TITLE: IS A HISTORY OF OPIOID ALLERGY A USEFUL PREDICTOR OF OPIOID-INDUCED ANAPHYLAXIS?

AUTHORS: Jonathan Moss, MD, PhD, J. Foss, MD, M. Drum, PhD
AFFILIATION: University of Chicago, Chicago, IL.

INTRODUCTION: Life-threatening allergic or pseudoallergic reactions occur in 1 in 3,500 anesthetics. Approximately 2% of these events are due to opioids (1). Despite the rarity of documented anaphylaxis to opioids (1:200,000 cases), our impression has been that many patients evaluated in the preoperative clinic report having had a life-threatening allergy to drugs of this class. To ascertain whether a history of allergy to opioids is a reliable predictor of opioid-induced anaphylaxis, we compared our observations in patients presenting for preopera- tive assessment at a large teaching hospital with the rate of opioid-induced anaphylaxis published in the literature.
METHODS: Following approval by the IRB, the comprehensive preoperative evaluations of 12,621 sequential patients scheduled for elective surgery (15 Dec 1996 - 30 June 1999) were reviewed retrospectively. Each patient was specifically questioned about drug allergies. The presence or absence of allergies to opioids and the severity of these reactions were tabulated. These data were then compared with the published literature and a chi-square goodness of fit test with one degree of freedom for actual and hypothetical observed number of cases was calculated.
RESULTS: Of the 12,621 patients whose history of allergy was ascertained, 887 (7%) reported a history of an adverse reactions to opioids. From this cohort, 75 serious reactions to opioids were reported by patients in their histories, 22 of which were self- identified as "anaphylactic." These 22 reported histories of anaphylactic reactions (1 male and 21 females) represented 0.17% of the total 12,621 patients analyzed. The 95% C.I. for the number of opioid reactions is (12,32). This reported incidence of opiate anaphylaxis was significantly higher than the literature- derived expected percentage of reactions when compared in a chi-square model (p<0.000001).
CONCLUSION: A history of anaphylaxis to opioids obtained during preoperative assessment is not a reliable predictor of opioid-induced anaphylaxis because it overstates the likelihood of actually having had such a reaction more than 100-fold. Although any history of allergy should be seriously considered, self-reported incidence of anaphylaxis to opioids is significantly overstated and may cause physicians and patients to omit appropriate pain medication in the perioperative period.
REFERENCES:

1. Ann Fr Anesth Reanim 1996; 15:1211-1218.