Safety and Efficacy of Intermittent Bolus and Continuous Infusion Neostigmine for Acute Colonic Pseudo-Obstruction

Purpose: To compare clinical response of intermittent bolus versus continuous infusion neostigmine for acute colonic pseudo-obstruction (ACPO). Acute colonic pseudo-obstruction occurs due to reduced colonic parasympathetic activity. Neostigmine is an acetylcholinesterase inhibitor that increases frequency of smooth muscle contraction by increasing acetylcholine at autonomic nervous system synapses. Although these administration modalities have been studied separately, they have never been compared.

Methods: This retrospective study compared bolus versus continuous infusion neostigmine for ACPO. The primary outcome was initial clinical response, defined as bowel movement (BM) within 4 hours of bolus dose or 24 hours of initiation of continuous infusion. Secondary outcomes included time to BM, bowel diameter reduction at 24 hours, incidence of bradycardia, additional neostigmine requirements, and need for colonic decompression or surgical intervention.

Results: Seventy-five patients were included (bolus n = 37; infusion n = 38). Median total 24-hour neostigmine dose was 2.0 mg (interquartile range [IQR]: 2.0-2.6) with bolus and 9.6 mg (IQR: 6.3-9.6) with continuous infusion. Initial clinical response was similar (infusion 81.6% vs bolus 62.2%, P = .06), but continuous infusion was associated with greater bowel diameter reduction (73.7% vs 40.5%, P = .004). Bolus administration had shorter time to BM (1.4 vs 3.5 hours, P = .0478) and increased need for colonic decompression (67.6% vs 39.5%, P = .0148). Bolus dosing was associated with less bradycardia (13.5% vs 39.5%, P = 0.011), with no difference in atropine usage (10.8% vs 5.3%, P = .43).

Conclusion: Initial clinical response was similar between groups; however, continuous infusion neostigmine was associated with greater bowel diameter reduction at 24 hours. Bolus administration resulted in less bradycardia; however, given the lack of difference in atropine use, clinical significance is unknown. This study is the first to compare bolus versus continuous infusion neostigmine for ACPO. Further studies are needed to confirm findings.