Effect of Surgical Subspecialty on Time to Development of Postoperative Venous Thromboembolism.

BACKGROUND: Postoperative venous thromboembolism (VTE) remains a major cause of surgical morbidity despite guideline-based prophylaxis. Whether VTE timing and thromboprophylaxis patterns differ across surgical subspecialties is incompletely characterized. STUDY DESIGN: Retrospective cohort study of adults with imaging-confirmed postoperative VTE during the index admission within a multihospital healthcare system (2013-2019). VTE events were identified using natural language processing and confirmed by chart review. Primary outcome was time to postoperative VTE; secondary outcome was time to thromboprophylaxis. Kaplan-Meier analyses and multivariable Cox proportional hazards models evaluated associations across surgical specialties. RESULTS: Among 1,520 patients with postoperative VTE, 24.9% had deep vein thrombosis (DVT) only, 67.2% pulmonary embolism (PE) only, and 7.9% both. Median time to VTE was 4 days (IQR 2.0-8.0); PE occurred earlier than DVT (3 vs 6 days; p<0.001). Neurosurgery had the highest VTE incidence (0.23% of neurosurgical cases), whereas orthopedic surgery demonstrated the highest adjusted hazard for postoperative VTE. Overall, 76% received postoperative thromboprophylaxis beginning a median of 1.3 days after surgery (IQR 0.8-1.7). Patients without thromboprophylaxis developed VTE earlier than those receiving prophylaxis (2.0 vs 4.0 days; p<0.001). Cardiac surgery demonstrated the lowest adjusted likelihood of thromboprophylaxis, whereas thoracic surgery had the highest (HR 5.8, 95% CI 2.8-12.1; reference cardiac), and trauma patients were less likely to receive prophylaxis (HR 0.44, 95% CI 0.34-0.57). CONCLUSIONS: Postoperative VTE risk, timing, and thromboprophylaxis practices vary substantially across surgical subspecialties. These findings support specialty-specific VTE risk assessment, prophylaxis strategies, and postoperative surveillance.