In patients with undifferentiated abdominal pain, under-analgesia has been explained as an effort to avoid masking diagnostic physical findings. Although early pain relief has been avoided in this patient population, physicians are often accused of providing suboptimal analgesia to many patients with pain. Thomas and associates used a randomized, double-blind, clinical trial to evaluate the effect of morphine sulfate on diagnostic accuracy and physical examination in patients with undifferentiated abdominal pain.

Adults presenting to the emergency department who were not pregnant, had severe abdominal pain for less than 72 hours, did not have clear indications for early opioid intervention, were not hypotensive, did not have a life-threatening condition, and were not allergic to morphine sulfate were eligible to participate. Of the 74 patients who were randomized, 38 received titrated doses of morphine sulfate and 36 received a saline placebo. Before receiving the study medication, pain level was assessed using a visual analog scale, and a physician examiner completed an initial evaluation form on each patient that included a narrow differential diagnosis (maximum of two entities) and an assessment of diagnostic confidence.

The dose and frequency of treatment medication was determined by the treating physician, with a maximum of 15 mg of morphine sulfate given over the 60-minute study period. After the study period, repeat pain and physician assessments were performed, including a question asking if the study medication had any effect on the quality of the examination. After the conclusion of the study, patients received further care as determined by their treating physicians. All patients were followed during the remainder of their emergency department stays, and hospital records were reviewed if patients were admitted. Telephone follow-up of all patients also was performed.

Patients in the morphine sulfate group were no more likely than control patients to have a change in the distribution or severity of abdominal tenderness, or the presence or severity of specifically assessed signs. The likelihood of a correct diagnosis between the two groups also was similar. Overall diagnostic accuracy was the same in both groups.

The authors conclude that there is no negative effect of early morphine sulfate administration in patients with undifferentiated abdominal pain. The correct diagnosis was still made in the same proportion of cases, and there was no instance in which morphine sulfate administration obscured the correct diagnosis. Because these findings are similar to those noted in other studies, there remains little reason not to relieve the pain of patients presenting with undifferentiated abdominal pain.