Management of anaphylaxis involves treating the acute emergency, in the community first (see adrenaline autoinjectors), then in hospital, and then arranging appropriate follow up.  See also anaphylaxis definition.

Hospital

APLS guidelines (updated 2021) on management of acute anaphylaxis from the United Kingdom Resuscitation Council.

No distinction between anaphylactic and anaphylactoid reactions – confusing and may lead to inadequate treatment. Patients taking beta blockers may have a more severe reaction and respond less well to adrenaline.

Adrenaline is the only evidence based treatment specified in the guidelines.  It is therefore the treatment of choice.  You could argue that anaphylaxis is the one condition in which the ABC approach is not appropriate – as soon as anaphylaxis is suspected, you should give intramuscular adrenaline, and then proceed to airway, breathing etc.

Adrenaline is underused. 34% of cases of anaphylaxis in Patel’s metanalysis did not receive adrenaline (my calculation from table III); 10% needed more than 1 dose [Patel JACI 2021]. In scenario based studies, adrenaline is often not given.

Adrenaline by the intramuscular route is safe. If in doubt, just give it! Dose is 0.15mg for under 6yrs, 0.3mg for 6-12yrs, 0.5mg for over 12.  This is slightly different from the adrenaline autoinjector dose the child may have been prescribed for home use.

Repeat within five minutes if there is no improvement or if the patient’s condition deteriorates – not based on any evidence!

New guideline does not mention steroids or antihistamines at all! But does include IV bolus with second dose IM adrenaline after 5 minutes . 

Posture emphasised in new guidance – Lie down with legs raised, or allow sitting up in semi-recumbent position if that helps breathing. Beware sitting up, standing and walking even if feeling better – reported trigger for cardiac arrest – so caution when transferring.

Refractory Anaphylaxis

After that, if still not improving, there is a new Refractory anaphylaxis guideline. 

• Get expert help.  Intravenous adrenaline should only be given by experienced practitioner.
• Give repeated IM doses of adrenaline, or if experienced, start low dose IV adrenaline infusion:
  • 1 mg (1 mL of 1 mg/mL [1:1000]) adrenaline in
    100 mL of 0.9% sodium chloride, ie 1:100 000.
  • Beware BP cuffs and piggy back lines that will interfere and potentially cause extravasation. 
  • Start at 0.5-1ml/kg/hr and titrate.
  • Use ECG monitoring. 
• Use nebulised adrenaline for stridor, neb salbutamol for wheeze or bronchospasm. 
• After that intubation, inhalational anaesthetics (good for bronchospasm), repeat fluid boluses.

Discharge

Before, advice was observe for 6-12 hours, or admit if child. Now this has been risk stratified, with 6-12 hour rule applying for most cases. Exceptions are:

• 2hr discharge if a) good response (5-10 minutes), to b) single dose adrenaline, c) given within 30 mins PLUS complete resolution PLUS already trained and with 2 unused AAIs PLUS adequate supervision
• At least 12 hours after resolution if any of:
  • severe, needed more than 2 doses adrenaline
  • severe asthma, or had severe respiratory compromise
  • possibility of ongoing absorption eg slow release medication
  • late at night or potential to not respond to any deterioration
  • areas where emergency care difficult
• or in context of supervised challenge

No reliable way to predict biphasic reaction so this should be discussed and decision made by senior clinician.

Follow up

See NICE guideline CG134.

Basic principles are to not discharge too soon, in case of a biphasic attack, but just as importantly, to consider prevention of further episodes (which involves making a diagnosis), and giving the patient and their family the appropriate information and skills to deal with an unexpected further allergic reaction.

Who needs an Adrenaline auto-injector?

EAACI position paper suggests:

• Absolute indications:
  • Previous cardiovascular or respiratory reaction to a food, insect sting or latex.
  • Exercise induced anaphylaxis.
  • Idiopathic anaphylaxis.
  • Child with food allergy and co-existent persistent asthma.
• Relative indications:
  • Any reaction to small amounts of a food (e.g. airborne food allergen or contact only via skin).
  • History of only a previous mild reaction to peanut or a tree nut.
  • Remoteness of home from medical facilities.
  • Food allergic reaction in a teenager.

Prescribing a pen is only part of the overall management: nothing worse than prescribing a pen and not properly discussing avoidance, or having a pen that does not get used when it should be, because it’s left at home or because no-one remembers how to use it or they are too scared to use it.

Referral to an allergist is highlighted.  According to a Mayo Clinic study, 35% of those referred by emergency department (ED) had an alteration in the diagnosis or suspected trigger after allergy/immunology follow up.  Either anaphylaxis was ruled out; or an unknown trigger was successfully identified; or the suspected trigger was ruled out.  Allergists are also good at identifying new triggers, different from the one suspected (JACI In Practice 2014)

In 1 study from Arkansas, n=187 patients (all under 19), food (44%) and stings (22%) were the main triggers, whereas 29% had no identifiable allergen. Only 47% (n = 87) received adrenaline in the ED and only 31% of those via the preferred IM route (the rest were treated subcutaneously). 61% received autoinjectors at discharge. Only 45% received an allergy referral. [Ped Emergency Care 2016] Similar results from Birmingham, Alabama in 2010.

Most cases of anaphylaxis are coded as “allergic reaction” rather than anaphylaxis, which suggests hospital statistics are likely to represent only a minority of the cases coming to hospital. In the study above, before the 2006 NIAID anaphylaxis guidelines, only 20% of cases were accurately coded.