Key Facts

Cardiac arrest is the cessation of effective cardiac mechanical activity, resulting in loss of consciousness and absence of pulse. Survival depends on rapid initiation of the chain of survival.

Epidemiology

• OHCA: ~30,000 per year in the UK; survival to discharge ~8-10%
• In-hospital cardiac arrest (IHCA): ~23,000 per year in the UK; survival to discharge ~25%
• Shockable rhythms: ~20-25% of OHCA (higher survival); ~20% of IHCA
• Male:female ratio ~2:1

Aetiology

Cardiac (~80%):

• Coronary artery disease / acute MI: most common cause
• Cardiomyopathy (DCM, HCM, ARVC)
• Channelopathies (Long QT, Brugada, CPVT)
• Valvular heart disease (AS)
• Heart failure, myocarditis

Non-cardiac (~20%):

• Pulmonary embolism
• Respiratory failure / hypoxia
• Hypovolaemia / haemorrhage
• Drug overdose / toxins
• Electrolyte disturbances (hyperkalaemia)
• Tension pneumothorax, cardiac tamponade
• Hypothermia / hyperthermia
• Anaphylaxis

Arrest Rhythms

• Shockable: VF, pulseless VT → defibrillation
• Non-shockable: PEA, asystole → CPR + adrenaline + identify/treat reversible causes

Recognition

• Unresponsive to stimulation
• Not breathing or only gasping (agonal breathing)
• No palpable carotid pulse (healthcare providers check for ≤10 seconds)

Arrest Rhythms on Monitor

• VF: chaotic, irregular waveform; no identifiable QRS complexes
• Pulseless VT: organised wide-complex tachycardia but no palpable pulse
• PEA: organised electrical activity on monitor but no palpable pulse or cardiac output
• Asystole: flat line (confirm in two leads; check connections)

Red Flags Before Arrest

• Deteriorating NEWS score
• Chest pain, dyspnoea, palpitations
• Bradycardia or tachycardia with hypotension
• Sudden collapse during exertion (consider HCM, long QT, ARVC)

During Arrest

• Cardiac monitor/defibrillator: identify rhythm (VF/pVT vs PEA/asystole)
• Blood gas: pH, potassium, lactate, glucose
• Bedside echo (if trained): identify tamponade, PE, hypovolaemia
• Glucose: exclude/treat hypoglycaemia
• Temperature: hypothermia

Post-ROSC

• 12-lead ECG: identify STEMI, arrhythmia
• Chest X-ray: pneumothorax, tube position, pulmonary oedema
• Bloods: FBC, U&Es (potassium), troponin, lactate, ABG, coagulation
• CT head: if no cardiac cause identified, or prolonged arrest
• CT pulmonary angiogram: if PE suspected
• Coronary angiography: if STEMI or strong suspicion of cardiac cause
• Echocardiography: LV function, structural abnormalities, tamponade

Neuroprognostication (≥72 hours post-ROSC)

• Clinical examination: pupillary reflexes, corneal reflexes, motor response
• EEG: background reactivity
• Somatosensory evoked potentials (SSEP): bilateral absent N20 responses
• MRI brain: diffuse cortical injury
• Neuron-specific enolase (NSE): elevated levels associated with poor outcome

Basic Life Support (BLS)

• Danger, Response, Airway, Breathing, Circulation
• Call 999 / 2222 (in-hospital)
• CPR: 30 compressions : 2 ventilations
  • Compression rate: 100-120/min
  • Compression depth: 5-6 cm
  • Full chest recoil between compressions
  • Minimise interruptions (<10 seconds)
• Defibrillation: AED as soon as available

Advanced Life Support (ALS)

Shockable rhythm (VF/pVT):

• Defibrillate (150-360J biphasic)
• Resume CPR for 2 minutes
• Check rhythm → shock if still VF/pVT
• After 3rd shock: adrenaline 1mg IV + amiodarone 300mg IV
• Continue: adrenaline 1mg every 3-5 min cycle; amiodarone 150mg after 5th shock

Non-shockable rhythm (PEA/asystole):

• CPR for 2 minutes
• Adrenaline 1mg IV as soon as IV access obtained
• Continue adrenaline every 3-5 min
• Identify and treat reversible causes (4 Hs and 4 Ts)

Reversible Causes:

• 4 Hs: Hypoxia, Hypovolaemia, Hypo/Hyperkalaemia (and other metabolic), Hypothermia
• 4 Ts: Tension pneumothorax, Tamponade (cardiac), Toxins, Thrombosis (PE or MI)

Post-Resuscitation Care

• Airway management: intubation if not already done, controlled ventilation
• Target: SpO₂ 94-98%, normocapnia (PaCO₂ 4.5-6.0 kPa)
• Haemodynamic support: IV fluids, vasopressors (noradrenaline) to maintain MAP ≥65 mmHg
• Targeted temperature management: maintain temperature ≤37.5°C for ≥72 hours (TTM2 trial: no benefit of targeting 33°C over 36°C, but fever prevention is key)
• Coronary angiography: immediately if STEMI; consider early angiography in other cardiac arrest survivors
• ICU admission: neurological monitoring, organ support
• Glucose control: target 7.8-10 mmol/L; avoid hypoglycaemia
• Neuroprognostication: multimodal assessment at ≥72 hours post-ROSC (clinical, EEG, SSEP, MRI, NSE)

Referral Criteria

• All cardiac arrest survivors: ICU admission
• STEMI on post-ROSC ECG: emergency coronary angiography
• Suspected channelopathy/inherited cardiac condition: electrophysiology referral after recovery
• Family screening: if inherited cause identified

• OHCA survival to discharge: ~8-10% overall; ~25-30% if shockable rhythm and bystander CPR
• IHCA survival to discharge: ~25%
• Bystander CPR: doubles survival
• Early defibrillation (<3-5 minutes): survival can exceed 50-70%
• Good neurological outcome (CPC 1-2): ~80% of hospital survivors
• TTM: prevents secondary brain injury; fever is harmful post-ROSC
• ICD implantation: reduces SCD risk in survivors with ventricular arrhythmias
• Predictors of good outcome: shockable rhythm, witnessed arrest, bystander CPR, short ambulance response time, ROSC <20 minutes

Resuscitation Council UK ALS Algorithm Summary

4 Hs and 4 Ts