Anaphylaxis

Objectives

To guide the management of a patient presenting to a medical facility with suspected anaphylaxis.

Scope

This guideline describes the management of the acutely unwell patient with suspected anaphylaxis:

Anaphylaxis is a potentially life-threatening allergic reaction, characterised by sudden onset and rapid progression of symptoms with Airway and/or Breathing and/or Circulatory compromise.

Skin and/or mucosal changes (flushing, urticaria, angioedema) are common but not universal. The diagnosis is supported if a patient has been exposed to an allergen known to affect them.

This guidance does not apply to patients suffering from mild/moderate allergic reactions without features of anaphylaxis. 

Audience

This guideline is intended for the use of registered healthcare professionals fulfilling a general role in a forward medical location or in an Emergency Department on Deployed Operations. However it should be noted that intramuscular (IM) adrenaline may be administered for anaphylaxis in an emergency by any person who is trained and competent to do so. 

Initial Assessment & Management

Immediate ManagementAssess the patient using a structured (MARCH) approach. If the patient does not have a life threatening airway, breathing or circulatory compromise, consider alternative diagnosis or manage as per mild allergic reactions.

Remove trigger if possible (stop infusions AND remove the affected line, remove sting etc)

Lay patient flat if able (with or without legs elevated)

Consider sitting position if patient very short of breath

If pregnant, position in left lateral position 

Without delay, if not already administered, give 500 micrograms of adrenaline via intramuscular (IM) injection into the anterior-lateral thigh.

If this site is not appropriate use deltoid. Adjust dose for paediatric patients (see paediatric considerations). 

Note that modules may contain EpiPens which have pre-filled devices with a dose of only 300 micrograms. Trained healthcare professionals should administer two of these together to give a total dose of 600 micrograms. Use the same limb for both pens.

Once first IM dose of adrenaline has been given, manage airway, give high flow oxygen, apply monitoring and gain IV access and commence 500ml IV bolus of crystalloid fluid.

If possible, while inserting IV access, obtain a blood sample into a biochemistry bottle, which should be labelled with the patient’s details and time taken. This should travel with the patient allowing analysis for Mast Cell Tryptase once it arrives in a suitable laboratory. 

If no response, after five minutes of initial dose, deliver another 500 microgram dose of IM adrenaline.

Refractory Anaphylaxis

Most patients respond to the initial dose of IM adrenaline, with 99% responding by the second dose, but in 1% of patients, there is insufficient improvement - this is refractory anaphylaxis.

Repeat doses of 500 microgram IM adrenaline every five minutes until the patient demonstrates an adequate response.

Concurrently optimise MARCH management:

Airway 

If signs of partial upper airway obstruction/stridor, give 5ml of 1mg/ml adrenaline via nebuliser mask.

In total upper airway obstruction seek expert help. If no expert available and impending complete airway obstruction, proceed to surgical airway if trained to do so.

Respiration 

Oxygenation is more important than advanced airway insertion. If apnoeic, use BVM to provide ventilation breaths at 12-14 breaths per minute.

If signs/symptoms of severe/persistent bronchospasm, give ipratropium 500 micrograms and salbutamol 2.5 mg through an oxygen driven nebuliser. 

If nebuliser unavailable, 10 puffs of salbutamol 100 microgram inhaler should be given via a spacer and repeat as required.

Circulation

Give further fluid boluses (500ml per bolus) with glucose-free crystalloid and titrate to response. Large volumes may be required (often 3-5 L in adults)

Intravenous adrenaline for refractory anaphylaxis should only be administered by experienced specialists in a high-acuity setting.

Other Pharmacological TreatmentSteroids and antihistamines do not form part of the emergency treatment of anaphylaxis, but once the patient's condition has stabilised:

Hydrocortisone 200 mg IV can manage symptoms of itchiness and oedema, followed by oral steroids (prednisone 30 mg once daily for the subsequent 5 days).

Chlorphenamine 10mg IV can manage allergic symptoms. This can be continued four times daily at 4mg orally, or alternatively give a non-sedating oral antihistamine (e.g. loratadine 10 mg once daily) after the initial anaphylactic reaction if the patient has ongoing symptoms such as rash or feeling itchy. 

Evacuation

All patients who have experienced anaphylaxis will require evacuation. Be aware that up to 5% of patients can experience biphasic ("rebound") anaphylaxis even without further allergen exposure.

Ensure emergency evacuation to higher level of care is being/has been arranged even if the patient appears to be improving.

While awaiting evacuation, continue to monitor using a MARCH framework for repeated assessment. If necessary, give further adrenaline and fluid to maintain blood pressure with a Mean Arterial Pressure of at least 65 mmHg. Seek expert advice if the patient is at risk of fluid overload or if the patient will receive more than 2-3 litres of fluid.

All patients transferred following suspected anaphylaxis, including those who appear to have made a complete recovery, must be accompanied by a person trained and equipped to administer further IM adrenaline if needed.

Advanced Assessment & Management

Management by an enhanced pre-hospital care team or in a deployed hospital setting will follow the same approach described above.

If dealing with refractory anaphylaxis, if expertise is available then escalate from IM adrenaline to a low dose intravenous adrenaline infusion:

Dilute 1mg of 1:1000 adrenaline in 100 ml of 0.9% sodium chloride.

Start infusion at 0.5-1.0 mL/Kg/hour and titrate to response.

Continuous blood pressure monitoring is essential - site an arterial line as soon as possible.

An infusion can take some time to set up - ensure that repeat doses of 500 micrograms of IM adrenaline continue to be given every five minutes until the infusion is up and running.

Concurrently optimise MARCH management including the following additional considerations: 

Airway

Oxygenation is more important than intubation. In event of complete upper airway obstruction, call expert help and follow difficult airway algorithm.

Respiration

If apnoeic, secure a definitive airway, ideally via tracheal intubation.

If signs/symptoms of severe/persistent bronchospasm, as well as nebulisers, an IV bolus and/or infusion of salbutamol or aminophylline may be helpful if available:

Salbutamol – 250 micrograms to be given IV 10-15 minutes followed by infusion. Infusion at 5 micrograms/minute to be adjusted according to response and tolerance.

Aminophylline – 250-500 mg (max per dose 5 mg/kg) IV as bolus followed by infusion at 500-700 micrograms/kg/hour adjusted according to aminophylline levels. An infusion is only appropriate if aminophylline levels can be measured.

Circulation

Expedite insertion of arterial line for blood pressure monitoring, especially in cases where IV adrenaline or other vasopressors are being used.

If possible, establish central venous access (or near-central IO access) to allow the administration of other ionotropic agents and vasopressors. 

If refractory to adrenaline infusion, add a second vasopressor in addition to adrenaline – noradrenaline, vasopressin or metaraminol.

If patient is on beta blockers, give glucagon 5mg IV/IO. 

Prolonged Casualty Care

In the event a patient has a prolonged hold time, optimise management as per MARCH steps above. In addition to the above actions regular re-assessment of the patent is essential. 

Airway

Monitor carefully for any worsening of angioedema and/ or tongue swelling.

Respiration

Once the ‘acute phase’ of the anaphylaxis is over, titrate oxygen aiming for oxygen saturations ≥  94%. Supplemental oxygen is not required if the patient is no longer critically unwell and is maintaining saturations on room air. 

If wheeze/ shortness of breath persists, 10 puffs of salbutamol 100 microgram inhaler via a spacer can be given as required. If oxygen is required to maintain saturations, salbutamol 2.5 mg - 5 mg could be given by oxygen driven nebuliser as required. Ipratropium 500 micrograms can also be given via nebuliser up to four times daily.

Circulation

Aim to maintain normotension – MAP > 65 mmHg.

If able to swallow, encourage oral intake. Monitor fluid balance hourly aiming for a minimum urine output of 0.5 ml/Kg/hour. Oral hydration should reduce need to use intravenous fluid. If unable to swallow or inadequate urine output despite good oral intake, give IV crystalloid fluids to maintain urine output and normotension. 

Other pharmacological management:

Hydrocortisone 200 mg IV can manage symptoms of itchiness and oedema, followed by oral steroids (prednisone 30 mg once daily for the subsequent 5 days).

Chlorphenamine 10mg IV can manage allergic symptoms. This can be continued four times daily at the same dose or as 4mg orally, or alternatively give a non-sedating oral antihistamine (e.g. loratadine 10 mg once daily) after the initial anaphylactic reaction if the patient has ongoing symptoms such as rash or feeling itchy. 

EpiPens - military personnel who have experienced anaphylaxis are unlikely to be discharged from medical care whilst on operations, but other patients should be discharged with two 300 microgram EpiPens after education on how to use them.

Paediatric Considerations

Age base dosing of drugs in anaphylaxis are shown below. Note, in the emergency management of anaphylaxis, adrenaline is the essential treatment, and other drugs administration should not take priority.

When possible, treat child in presence of parent or caregiver to help calm patient. Where possible, treat child while sitting on parent or caregiver's lap for comfort.

Airway

Remember that children have smaller airways that are more prone to obstruction than adults. IM adrenaline should be given as soon as possible to treat pending airway obstruction in anaphylaxis.

Causing distress to the child may precipitate airway obstruction. Keep the child as calm as possible.

Respiration

Give high flow oxygen early. If distressed and not tolerating oxygen mask, allow parent or caregiver to waft oxygen in-front of patient

Circulation 

Give IV crystalloid fluid in boluses of 10ml/Kg and repeat as required. Early IO access may be appropriate if peripherally shut down.