P0828 - Decreased Length of Stay with Oral Methylnaltrexone Following Posterior Spinal Fusion for Adolescent Idiopathic Scoliosis

Background/Purpose: 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 PO methylnaltrexone in inducing bowel movements (BM) in patients with adolescent idiopathic scoliosis (AIS) who underwent a posterior spinal fusion and instrumentation (PSFI). Secondary outcomes include hospital length of stay, post-operative pain scores, and post-operative opioid usage.

Methods: Retrospective chart review identified all AIS patients >10 years of age who underwent PSFI with a minimum of 24 hours of post-operative opioid analgesia after the initiation of the new bowel regimen protocol. The bowel regimen included daily administration of PO methylnaltrexone starting on postoperative day POD#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, BMI, and curve severity. T-tests and Pearson’s chi-squared tests were used for statistical analysis.

Results: 52 patients received oral methylnaltrexone (14 ± 2.6 years) and 52 patients were included in the case-matched control group (14 ± 2.1 years). The methylnaltrexone group had a significantly shorter hospital length of stay (3.09 ± .66) compared to controls (3.69 ± .80) (p<0.01). 59% (31 of 52) of the methylnaltrexone group had a BM by post-operative day POD#2, compared to 30% (16 of 52) of the control group (p<.01). In the methylnaltrexone group, 44% (23 of 52) of the patients required a Dulcolax suppository and 11% (6 of 52) required an enema, compared to 50% (26 of 52) and 33% (12 of 52) of the control group respectively (p=0.43 and p=0.12). In addition, significantly less patients had abdominal distension during their post-operative stay in the methylnaltrexone group (17%, 9 of 52) compared to 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).

Conclusion: 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 to controls.