As a cardiovascular ICU intensivist, postoperative ileus (POI) is a condition I deal with frequently following laparotomies and even abdominal aorta endovascular repairs with gut dysmotility, inflammation, and neural inhibition all contributing. If conventional “bowel regimen” therapies (ambulation, enemas, etc.) fail, and I’m convinced the pathology is colonic pseudo-obstruction (not a mechanical obstruction), I’ll consider neostigmine.
Neostigmine is a reversible acetylcholinesterase inhibitor that prevents the breakdown of acetylcholine (ACh), thereby allowing more ACh to enhance effects at muscarinic and nicotinic receptors. This increased cholinergic activity in the gut stimulates smooth muscle contraction through M3 muscarinic receptors, promoting peristalsis.
Due to systemic parasympathomimetic effects, close monitoring is essential, particularly for bronchospasm and bradycardia. I’ll give 2 mg IV neostigmine in addition to 0.4 mg IV glycopyrrolate (an anticholinergic) to offset the parasympathetic effects on the cardiopulmonary system. Because of its polar, quaternary amine structure, glycopyrrolate does NOT cross the blood-brain barrier, unlike atropine, which can put vulnerable patients at risk for central anticholinergic syndrome.
If successful, one can expect the patient to have bowel movements within minutes-to-hours. Pictured is serial abdominal imaging before-and-after neostigmine administration (and plenty of BMs!)
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