Factors predicting successful outcome following neostigmine therapy in acute colonic pseudo-obstruction: a prospective study

AIM: To evaluate predictors of neostigmine response in patients with acute colonic pseudo-obstruction. METHODS: Twenty-seven patients with acute colonic pseudo-obstruction were enrolled in the study. All patients had received initial conservative management such as nil orally, nasogastric suction, rectal tube placement and correction of electrolyte imbalance for the first 24 h. Those who did not resolve with conservative management received 2 mg neostigmine intravenously. The same dose was repeated after 24 h in patients who did not response to the first dose (initial non-responders), or in those patients who relapsed after an initial response (initial responders). All non-responders to neostigmine underwent colonoscopic decompression followed by 2 mg neostigmine infusion for 30 min. A sustained response was defined as the resolution of symptoms and colonic dilatation on a plain radiograph. RESULTS: The study enrolled 27 patients; 18 were male (67%), and the median age was 60 years (range 18-78 years). Eight (30%) patients had spontaneous resolution. Initial response with neostigmine was observed in 16 (84%) patients, of which 10 (63%) had a sustained response. Nine patients (three initial non-responders and six initial responders) had received a second dose of neostigmine. A sustained response was seen only in five initial responders. Four patients who did not respond to neostigmine underwent colonoscopic decompression followed by neostigmine infusion and had a sustained response. Neostigmine responders were more likely to be postoperative patients (11 of 15 (73%) vs one of four (25%), P = 0.07), less likely to have electrolyte imbalance and to be on antimotility agents (three of 15 (20%) vs four of four (100%), P = 0.009 and two of 15 (13%) vs four of four (100%), P = 0.003). CONCLUSIONS: Electrolyte imbalance and usage of anti-motility agents are factors associated with a poor response, while postoperative patients showing good response to neostigmine therapy.