FFinalistSouthampton · 2027
Acute care
AKT · Acute care/Resuscitation & shock

Cardiac arrest (ALS)

Loss of cardiac output — shockable vs non-shockable rhythms

Overview

Absent cardiac output requiring CPR and the Advanced Life Support algorithm. The pivotal split is the rhythm: SHOCKABLE (VF/pulseless VT — defibrillate) vs NON-SHOCKABLE (PEA/asystole — no shock), with reversible causes (4 Hs & 4 Ts) sought throughout.

Recognise

  • Unresponsive, not breathing normally, no pulse → start CPR 30:2
  • Shockable: ventricular fibrillation / pulseless VT
  • Non-shockable: pulseless electrical activity / asystole

Red flags

  • Reversible causes — 4 Hs (Hypoxia, Hypovolaemia, Hyper/hypokalaemia & metabolic, Hypothermia) & 4 Ts (Thrombosis, Tamponade, Tension pneumothorax, Toxins)

Differentials & how to tell them apart

Shockable (VF/pVT)defibrillate immediately, then 2 min CPR; adrenaline after 3rd shock, amiodarone after 3rd shock
Non-shockable (PEA/asystole)NO shock; adrenaline 1 mg ASAP then every 3–5 min; treat cause
Profound bradycardia (peri-arrest)atropine/pacing — not arrest

Investigations

Rhythm check every 2 minutes; identify reversible causes (ABG/K+, bedside echo, history).

Management

CPR 30:2; defibrillate if shockable; adrenaline (timing by rhythm) + treat 4 Hs & 4 Ts

  1. 1High-quality CPR 30:2, attach defibrillator, rhythm check every 2 min. Shockable → shock then 2 min CPR. Non-shockable → CPR + adrenaline now.Gate: In a SHOCKABLE rhythm give adrenaline only AFTER the 3rd shock (and amiodarone 300 mg); in NON-shockable give adrenaline immediately
  2. 2Search and treat reversible causes (4 Hs & 4 Ts) every cycle; consider airway/ETCO2.
Adrenaline 1 mg IV — every 3–5 min; immediately in non-shockable, after 3rd shock in shockable
Amiodarone 300 mg IV — after the 3rd shock in VF/pVT (further 150 mg after 5th)

Key points

Adrenaline timing differs by rhythm — immediate in PEA/asystole, after the 3rd shock in VF/pVT. Amiodarone is only for shockable rhythms.

Monitor & prognosis

Rhythm/pulse checks every 2 min; ETCO2; post-ROSC care (targeted temperature, coronary angiography).

Best with witnessed VF + early defibrillation.

Source: Resuscitation Council UK ALS 2021