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We were concerned to find that Start and Cross's otherwise comprehensive Best Practice artcle on the investigation of medical accidents1 failed to discuss the investigation of possible anaphylactic reactions. Fatal anaphylaxis can occur during approximately 1/100 000 general anaesthesia administrations. Anaphylactoid reactions, where IgE mediated allergy is not involved in reactions to—for example, contrast media, account for a further number of deaths. In some instances, an anaphylactic reaction might be obvious and postmortem examination may simply confirm the cause of death. In many other instances—for example, reactions to anaesthetic agents, antibiotics, or latex that occur during unconsciousness, the cause may be much less clear. A review of the patient's history should be carried out, but will be unrewarding in most cases, which occur de novo. Repeated procedures are a well recognised risk factor and account for the high risk of latex anaphylaxis in children with spina bifida.2
Macroscopic examination might reveal skin and airways angioedema, lung hyperinflation, or the consequences of hypovolaemia. Blood may be taken in the first two to three days after death to confirm raised mast cell tryptase,3 which is released during anaphylactic or anaphylactoid reactions. Caution is required in interpreting mast cell tryptase concentrations because they can be increased after exposure to opiates. IgE against specific allergens can be sought in postmortem blood samples.4 The absence of specific IgE cannot rule out allergy as the cause of death, but confirmation of sensitivity to specific agents may add weight to a diagnosis of anaphylaxis. Unfortunately, specific IgE testing is not available to many anaesthetic or antibiotic drugs. We advise collecting samples of clotted and EDTA anticoagulated blood as soon as possible after death and guidance from an expert laboratory.
Is postmortem testing for anaphylaxis important? We believe that collecting important data on drugs and other interventions requires such examinations to be carried out. For example, collection of data on a series of mishaps related to desensitisation led to improved guidelines for this procedure and a reduction in mortality. We are unaware of litigation arising from alleged anaphylaxis, but again in this situation, assiduous collection of data may form an important part of a legal defence.
The authors reply
We thank Drs Helbert and Robinson for pointing out this area that we did not cover in our review,1 and the useful information contained in their letter. It is obviously impossible to cover every aspect of the investigation of deaths following anaesthetics but anaphylaxis, although rare, is important and we will include it in future versions of the ACP Best Practice Guidelines.