Anaphylaxis
13/5/11
FANZCA Notes
= IgE mediated hypersensitivity reaction to an antigen -> profound histamine and serotonin release from basophil and mast cell degranulation.
Clinically
Within minutes of exposure
- stings
- foods
- antibiotics
- contrast media
- thrombolytics
- NSAIDs
- sux & NDNMBD
Flush or pallor
Urticaria
Angioedema
Stridor
Hypotension - cardiovascular collapse
Bronchospasm
Abdominal cramps
Diarrhoea
Coagulopathy
Management
Stop administering trigger
Call for help
Position supine (head down)
O2
Exclude alternatives
Pulse
Adrenaline 0.5mg IM
IV access
Colloid or N/S
(SBP >90mmHg)
Promethazine
25-50mg IV
Hydrocortisone
250mg IV
Persistant hypotension/bronchospasm
Adrenaline 0.5mg IM
No Pulse
CPR
Raise legs
2 large IV's
2 L IVF
Increasing Adrenaline
(adult - 1-4mg)
(children - 10-100mcg/kg)
H1 & H2 antagonists
Extended CPR
Persisting hypotension
- Ranitidine (H2 antagonism)
- Adrenaline/Norad infusion
- Invasive monitoring
- Colloid
Persistant bronchospasm
- As per asthmatic emergencies
Persisting angioedema
- Nebulised adrenaline (1mg)
- ETT
- Cricothyroidotomy
- Tracheostomy
Intra-operative Anaphylaxis
Presentation
Cardiovascuar collapse (most common)
Erythema
Bronchospasm
Angio-oedema
Rash
Urticaria
Most frequent culprits - muscle relaxants, antibiotics, NSAIDS
Management
Stop trigger
A -
B - FiO2 1.0
C - lay flat with legs elevated, adrenaline 50mcg IV increments, fluid
Promethazine 25-50mg IV
Hydrocortisone 100mg IV
Adrenaline infusion 0.05-0.1mcg/kg/min
Acidosis - 50mL of 8.4% NaHCO3
Check for cuff leak before extubation
Bronchodilators as above
Anaphylaxis Follow Up
4/3/09
OHOA pages 954-956
Incidence - 1:6,500
Differential
- anaphylactoid reaction (histamine or complement activation)
- drug induced reaction related to genetic status (angio-oedema)
- machine or operator error
- asthma
- systemic mastocytosis
- malignant hyperthermia
- vasovagal episode
Main Cuprits
- NMBD (70%)
- antibiotics
Clinical presentation
- rapid after an IV bolus
- slower if other route
- cardiovascular collapse (80%)
- cutaneous signs (50%)
- bronchospasm (36%)
- angio-oedema (24%)
Investigations
SERUM TRYPTASE
- released from secretory vesicles of mast cells
- take @ 1, 6 and 24 hours
- serum separated and stored @ 20 C
- normal - <1ng/mL
- non-specific and anaphylactoid reactions - 1-15ng/mL
- true anaphylaxis - levels higher than this
RAST TESTING
- radioallergosorbent test for antigen-specific IgE antibodies
CAP TESTING
- an antigen coated capsule is exposed to the patients serum under laboratory conditions
- if serum contains antigen specific IgE a measurable colour change is produced
- superceeded RAST testing
- available for testing pencillin, sux and latex allergy
- sensitivity low -> thus negative result requires skin testing
SKIN or INTRADERMAL TESTING
- skin testing has been shown to be diagnostic for anaphylaxis (but not for anaphylactoid reactions)
- should take place 4-6 weeks post event to allow regeneration of IgE
- antihistamines should not have been given within the last 5 days
- use skin prick testing first
- test all drugs given before the event
- use a saline as a negative control
- use histamine solution as a positive control
- weal >2mm wider than saline = positive
- repeat positive test with a 1:10 dilution to reduce the chance of a false positive
- once positive drug detected -> test other drugs in same class
- if history is strong, but skin prick test negative -> test intradermally with diluted drugs
Management
- communicate importance of finding to patient
- letter
- medic alert bracelet
- mark hospital notes
- inform GP
- report reaction to Med Safe
- avoid all untested and related drugs
- do not use an IV test dose
- if unsure about IV induction agents -> gas induction
- if NMBD reaction -> use a relaxant free anaesthetic, if must be used by guided by skin prick test result, give chlorphenamine (10mg) and hydrocortisone (100mg) IV pre-induction
Jeremy Fernando (2011)