Key Facts

Cardiac arrest is the cessation of effective cardiac output requiring immediate intervention. Survival depends on the chain of survival: early recognition and call for help, early CPR, early defibrillation, and post-resuscitation care.

Epidemiology

Approximately 30,000 out-of-hospital cardiac arrests occur annually in the UK. Bystander CPR is performed in approximately 40-50% of cases and doubles survival. VF/pVT is the presenting rhythm in approximately 20-25% of OHCA. In-hospital cardiac arrest survival to discharge is approximately 23-25% (NCAA data).

Aetiology

Shockable rhythms (VF/pVT): Most commonly caused by acute coronary syndrome, structural heart disease, inherited channelopathies (long QT, Brugada), electrolyte abnormalities, drug toxicity.

Non-shockable rhythms (PEA/asystole): Often represent a final common pathway of advanced pathology.

Reversible causes (4Hs and 4Ts):

• Hypoxia, Hypovolaemia, Hypo/hyperkalaemia, Hypothermia
• Tension pneumothorax, Tamponade, Toxins, Thrombosis (PE/MI)

Pathophysiology

Cardiac arrest results in immediate cessation of cerebral and coronary perfusion. Brain injury begins within 3-5 minutes of normothermic cardiac arrest. CPR generates approximately 25-30% of normal cardiac output. Defibrillation terminates VF/pVT by depolarising a critical mass of myocardium, allowing resumption of organised electrical activity.

Recognition

• Unresponsive patient
• Absent or abnormal (agonal) breathing
• No palpable pulse (do not spend >10 seconds checking)

Shockable Rhythms

• VF (Ventricular Fibrillation): Chaotic, disorganised electrical activity; no cardiac output
• Pulseless VT: Organised wide-complex tachycardia without cardiac output

Non-Shockable Rhythms

• PEA (Pulseless Electrical Activity): Organised ECG rhythm but no pulse — search for reversible cause
• Asystole: No electrical activity (flat line — confirm in 2 leads)

Red Flags

• Any delay in starting CPR reduces survival — do NOT leave patient to find equipment
• Agonal breathing is NOT normal breathing — start CPR
• Do not interrupt CPR for rhythm checks longer than 10 seconds
• Consider treatable causes throughout — VF will not respond if caused by ongoing hypoxia or metabolic derangement

Bedside

• Cardiac monitor/defibrillator: Immediate rhythm assessment
• Capnography (ETCO2): Confirms tracheal intubation; ETCO2 >20 mmHg indicates adequate CPR quality; sudden rise suggests ROSC
• Point-of-care USS: During rhythm check — cardiac standstill vs organised activity, tamponade, RV dilatation (PE)
• Blood glucose: Capillary

Bloods

• ABG/VBG: pH, K⁺, lactate, Hb — guide treatment of reversible causes
• U&Es: Potassium, renal function
• Troponin: Post-ROSC — assess for MI

Imaging

• CXR: Post-ROSC — ETT position, pneumothorax, pulmonary oedema
• CT head/CTPA: Post-ROSC if cause unclear
• Echocardiography: Post-ROSC — assess cardiac function, regional wall motion abnormalities

Special Tests

• 12-lead ECG post-ROSC: STEMI → emergency PCI
• Coronary angiography: If cardiac cause suspected
• EEG: Neuroprognostication at ≥72 hours post-arrest

Non-pharmacological

• Call for help: 2222 (in-hospital) or 999 (out-of-hospital)
• High-quality CPR: 30:2 ratio; 100-120/min; 5-6cm depth; full recoil; minimise interruptions
• Defibrillation: VF/pVT — 150-360J biphasic (150-200J typical); single shock then immediately resume CPR for 2 minutes
• Advanced airway: Endotracheal intubation or supraglottic airway device; once placed, continuous compressions without pausing for ventilation (10 breaths/min)

Pharmacological

Shockable (VF/pVT):

• Adrenaline 1mg IV after 3rd shock, then every 3-5 min
• Amiodarone 300mg IV after 3rd shock; 150mg after 5th shock

Non-shockable (PEA/Asystole):

• Adrenaline 1mg IV as soon as IV access, then every 3-5 min
• Treat reversible causes

Post-ROSC:

• Target SpO2 94-98%, PaCO2 4.5-6 kPa
• Target MAP >65 mmHg (fluids ± noradrenaline)
• Targeted temperature management (TTM) — target 36°C for 24 hours (TTM2 trial)
• Emergency PCI if STEMI on ECG
• Seizure prophylaxis/treatment as needed

Surgical/Interventional

• Emergency PCI: For STEMI post-ROSC
• Pericardiocentesis: Cardiac tamponade
• Emergency thoracotomy: Penetrating trauma with cardiac arrest
• Thrombolysis: For suspected massive PE causing arrest (alteplase 50mg IV bolus; continue CPR for 60-90 min)

Referral Criteria

• All ROSC patients — ICU admission for post-resuscitation care
• STEMI on post-ROSC ECG — emergency cardiac catheterisation
• Refractory VF — consider ECPR (extracorporeal CPR) if available
• All cardiac arrest survivors — cardiac risk stratification

• OHCA survival to discharge: ~8-10% overall; ~25-30% if initial rhythm VF and bystander CPR
• IHCA survival to discharge: ~23-25% (NCAA data)
• Bystander CPR: Doubles survival
• Public access defibrillation: Increases VF survival from ~10% to ~50-70%
• Good neurological outcome: ~80% of survivors have CPC 1-2 (good/moderate cerebral performance)
• Neuroprognostication: Multi-modal approach at ≥72 hours — EEG, SSEP, imaging, clinical exam

Adult ALS Algorithm (Resuscitation Council UK 2021)

Post-ROSC Care Bundle