Background: Several studies have identified neuromuscular blocking agents as the most common cause of anaphylaxis during general anesthesia. The reported frequencies vary considerably between countries. There are few reports from Spain, probably due to the low prevalence of reactions.

Methods: For 5 years (1998-2002), all the patients who presented perioperative anaphylactic-type reactions, were studied in 2 Spanish allergy departments (Santiago Apostol, Vitoria-Gasteiz and San Pedro, Logroño). The diagnostic protocol consisted of a case history (age, gender, number of previous interventions, characteristics of the reaction, reaction phase, previously administered drugs), serum tryptase measurements, skin tests, and specific immunoassays (immunoglobulin [Ig] E determination against latex, penicillin, and Echinococcus).

Results: Forty-eight patients were studied, with ages ranging from 7 to 86 years. The ratio of women to men was 3:2. An IgE-mediated mechanism was confirmed in 27/48 patients (56%). The etiological agents were antibiotics in 12 cases (44%) (10 betalactams, 1 vancomycin, and 1 ciprofloxacin), muscle relaxants in 10 cases (37%), pyrazolones in 2 cases, latex in 2 cases, and Echinococcus in 1 case.

Conclusions: Fifty-six percent of the perianesthetic reactions studied were IgE-mediated. Antibiotics and neuromuscular blocking agents were the most frequent causal agents, as verified by skin tests, and specific IgE and/or challenge tests. It is important to keep appropriate documentation on any of the drugs used during surgery, since our results show that those drugs involved in the reaction as the etiological agent, such as antibiotics and nonsteroidal anti-inflammatory agents, can be used again outside the context of surgery.

Key words: Anesthesia. Hypersensitivity. Anaphylaxis. Muscle relaxants. Antibiotics. Perianesthetic reactions.