Page 504 - Medicine and Surgery

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500 Chapter 12: Haematology and clinical immunology

Aetiology/pathophysiology an episode of anaphylaxis with hypotension and/or
AnaphylaxisisatypeIhypersensitivityreaction(seepage bronchospasm patients should carry at least a self-
498). On exposure to the allergen pre-sensitised mast administrationadrenalinedeviceandinmanycasesafull
cellssecrete histamine, leukotrienes, prostaglandins and anapylaxis kit including chlorpheniramine and steroids.
other mediators which increase bronchial smooth mus-
cle tone, cause vasodilation and increase capillary per- Hereditary angioedema
meability. Common allergens include foods (such as
peanuts,eggs,shellfishandmanyothers),antibioticsand Definition
bee/wasp stings. Inherited complement disorder resulting in episodic an-
gioedema .
Clinical features
Patients develop rapid onset of urticaria, erythema, pru- Age
ritus and/or localised tissue swelling due to increased Hereditary but may present in adulthood.
vascular permeability (angioedema). Bronchoconstric-
tion and upper airway oedema may lead to severe
Aetiology
airway obstruction. Patients may also develop vomit-
Inherited in an autosomal dominant pattern. Acute
ing and/or diarrhoea. On examination there may be
episodes may be triggered by trauma, exercise, menses
tachypnoea, tachycardia, hypotension, wheeze and stri-
or emotional stress.
dor. In severe cases vasodilation leads to severe hypoten-
sion, cardiovascular collapse and, if untreated, may be
Pathophysiology
fatal.
Associated with C1 esterase inhibitor deficiency, which
may be quantitative or qualitative. C1 esterase is a non
Management
competitive protease inhibitor that inactivates C1. In ab-
Anaphylaxis is an acute medical emergency. Patients re-
sence or low levels there is uncontrolled C1 activity with
quire a rapid assessment of their airway, breathing and
consumptionofC4andC2,C2afragmentscauseoedema
circulation:
of the epiglottis and extremities due to release of vasoac-
Airway/breathing: Patients with airway compromise

tive compounds (see Fig. 12.16).
including significant stridor should be treated with
intramuscular adrenaline. Intubation may be diffi-
Clinical features
cult due to oedema and even with airway compro-
Patientscomplainofrecurrentepisodesofswellinginthe
mise bag & mask ventilation may be effective whilst
awaiting response to adrenaline. Surgical airway by arms, legs, lips, eyes, tongue or throat. Intestinal swelling
cricothyroidotomy may be necessary. Wheezing may canbesevereandresultinabdominalpain,vomiting,and
be treated with nebulised β agonists, wheeze and mild dehydration. Oedema of the upper airway may result in
stridor can treated by nebulised adrenaline. airway obstruction.
Circulation: If there is hypotension patients require

intramuscular adrenaline. Large volume fluid resus- Investigations
citation with crystalloids may also be required in re- C1 esterase levels are low.
fractory hypotension. Intravenous adrenaline is not
used unless cardiovascular collapse and cardiac arrest Management
have occurred. Stanozolol and danazol may be used in an at-
H 1 antihistamines(e.g.chlorpheniramine)andcorticos- tempt to raise serum levels of C1 esterase inhibitor
teroids are also given intravenously to all patients with for long term treatment but their use in females
anaphylaxis. leads to menstrual irregularities, fluid retention and
Subsequent events may be prevented by allergen androgenicity.
avoidance, this may require referral to an allergy spe- Acute attacks may require treatment with fresh frozen
cialist for allergen testing (see page 467). Following plasma or purified inhibitor.