Anaphylaxis

Question 1

definition of anaphylaxis

Answer 1

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

type 1 IgE hypersensitivity reaction

Question 2

classifications of aetiology of anaphylaxis

Answer 2

immunologic

non-immunologic

Question 3

immunogenic aetiology of anaphylaxis

Answer 3

IgE mediated or immune complex/complement mediated

Question 4

non-immunologic aetiology of anaphylaxis

Answer 4

mast cell or basophil degranulation w/o involvemnet oif Ab

eg reactions caused by vancomycin, codeine, ACEi

Question 5

general aetiology of anaphylaxis

Answer 5

inflam mediators eg histamine, tryptase, chymase, histamine-releasing factor, PAF, prostaglandins and leucotrienes

cause bronchospasm, increased capillary permeability and reduced vascular tone

= tissue oedema

Question 6

common allergens for anaphylaxis

Answer 6

drugs - penicillin,

radiological contrast agents,

latex,

insect stings

egg

peanuts

shellfish

fish

repeated admin pf blood products in pts with selective IgA deficiency as a result of formation of anti-IgA Ab

can be induced by exercise

Question 7

epidemiology of anaphylaxis

Answer 7

relatively common

1 in 5000 exposures to parenteral penicillin or cephalosporins

1-2% patients recieving IV radiociontrast experience hypersensitivity reaction

0.5-1% children have peanut allergy

1 in 700 pts have selective IgA deficiency

Question 8

symptoms of anaphylaxis

Answer 8

acute onset of symptoms:

• wheeze, SOB or sensation of choking
• swelling of lips and face
• pruritis, rash
• diarrhoea and vomiting

severity of previous rns doesnt predict future

may have history of other allergic hypersensitivity disorders eg asthma, allergic rhinitis.

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

Question 9

signs of anaphylaxis

Answer 9

tachypnoea

wheeze

cyanosis

swollen upper airways and eyes, rhinitis, conjunctival injection

urticarial rash (erythematous wheals)

hypotension

tachycardia

oedema - larynx, lids, tongue, lips

erythema

laryngeal obstruction

Question 10

investigations for anaphylaxis

Answer 10

clinical dx

serum tryptase (measured in 15min-3hr after onset of symptoms)

histamine levels (30min after symptom onset)

urinary metabolites of histamine (may remain elevated for several hours after symptoms)

normal levels dont exclude anaphylaxis

Question 11

investigations after anaphylaxis

Answer 11

allergen skin testing - should identify allergen - performed by allergy specialist because of risk of anaphylaxis and skill required for proper interpretation

radioallergosorbant gtests (RASTs) to identify food-specific IGE in the serum

Question 12

management of anaphylaxis

Answer 12

stop suspected drugs

resys - ABC

secure airway - give 100% ox, intibation and transfer to ITU might be necessary

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

antihistamine IV - 10mg chlorpheniramine

steroids IV - 100mg hydrocortisone

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

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

Question 13

advice for anaphylaxis

Answer 13

educate on use of adrenaline pen for IM admin

medicalert bracelet

make note in patients notes and drug charts

referral to an allergy specialist for identification of allergen

education in allergen avoidance

Question 14

complications of anaphylaxis

Answer 14

resp failure

shock

death

Question 15

prognosis of anaphylaxis

Answer 15

good if prompt treatment is given