Acute Abdominal Pain: Manage Without Delay

Accuracy of Diagnosis After Analgesic Administration

Abdominal pain is one of the most common symptoms in children^[1] and is the leading reason for people of all ages to seek care in the ED setting.^[2] It was standard practice for many years for clinicians in the ED to withhold pain medication during the diagnostic process in patients with acute, severe, undifferentiated abdominal pain, based on a recommendation proposed by Sir Zachary Cope in a 1957 publication of a monograph on the subject.^[3] The rationale for his recommendation was that analgesia would impair diagnostic accuracy.^[3,4]

Several studies conducted since then challenge Cope's recommendation,^[5,6] but the practice has been slow to change, and it was common as late as the 1990s to find ongoing strong support for the practice.^[4,6] Although less common today, the practice persists in many hospitals throughout the world. For example, a Canadian study published in 2008 that reviewed the medical records of 582 children presenting with nontraumatic abdominal pain in a pediatric ED found that only 9% of children received analgesia and 77% of the analgesics given were below the recommended dose for the child.^[1]

One of the first studies to challenge Cope's recommendation used a prospective double-blind design to evaluate nearly 300 patients aged 16 years or older who were given sublingual buprenorphine (an opioid) or saline (placebo) after admission to the ED with acute abdominal pain.^[7] The researchers concluded that the buprenorphine and placebo were equally effective in relieving pain, physical changes occurred in an inconsistent manner, and the changes did not alter the diagnosis. In fact, the correct diagnosis was clarified in 4 patients who received the opioid and was obscured in none.

Another early study administered intramuscular (IM) opioid or IM saline to 100 consecutive patients older than 16 years with clinically significant abdominal pain admitted to an ED in England.^[8] Incorrect diagnoses and management decisions were made in 2 patients who received opioid analgesia and in 9 patients who received saline. The researchers concluded that early administration of opioid analgesia "greatly" reduced pain, did not interfere with diagnosis, and may have actually facilitated diagnosis. Others have suggested that a more accurate diagnosis may be possible when the patient is comfortable during examination.^[9,10]

Later research in adults has shown similar results. A prospective, randomized, placebo-controlled study of 74 adults with abdominal pain found no instance of masking physical findings after intravenous (IV) morphine administration.^[11] These findings support the practice of early provision of analgesia to patients with undifferentiated abdominal pain.^[11]

The pediatric literature also supports the administration of analgesia during the diagnostic process. A randomized, double-blind trial in an ED in a children's hospital administered IV morphine or an equal volume of IV saline to 60 children, aged 5-18 years, with moderate-to-severe nontraumatic abdominal pain.^[12] An ED physician and a consulting surgeon independently recorded their physical examination findings and the diagnosis of each patient before and after the morphine or saline. Pain was reduced from a median pain rating of 9 to 5 on a scale of 0-10 in those who received morphine and from 8 to 7 in those who received placebo. There was no significant difference in diagnostic accuracy between the groups. Other important findings were that the children requiring laparotomy were identified and no significant complications were found in those who received morphine. Another larger, multicenter, randomized, controlled study also demonstrated reductions in pain intensities and no difference in diagnostic accuracy in 108 children with acute abdominal pain who received IV morphine or placebo early in the diagnostic process.^[13]

Systematic reviews of the literature are the highest form of evidence. Reviews over the years,^[2,5,14] including a 2011 Cochrane review of 8 eligible studies,^[15] have demonstrated that opioid administration during diagnosis of acute abdominal pain does not increase the risk for diagnostic error or the risk for error in making decisions about treatment.

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