Anaphylaxis

Adrenalin

0.5 mg of Adrenalin IMI in adults 0.3 mg in children

1:1000 Adrenalin 1 g in 1000 mL 1mg per mL 0.5 mLs = 0.5 mg 0.5 mLs is appropriate for both deltoid (< 1 ml), thigh (<3 mls) or ventrogluteal (< 5mls)

For children 1:10 000 That’s 3 mls Anterolateral thigh

Repeat Adrenalin after 5 minutes of no response

oxygen

If can tolerate, spacer is preferred Why? Apparently Neb has more side effects (this doesn’t make sense)

Adults 12 puffs (each puff = 4 breathes) q20 min then stretch to 1hr, 2hr, then 3 hr

Children 6 puffs and stretch according to local protocol

Salbutamol is a b2 agonist

b1 spillover causes tachycardia and contractility b2 is found in peripheral blood vessels and causes dilation. This causes reflex tachycardia b2 drives k into cells, causing hypokalaemia. Low potassium causes excitable heart with tachycardia and extra systoles

steroid

Hydrocortisone is the fastest acting IV steroid Here it is used to prevent rebound Hydrocortisone 200 mg IV stat

antihistamine

Loratadine Apparently just for skin symptoms

how does Adrenalin treat anaphylaxis

a1 agonism causes vasoconstriction, this - pumps up blood pressure - Reduces mucosal oedema

b1

  • keeps bp high through contractile and rate

b2

  • bronchodilation
  • reduces mast cells bursting

Adrenalin in arm vs thigh

Thigh has quicker absorption Higher peak drug level

Adrenalin vs nor Adrenalin?

Adrenalin is a1, b1, b2 Heart rate and contractility and blood pressure

Nor Adrenalin is a1, b1

  • Normally b2 causes peripheral vasoconstriction.

This counteracts a1. Nor ad thus has uninhibited a1, so is a very profound vasopressor.

  • b1 activation is lower than in adrenaline. Potent htn also causes reflex Brady. These two factors mean that not Adrenalin has little effect on the heart rate. Whereas Adrenalin will cause tachycardia

Adrenalin has b2 which does

  • bronchodilation
  • stabilises mast cells

Adrenaline is a mixed α/β drug that raises BP, boosts cardiac output, bronchodilates, and stops allergic degranulation — making it perfect for anaphylaxis. Noradrenaline is a pure vasopressor (α1-dominant) that powerfully elevates BP with minimal β2 activity — making it ideal for septic shock.

antihistamine

1st generation = sedating + higher frequency = promethazine

2nd generation = less sedating + once daily

  • cetirizine
  • Fexofenadine
  • Loratadine