Improved Bowel Function With Oral Methylnaltrexone Following Posterior Spinal Fusion for Adolescent Idiopathic Scoliosis

Background: Methylnaltrexone, a peripheral opioid antagonist, is used to decrease opioid-induced constipation; however, there is limited evidence for its use in children. The primary objective of the study is to assess the efficacy of per os (PO) methylnaltrexone in inducing bowel movements (BMs) in patients with adolescent idiopathic scoliosis who underwent a posterior spinal fusion and instrumentation (PSFI). Secondary outcomes include hospital length of stay, postoperative pain scores, and postoperative opioid usage. Methods: Retrospective chart review identified all adolescent idiopathic scoliosis patients above 10 years of age who underwent PSFI with a minimum of 24 hours of postoperative opioid analgesia after the initiation of the new bowel regimen protocol. The bowel regimen included daily administration of PO methylnaltrexone starting on postoperative day 1 until BM is achieved. A case-matched cohort was obtained with patients who did not receive PO methylnaltrexone and otherwise had the same bowel function regimen. Case-matched controls were also matched for age, sex, body mass index, and curve severity. t Tests and Pearson chi(2) tests were used for statistical analysis. Results: Fifty-two patients received oral methylnaltrexone (14 +/- 2.6 y) and 52 patients were included in the case-matched control group (14 +/- 2.1 y). The methylnaltrexone group had a significantly shorter hospital length of stay (3.09 +/- 0.66) compared with controls (3.69 +/- 0.80) (P<0.01). 59% (31 of 52) of the methylnaltrexone group had a BM by postoperative day postoperative day 2, compared with 30% (16 of 52) of the control group (P<0.01). In the methylnaltrexone group, 44% (23 of 52) of the patients required a Dulcolax (bisacodyl) suppository and 11% (6 of 52) required an enema, compared with 50% (26 of 52) and 33% (12 of 52) of the control group respectively (P=0.43 and 0.12). In addition, significantly less patients had abdominal distension during their postoperative stay in the methylnaltrexone group (17%, 9 of 52) compared with the control group (40%, 21 of 52) (P<0.01). There was no significant difference in self-reported average FACES pain score (P=0.39) or in opioid morphine equivalents required per hour (P=0.18). Conclusions: Patients who received PO methylnaltrexone after PSFI had decreased length of stay and improved bowel function. Administration of methylnaltrexone did not increase maximum self-reported FACES pain values or opioid consumption compared with controls. The use of oral methylnaltrexone after PSFI reduces postoperative constipation, which has implications for reducing hospital length of stay and overall morbidity.