The Impact of Marijuana Use on Postoperative Outcomes in Abdominal-Based Free Flap Breast Reconstruction

Background: There is an increasing prevalence of marijuana use in the general population yet clinical studies on marijuana's effect on surgical outcomes remain limited. Marijuana's effect on wound healing, venous thromboembolism due to endothelial inflammation, and bleeding due to inhibited platelet function have been cited based on animal models but have not been evaluated clinically in patients undergoing microsurgical reconstruction. Methods: Retrospective chart review was performed on all patients who underwent abdominal-based free flap breast reconstruction in a single institute from August 2018 to December 2022. Patient self-reported marijuana use, demographics, total narcotic use during hospitalization converted to oral morphine milligram equivalent (MME), and 90-day complications were collected and compared. Results: Total of 162 patients were included and 13 patients (8.5%) had reported marijuana use on pre-surgical history. Marijuana users are more likely to be younger and report concurrent nicotine smoking. Marijuana users were also at a significantly elevated risk of developing symptomatic venous thromboembolism (15% vs 1%; OR13.4 [95%CI 1.71-104.2], p=0.01) and marijuana use remained a significant risk factor with multivariate analysis. On postoperative 90-day complications, there was no increased risk of flap loss, re-operation, post-operative transfusion, or hematoma associated with marijuana use, and no significantly increased risk for overall donor or recipient site complications. Marijuana users required significantly more narcotics for pain control during hospitalization (100 ±77 MME vs 49 ±45 MME; p=0.0003), although they had similar lengths of stay, achievement of mobilization on POD1, and maximal pain scores. Conclusion: Marijuana use increases the risks of postoperative venous thromboembolism and increased postoperative narcotic requirements in patients who underwent abdominal based free flap breast reconstruction. Future prospective cohort study is required to further understand marijuana associated risks in microsurgical procedures.