Opioid tolerance impacts compliance with enhanced recovery pathway after major abdominal surgery

Background: Opioid tolerant patients have been shown to have poor postoperative outcomes. Enhanced recovery pathways are evidence-based interventions that focus on optimizing recovery, and their effectiveness depends on the degree of compliance with the pathway. We wish to determine pathway compliance and its impact on postoperative outcomes in opioid tolerant patients undergoing abdominal surgery on an enhanced recovery pathway. Methods: From December 2014 to June 2017, 646 patients undergoing major abdominal surgery on an enhanced recovery pathway were included. Patients <18 years and having emergency surgery were excluded. Compliance was measured to 14 perioperative pathway standards and high-compliance was defined as adhering to ≥75% standards. Opioid tolerance was defined as any patient taking a prescribed opioid medication equivalent to 60 mg of oral morphine per day for 1 week prior to surgery. The Colorectal Physiological and Operative Severity Score for the Enumeration of Mortality and Morbidity was used for risk-adjusted analyses. Outcomes of interest include length of stay, major complications (Clavien-Dindo ≥2), 30-day readmission rates, and mortality. Results: Overall, 114 (18%) patients were opioid tolerant and 532 (82%) were not opioid tolerant. Opioid tolerant patients were less likely to be highly compliant with enhanced recovery pathway standards than non-tolerant patients (35% vs 54%; P <.001); particularly postoperative care standards. On adjusted analysis, opioid tolerance was associated with a 2-fold increase in readmissions following major abdominal surgery. Examining only those patients with opioid tolerance, adjusted analysis demonstrated that high compliance with the enhanced recovery pathway standards was independently associated with a 26% reduction in length of stay, over a 90% reduction in major complications, and mitigated the effect on readmissions. Conclusion: The authors provide evidence that opioid tolerance is associated with less favorable outcomes in patients undergoing major abdominal surgery on an enhanced recovery pathway, and this is likely due to a lack of pathway compliance. Establishing strategies to improve compliance in this challenging patient cohort may serve to mitigate the negative impact of opioid tolerance.