Memorandum by Dr Nigel J N Harper, Royal
College of Anaesthetists
ANAPHYLACTIC REACTIONS OCCURING DURING ANAESTHESIA
BACKGROUND
Severe anaesthetic anaphylaxis is relatively
uncommon. The incidence in the UK is not known accurately. The
true incidence probably lies between 1:10,000 and 1:20,000 anaesthetics.
Approximately 5 million anaesthetics are administered
per annum in the UK for a wide variety of healthcare procedures
including major surgery, childbirth and radiological imaging.
Many individuals require repeated anaesthetics.
Modern anaesthesia takes advantage of the specific
attributes of several different drugs, each administered for a
specific purpose. Thus, a typical anaesthetic may comprise an
induction drug, a maintenance drug, a potent analgesic, a muscle
relaxant drug, an anti-emetic drug, reversal agents and synthetic
intravenous fluids. In addition, the surgical procedure may necessitate
the administration of antibiotics, radiological contrast agents
and drugs which manipulate blood coagulation. All these drugs
are administered in large doses, directly into the circulation
and are capable of eliciting life-threatening anaphylaxis. The
anaesthetic environment also includes latex and skin-antiseptics
which may precipitate anaphylaxis during anaesthesia. The severity
of anaesthetic anaphylaxis varies from the appearance of a rash,
a moderate fall in blood pressure or the onset of treatable wheeze,
to catastrophic hypotension, intractable bronchospasm, and cardiac
arrest.
The majority of these reactions are not fatal
but there are approximately 5-10 deaths per annum. A considerably
larger number of patients suffer with a range of permanent disabilities
as a result of cerebral or cardiac hypoxia during the anaphylactic
reaction, for example; poor memory, loss of balance, poor spatial
awareness and permanent cardiac damage.
The incidence of anaesthetic anaphylaxis appears
to be increasing in line with the general increase in allergy.
Previous exposure to the culprit anaesthetic drug is not a pre-requisite
for anaesthetic anaphylaxis. Components of the molecular structure
of many drugs given during anaesthesia are found in everyday life,
for example in detergents, cosmetics or cough medicines. There
is considerable cross-sensitivity between some anaesthetic drugs,
especially muscle relaxant drugs. Following a relatively minor
anaphylactic reaction, a second exposure may be life-threatening.
Although the incidence of proven anaesthetic
anaphylaxis is approximately only 1:10-20,000, many more patients
require investigation because the clinical signs of anaesthetic
anaphylaxis can be imitated by more common and benign events.
For example, a significant fall in blood pressure may be the result
of the interaction between the hypotensive effect of the anaesthetic
induction agent and long-term anti-hypertensive medication. Severe
wheeze during anaesthesia may be the consequence of the mechanical
effects of tracheal intubation in a patient with irritable airways
through asthma or heavy smoking. Most anaesthetists would see
these events several times a year. The consequences of not investigating
these phenomena may be serious. If these clinical events were,
indeed, caused by allergic anaphylaxis, it is likely that future
exposure to the anaesthetic drug, or an anaesthetic drug with
a similar molecular structure, would endanger the patient's life.
A recent case in law emphasised the responsibility of the anaesthetist
to refer this group of patients for expert investigation and diagnosis
(Eastwood v Wright 2005).
ISSUES
It is important that every case of suspected
anaesthetic anaphylaxis is investigated by an expert team to:
(a) Identify the causative agent so that
it can be avoided in future.
(b) Establish whether there is cross-sensitivity
with other drugs.
(c) Enable recommendations to be made concerning
future anaesthesia on an individual patient basis.
(d) Gather data concerning the patterns of
allergy to individual drugs (a worthwhile report to the Medicines
Control Agency can be made only when the causative agent has been
established).
(e) Establish whether certain factors predispose
to anaesthetic anaphylaxis.
(f) Identify optimal resuscitation management
protocols.
The expertise required for investigation anaesthetic
anaphylaxis is required in a relatively small number of centres
in the UK, but that expertise should be readily available to all
patients. A number of immunologists, allergists and anaesthetists
have expertise in the investigation of anaesthetic anaphylaxis.
A high proportion of patients are required to travel long distances
to their nearest specialist clinic, and waiting times are long.
It is not unusual for a patient to have to travel 30 miles. Many
cases of anaesthetic anaphylaxis are not referred for immediate
investigation.
Because of the complexities of modern anaesthesia
it is necessary for patients to be seen by an anaesthetist with
a special interest in anaphylaxis at the same time as seeing an
immunologist or allergist. The author started the first combined
anaesthesia and immunology clinic in the UK in Manchester in 1997
but expansion of bi-specialty clinics has been relatively slow
and, currently, there are only 3 similar combined clinics. There
are approximately six additional uni-specialty clinics in which
patients are seen only by an immunologist or allergist. Nevertheless,
progress has been made and The Association of Anaesthetists of
Great Britain and Ireland (AAGBI) has set up a working group to
update its 2003 publication "Suspected Anaphylactic reactions
Associated with Anaesthesia" in collaboration with the British
Society of Allergy and Clinical Immunology and The Royal College
of Anaesthetists. These bodies will shortly announce a national
database for anaesthetic anaphylaxis, with on-line reporting.
The Royal College of Anaesthetists runs an educational programme
on anaesthetic anaphylaxis. Focused resources are needed to expand
the number of bi-specialty clinics for the investigation of anaesthetic
anaphylaxis.
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