Preoperative Weight Loss for Patients with Obesity Prior to Non-Bariatric Surgery

Abstract

Background: Improved preoperative weight loss strategies for patients with obesity undergoing major non-bariatric surgery are necessary. As such, this research program focusing on evaluating different preoperative weight loss interventions, namely very low energy diets (VLEDs) and bariatric surgery, for patients with obesity undergoing major non-bariatric surgery was developed. Methods: The first chapter is a systematic review evaluating the use of preoperative VLEDs reported according to PRISMA. Medline, EMBASE, CENTRAL, and PubMed were systematically searched from inception through to July 2021. Articles were included if they evaluated VLED utilization prior to non-bariatric surgery. Pairwise meta-analyses using inverse variance random effects were performed. The second chapter is a retrospective study investigating the impact of a history of bariatric surgery on patients undergoing surgery for colorectal cancer. Adult patients undergoing resection for colorectal cancer from 2015-2019 were identified from the National Inpatient Sample (NIS). Patients were stratified according to their history of bariatric surgery. Propensity score matching with 4:1 nearest-neighbor matching was performed. Results: In Chapter 1, 13 studies with 395 patients with obesity receiving VLEDs preoperatively in preparation for non-bariatric surgery were included. Adherence with VLEDs ranged from 94- 100%. Mean preoperative weight loss ranged from 3.2-19.2kg. Patients using VLEDs had decreased intraoperative blood loss (MD 305.20mL, 95%CI 208.18-402.23, p<0.00001). In Chapter 2, 1,197 patients without prior bariatric surgery and 376 patients with prior bariatric surgery were included. Patients with prior bariatric surgery had an absolute reduction of 6.5% in overall in-hospital postoperative morbidity (19.1% vs. 25.6%, p<0.0001) and a $5,256 decrease in hospitalization cost ($70,344 vs. $75,600, p=0.034). iv Conclusion: These studies support the use of preoperative weight loss techniques for patients with obesity prior to non-bariatric surgery. VLEDs and bariatric surgery have the potential to become cornerstones of pre-habilitation protocols for patients with obesity undergoing elective operations. Further adequately powered prospective study is warranted.