Anaphylaxis

Question 1

Adrenaline (epinephrine)

Common indications

Answer 1

1. Cardiac arrest- adrenaline is routinely administered as part of the advanced life support (ALS) treatment algorithm
2. Anaphylaxis- adrenaline is a vital part of immediate management
3. Adrenaline may be injected directly into tissues to induce local vasoconstriction. For example, it is used during endoscopy to control mucosal bleeding, and it is sometimes mixed with local anaesthetic drugs (e.g. lidocaine) to prolong local anaesthesia

Question 2

Adrenaline (epinephrine)

MOA

Answer 2

• Adrenaline is a potent agonist of the a1, a2, b1 & b2 adrenoreceptors, and correspondingly has a multitude of sympathetic (fight or flight) effects.
• These include: Vasoconstriction of vessels supplying skin, mucosa and abdominal viscera (mainly a1-mediated); increases in HR, the force of contraction and myocardial excitability (b1) and vasodilation of vessels supplying the heart and muscles (b2)
• These explain its use in cardiac arrest, where the redistribution of blood flow in favour of the heart is desirable, at least theoretically, and may improve the chances of restoring an organised rhythm.
• Additional effects of adrenaline, mediated by b2-R, are bronchodilation and suppression of inflammatory mediator release from mast cells.
• Together with its vascular effects, these underpin its use in anaphylaxis, where the widespread release of inflammatory mediators from mast cells produce generalised vasodilation, profound hypotension and often. bronchoconstriction

Question 3

Adrenaline (epinephrine)

Adverse effects

Answer 3

• Adrenaline is a dangerous drug, but its risks are balanced against the severity of the condition being treated
• In cardiac arrest, restoration of output is often followed by adrenaline-induced HTN.
• When given to conscious patients in anaphylaxis or in an attempt to produce local vasoconstriction, it often causes anxiety, tremor, headache and palpitations
• It may also cause angina, MI and arrhythmias, particularly in patients with existing heart disease

Question 4

Adrenaline (epinephrine)

Interactions

Answer 4

• In patients receiving treatment with a BB, adrenaline may cause widespread vasoconstriction because of the a1-mediated vasoconstriction effect is not opposed by b2-mediated vasodilation

Question 5

Adrenaline (epinephrine)

Communication

Answer 5

• In anaphylaxis- simultaneously with providing treatment, explain to the patient that they are experiencing a severe allergic reaction and that you are giving them an injection of adrenaline to treat this