120. Operative Time is an Independent Predictor of Postoperative Outcomes in Bilateral DIEP Flap Breast Reconstruction: A Multivariate Analysis of 1000 Flaps

Abstract

Purpose: The deep inferior epigastric perforator (DIEP) flap is the gold standard autologous breast reconstruction, with a rapid increase in regularity in recent years. Operative time (OT) as a risk factor for adverse postoperative outcomes in microvascular breast reconstruction has not been thoroughly investigated. This study evaluates the impact of OT on length of stay (LOS), overall morbidity, individual complications, and unplanned reoperation (UR) in DIEP flaps, with a primary objective of identifying a clinically relevant time of decreased risk. Methods: Patients treated with bilateral DIEP flaps from 2010-2021 by two senior surgeons (NTH, SST) with standardized surgical and postoperative protocols were retrospectively reviewed. 1000 flaps (500 patients) were analyzed with multivariate regressions to adjust for potential confounders, including microsurgeon experience, and isolate the impact of OT on postoperative outcomes. We rounded the 25%ile, 50%ile, and 75%ile of OT quartiles (I.e. 4.92, 6.60, and 8.87 hours) to the nearest hour (I.e. 5, 7, and 9 hours) for ease of use as an easy-to-follow guideline for OT intervals. To identify a cutoff, beyond which risk for postoperative complications, extended LOS (eLOS, defined as ≥5 days), and UR significantly increases, adverse outcomes were compared amongst OT intervals. Results: The occurrence of all adverse outcomes with more than one incidence was associated with longer operative times. Procedures with and without complications had an average of 8.05±3.29 and 6.33±2.51 hours (p<0.001) respectively. With risk-adjustment, each hour of OT increased morbidity by 22% (p<0.001) and LOS by 4.8 hours. Procedures >5 hours had 3.9, 4.8, and 2.6-fold increased risk of UR (p=0.029), eLOS (p=0.007), and overall complications, respectively. Breast fat necrosis, abdominal donor-site morbidity, and medical complications also had significantly higher risk after 5 hours. Lastly, a risk-adjusted linear regression showed that LOS can be calculated from OT: LOS (days) =1.702 + 0.201 x OT (hours) (p<0.001, R2=0.369). Conclusions: For the first time, operative time is shown as an independent predictor of morbidity, LOS, and UR in DIEP flaps, with significantly greater risk >5 hours. The findings emphasize the importance of decreasing OT through efficiency models, such as process analysis, team-based protocols, and co-surgery.