 1.15-2.71; p = 0.014). The type of AT agent did not affect the frequency of any postoperative complications. Patients on any preoperative AT regimen experienced earlier postoperative major hemorrhages (mean 16.2 vs 26.5 days; p = 0.052) and thromboembolic events (mean 2.7 vs 51.5 days; p = 0.036) than those patients without a history of AT; the type of AT agent did not affect timing of complications. Patients who were restarted on any AT therapy postoperatively were at decreased risk of major rebleeding following resumption than those patients who were not restarted (OR 0.06; 95% CI 0.02-0.2; p < 0.01).
  
  
  CONCLUSIONS
  Patients with a history of preoperative AT experienced thromboembolic complications significantly earlier than those patients without AT, which peaked at 3 days postoperatively with no increase in hemorrhage risk when AT was restarted. Cursory evidence is presented that shows resuming AT early following the surgical evacuation of cSDH at 3 days postoperatively may be safe. However, much larger prospective studies are required prior to providing any definitive recommendations regarding the optimal timing and method of resumption of individual agents.
authors.affiliation: Division of Neurosurgery, St. Michael's Hospital;|Keenan Research Centre for Biomedical Science and the Li Ka Shing Knowledge Institute of St. Michael's Hospital, Department of Surgery, University of Toronto, Ontario, Canada; and.
authors.forename: Daipayan
authors.initials: D
authors.lastname: Guha
authors.affiliation: Faculty of Medicine, The Royal College of Surgeons in Ireland, Dublin, Leinster, Ireland.
authors.forename: Shona
authors.initials: S
authors.lastname: Coyne
authors.affiliation: Division of Neurosurgery, St. Michael's Hospital;|Keenan Research Centre for Biomedical Science and the Li Ka Shing Knowledge Institute of St. Michael's Hospital, Department of Surgery, University of Toronto, Ontario, Canada; and.
authors.forename: R Loch
authors.initials: RL
authors.lastname: Macdonald
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D003399:Craniotomy; D004322:Drainage; D004334:Drug Administration Schedule; D005260:Female; D005343:Fibrinolytic Agents / Q000008:administration & dosage*; D020200:Hematoma, Subdural, Chronic / Q000601:surgery*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications; D012189:Retrospective Studies; D012307:Risk Factors
chemical_list: D005343:Fibrinolytic Agents
keywords: ADP = adenosine diphosphate; ASA = acetylsalicylic acid; AT = antithrombosis; CAD = coronary artery disease; DVT = deep venous thrombosis; INR = international normalized ratio; LMWH = low-molecular-weight heparin; TIA = transient ischemic attack; anticoagulation; antiplatelet; antithrombosis; cSDH = chronic subdural hematoma; chronic subdural hematoma; vascular disorders