Background: Because of concern that opiate analgesia in patients with acute abdominal pain may mask diagnostically useful physical findings, opiate administration often is deferred pending surgical evaluation.

The Review: This review sought to determine whether administration of opiates to patients with abdominal pain was associated with a delay in necessary surgery or, conversely, with performance of unnecessary surgery.

The authors suggest that relaxation induced by opiates could result in a more reliable examination for peritoneal signs. The authors searched Medline for studies addressing whether opiate administration alters clinical decision making in patients with acute abdominal pain. Placebo-controlled trials with data on changes in history, physical examination, or clinical management were included.

Results: Twelve studies met the inclusion criteria. None of the studies directly assessed whether administration of opiates altered the accuracy of the patient history. However, adequacy of blinding (i.e., examiners' inability to tell which patients received opiates) suggests that the history is not significantly affected by opiate administration. Although several analyses showed that physical examination changes occurred after opiate administration, there was significant heterogeneity of results. One possible explanation for this is that the studies did not evaluate whether the pain became more or less localizable with opiates. Two studies documented changes in peritoneal signs, showing greater loss of these signs in patients receiving opiates than in those receiving placebo.

The studies with enough information to draw conclusions about diagnostic accuracy suggested that administration of opiates did not alter the rate of errors in management decisions. Further analysis to determine whether there were important delays in surgery when patients received opiates yielded no information because the confidence intervals were too wide. Surgeries were delayed in 1.3 percent of patients overall. There was a nonsignificant trend toward a reduction in unnecessary surgeries in patients who received opiates.

Conclusion: In spite of methodologic limitations in the studies, the authors conclude that opiates appear to alter physical examination findings but have no negative impact on clinical management. They calculate a number needed to harm (NNH) of 909, with estimates at the higher end of the confidence interval representing the possibility of a 3.6 percent increase in management errors (NNH = 28). This reflects a conservative analysis by which decisions that fell within the acceptable practice of performing exploratory surgery (i.e., subjecting more patients to surgery than are likely to have surgical pathology) may have been labeled errors. Overall, relieving abdominal pain promptly with opiates is appropriate and unlikely to cause harm.