Preoperative Administration of Low-Molecular Weight Heparin is Associated With Increased Transfusion Rate in Elective Colorectal Surgery Patients

Background Colorectal surgery patients have a disproportionate risk of venous thromboembolism (VTE); thus, efforts to mitigate these events include both pre- and postoperative chemoprophylaxis. No studies have compared the efficacy and safety of low-molecular weight heparin (LMWH) and low-dose unfractionated heparin (UFH) as preoperative chemoprophylactic agents in colorectal surgery patients. We hypothesize that colorectal surgery patients who receive preoperative prophylactic doses of LMWH or UFH will have similar rates of VTE and bleeding. Methods The National Surgical Quality Improvement Program (NSQIP) database was queried for adult patients who had elective colorectal operations at a single institution from October 2018 to November 2022. Patients were separated based on preoperative chemoprophylaxis with LMWH (PRE LMWH), UFH (PRE UFH), or no preoperative chemoprophylaxis (NO PRE). All patients received enoxaparin for postoperative chemoprophylaxis. Primary outcomes were VTE rates and bleeding as defined by postoperative blood transfusion. Statistical analysis included Chi-squared test, Fishers exact test, univariate, and multivariate regression. Results A total of 596 patients were eligible. PRE LMWH n = 82, PRE UFH n = 178, and NO PRE n = 336. PRE LMWH had an increased risk of bleeding relative to PRE UFH (23% vs 6%, P < 0.01 ). PRE LMWH was an independent predictor of postoperative blood transfusion (OR = 1.72, 95% CI [1.43, 2.03], P < 0.001). There was no difference in VTE rates among all 3 groups ( P = .20 ). Discussion For CRS patients, preoperative initiation of LMWH VTE prophylaxis increases the risk of bleeding and transfusion when compared to UFH and NO PRE without decreasing the rate of VTE.