Investigation of anaphylaxis during general anaesthesia requires an accurate record of events including information on timing of drug administration provided by the anaesthetist, as well as timed acute tryptase measurements. Referrals should be made to a centre with the experience and ability to investigate reactions to a range of drug classes/substances including neuromuscular blocking agents (NMBAs) intravenous (i.v.) anaesthetics, antibiotics, opioid analgesics, non-steroidal anti-inflammatory drugs (NSAIDs), local anaesthetics, colloids, latex and other agents. About a third of cases are due to allergy to NMBAs. Therefore, investigation should be carried out in a dedicated drug allergy clinic to allow seamless investigation of all suspected drug classes as a single day-case. This will often require skin prick tests, intra-dermal testing and/or drug challenge. Investigation must cover the agents administered, but should also include most other commonly used NMBAs and i.v. anaesthetics. The outcome should be to identify the cause and a range of drugs/agents likely to be safe for future use. The allergist is responsible for a detailed report to the referring anaesthetist and to the patient’s GP as well as the surgeon/obstetrician. A shorter report should be provided to the patient, adding an allergy alert to the case notes and providing an application form for an alert-bracelet indicating the wording to be inscribed. The MHRA should be notified. Investigation of anaphylaxis during general anaesthesia should be focussed in major allergy centres with a high throughput of cases and with experience and ability as described above.We suggest this focus since there is a distinct lack of validated data for testing, thus requiring experience in interpreting tests and because of the serious consequences of diagnostic error.
- This document describes the investigation of suspected anaphylaxis during anaesthesia focussing on the allergist’s role.
- Referral should be made to a major allergy centre with expertise in drug allergy and high throughput of anaesthetic anaphylaxis because of the need for experience in interpreting tests and the serious consequences of diagnostic error. The anaesthetist is responsible for referral.
- The centre should be able to investigate all potential causes. This involves a range of drug classes/substances including neuromuscular blocking agents (NMBAs), intravenous (i.v.) anaesthetics, antibiotics, opioid analgesics, non-steroidal anti-inflammatory drugs (NSAIDs), local anaesthetics (LAs), colloids, latex, skin antiseptics and other agents used during general anaesthesia.
- A lead anaesthetist should be identified in each major hospital for clinical governance and notified of each case of anaphylaxis. The responsibility would be to provide initial guidance on blood sampling for serum tryptase and to assist in the process of referral to a specialist centre for further investigation.
- Investigation should be in a dedicated drug allergy clinic so that in most cases a seamless approach to investigation can be undertaken to allow all suspected drug classes to be considered and investigation completed in one day.
- Before the patient is seen, it is essential to obtain the anaesthetic record, drug charts and anaesthetist’s notes as well as results of acute tryptase measurements. This provides a shortlist of likely cause(s) and guides subsequent investigation.
- Serum tryptase is the only helpful blood test required at the time of the reaction to confirm anaphylaxis. Two timed blood samples (5 mL clotted) should be taken: one immediately after resuscitation and one at 1–2 h. If this is missed, a timed sample may be taken up to 6 h, although this may be less helpful. A baseline sample should also be taken at 24 h or later by the investigating allergist.
- Stepwise investigation is necessary and depends on the likely cause, but a suspected IgE-mediated reaction (e.g. NMBAs, i.v. anaesthetics, antibiotics, latex) requires skin testing and in some cases drug challenge.
- For other causes, e.g. a non-IgE-mediated reaction to NSAIDs or opioids, there are no useful skin/blood tests and a clinical diagnosis is reached either by excluding other potential causes or by confirmation with an oral challenge.
- Because of lack of validated data for most drugs, clinical judgment is essential in the interpretation of the investigations and any conclusions reached must be compatible with the clinical history. Hence, guidelines need to be adapted for individual patients.
- When it is clinically likely that an agent given at induction has caused an allergic reaction but the cause has not been identified on the initial visit, the skin tests should be repeated at a later date.
- The aim of the investigation should be to identify the cause of anaphylaxis and to recommend a range of drugs/agents likely to be safe for future use.
- The allergist is responsible for a detailed report to the referring doctor and GP, and a shorter report and provision of ‘medical alert’ wording to the patient.
- An allergy alert and appropriate coding should be added to the patient’s hospital and GP records. This is the responsibility of the investigating allergist, referring anaesthetist and GP after the report has been received.
This guideline focuses on investigation of anaphylaxis during general anaesthesia to determine aetiology. However, it is important for the investigating physician to be aware that some of the clinical features of anaphylaxis may be mimicked by other complications of anaesthesia including difficulty in tracheal intubation, equipment failure or covert haemorrhage. In some instances, adverse reactions can be related to the underlying medical condition, e.g. septicaemia, or can be due to the expected pharmacological actions of drugs administered, e.g. hypotension. Investigation can be challenging, as the patient is exposed to many co-administered drugs and agents, any of which may be implicated although NMBAs are a major cause. Antibiotic, NSAID and latex sensitivity are included but detailed investigation is described in separate guidelines. There are no reported cases of allergy to inhalational anaesthetics.
This guidance for the investigation of suspected anaphylaxis during general anaesthesia has been prepared by the Standards of Care Committee of the British Society for Allergy and Clinical Immunology (BSACI). The guideline is based on evidence as well as on expert opinion and is for use by specialists practising in drug allergy. Evidence for the recommendations was obtained from electronic literature searches using the primary key words – general anaesthesia, general anaesthetic, neuromuscular blocking drugs/agents, antibiotics, plasma substitute, patent blue dye, latex and local anaesthetic, and combining these search terms with allergy, anaphylaxis or skin tests. Each article was reviewed for suitability for inclusion in the guideline. Where evidence was lacking, consensus on recommendations was reached in consultation with experts in allergy, immunology and anaesthesia. The recommendations in the executive summary were not evidence graded in this guideline; most are based on expert consensus and best-practice because validation of tests to general anaesthesia drugs is not practical as challenge with anaesthetic drugs is not possible. During the development of these guidelines, all BSACI members were included in the consultation process using a web-based system. Their comments and suggestions were considered by the Standards of Care Committee.
Download the full article in pdf format here