Anaphylaxis

Question 1

What are the most common triggers for perioperative anaphylaxis?

Answer 1

Antibiotics (47%)
Muscle Relaxants (33%)
Chlorhexidine (9%)
Patent Blue Dye (5%)

Question 2

What is the estimated incidence of perioperative anaphylaxis

Answer 2

1 in 10,000

Question 3

Outline the pathological process underlying immunoglobulin E mediated anaphylaxis

Answer 3

Sensitisation: IgE antibodies develop against a trigger agent

Re-exposure - the allergen binds to and bridges between 2 IgEs bound to the cell membrane of a mast cell or basophil

A signal transduction cascade results in the release of preformed (histamine and tryptase for example) and newly made (leukotrienes , thromboxane A2 and cytokines for example) inflammatory mediators

This has the effect of causing vasodilation, capillary leak and bronchospasm which cause the clinical effects seen in anaphylaxis

Question 4

What was the most common presentation of anaphylaxis according to NAP 6

Answer 4

Hypotension

Question 5

What other presenting features of perioperative anaphylaxis are there

Answer 5

Bronchospasm
Tachycardia
Angioedema
Cardiac Arrest

Cutaneous Flushing (often absent)

Bradycardia : This is thought to result from the Bezold Jarisch reflex. Which is where the profound vasodilation associated with anaphylaxis results in poor venous return triggering a vagally mediated reflex which results in bradycardia to preserve diastolic filling

Question 6

What are the indications for the initiation of chest compressions in a case of suspected anaphylaxis

Answer 6

Cardiac Arrest

Hypotension with a systolic blood pressure < 50mmHg

Question 7

What are the pharmacological treatment options for the treatment of hypotension associated with anaphylaxis in an adult.

Please state their bolus doses where applicable

Answer 7

Crystalloid 20ml/kg

Adrenaline 50mcg

Glucagon 1mg if beta blocked and unresponsive to adrenaline

Vasopressin 2 units

Metaraminol or Noradrenaline if inadequate response

NB Hydrocortisone and Chlorphenamine no longer have an acute role in the management of anaphylaxis

Question 8

What are the timings of the tryptase samples that are taken in the event of a suspected anaphylaxis

Answer 8

As soon as the situation allows (i.e. when the patient is stable)

One or two hours after the event

24 hours after the event

NB The anaesthetist caring for the patient is responsible for liaising with the departmental lead for anaphylaxis for referring for immunological testing, reporting to the Medicines and Healthcare products Regulatory Agency (MHRA ), informing the surgeon and the patient’s GP, as well as informing the patient and advising them regarding alert bracelet use.