Does neostigmine increase gastric emptying in the critically ill?--results of a pilot study

Based on the successful use of neostigmine for the treatment of acute colonic pseudo-obstruction, we hypothesised that neostigmine would increase gastric emptying and improve tolerance to enteral feeding in the critically ill patient.

Eleven patients intolerant of enteral feeds due to high gastric aspirates, were randomised to receive a 'study infusion' consisting of either neostigmine (0.4 mg/hr) or 0.9% saline. If, after 12 hours the patient was deemed intolerant of the nasogastric feed, the rate of the 'study infusion' was doubled. Those who remained intolerant after 24 hours of the 'study infusion' were 'crossed-over' and continued on the other infusion for a further 24 hours. Gastric emptying was assessed in each group before and after the infusion by measuring the hourly rates of feed "absorption" [(delivery rate + returned aspirates) - total aspirates] and paracetamol absorption using the area under a time-concentration curve at 120 minutes (AUC120). Differences within and between groups were analysed using Students t test and one-way analysis of variance.

Six patients received neostigmine first and 5 received the placebo first. Four of the 6 patients receiving the neostigmine first compared with all of those receiving placebo first required to be 'crossed-over' to the other infusion. While the hourly rates of feed "absorption" were greater for patients receiving neostigmine than for placebo, these differences did not achieve statistical significance. The mean paracetamol AUC120 for all patients who received neostigmine was 3996 mg/min/L while that for placebo was 1929 mg/min/L (p = 0.21).

These data suggest that while neostigmine may have a positive effect on gastric emptying and enteral feed absorption in critically ill patients, the results did not reach statistical significance and an adequately powered study will be required to confirm this effect.