Mnemonic

Cardiac Arrest Rhythms

A memory aid for shockable and non-shockable rhythms and the reversible causes.

Expansion

Two shockable, two non-shockable, and the four Hs and four Ts

Expansion

Shockable

  • Ventricular fibrillation
  • Pulseless ventricular tachycardia

Non-shockable

  • Pulseless electrical activity
  • Asystole

Drug timing differs, which is the point most often confused:

  • Shockable: adrenaline 1 mg after the third shock, then every 3 to 5 minutes. Amiodarone 300 mg after the third shock, and a further 150 mg after the fifth
  • Non-shockable: adrenaline 1 mg immediately, then every 3 to 5 minutes. No amiodarone

Reversible causes: the four Hs and four Ts

  • H - Hypoxia
  • H - Hypovolaemia
  • H - Hypo or hyperkalaemia and metabolic disorders
  • H - Hypothermia
  • T - Thrombosis, coronary or pulmonary
  • T - Tension pneumothorax
  • T - Tamponade
  • T - Toxins

Compressions at 30:2 with minimal interruption, depth 5 to 6 cm at 100 to 120 per minute, and continuous compressions once the airway is secured. PEA with a very slow rate suggests hypovolaemia, hypoxia or tamponade, and prompts a search rather than more adrenaline.