Acute anaphylaxis
Theory
Immunoglobulin E mediated response to antigenic stimulus involving MAST cell degranulation.
Histamine release causes generalised systemic response.
Airway – angio-oedema and laryngeal oedema leading to progressive and rapid airway obstruction and respiratory arrest.
Breathing – bronchospasm resulting in progressive obstruction and increased work of breathing.
Circulation – vasodilatation with resultant hypotension, tachycardia and cardiovascular collapse – (shock).
The combination, the rate of progression, and the severity of symptoms are variable; therefore, all patients with anaphylaxis who are still deteriorating are potentially at risk of death and require prompt treatment.
Immediate intern management
Attend patient and make rapid assessment.
Patient unconscious
- Tell nursing staff to call Code Blue then move to head end of bed.
- Perform triple manoeuvre – chin lift, jaw thrust, head tilt.
- Bag and mask patient with oxygen. (Be careful with instrumenting an airway in anaphylaxis – can make it worse. Secure airway with bag and mask.)
- When help arrives obtain IV access, send off blood tests.
- Give IV adrenaline one ampoule in 500 ml Gelofusine stat.
Patient conscious
- Tell nursing staff to call code MET.
Then:
- Give oxygen by mask.
- Get crash trolley, obtain IV access and send off blood tests (FBE, U&E, LFT, CRP).
Patient normotensive
- Give 300 micrograms adrenaline S/C or IM.
- Give 500 ml Gelofusine stat.
Help should arrive by now.
Patient hypotensive
Give IV adrenaline 50 micrograms bolus and repeat every two to three minutes.
If the patient has known anaphylaxis, an Epi-Pen (subcutaneous adrenaline pen) may be available for use in an emergency.
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Clinical features (obtain rapidly)
History
- Rapid onset inability to breathe
- Collapse
- Known allergy/allergies
- Recent administration (drug, tape, procedure)
Examination
- Stridor
- Respiratory distress
- Hypotension, tachycardia
- Collapse
- Warm periphery
- Urticarial rash
Other (obtain later)
Risk factors: past history anaphylaxis, family history, asthmatic
Suspect the diagnosis when there are two or more of:
- Itch, urticaria
- Angio-oedema
- Upper airway swelling
- Wheeze
- Hypotension
Further definitive management
Airway
- Patient may require intubation if progressing to angio-oedema and respiratory arrest; however, this may be very difficult due to oedema and laryngeal spasm (the anaesthetists and surgeons can address this)
- In this setting 5 mg nebulised adrenaline may be helpful
- If intubation impossible and patient in extremis, surgical airway may be required. Hopefully early definitive management can prevent deterioration to the point of requiring intubation
Breathing
Circulation
- IV access and fluid resuscitation
- IV adrenaline one ampoule diluted as required to stabilise cardiovascular system
Other
- Transfer patient to ICU for observation and further management
- If intubated, leave ventilated until spasm and oedema settles
- Consider using IV steroids (hydrocortisone) to settle inflammation
- Identify underlying cause and ensure allergy clearly documented
- Consider allergy testing and referral to immunologist
- Provide patient education and appropriate documentation
- Consider organising Epi-Pen (subcutaneous adrenaline pen)
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