(963) Subcutaneous Versus Intravenous Neostigmine in Acute Colonic Pseudo-Obstruction

Introduction: Acute colonic pseudo-obstruction (ACPO) is a severe form of colonic ileus seen in medical, surgical, and trauma patients. Neostigmine has been shown to improve clinical response in ACPO by enhancing smooth muscle contraction and colonic motor activity. Multiple routes of administration have been studied: subcutaneous injection (SQ), intravenous (IV) bolus, and IV continuous infusion. While there are multiple studies comparing various dosing strategies of IV bolus and IV continuous infusion, there is no literature directly comparing outcomes with SQ and IV administration. Due to the lack of literature in this area, we aimed to evaluate the efficacy and safety of SQ versus IV administration of neostigmine for the treatment of ACPO and severe post-operative constipation

Methods: A propensity score-matched, retrospective analysis of adult patients admitted to the University of Oklahoma Medical Center surgical or trauma intensive care unit from July 1, 2021 – June 30, 2022 was conducted. The primary efficacy outcome was time to bowel movement. Total duration of neostigmine treatment, need for colonoscopic decompression or surgery, reduction in bowel diameter on repeat scan, and rates of bradycardia and antiemetic use were evaluated.

Results: A total of 69 patients were included, with 23 (33%) in the IV group and 46 (66%) in the SQ group. Patients included were predominantly male (87%), had a mean colonic distension of 10.4 cm, and a mean age of 57 years. For the primary outcome, the percent of patients with a bowel movement within 72 hours of neostigmine was 82.6% in the IV group and 93.4% in the SQ group (p=0.21). There was no difference in median hours to bowel movement (28.1 hours IV vs 35.4 hours SQ, p=0.78), and the need for colonoscopic decompression or surgery was numerically lower in the SQ group (11.1% IV vs 0% SQ, p=0.08). The incidence of bradycardia was numerically higher in the SQ group (0% IV vs 8.7% SQ, p=0.29).

Conclusions: Neostigmine administered IV vs SQ resulted in equivalent safety and efficacy for patients in a surgical and trauma intensive care unit population. Further research is needed to evaluate pharmacokinetic parameters and effect on colonic diameter amongst a larger cohort of patients.