Adverse outcomes and opioid analgesic administration in acute abdominal pain

To the authors' knowledge, no outcome-based, randomized clinical trial of the safety of opioid analgesics in acute abdominal pain exists.

1) To assess the feasibility of a randomized clinical trial of opioid safety by estimating the adverse outcome rate among patients with abdominal pain severe enough to necessitate opioid analgesics. 2) To explore the association of opioid administration with adverse outcomes in acute abdominal pain.

The authors conducted a prospective observational study of emergency department (ED) abdominal pain patients, and followed them by telephone at three weeks to determine whether an adverse outcome occurred (defined as obstruction, perforation, ischemia, hemorrhage, peritonitis, sepsis, or death). A logistic regression of factors predicting adverse outcome was performed.

Adverse outcomes occurred in 67 of 860 abdominal pain patients (7.8%, 95% CI = 6.1% to 9.8%), and 252 of 860 (29%) received opioids. The adverse outcome rate was 12.7% (95% CI = 9.0% to 17.0%) among patients who received opioids. Variables predictive of adverse outcome in logistic regression included: ED diagnosis of adverse outcome (OR 12.4), age (OR 1.6 per decade), fever (OR 4.6), received opioids (OR 2.1), pain duration (OR 1.5 per day), and leukocytosis (OR 2.0).

A clinical trial would need to randomize more than 1,500 patients to establish the equivalent adverse outcome rates of opioids and placebo: the sample size of all existing studies combined is insufficient to make such a conclusion. Although opioids were associated with a higher adverse outcome rate in this logistic regression, the authors believe this may be due to confounding by pain severity. They emphasize that the study's design precludes conclusion of a causal link. No change in clinical practice is warranted. A randomized clinical trial of sufficient size to definitively resolve this issue is needed.