Do opiates affect the clinical evaluation of patients with acute abdominal pain?

Clinicians have traditionally withheld opiate analgesia from patients with acute abdominal pain until after evaluation by a surgeon, out of concern that analgesia may alter the physical findings and interfere with diagnosis.

To determine the impact of opiate analgesics on the rational clinical examination and operative decision for patients with acute abdominal pain.

MEDLINE (through May 2006), EMBASE, and hand searches of article bibliographies to identify placebo-controlled randomized trials of opiate analgesia reporting changes in the history, physical examination findings, or diagnostic errors (those resulting in "management errors," defined as the performance of unnecessary surgery or failure to perform necessary surgery in a timely fashion).

Two authors independently reviewed each study, abstracted data, and classified study quality. A third reviewer independently resolved discrepancies.

Studies both in adults (9 trials) and in children (3 trials) showed trends toward increased risks of altered findings on the abdominal examination due to opiate administration, with risk ratios for changes in the examination of 1.51 (95% confidence interval [CI], 0.85 to 2.69) and 2.11 (95% CI, 0.60 to 7.35), respectively. When the analysis was restricted to the 8 adult and pediatric trials that reported significantly greater analgesia for patients who received opiates compared with those who received placebo, the risk of physical examination changes became significant (risk ratio, 2.13; 95% CI, 1.14 to 3.98). These trials exhibited significant heterogeneity (I2 = 68.6%; P = .002), and only 2 trials distinguished clinically significant changes such as loss of peritoneal signs from all other changes; consequently, we analyzed risk of management errors as a marker for important changes in the physical examination. Opiate administration had no significant association with management errors (+0.3% absolute increase; 95% CI, -4.1% to +4.7%). The 3 pediatric trials showed a nonsignificant absolute decrease in management errors (-0.8%; 95% CI, -8.6% to +6.9%). Across adult and pediatric trials with adequate analgesia, opiate administration was associated with a nonsignificant absolute decrease in the risk of management errors (-0.2%; 95% CI, -4.0% to +3.6%).

Opiate administration may alter the physical examination findings, but these changes result in no significant increase in management errors. The existing literature does not rule out a small increase in errors, but this error rate reflects a conservative definition in which surgeries labeled as either delayed or unnecessary may have met appropriate standards of care. In published research reports, no patient experienced major morbidity or mortality attributable to opiate administration.