Below is an outline from a talk given to the Department of Anesthesia at UCSF. A case presentation was given on a patient who had two life-threatening episodes of anaphylaxis after opthalmologic surgery. The second episode might have been prevented if the proper workup had been performed.
Although specific skin testing instructions are given below, the following is not intended as a guide for diagnosing and treating surgical anaphylaxis.
▪ Females in regards to muscle relaxant allergy. There may be sensitization to quaternary ammonium compounds common in cosmetics.
▪ Atopic patients (?). There is a higher (in some studies) incidence of atopics in reactors.
As mentioned above, skin testing may be helpful in certain cases. Immediate-type skin tests are the most rapid and reliable method for demostrating the presense of IgE-antibody. They are best used to evaluate allergy to drugs that are high-molecular weight proteins, i.e., complete antigens (chymopapain, insulin, streptokinase, heterologous serum). Skin testing for low-molecular weight drugs, or incomplete antigens (sulfas, thiobarbiturates, muscle relaxants) are less reliable because we don’t know the metabolites that end up forming the haptens. These haptens are essential in promoting the immune response.
Exception: penicillin and related drugs, since the metabolites are well characterized. So, skin testing can be very informative.
Considerations when doing skin testing:
Sensitivity and Specificity of skin testing for most drugs is not known because of lack of challenge data (mainly due to ethical considerations – near deaths have resulted from challenges). For penicillin and hymenoptera venom, rechallenge of skin test positive patients results in 50% reaction rate. Reaction rate for skin test negative patients is very low for PCN and hymenoptera – but these antigens are well characterized.
Because of the paucity of studies on this subject, there is only relatively reliable evidence of validity of testing to thiopental, succinylcholine, and latex. These three have had an IgE mechanism reasonably confirmed by RAST testing. However, it is reasonable to test to other drugs.
PREMEDICATION IS NOT A SUBSTITUTE FOR AVOIDANCE – IT WILL NOT RELIABLY PREVENT IgE-MEDIATED ANAPHYLAXIS
Lastly, it’s important to note that you can you can confirm a anaphylactic(-oid) reaction with serum tryptase within 4 hours of the event. Tryptase is a protease contained in mast cells, and is a very good marker for mast cell activity. Histamine levels may also be helpful, but it must be drawn immediately after the event (histamine has a much shorter half-life than tryptase).
Neil Gershman, M.D.
May 13, 1994
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