Cardiac arrest and advanced life support

• Cardiac arrest is the sudden failure of the heart to pump blood. It is recognised clinically, not by monitors: an unresponsive person whose breathing is absent, slow and laboured, gasping (agonal) or panting. ^[1]
• The first and most important acts are to call for help and start high-quality chest compressions, while someone fetches a defibrillator. Compressions buy time for the brain and heart; defibrillation fixes the rhythm. ^[1][2]
• Compressions are delivered 100 to 120 per minute, 5 to 6 cm deep in an adult in the European/RCUK and AHA convention (4 to 6 cm in the Singapore guidelines), with full recoil of the chest, minimal interruptions, and as few hands-off seconds as possible. ^[1][2][5]
• The rhythm is either shockable (ventricular fibrillation or pulseless ventricular tachycardia) and treated by defibrillation, or non-shockable (pulseless electrical activity or asystole) and treated by adrenaline plus a rapid search for the cause. ^[2]
• While resuscitating, search for and treat reversible causes (the Hs and Ts) in parallel, and after return of spontaneous circulation (ROSC) target oxygenation, carbon dioxide, blood pressure, temperature control, coronary angiography when indicated and multimodal neuroprognostication. ^[2][3]

By the end of this page you should be able to:

1. Recognise cardiac arrest from unresponsiveness and abnormal breathing and act without waiting for certainty.
2. Perform adult high-quality cardiopulmonary resuscitation with the correct rate, depth, recoil, ventilation and interruption limits.
3. Distinguish shockable from non-shockable rhythms and state the definitive treatment of each.
4. Apply the doses and timing of adrenaline and amiodarone, describe defibrillation strategy and energy levels, and manage peri-arrest bradycardia and tachycardia.
5. List and explain the reversible causes of cardiac arrest and how to look for them during resuscitation.
6. Outline post-arrest care: targets for oxygen, carbon dioxide, blood pressure and temperature, coronary angiography, seizure control and neuroprognostication.
7. State when to withhold or stop resuscitation, with reference to current European and US guidance, and note where they differ.

Cardiac arrest is not a single disease. It is the final pathway of many conditions in which the heart stops generating a cardiac output: electrical activity may become chaotic (ventricular fibrillation), may stop (asystole), or may be organised on the monitor without a palpable pulse (pulseless electrical activity). ^[2] Resuscitation is therefore two jobs at once: restoring circulation, and finding out why the heart stopped, because treating the cause is what prevents re-arrest. ^[2]

This page is written from a cardiology and critical-care perspective and follows the adult 2025 guidance of the Resuscitation Council (UK), which translates the International Liaison Committee on Resuscitation (ILCOR) 2025 Consensus on Science with Treatment Recommendations and the European Resuscitation Council (ERC) 2025 guidelines into practice. ^[2][4] It also draws on the 2026 Singapore advanced cardiac life support guidelines, which in turn follow the 2025 American Heart Association (AHA) and ERC guidance. ^[5] Where the European and AHA-aligned conventions differ (for example on the dose of atropine or on when adrenaline is given in a shockable rhythm), this is stated with both values rather than resolved. ^[1][2][5]

This page covers adult cardiac arrest only. Paediatric, newborn and maternal arrest follow different protocols and are not addressed here.

Cardiac arrest is recognised clinically rather than by monitors. Suspect it in any unresponsive person. Call for help (999 or the local equivalent) as soon as possible and assess breathing while the call is answered. ^[1] Slow, laboured breathing, agonal gasping and even a near-normal or panting pattern early after onset, particularly in athletes, are all signs of cardiac arrest. ^[1] A short seizure-like episode can occur at the onset of arrest and makes diagnosis harder; once the shaking stops, assess breathing again. ^[1] If there is any doubt, assume cardiac arrest and start compressions: the harm of CPR in someone not in arrest is small, while withholding it is fatal. ^[1]

Dispatcher-assisted CPR is a key link in the chain. Once arrest is suspected, the call handler gives chest-compression-only instructions and moves to 30 compressions to 2 breaths if the caller can give breaths. ^[1] In hospital, early warning scores, rapid response teams and clear escalation policies aim to identify deterioration before arrest, because many arrests have premonitory signs. ^[2]

Every hospital system should aim to recognise arrest, start CPR immediately, defibrillate a shockable rhythm within 3 minutes, give adrenaline rapidly for a non-shockable rhythm, and identify and treat reversible causes. ^[2] A standard "cardiac arrest" call number (2222 in the UK) and immediately available, standardised resuscitation equipment support this. ^[2]

Resuscitation is the default, but it is not mandatory in every circumstance. Current guidance supports withholding CPR when:

• attempting CPR would place the rescuer at serious risk of physical harm, such as an unsafe scene or an ongoing threat; ^[6]
• objective signs of irreversible death are present; ^[6]
• a valid advance care plan requests "do not attempt CPR" (written and signed directives are honoured; some systems now accept verbal family requests with medical oversight); ^[6]
• a person has severe comorbidity with no realistic prospect of benefit (some systems describe "informed non-dissent", where the clinician tells the family that resuscitation will not be attempted unless they object). ^[6]

When benefit is uncertain, the default remains resuscitation while wishes and better information are established. ^[6]

Termination is a team decision, made holistically using patient values, duration of CPR, absence of reversible causes, and absence of response to advanced life support. ^[4] A reasonable practical trigger is persistent asystole from the time of confirmation of arrest despite at least 45 minutes of advanced life support with no reversible cause and no factor arguing against stopping. ^[4] Persistently low end-tidal carbon dioxide is a strong supportive marker but must not be used alone; cardiac ultrasound, blood gases and pupil reactivity should not be the sole basis for stopping. ^[2][4] Termination rules validated for out-of-hospital arrest must not be applied as the sole strategy in hospital, and are not supported for children or newborns. ^[2][4] Debrief the team immediately afterwards. ^[4]

Other ethical points: families should be offered the choice to be present during resuscitation; ^[4] organ donation should be considered in every patient who initially achieves ROSC and later dies, or who is declared dead after unsuccessful resuscitation; ^[3][4] and biases and protected characteristics must not influence resuscitation decisions. ^[4][6]

The aim of external compressions is to pump blood from the chest. Place the heel of one hand on the lower half of the sternum in the centre of the chest; place the heel of the other hand on top, fingers interlocked so pressure is not applied over the ribs. ^[1] Keep the arms straight and position the shoulders vertically above the chest. ^[1] If clothing prevents seeing the sternum, displace or remove it. ^[1] The person is best on a firm surface; do not move them off a bed, but compress a little deeper to compensate for a soft mattress. ^[1]

Defibrillator pad placement matters: place one pad to the right of the sternum below the clavicle and the other in the mid-axillary line below the armpit, making sure the lateral (apical) pad sits directly below the armpit rather than too high on the chest. ^[2] For vector change after three failed shocks, move to an antero-posterior position, with the anterior pad to the left of the sternum and the posterior pad centred just medial to the left scapula. ^[2] Keep pads more than 8 cm from an implanted pacemaker or defibrillator (Resuscitation Council (UK) wording). ^[2] If the person is prone, use an alternative position such as bi-axillary. ^[2]

A resuscitation attempt needs personal protective equipment, a firm surface, a defibrillator (manual or AED), electrode pads, oxygen and airway equipment (bag-valve-mask with reservoir, oral and nasal airways, supraglottic airway, tracheal tube and waveform capnography), suction, vascular access (intravenous cannulae, intraosseous needles), drugs, and a clock or timer. ^[1][2]

AEDs can be used by anyone and should be in unlocked cabinets, accessible 24 hours a day, clearly signposted. ^[1] Manual defibrillators are used only by rescuers who can recognise an arrest rhythm within 5 seconds and shock with minimal interruption to compressions. ^[2] Waveform capnography is essential to confirm tracheal tube placement and to monitor compression quality. ^[2] Mechanical compression devices are not superior to high-quality manual compressions but may be used when manual compressions are impractical or unsafe, for example during transfer or prolonged resuscitation. ^[2] Intra-arrest ultrasound may be used by a skilled operator to look for tamponade or tension pneumothorax but must not interrupt compressions. ^[2]

In hospital, resuscitation teams should meet at the start of each shift to introduce members and allocate roles (compressor, airway, team leader, recorder). ^[2] Staff should have standardised equipment and accredited advanced life support training; the resuscitation call should be answered by a team able to perform manual defibrillation, advanced airway management, intravenous and intraosseous access, and identification of reversible causes. ^[2] Team introductions sound administrative, but role clarity is what keeps the hands-off time under 5 seconds when the rhythm is re-checked. ^[2]

Best practice also includes data-driven, performance-focused debriefing after every arrest, using recordings of compression depth, rate and fraction where available. ^[2] Rescuers should be told in advance that consciousness without ROSC can occur during CPR, which is uncommon but distressing; small doses of sedative or analgesic drugs (fentanyl, ketamine or midazolam) may be given, and neuromuscular blocking drugs should never be used alone in a conscious person. ^[2]

Advance care planning makes a difference before the arrest. Plans such as ReSPECT (Recommended Summary Plan for Emergency Care and Treatment) record patient values, CPR recommendations and other treatment preferences in a single document that travels across settings; clinicians are expected to have these conversations early, honestly and repeatedly. ^[4][6] When views genuinely differ, seek a second opinion, an ethics opinion or legal advice. ^[4] Consent for resuscitation itself is usually implied in an arrest; the work is in the conversations that happen before it.

See the recognition section above. Call first, because the call handler can prompt assessment of breathing and begin compression instructions. ^[1] If you are alone without a phone, shout for help, quickly assess breathing, and if no one responds leave briefly to call, then return and start CPR if the person is still unresponsive and not breathing normally. ^[1]

The 2025 standard is precise and should be memorised exactly:

• Rate: 100 to 120 compressions per minute. ^[1]
• Depth: 5 to 6 cm in the European/RCUK and AHA convention; the 2026 Singapore guidelines use 4 to 6 cm. ^[1][5]
• Recoil: allow the chest to recoil completely after each compression and avoid leaning on the chest. ^[1]
• Interruptions: as few as possible, in practice aiming for a chest compression fraction of at least 60 percent and peri-shock pauses under 10 seconds. ^{[2] [5]}
• Surface: CPR is most effective on a firm surface; do not delay to move someone from a bed. ^[1]
• Position and landmark: lower half of the sternum, as described above. ^[1]
• Ventilation: if trained, 30 compressions to 2 breaths; each breath over about 1 second just enough to produce visible chest rise, roughly 400 to 600 mL (Singapore and ILCOR 2026 wording) or around 500 to 600 mL (AHA-aligned convention). ^[1][2][5]
• Untrained rescuers perform chest compressions only. ^[1]

Total peri-shock pauses longer than 10 seconds reduce both ROSC and survival to hospital discharge. ^[5] A single shock followed by immediate resumption of compressions is preferred over stacked shocks. ^[2]

High-quality CPR also includes checking rhythm and perfusion signs during the brief rhythm check: return of consciousness or purposeful movement, a pulsatile arterial waveform, or a sharp rise in end-tidal carbon dioxide. ^[2] A sharp rise in carbon dioxide alone is suggestive, but compressions should not stop on that sign alone. ^[2]

Begin with basic airway techniques and progress stepwise according to the skills available: manoeuvres to open the airway, then bag-mask ventilation (two person if possible), then a supraglottic airway or tracheal tube. ^[2] Each breath takes about 1 second and should make the chest visibly rise. ^[2] Only rescuers who succeed very often with the tracheal tube should place one in cardiac arrest (above 95 percent within two attempts) and with continuous waveform capnography; the aim is an interruption of less than 5 seconds. ^[2] Once an advanced airway is in place, confirm it with a sustained carbon-dioxide trace; without one, assume oesophageal placement. ^[2] Videolaryngoscopy is preferred to direct laryngoscopy when available. ^[2]

With an advanced airway in place, pause compressions only if ventilation through the device is inadequate, otherwise ventilate at 10 breaths per minute while compressions continue uninterrupted. ^[2][5] Give the highest feasible inspired oxygen concentration during CPR. ^[2] If bag-mask ventilation is used, a two-person technique improves seal and patency. ^[2]

If a mechanical ventilator is used during compressions, set a volume-controlled mode with tidal volume 6 to 8 mL per kg of ideal body weight (European/RCUK convention; 6 to 7 mL per kg in the Singapore convention), respiratory rate 10 per minute, maximum inspired oxygen, inspiratory time 1 to 2 seconds, PEEP 0 to 5 cm of water, peak pressure alarm 60 to 70 cm of water, and the flow trigger off. ^[2][5] Check that ventilation is effective; if not, return to manual ventilation. ^[2] Should basic and advanced techniques both fail, trained rescuers should attempt a surgical cricothyroidotomy. ^{[2] [3]}

Aspiration must always be considered. If the chest cannot be inflated after two attempts, think of a foreign body and follow the choking algorithm. ^[1]

Defibrillation treats ventricular fibrillation and pulseless ventricular tachycardia, and the earlier it is delivered the better. Continue CPR while the defibrillator is brought and pads applied, then shock as early as is practical. ^[2] When a defibrillator is immediately available in a witnessed arrest, it is reasonable to shock before starting compressions. ^[5]

Strategy points supported by current guidance:

• Use a single shock, then immediately resume compressions. ^[2][5]
• Compressions continue through charging and stop only at the moment of shock. ^[2][5]
• Initial biphasic energy should be at least 150 J (or the manufacturer's recommended setting); for pulsed biphasic waveforms 130 to 150 J; 360 J for monophasic waveforms. ^[2][5]
• If the first shock fails, escalate energy for subsequent shocks. ^[2][5]
• Use standard energy in obese patients. ^[2]
• Stacked (three in a row) shocks are reserved for witnessed, monitored arrest with a defibrillator immediately available, for example during cardiac catheterisation; even then they count as the first shock for the purposes of giving adrenaline and amiodarone. ^[2]
• For refractory ventricular fibrillation, after ensuring correct pad placement, use a vector change to antero-posterior pads after the third failed shock. ^[2]
• Double sequential defibrillation is not routinely recommended because evidence is limited and the technique is cumbersome. ^[2][5]
• Charge the defibrillator in anticipation of the rhythm check where possible, keep oxygen sources at least 1 metre from the chest, and never defibrillate during manual compressions even with gloves. ^[2]
• If an implanted defibrillator fires during compressions you may feel a shock; if it fails to terminate the rhythm, deliver external shocks with pads placed more than 8 cm from the device. ^[2]

A crucial practical note: whenever asystole is diagnosed, inspect the electrocardiograph carefully for P waves, because true asystole is more likely to respond to pacing than ventricular standstill with atrial activity. ^[2]

Vascular access first: attempt intravenous access before intraosseous, and if two attempts fail within a reasonable time, switch to intraosseous. ^[2][5]

Adrenaline (epinephrine) is the vasopressor of cardiac arrest: give 1 mg intravenously or intraosseously. ^[2][5]

• For a non-shockable rhythm (asystole or pulseless electrical activity), give adrenaline 1 mg as soon as possible after vascular access. ^[2][5]
• For a shockable rhythm (ventricular fibrillation or pulseless ventricular tachycardia), give adrenaline 1 mg after the third shock according to Resuscitation Council (UK) and ERC 2025 guidance. ^[2] Some guidance aligned with the 2025 AHA and 2026 Singapore conventions gives adrenaline after the second defibrillation attempt instead. ^[5]
• Repeat adrenaline 1 mg every 3 to 5 minutes while resuscitation continues. ^[2][5]
• In a highly monitored arrest with an arterial line in place, consider smaller initial increments (50 to 100 micrograms) before moving to 1 mg doses if there is no response. ^[2]

Amiodarone is the antiarrhythmic: give 300 mg intravenously after a total of three shocks in ventricular fibrillation or pulseless ventricular tachycardia, and a further 150 mg after a total of five shocks. This timing applies whether the shockable rhythms occur in sequence (refractory) or recur intermittently. ^[2][5] When amiodarone is unavailable, or local policy prefers it, lidocaine 100 mg intravenously is the alternative (with an additional 50 mg after five shocks in the European convention; 1 to 1.5 mg per kg initially, with 0.5 to 0.75 mg per kg further, in the Singapore convention). ^[2][5]

Thrombolysis: consider immediate thrombolytic therapy when pulmonary embolism is the suspected or confirmed cause, and in selected patients perform CPR for 60 to 90 minutes after administration. ^[2][5]

Fluids: give fluids only if the arrest is hypovolaemic, using isotonic saline or balanced crystalloids. ^[2][5]

Do not routinely give calcium, sodium bicarbonate or corticosteroids during arrest. ^[2][5]

Other useful points: waveform capnography confirms tracheal tube placement, guides compression quality, and signals possible ROSC; a sudden rise in carbon dioxide should make the team look at the patient but not stop compressions on that sign alone. ^[2] With an arterial line in place, aim for a diastolic blood pressure of at least 30 mmHg and end-tidal carbon dioxide of at least 25 mmHg during physiology-guided CPR, and consider starting compressions if systolic pressure falls and remains under 50 mmHg. ^[2] A sudden fall in end-tidal carbon dioxide can signal arrest in a monitored patient. ^{[2] [5] [1]}

Reversible causes must be considered from the outset and in parallel with standard resuscitation, because correcting the cause shortens the arrest and reduces re-arrest. ^[2][5]

Task-directed detail on selected causes:

• Hypovolaemia: an empty ventricle, as in haemorrhage, severe dehydration, or a ruptured aneurysm. Correct by stopping bleeding, giving fluids, and blood products if the rate is fast enough. ^[2][5]
• Hypoxia: a blocked or flooded airway, severe asthma, or pneumonia. Correct by opening the airway, delivering high-flow oxygen, and intubating early if needed. ^[2][5]
• Hydrogen ion (acidosis): severe tissue hypoperfusion or toxin. Do not routinely give sodium bicarbonate; correct ventilation, perfusion and cause instead. ^[2][5]
• Hyper- or hypokalaemia: particularly after renal failure, crush injury, succinylcholine, or insulin excess. Treat hyperkalaemia with calcium, insulin and glucose, beta-2 agonists, and bicarbonate as indicated; hypokalaemia with potassium. ^[5]
• Hypothermia: low core temperature. Do not give up: outcomes can be good with prolonged CPR. Rewarm gradually alongside standard CPR and post-arrest care. ^[2]
• Tension pneumothorax: look for distended neck veins (if present), tracheal deviation, absent breath sounds and hyper-resonance. Relieve with needle decompression followed by a chest drain. ^[2][5]
• Tamponade: in trauma, after cardiac surgery, or with cancer or infection. Beck's triad (hypotension, distended neck veins, muffled heart sounds) may be present. Relieve with pericardiocentesis or thoracotomy. ^[2][5]
• Toxins: poisoning and overdose (opioids, local anaesthetic, organophosphates, beta-blockers, calcium channel blockers). Use specific antidotes (naloxone for opioid poisoning, lipid emulsion for local anaesthetic systemic toxicity) alongside high-quality CPR. ^[2][5]
• Thrombosis: coronary (acute coronary syndrome) or pulmonary (massive pulmonary embolism). For massive pulmonary embolism, thrombolysis or percutaneous or surgical embolectomy should be considered even during arrest. ^[2][5]
• Special circumstances deserve their own algorithms: pregnancy (perimortem caesarean delivery within 5 minutes if no ROSC), drowning (prioritise rescue breathing, then CPR), and massive pulmonary embolism (as above) are discussed in current resuscitation guidance. ^[5]

Point-of-care ultrasound may reveal tamponade or gross right ventricular dilatation suggestive of massive pulmonary embolism, but right ventricular dilatation alone should not be used to diagnose pulmonary embolism. ^[2]

These algorithms apply to an unstable patient immediately before or after cardiac arrest, or a patient who has achieved ROSC.

Bradycardia is defined as a heart rate under 50 beats per minute in the Singapore convention. ^[5] Not every bradycardia needs treatment; intervene when there are adverse signs: hypotension (systolic under 90 mmHg), syncope, heart failure (pulmonary oedema or raised jugular venous pressure), or myocardial ischaemia. ^[2]

• Atropine: give 500 micrograms intravenously, repeating every 3 to 5 minutes to a maximum of 3 mg in the European convention; the equivalent in the Singapore convention is 0.6 mg repeated to 3 mg. ^[2][5]
• If atropine fails or is contraindicated: use isoprenaline (starting at 5 micrograms per minute) or an adrenaline infusion of 2 to 10 micrograms per minute. ^[2]
• Transcutaneous (transthoracic) pacing is a temporary measure that buys time until a transvenous wire can be placed. ^[2]
• Aminophylline 100 to 200 mg by slow intravenous injection is useful for bradycardia after cardiac transplantation or spinal cord injury; atropine should not be given in cardiac transplant recipients because it can worsen atrioventricular block. ^[2]
• Consider glucagon if beta-blockers or calcium channel blockers are suspected as the cause. ^[2]
• Do not give atropine in high-degree atrioventricular block with a wide QRS (it is ineffective and may worsen the block) and it may be ineffective in second-degree Mobitz type II or complete heart block. ^[2][5]
• Whenever asystole is suspected, look for P waves, because this rhythm is more likely to respond to pacing. ^[2]
• If atropine is ineffective and a pacer is not yet at hand, rhythmic blows with a fist over the heart (fist pacing) can be tried until the equipment arrives. ^[2]

Tachyarrhythmias. Electrical cardioversion is the treatment for a tachyarrhythmia in an unstable patient (shock, syncope, heart failure, or myocardial ischaemia) immediately after return of spontaneous circulation. ^[2] A conscious patient needs careful anaesthesia or sedation first. ^[2] Cardioversion shocks must be synchronised with the R wave. ^[2]

Energy levels for the first shock (European convention):

• atrial fibrillation: an initial synchronised shock at maximum output (European convention) or 200 J (Singapore/AHA-aligned convention). ^[2][5]
• atrial flutter and paroxysmal supraventricular tachycardia: 70 to 120 J (European convention), with stepwise increases after that; the Singapore convention begins at 50 J. ^[2][5]
• ventricular tachycardia with a pulse: 120 to 150 J for the initial shock, with stepwise increases; ^[2]
• unstable wide complex tachycardia (Singapore convention): 100 J escalating to the maximum permitted by the defibrillator; ^[5]
• polymorphic ventricular tachycardia and torsades de pointes: do not activate synchronisation; give amiodarone with a normal QT interval, or magnesium 1 to 2 g over 15 minutes if the QT is prolonged. ^[5]

If cardioversion fails and the patient remains unstable, give procainamide 10 to 15 mg per kg (maximum 1 g) over 20 minutes, or amiodarone 300 mg intravenously over 10 to 20 minutes, then re-attempt cardioversion; the amiodarone load may be followed by an infusion of 900 mg over 24 hours. ^[2] Pharmacological treatment may be considered in stable patients with monomorphic ventricular tachycardia. ^[2]

For atrial fibrillation, consider digoxin or amiodarone for acute rate control in instability with severely reduced left ventricular ejection fraction; for stable patients with an ejection fraction under 40 percent, consider digoxin or a beta-blocker to reach a heart rate under 110 per minute. ^[2]

Supraventricular tachycardia can also be managed medically: vagal manoeuvres first in a stable patient, then adenosine 6 mg rapid intravenous bolus followed by 12 mg and then 18 mg if needed; intravenous verapamil 5 to 10 mg or diltiazem 0.25 mg per kg are alternatives with monitoring. ^[5] Beta-blockers and calcium channel blockers should be used cautiously in heart failure with reduced ejection fraction and avoided in pre-excitation. ^[5]

Post-arrest care should be systematic, beginning at the bedside immediately after ROSC and continuing in the intensive care unit. ^[2][3]

• Airway: insert an advanced airway (tracheal intubation where skills are available) for comatose patients, confirm placement with waveform capnography, and provide lung-protective ventilation (6 to 8 mL per kg ideal body weight). ^[3]
• Oxygen: use 100 percent oxygen immediately until oxygen saturation can be measured, then titrate to an arterial oxygen saturation of 94 to 98 percent, avoiding hypoxaemia (partial pressure of oxygen under 8 kPa or 60 mmHg) and hyperoxaemia. ^[3][5]
• Carbon dioxide: target normocapnia (35 to 45 mmHg, 4.7 to 6.0 kPa) and avoid hypocapnia, with arterial blood gas monitoring. ^[3][5]
• Blood pressure: aim for systolic over 100 mmHg or mean arterial pressure over 60 to 65 mmHg (RCUK/ERC) or at least 65 mmHg (Singapore); treat with fluids, noradrenaline, or dobutamine as needed, and avoid hypokalaemia and hyperkalaemia. ^[3][5]
• Diagnosis of cause: prioritise immediate coronary angiography for ST-segment elevation or other high suspicion of coronary occlusion. ^[3][5] If angiography does not show the cause, a head-to-pelvis computed tomography (including CT pulmonary angiography) should be considered. ^[3]
• Temperature control: actively prevent fever, targeting 37.5 degrees C or less in comatose patients for at least 36 to 72 hours. ^[3][5] Do not actively warm a comatose patient who is mildly hypothermic (32 to 36 degrees C) to normothermia. ^[3] Previous routine deep cooling is no longer the standard; current guidance emphasises fever prevention. ^[3][5] Some AHA-aligned protocols still describe a target range of 32 to 37.5 degrees C for at least 36 hours. ^[5] Pre-hospital infusion of large volumes of cold fluid is not recommended. ^[3]
• Seizures: perform EEG from day 1, treat clinical or electrographic seizures with levetiracetam or sodium valproate; do not give prophylactic antiepileptic drugs. ^[3]
• Do not routinely give prophylactic antiarrhythmics, prophylactic antibiotics, steroids, or neuromuscular blocking agents in post-arrest patients, although have a low threshold for antibiotics if pneumonia is suspected. ^[3]
• General care: nurse 30 degrees head-up, short-acting sedation with daily holds, low-rate ("trophic") gastric feeding, stress-ulcer prophylaxis when coagulopathic, and normal glucose management. ^[3]
• Neuroprognostication: in comatose patients, assess after excluding confounders, using clinical examination (pupil and corneal reflexes, myoclonus), EEG, somatosensory evoked potentials, neuron-specific enolase, and brain imaging, with a multimodal strategy at 72 hours or later; no single predictor is 100 percent accurate. ^[3]
• Long-term management of the unexplained arrest: toxicology, genetic testing, device interrogation, repeated ECG and monitoring, cardiac MRI, exercise testing. ^[3]
• Rehabilitation: early mobilisation, ICU diaries, functional assessment before discharge, cardiac rehabilitation as indicated, and follow-up within three months. ^[3]
• Cardiac arrest centres: adults with non-traumatic out-of-hospital cardiac arrest should be cared for at a cardiac arrest centre whenever possible, according to local protocols. ^[3]

Complications arise from both the arrest and its treatment:

• Rib or sternal fractures, pneumothorax, haemothorax and, rarely, liver or splenic injury from compressions. These are common and are not a reason to withhold CPR, because a live person with a fracture is preferable to a dead one. ^[2]
• Hypoxic-ischaemic brain injury, seizures, myoclonus and persistent coma after resuscitation. ^[3]
• Airway injury, aspiration, hypotension or cardiogenic shock after return of spontaneous circulation. ^[3]
• CPR-induced consciousness during compressions. ^[2]
• Renal and multi-organ dysfunction from prolonged low flow. ^[3]

Teams should learn from these events in debrief, since even experienced teams see mechanical quality deteriorate over time. ^[2]

• A transthoracic echocardiogram, available even in some emergency departments, is a key test in the work-up of unexplained arrest; in the arrest itself, clinical emphasis falls on recognition, compression quality and early defibrillation. ^[2]
• Where manual defibrillation is not available, an AED should still be sought and used by anyone at the scene. ^[1]
• Adrenaline is inexpensive and widely available; the priority is giving it rapidly and regularly in non-shockable rhythms. ^[2]
• Where intensive care, coronary angiography and advanced imaging are unavailable, focus on the modifiable factors: oxygenation, ventilation, blood pressure support, fever prevention, and careful airway and sedation management. ^[3]
• Termination and withdrawal decisions must follow local law and ethics; the European guidance used here recognises that standards vary worldwide. ^[4][6]
• Unexplained arrest still merits structured investigation where possible, because of the risk of recurrence. ^[3]

Plain text only (no links): shock; severe haemorrhage and blood products; sepsis; anaphylaxis; airway assessment and management; acute coronary syndromes; pulmonary embolism; stroke; eclampsia and pregnancy emergencies; therapeutic hypothermia and fever control; organ donation; communication of poor news; resuscitation ethics; bradyarrhythmias; ventricular arrhythmias; post-cardiac arrest care.