Assessment of predictors of response to neostigmine for acute colonic pseudo-obstruction

Acute colonic pseudoobstruction (ACPO) most commonly develops after surgery, with narcotic administration, or in association with severe illness. Most cases resolve with conservative management. Colonoscopic decompression may be required in patients failing to respond to conservative treatment. Neostigmine has been proposed as an effective treatment for ACPO as an alternative to colonoscopic decompression. We sought to identify factors associated with spontaneous resolution of ACPO and to identify variables associated with a response to i.v. administration of neostigmine for the treatment of ACPO.

Retrospective analysis of Mayo Clinic's diagnostic index revealed all patients who developed ACPO between July, 1999 and September, 2001 at the Mayo Clinic Medical Center. We separately analyzed those patients who did not resolve ACPO with conservative management and to whom i.v. neostigmine was administered. Patient records were abstracted for demographic data, etiology of ACPO, management, and response to treatment.

A total of 151 patients were identified with ACPO between July, 1999 and September, 2001; 117 patients (77%) had spontaneous resolution of symptoms. Of the 34 "nonresolvers," 18 patients received neostigmine, whereas 16 did not receive neostigmine. Of those 16 patients, 11 required colonoscopic decompression, two underwent surgery, and three died of underlying illness. "Spontaneous resolvers" were less likely to be taking narcotics (59% vs 74%, p = 0.08). Of the 16 nonresolvers who did not receive neostigmine, only one had a contraindication to neostigmine use. Of the 18 patients that who received neostigmine, 16 patients (89%) had prompt evacuation (<30 min) of flatus or stool. Sustained clinical response to neostigmine was noted in 11 of 18 (61%); the remaining seven patients (39%) required colonoscopic decompression or surgery for recurrent or persistent colonic dilation. Neostigmine-responders were more likely to be older (mean age, 76 yr vs 54 yr, p = 0.03), than nonresponders. Preneostigmine cecal diameter did not differ significantly between responders (median, 12 cm) and nonresponders (median, 13 cm), p = 0.9. Median time to resolution of ACPO in spontaneous resolvers was 4 days compared to 2 days in patients responding to neostigmine; p = 0.038.

Most patients with ACPO respond to conservative treatment. Female gender and older age are associated with a response to neostigmine in those patients who do not respond to conservative management. Neostigmine appears to be under-used in patients with ACPO who do not have a true contraindication to its use.