anaphylaxis

Question 1

definition of anaphylaxis

Answer 1

acute life threatening multisystem syndrome caused by sudden release of mast cell and basophil derived mediators into the circulation

Question 2

classifications of anaphylaxis

Answer 2

immunogenic - IgE mediated or immune complex/complement mediated

non-immunogenic - mast cell/basophil degranulation w/o involvement of Ab (Eg reactions caused by vancomycin, codeine, ACEi)

Question 3

pathology of anaphylaxis

Answer 3

inflam mediators (histamine, tryptase, chymase, histamine-releasing factor, PAF, prostaglandins and lencotrienes) cause bronchospasm, increased capillary permeability and reduced vascular tone = tissue oedema

Question 4

common allergens for anaphylaxis

Answer 4

drugs eg penicillin

radiological contrast agents

latex

insect stings

egg

peanuts

shellfish and fish

repeated admin of blood products in people with IgA deficiency as a result of formation of IgA Ab

can be induced by exercise

Question 5

epidemiology of anaphylaxis

Answer 5

relatively common

in 1 in 5000 exposures to parenteral penicillin or cephalosporins

1-2% pts receiving IV radiocontrast experience hypersensitivity reaction - often minor

0.5-1% of children suffer peanut allergy

1 in 700 have selective IgA deficiency

Question 6

symptoms of anaphylaxis

Answer 6

acute onset of symptoms on exposure to allergens

wheeze, SOB, sensation of choking

swelling of lips and face

pruritus, rash

severity of previous reactions doesnt predict the severity of future

may have history of other allergic hypersensitivity disorders -asthma, allergic rhinits

biphasic reactions occur 1-72hr after the 1st reaction in up to 20% pts

Question 7

signs of anaphylaxis

Answer 7

tachypnoea, wheeze, cyanosis

swollen upper airways and eyes, rhinitis, conjunctival injection

urticarial rash (erythematous wheals)

hypotension, tachycardia

Question 8

investigations of anaphylaxis

Question 9

management for anaphylaxis

Answer 9

stop any suspected drugs

resus - ABC

secure airway - give 100% oxygen, intubation and transfer to ITU may be necessary so anaesthetist must be informed early

adrenaline IM (0.5mL of 1:1000) - repeated every 10mins according to response of pulse and BP

antihistamine IV - 10mg chlorpheniramine

steroids IV - 100mg hydrocortisone

IV crystalloid or colloid to maintain BP, if hypotensive lie flat with head tilted down

treat bronchospasm - with salbutamol +- ipratropium inhaler. Aminophylline IV infusion may be required

advive - educate on use of adrenaline pen for IM. Medicalert bracelet. Make note in notes and drug charts. referral to an allergy specialist for identification of the culprit allergen and education in allergen avoidance

Question 10

complications in analphylaxis

Answer 10

resp failure

shock

death

Question 11

prognosis

Answer 11

good if prompt treatment