Anaphylaxis
SHO presentation
Tom Francis ICU Registrar
Anaphylaxis
•
•
•
•
•
•
What is it
Pathophysiology
Common causes / precipitants
Features / signs
Treatment
After-care / discharge
Anaphylactic shock
• Type 1 IgE mediated (usually) hypersensitivity
reaction
• Chain Reaction
• Release of histamine and other cytokines from
mast cells and basophills
• Causes contraction of bronchial smooth
muscles, vasodilation of peripheral
vasculature, capillary leak and cardiac muscle
depression
ADRENALINE
• Mainstay of treatment is Adrenaline
0.5mg IM ADRENALINE
Precipitants / causes
• Drugs
– Abx, cross reactivity B-lactams
– Muscle relaxants
– IV contrast
• Food
• Bee stings / wasp / horse fly
IM injection
UPPER OUTER THIGH
DELTOID
Recognition
• Airway
– Airway oedema – larynx, lips, tongue, eyelids
– Stridor is a sign of airway obstruction
• Breathing
– Bronchial smooth muscle constriction – wheeze,
respiratory distress, increased work of breathing
• Circulation
– Relaxation of vascular smooth muscle – Vasodilation,
hypotension and erythema
– Increased capillary permeability leading to loss of fluid
from circulation : hypotension, tissue swelling, urticaria
and Angioedema
Urticaria
Angioedema
ADRENALINE
•
•
•
•
0.5mg IM
Half of 1/1000 vial (the small one)
Found in emergency box on all wards
Can repeat every 5 mins
0.5mg ADRENALINE IM
Adrenaline
• α1 – peripheral vasoconstriction via smooth muscle
constriction
– Increased SVR
• Β1 – Increased Cadiac output through +ve chrnontropy
and inotropy
• Β2 – Bronchial smooth muscle relaxation
• Also acts directly on mast cells preventing further
histamine release
Promethazine (Phenergan)
• 25mg slow IV injection (can use IM)
• Sedating anti-histamine (H1)
• Prevents capillary leak and helps treat
hypotension due to loss of intravascular fluid
• If persistant hypotension despite treatment
with adrenaline can use ranitidine (H2) as
second line. 50mg Ranitidine IV slowly
Hydrocortisone
•
•
•
•
200mg IV hydrocortisone
Requires reconstituion with sterile water
OF NO VALUE IN IMMEDIATE RESUSCITATION
Is of value to prevent rebound anaphylaxis
though onset of several hours, should be given
to prevent further deterioration in severely
affected patients
IV Fluids
• Vasodilation and increased vascular
permeability
• 3rd spacing of fluid into interstitial space
• DISTRIBUTIVE SHOCK
• 1 litre Crystalloid or colloid STAT once
Adrenaline given IM
• 1 – 3 litres commonly required
• 50mg Ranitidine can help persitant low BP
Treatment
ADRENALINE 0.5mg IM
• Airway (and supplemental Oxygen)
– nebulised adrenaline 5mg (5 x 1/1000)
– Consider intubation.
• Breathing – bronchospasm usually responds to
adrenaline, can give nebulised salbutamol 5mg if
wheeze persists. Treat as acute asthma
• Circulation
–
–
–
–
Raise legs / head down on bed if hypotension
Large bore IV access
1 litre IVI stat
50mg Ranitine IV if persistant
Treatment
• Mainstay of treatment is Adrenaline
0.5mg IM ADRENALINE
Where now?
• Pts who require treatment for anaphylaxis
need to be discussed with ICU
• Rebound Anaphylaxis is a concern
• Tryptase levels to confirm diagnosis
– <1 Hour, 8 hours, 24 hours
Discharge post anaphylaxis
• Oral antihistamine e.g loratadine 3/7
• Oral Steroid 3/7
– Reduces risk of further reaction
• Refer for specific allergy diagnosis
• Epi-pen prescription
– 300mcg Adrenaline
Further Mx…
• ACC form
• Refer to GP for Medic Alert bracelet
• Fill out an Alert/Adverse Reactions/Allergies form
• Complete CARM report if a medication allergy
– (Centre for adverse reactions monitoring)
– https://nzphvc-01.otago.ac.nz/carm/
– Or easily found on google!
Don’t forget!!!
0.5mg IM ADRENALINE
Paediatrics
• Adrenaline 0.01ml/kg of 1:1000 IM
– Minimum 0.1 ml
– Maximum 0.5 ml
(10kg)
(50kg)
• Dose will be between 100 – 500mcg IM
Airway obstruction
• Sit child upright
• Neb adrenaline 1:1000 0.5ml/kg, max 6ml.
Dilute to at least 4ml
Cardiovascular compromise
•
•
•
•
•
Poor perfusion, tachycardia, hypotension
IV access – Consider IO
20ml/kg NaCl
Rpt as required – 4% albumin after 2nd bolus
Adrenaline infusion
Bronchospasm
• Salbutamol neb 5mg PRN/continuous
• Consider IV salbutamol
• Intubation / ventilation
Further Mx
• Hydrocortisone 4mg/kg IV Q6H
• H1 antihistamine (loratadine / cetirizine)
– Itch
– Angioedema
• PO Ranitidine 1-2mg/kg (max 150mg) in sever
reactions
• If require more than 1x dose Adrenaline require 24
hour admission
References:
•
•
•
•
ALS handbook (UK)
ACLS level 7 handbook (NZ)
NZ resuscitation website
Starship PICU guidelines