3-1. Anaphylaxis

• Unexplained hypotension

• Unexplained bronchospasm (wheeze may be absent if severe)

• Unexplained tachycardia or bradycardia

• Angioedema (often absent in severe cases)

• Unexpected cardiac arrest where other causes are excluded

• Cutaneous flushing in association with one of more of the signs above (often absent in severe cases)

START

❶ Call for help. Note the time. Stop or do not start non-essential surgery.

❷ Call for cardiac arrest trolley, anaphylaxis treatment pack and investigation pack.

❸ Remove all potential causative agents and maintain anaesthesia.

• Important culprits: antibiotics, neuromuscular blocking agents, patent blue.
• Consider chlorhexidine as cause (impregnated catheters, lubricants, cleansing agents).
• Consider i.v. colloids as a possible cause.
• Change to inhalational anaesthetic agent (if not already).

❹ Give 100% oxygen and ensure adequate ventilation:

• Maintain the airway and, if necessary, secure it with tracheal tube.

❺ Elevate patient’s legs if there is hypotension.

❻ If systolic blood pressure < 50 mmHg or cardiac arrest, start CPR immediately.

❼ Give drugs to treat hypotension (Box A):

• Hypotension may be resistant and may require prolonged treatment.
• Give adrenaline bolus and repeat as necessary.
• Consider starting an adrenaline infusion after three boluses.
• If hypotension resistant, give alternate vasopressor (e.g. metaraminol, noradrenaline infusion +/- vasopressin)
• Give glucagon in ß-blocked patient unresponsive to adrenaline.

❽ Give rapid i.v. crystalloid: 20 ml.kg^-1 initial bolus, repeated until hypotension resolved.

❾ Give hydrocortisone as part of resuscitation (Box B).

❿ If bronchospasm is persistent, consider → 3-4

⓫ Take 5-10 ml clotted blood sample for serum tryptase as soon as patient is stable.

• Plan for repeat sample at 1-2 hours and >24 hours.

⓬ Give chlorphenamine when feasible (Box B).

⓭ Plan transfer of the patient to an appropriate critical care area. Note tasks in Box D.

⓮ Prevent re-administration of possible trigger agents (allergy band, annotate notes/drug chart)

Box A: DRUGS TO TREAT HYPOTENSION IF CARDIAC ARREST → 2-1

• Adult adrenaline:  

i.v. 50 μg (= 0.5 ml of 1:10 000)
i.m. 0.5 mg (= 0.5 ml of 1:1000) if i.v. not possible

• Paediatric adrenaline:

i.v. 1.0 μg.kg^-1 (0.1 ml.kg^-1 of 1:100 000) 

[1:100 000 solution made by diluting 1 ml of 1:10 000 up to 10 ml]

• If no i.v. access, intraosseous adrenaline dose same as i.v.

• Suggested adrenaline infusion regimes (adult):

5 mg in 500 mL dextrose = 1:100 000, titrate to effect

3 mg in 50 mL saline. Start at 3 ml.h^-1 (= 3 μg.min^-1), titrate to maximum 40 ml.h^-1 (= 40 μg.min^-1)

• Glucagon (adult): 1 mg, repeat as necessary
• Vasopressin (adult): 2 units, repeat necessary (consider infusion)

Box B: OTHER DRUGS

Hydrocortisone i.v. doses:

• Adult: 200 mg
• Child 6-12 years: 100 mg
• Child 6 months-6 years: 50
• Child <6 months: 25 mg

Chlorphenamine i.v. doses:

• Adult: 10mg
• Child 6-12 years: 5mg
• Child 6 months - 6 years: 2.5mg
• Child < 6 months: 250μg.kg^-1

Box C: CRITICAL CHANGES

CARDIAC ARREST → 2-1

Box D: DON'T FORGET

• Repeat testing for serum tryptase at 1-2 hours and >24 hours.
• Liaise with hospital laboratory about analysis of samples.
• Liaise with department anaphylaxis lead regarding referral to a specialist allergy or immunology centre to identify the causative agent (see www.bsaci.org for details).
• Inform the patient, surgeon and general practitioner.
• Report to MHRA (www.mhra.gov.uk/yellowcard).
• NAP6 online resource: click here