Anaphylaxis

SHO presentationTom 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

DELTOID

UPPER OUTER THIGH

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 (10kg)– Maximum 0.5 ml (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