Memorandum by Dr Richard Pumphrey
FATAL ANAPHYLAXIS
(FATAL ACUTE
ALLERGIC REACTIONS)
31 JANUARY 2007
The UK fatal anaphylaxis register has attempted
to record every fatal acute allergic reaction in the UK since
1992 and is the most accurate source available in the world for
statistics on fatal anaphylaxis. From 1992-98, around half the
UK fatalities were to medical interventions such as drugs used
in anaesthesia or injections for special X-ray investigations.
The remainder comprised fatal reactions to stings and to foods
together with rare causes such as anaphylactic reactions to latex,
hair dye, parasitic worms (hydatid cysts) and so on. Fatal anaphylaxis
to food in the seven years 1999-2006 has followed a very similar
pattern to the previous seven years: the data for stings and drugs
is incomplete and further study is needed; from the data in the
register so far it seems probable that the pattern will also be
similar to the previous seven years.
A third of the population suffers from allergy
but mostly their reactions are not dangerous. At least one person
in a thousand has one or more serious reactions but fewer than
one in a million will die from their allergy; of those who die,
over half did not have any previous serious reaction, which makes
it very hard to know who should take specific precautions, such
as carrying an adrenaline pen for emergency self-treatment. Of
the last 48 fatal reactions to foods, adrenaline pens had been
provided to 19 (40 per cent) including 11/13 with previous severe
reactions. Despite this, the rate of food allergy deaths is somewhat
higher than it was in the previous seven years when fewer had
pens. The reason the pens failed was in some cases obvious (pen
time-expired, pen used too late in the reaction, pen not carried
that day). Some of the pens may have failed because the patient
was too fat for the pen to give the necessary intramuscular injection.
Others used the pen correctly, were thin, had the correct dose
and still died. One 16-year-old girl took the risk of eating a
chocolate labelled "may contain nuts" because she had
her pen with her. She used the pen immediately she saw nuts in
the chocolate but nevertheless died from her reaction. Clearly
pens cannot be relied upon to save someone with a food allergy
reaction and patients must continue to take great care to avoid
their trigger food even when they have a pen.
It seems that the mechanism by which anaphylactic
reactions are fatal depends on the patient's state of health.
Those with asthma will usually die from an acute attack of asthma
brought on by the allergic reaction; for such people, optimal
daily control of their asthma will protect them from a fatal allergic
reaction. Those with heart disease are more likely to die from
shock; medical treatment for raised blood pressure makes allergic
reactions more severe. Rarely, inflammation in other sites such
as around the brain will be affected during an anaphylactic reaction,
leading to different mechanisms of fatality. In some cases a very
severe allergic reaction can kill an otherwise fit and healthy
person by redistribution of the fluids in the body leading to
shock; in such cases an upright posture may make an otherwise
survivable reaction fatal.
These and other observations from the fatal
anaphylaxis register have provided the evidence for logical treatment
guidelines for anaphylaxis. The details of new cases on the register
still provide new insights and it is essential this recording
is continued in the future.
15 January 2007
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