General Anesthetic Agents and Neuromuscular Blocking Agents

The main agents used for induction of anesthesia are hypnotics (thiopentone, propofol, and etomidate), opioids (fentanyl), neuroleptics, and benzodiazepines (Thong and Yeow-Chan 2004). The majority of intraoperative anaphylactic reactions are caused by the neu-romuscular blocking agents commonly used to induce paralysis to facilitate endotracheal intubation or to optimize surgical exposure (Birnbaum et al. 1994).

The use of intradermal skin tests for the diagnosis of IgE-mediated anaphylaxis to agents during general anesthesia is well established (Moscicki et al. 1990; Rose and Fisher 2001). Some authors have reported the usefulness of skin prick tests (Fisher and Bowey 1997). The advantage of skin prick tests is that by doing intradermal testing, potentially dangerous reactions can be prevented. However, there are no data available on the safety of subsequent anesthesia based on the results of prick testing alone, and reliability over time has not been assessed.

Skin testing is useful because alternative muscular relaxants that produce a negative skin test reaction may be used safely if skin tests show that a neuromuscular agent could cause problems (Fisher 1994). However, the true-negative predictive value for these skin tests is unknown, and false-negative skin reactions have been reported (Fisher et al. 1999).

Patients with previous reactions to an agent used during general anesthesia should have intradermal testing done for both putative agents and an alternative neuromuscular block. Low-risk agents such as pancur-onium should be given preference over high-risk agents such as succinylcholine, if both yield negative skin tests. However, a negative skin test result does not eliminate the possibility of developing a reaction to one of these agents. Pretreatment for neuromuscular blocking agent allergy has been found to be ineffective.

Drug-specific IgE can be demonstrated by radioim-munoassay and radioallergosorbent testing (RAST). However, there is only one commercially available test for muscular relaxants (suxamethonium; Pharmacia, Uppsala, Sweden).

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