Thank you for your inquiry.
As you have stated, true IgE-mediated reactions to amide local anesthetics are extremely rare. Therefore, I feel that, in actuality, the risk of a true anaphylactic event due to testing/challenge with mepivacaine in your patient is extremely low. Personally, I have therefore proceeded with all testing/challenge procedures to local anesthetics in the office and have never considered doing one in the hospital. However, the decision as to the location is very highly dependent upon your own personal comfort in doing the procedure as well as your assessment of the likelihood that this patient may have another vocal cord dysfunction reaction. In actuality, I think doing this procedure in-hospital may make it more likely that she would experience a somatoform reaction to the procedure by elevating her sense of danger involved. So, I would think that it might be an advantage for you, if you feel comfortable in performing it in the office, to do it there for at least that reason.
The other issue of course is the lack of being able to skin test her because of your inability to stop antihistamines. In this instance, the skin testing procedure actually has two purposes. One is of course to detect whether there is IgE-mediated sensitization to the drug. The second, however, is extremely important in your case. It is to give the patient some reassurance that the challenge would be safe by demonstrating to her that the test was negative. In our experience, this helps reassure the patient that they can receive the challenge drug safely.
Thus, I think it would be ideal for you to be able to skin test her. One method that you might consider is to suppress her hives with a brief course of prednisone (perhaps 20 to 30 mg a day for three to four days). The prednisone will not suppress her skin test reactivity and she should therefore respond positively to histamine. You can then restart the antihistamine after the tests.
In summary, I cannot give you a definitive answer as to where you should perform the testing/challenge procedure because, as noted, it depends on your own comfort level with performing it. However, personally, I would make every effort to do it in your office for the reasons noted above. I would also consider trying to test her by controlling her hives temporarily with prednisone.
Thank you again for your inquiry and we hope this response is helpful to you.
Phil Lieberman, M.D.