This document provides information on the treatment of anaphylaxis. It begins by defining anaphylaxis as an acute hypersensitivity reaction and describes the pathophysiology involving the release of histamine. The mainstay treatment is identified as adrenaline (epinephrine) injected intramuscularly. Common causes and signs/symptoms are outlined involving the airways, breathing and circulation. Additional treatment steps are described including IV fluids, antihistamines, steroids, and monitoring. Guidance is provided on discharge instructions and managing pediatric cases.

1. Anaphylaxis
SHO presentation
Tom Francis ICU Registrar

2. Anaphylaxis
• What is it
• Pathophysiology
• Common causes / precipitants
• Features / signs
• Treatment
• After-care / discharge

3. 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

4. ADRENALINE
• Mainstay of treatment is Adrenaline
0.5mg IM ADRENALINE

5. Precipitants / causes
• Drugs
– Abx, cross reactivity B-lactams
– Muscle relaxants
– IV contrast
• Food
• Bee stings / wasp / horse fly

6. IM injection
DELTOID
UPPER OUTER THIGH

7. 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

8. Urticaria

9. Angioedema

10. 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

12. 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

14. 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

15. 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

16. 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

17. 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

19. Treatment
• Mainstay of treatment is Adrenaline
0.5mg IM ADRENALINE

22. 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

23. 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

24. 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!

25. Don’t forget!!!
0.5mg IM ADRENALINE

26. Paediatrics
• Adrenaline 0.01ml/kg of 1:1000 IM
– Minimum 0.1 ml (10kg)
– Maximum 0.5 ml (50kg)
• Dose will be between 100 – 500mcg IM

27. Airway obstruction
• Sit child upright
• Neb adrenaline 1:1000 0.5ml/kg, max 6ml.
Dilute to at least 4ml

28. Cardiovascular compromise
• Poor perfusion, tachycardia, hypotension
• IV access – Consider IO
• 20ml/kg NaCl
• Rpt as required – 4% albumin after 2nd bolus
• Adrenaline infusion

29. Bronchospasm
• Salbutamol neb 5mg PRN/continuous
• Consider IV salbutamol
• Intubation / ventilation

30. 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

31. References:
• ALS handbook (UK)
• ACLS level 7 handbook (NZ)
• NZ resuscitation website
• Starship PICU guidelines