Effect of Length of Surgery on the Incidence of Venous Thromboembolism after Benign Hysterectomy.

BACKGROUND Venous thromboembolism is a leading cause of morbidity and mortality postoperatively. Current venous thromboembolism risk assessment tools have not been validated in gynecologic patients. Most patients undergoing hysterectomy for benign indications will receive mechanical or pharmacological prophylaxis based on preoperative risk assessment. However, current guidelines do not incorporate newer data that indicate additional risk of venous thromboembolism with prolonged surgery times or mode of hysterectomy. OBJECTIVE Determine effect of length of surgery / operative time on risk of VTE within 30 days after hysterectomy and determine if differences in the effect of operative time exist across age, body mass index (BMI), and surgical approach. STUDY DESIGN We performed a secondary analysis of prospectively-collected surgical quality improvement data using the American College of Surgeons National Surgical Quality Improvement Program database, which contains demographic, perioperative information and 30-day postoperative outcomes from >500 hospitals, and targeted data files including procedure-specific risk factors and outcomes for a subset of hospitals. We analyzed patients undergoing abdominal, vaginal, or laparoscopic hysterectomy for benign conditions from 2014-2017, identified by Current Procedural Terminology (CPT) codes. We excluded patients with cancer, surgery not performed by a gynecologist, not in targeted files, missing operative time, or with an operative time <30 minutes. Patients were compared with respect to incidence of venous thromboembolism and operative time, stratified by age, BMI, and surgical approach. Multivariable logistic regression was performed; operative time was treated as a continuous, linear variable. RESULTS 70,606 patients were included. 30-day venous thromboembolism incidence was 0.4% (n=259). Patients with venous thromboembolism were more likely to be obese, have inpatient procedures, and had, on average, greater uterine weight. Hysterectomy approach was vaginal in 11,641 patients, laparoscopic in 41,557 patients, and abdominal in 17,408 patients. After adjustment, for each 60 minute increase in operative time, there was a 35% increase in the odds of venous thromboembolism (aOR 1.35, 95% CI 1.25, 1.45). Stratified by surgical approach, odds of venous thromboembolism per 60 minute increase in operative time was greatest among abdominal hysterectomy (aOR 1.49, 95% CI 1.35, 1.65) compared to laparoscopic hysterectomy (aOR 1.20, 95% CI 1.05, 1.38) and vaginal hysterectomy (aOR 1.27, 95% CI 0.97, 1.66), p=0.01. Increasing BMI and increasing age did not modify the impact of operative time on venous thromboembolism incidence (p=0.66, p=0.58, respectively). CONCLUSION Every 60-minute increase in operative time was independently associated with a 35% increased odds of venous thromboembolism within 30 days of hysterectomy and this risk was cumulative. Minimally invasive hysterectomy had lower odds of venous thromboembolism, compared to abdominal hysterectomy across all time points.