Acute Medicine: Cardiac arrest, advanced life support and peri-arrest arrhythmias

• Basic resuscitation: The Chain of Survival | Adult Basic Life Support | In-hospital Resuscitation -the First Minutes | Choking
• Advanced life support: The ALS Algorithm | Shockable Rhythms -VF and Pulseless VT | Non-shockable Rhythms -PEA and Asystole | Reversible Causes -4 Hs and 4 Ts | Airway, Capnography and Drugs in Cardiac Arrest | Special Circumstances
• After resuscitation: Post-resuscitation Care | Stopping Resuscitation and Prognosis
• Peri-arrest arrhythmias: Bradycardia | Tachycardia
• Children and newborns: Paediatric and Newborn Life Support
• Revision: Resuscitation at a Glance | Spot the Rhythm or Action | Exam-style Scenarios | Key Points | Guidelines and Further Reading

🩺 Cardiac arrest, advanced life support and peri-arrest arrhythmias. Survival from cardiac arrest depends on early recognition, high-quality chest compressions with minimal interruptions, and early defibrillation for shockable rhythms. Every doctor must be able to lead the first minutes of a resuscitation attempt. This page follows Resuscitation Council UK (RCUK) 2021 guidelines; arrhythmia management outside arrest is in the Cardiology chapters.
Your four questions in every cardiac arrest: Is CPR high-quality and continuous? Is the rhythm shockable? What is the reversible cause (4 Hs and 4 Ts)? Is resuscitation in this patient's interests -is there a DNACPR decision or ReSPECT form?

The Chain of Survival

• Four links:
  1. Early recognition and call for help -prevent arrest where possible (respond to deterioration -page 1).
  2. Early CPR -buys time (doubles or triples survival from out-of-hospital arrest).
  3. Early defibrillation -survival from VF falls by about 10% for every minute without defibrillation; public access defibrillators (AEDs).
  4. Post-resuscitation care -restores quality of life.
• Outcomes -survival to hospital discharge after in-hospital cardiac arrest is about 1 in 5 overall (much higher for monitored VF, much lower for unmonitored PEA/asystole or with frailty and multiple comorbidities); out-of-hospital survival in the UK is under 1 in 10.
• Most in-hospital arrests are non-shockable (PEA or asystole) and follow progressive deterioration -prevention is key.
• Decisions about CPR should be made in advance where possible (DNACPR, ReSPECT) -see page 1 and the Older Person chapter.

Adult Basic Life Support

• Safety -make sure the scene is safe.
• Check for a response -shake shoulders, shout "Are you all right?"
• Open the airway (head tilt–chin lift) and check breathing for no more than 10 seconds -agonal gasps (infrequent, noisy breaths) are not normal breathing -treat as cardiac arrest.
• Call for help -999 (or 2222 in hospital); send someone for an AED; put the phone on speaker.
• Start chest compressions:
  • Hands in the centre of the chest (lower half of the sternum).
  • Depth 5–6 cm; rate 100–120 per minute.
  • Allow full recoil; minimise interruptions.
• Rescue breaths -30 compressions : 2 breaths (each breath over about 1 second, enough to make the chest rise); compression-only CPR if unable or unwilling to give breaths.
• AED -switch on and follow the prompts; continue CPR while pads are applied; stand clear for analysis and shocks; resume CPR immediately after a shock.
• Swap compressors every 2 minutes to keep quality high.
• Continue until help arrives, the patient shows signs of life (waking, moving, opening eyes, breathing normally), or you are exhausted.

In-hospital Resuscitation -the First Minutes

• Recognise -unresponsive and not breathing normally → shout for help and call the resuscitation team (2222); note the time.
• Start CPR -30:2 with bag–valve–mask and oxygen (or a pocket mask); use a firm surface (CPR mode on the bed).
• Attach the defibrillator (self-adhesive pads -one below the right clavicle, one in the left mid-axillary line at V6 position) and check the rhythm as soon as possible.
• Monitored and witnessed VF/VT (e.g. coronary care, cath lab) -give up to three quick successive (stacked) shocks before starting compressions.
• Team roles -team leader, airway, compressions (rotate every 2 minutes), defibrillator, IV/IO access and drugs, scribe (times, rhythms, drugs, shocks).
• Gather information -the patient's history, observations before arrest, DNACPR or ReSPECT status, recent investigations (potassium, troponin).
• Patient wishes -if a valid DNACPR decision exists, don't start CPR (but treat reversible problems like choking).

Choking

• Recognise -sudden onset while eating, clutching the throat, unable to speak or breathe (severe), or coughing effectively (mild).
• Mild obstruction (effective cough) -encourage coughing; monitor.
• Severe obstruction (ineffective cough), conscious:
  • Up to 5 back blows (between the shoulder blades, leaning forward).
  • Then up to 5 abdominal thrusts (Heimlich).
  • Alternate until relieved or the person becomes unconscious.
• Unconscious -call for help and start CPR (compressions may dislodge the object); look in the mouth before breaths; experienced staff may use laryngoscopy and Magill forceps.
• After abdominal thrusts -medical review (internal injuries).
• Children -back blows and abdominal thrusts (chest thrusts for infants under 1 year).

The ALS Algorithm

• Unresponsive and not breathing normally → call the resuscitation team → CPR 30:2 → attach defibrillator/monitor → minimise interruptions.
• Assess the rhythm (pause CPR briefly -under 5 seconds):
  • Shockable (VF or pulseless VT) → one shock → immediately resume CPR for 2 minutes.
  • Non-shockable (PEA or asystole) → immediately resume CPR for 2 minutes.
• Repeat rhythm checks every 2 minutes.
• During CPR:
  • Ensure high-quality chest compressions (rate, depth, recoil).
  • Minimise interruptions -under 5 seconds for rhythm checks and shocks; charge the defibrillator during compressions.
  • Give oxygen; use waveform capnography.
  • Continuous compressions once an advanced airway is in place (ventilate at about 10 breaths per minute).
  • Vascular access -IV, or intraosseous if IV is difficult.
  • Give adrenaline every 3–5 minutes; amiodarone after 3 shocks.
  • Identify and treat reversible causes.
  • Consider ultrasound imaging (without interrupting compressions), mechanical CPR (transfer or prolonged CPR), coronary angiography and PCI, and extracorporeal CPR in selected settings.
• Return of spontaneous circulation (ROSC) → post-resuscitation care (ABCDE approach, see below).

Shockable Rhythms -VF and Pulseless VT

• Ventricular fibrillation (VF) -chaotic, irregular waveform with no identifiable QRS complexes; coarse or fine.
• Pulseless ventricular tachycardia (pVT) -regular broad complex tachycardia with no pulse.
• Sequence:
  • Shock 1 → CPR 2 minutes → rhythm check.
  • Shock 2 → CPR 2 minutes → rhythm check.
  • Shock 3 → CPR → give adrenaline 1 mg IV and amiodarone 300 mg IV (after the third shock).
  • Then adrenaline 1 mg every 3–5 minutes (alternate cycles).
  • Amiodarone 150 mg after the fifth shock.
  • Lidocaine (1 mg/kg) is an alternative if amiodarone is unavailable.
• Energy -biphasic shocks -first shock at least 150 J (per manufacturer); subsequent shocks at the same or higher energy.
• Safety -remove oxygen from the immediate area during shocks; everyone clear; continue compressions while charging.
• Refractory VF -check pad position (consider changing to anterior–posterior), treat reversible causes (ischaemia -PCI; hyperkalaemia; toxins), consider double sequential defibrillation (specialist), mechanical CPR and ECPR.
• Causes -acute coronary occlusion (commonest), cardiomyopathies, channelopathies (long QT, Brugada), electrolyte disturbance, drugs, electrocution.

Non-shockable Rhythms -PEA and Asystole

• Pulseless electrical activity (PEA) -organised electrical activity that would normally produce a pulse, but there is no output -usually from a reversible cause (hypovolaemia, hypoxia, tamponade, tension pneumothorax, PE, metabolic).
• Asystole -no electrical activity (check leads are connected and gain is up; look for P waves -"P-wave asystole" may respond to pacing).
• Sequence:
  • CPR 30:2 (or continuous with an advanced airway).
  • Adrenaline 1 mg IV as soon as access is obtained, then every 3–5 minutes.
  • Rhythm check every 2 minutes; if it changes to VF/pVT, follow the shockable pathway.
  • If organised rhythm, check for a pulse (central) and signs of life -ROSC.
• Focus on reversible causes -this is how PEA is survived; use point-of-care ultrasound (tamponade, pneumothorax, right ventricular dilatation, hypovolaemia) by trained operators during rhythm checks.
• Atropine is no longer recommended in asystole or PEA.

Reversible Causes -4 Hs and 4 Ts

Airway, Capnography and Drugs in Cardiac Arrest

• Airway -start with basic techniques (bag–valve–mask with oropharyngeal airway, two-person technique); supraglottic airway (i-gel) or tracheal intubation by skilled staff with minimal interruption to compressions.
• Waveform capnography (end-tidal CO₂):
  • Confirms tube placement (no trace = oesophageal intubation -"no trace = wrong place").
  • Monitors CPR quality (low values suggest poor compressions).
  • Sudden rise may indicate ROSC (reduce unnecessary interruptions for pulse checks).
  • Persistently very low values after prolonged CPR may help (with other factors) inform decisions to stop.
• Drugs:
  • Adrenaline 1 mg IV (10 mL of 1:10,000 or 1 mL of 1:1,000) -increases ROSC; give with flushes.
  • Amiodarone 300 mg IV after 3 shocks; 150 mg after 5 shocks (VF/pVT).
  • Calcium chloride 10% 10 mL -hyperkalaemia, hypocalcaemia, calcium channel blocker overdose.
  • Sodium bicarbonate -hyperkalaemia, tricyclic overdose (not routinely).
  • Magnesium 2 g IV -torsades de pointes, hypomagnesaemia.
  • Thrombolysis -suspected or confirmed PE.
  • Fluids -only if hypovolaemia is suspected.
• Intraosseous access -proximal humerus or tibia; all resuscitation drugs can be given.
• Don't give drugs via the tracheal tube (no longer recommended).

Special Circumstances

• Pregnancy (over about 20 weeks):
  • Manual left uterine displacement (relieves aortocaval compression).
  • Early advanced airway (aspiration risk); hand position may be slightly higher.
  • Resuscitative hysterotomy (perimortem caesarean) -start by 4 minutes and deliver within 5 minutes if no ROSC -improves the mother's chance of survival.
• Hypothermia -"not dead until warm and dead"; check for signs of life for up to 1 minute; up to 3 shocks then withhold further shocks and adrenaline until the core temperature is above 30°C; double drug intervals between 30–35°C; rewarm (ECMO in specialist centres).
• Drowning -5 initial rescue breaths, then CPR; hypoxia is the main problem.
• Traumatic cardiac arrest -treat reversible causes simultaneously (control bleeding, hypovolaemia, hypoxia, tension pneumothorax, tamponade) -compressions are less of a priority (see the Major Trauma page).
• Anaphylaxis -adrenaline per ALS; large fluid volumes; prolonged CPR.
• Hyperkalaemia -IV calcium, insulin–glucose, sodium bicarbonate; consider dialysis during CPR.
• Opioid overdose -naloxone if respiratory arrest with a pulse; in cardiac arrest follow ALS (naloxone has limited role).
• Local anaesthetic toxicity -20% lipid emulsion; prolonged CPR.
• After cardiac surgery -up to 3 stacked shocks for VF; pacing via epicardial wires; emergency resternotomy within 5 minutes (see the Cardiothoracic Surgery page).
• Patients with tracheostomies or laryngectomies -ventilate via the stoma (laryngectomy patients can't be oxygenated via the mouth).
• Obesity -adequate compression depth; rotate rescuers more often.
• Prone patients -may start CPR in the prone position (e.g. ICU) until turned.

Post-resuscitation Care

• Immediately after ROSC -ABCDE:
  • Airway and breathing -maintain the airway; SpO₂ 94–98% (avoid hypoxia and hyperoxia); normal PaCO₂ (ventilate to normocapnia); chest X-ray.
  • Circulation -12-lead ECG; aim for systolic BP over 100 mmHg or MAP of at least 65 mmHg (fluids, vasopressors, inotropes); echo.
  • Coronary angiography and PCI -emergently for STEMI; consider for suspected cardiac cause without STEMI.
  • Disability -glucose (treat high levels; avoid hypoglycaemia), treat seizures; CT head if a neurological cause is possible.
• Temperature control -prevent fever (above about 37.7°C) for at least 72 hours in patients who remain comatose (ERC–ESICM guidance).
• Critical care admission for most patients who remain unconscious -sedation, ventilation, organ support.
• Find and treat the cause -ischaemia, electrolytes, PE, drugs, sepsis, bleeding.
• Prognostication -not before 72 hours after ROSC in comatose patients (off sedation), using a multimodal approach -clinical examination (pupillary and corneal reflexes, myoclonus), EEG, somatosensory evoked potentials, neuron-specific enolase, brain imaging.
• Secondary prevention -ICD for survivors of VF/VT without a reversible cause; investigate inherited cardiac conditions (and family screening); rehabilitation and psychological support.
• Organ donation -consider when treatment is withdrawn or brain death occurs.

Stopping Resuscitation and Prognosis

• Deciding to stop -a team decision led by the team leader, considering:
  • Duration of CPR and response.
  • The initial rhythm (asystole worse than VF).
  • Whether the arrest was witnessed and how quickly CPR started.
  • Reversible causes treated or not (prolonged CPR is reasonable in hypothermia, drowning, poisoning, PE after thrombolysis).
  • The patient's premorbid health, frailty and known wishes.
  • Capnography and ultrasound findings (supporting information only).
• No fixed time limit -but very prolonged CPR in asystole without a reversible cause is rarely successful.
• After stopping -confirm death (observe for at least 5 minutes for absent cardiorespiratory function), record the time; inform the family sensitively; support the team (debrief); consider whether the death needs coroner referral (e.g. unexpected).
• Family presence during resuscitation -can be helpful for some families if supported by a dedicated staff member.
• DNACPR -if CPR is unlikely to succeed or is not wanted, decisions should be made before arrest (see page 1 and the Older Person chapter).

Bradycardia

• Assess with ABCDE, 12-lead ECG, IV access, correct electrolytes (potassium, magnesium, calcium), and look for causes (MI, drugs -beta-blockers, calcium channel blockers, digoxin, amiodarone, hypothermia, hypothyroidism, raised intracranial pressure, hyperkalaemia).
• Adverse features (life-threatening):
  • Shock (hypotension, pallor, sweating, cold extremities, confusion).
  • Syncope.
  • Myocardial ischaemia.
  • Severe heart failure.
• If adverse features:
  • Atropine 500 micrograms IV; if not effective, repeat to a maximum of 3 mg.
  • If still not responding -isoprenaline or adrenaline infusion (2–10 micrograms/minute), or other drugs (dopamine; glucagon for beta-blocker or CCB overdose; DigiFab for digoxin toxicity), and/or transcutaneous pacing (with analgesia and sedation).
  • Seek expert help for transvenous pacing.
• Risk of asystole (even without adverse features -seek expert help for pacing):
  • Recent asystole.
  • Mobitz type II AV block.
  • Complete (third-degree) heart block with broad QRS.
  • Ventricular pause over 3 seconds.
• Caution with atropine -after heart transplant (can cause paradoxical block -use aminophylline) and in acute MI (may increase ischaemia).

Tachycardia

• Assess with ABCDE, oxygen if hypoxic, IV access, 12-lead ECG, correct electrolytes, look for causes (sepsis, hypovolaemia, pain, PE, thyrotoxicosis).
• Sinus tachycardia is a response -treat the cause, not the rate.
• Unstable -adverse features (shock, syncope, myocardial ischaemia, severe heart failure; or heart rate over 150 for broad complex rhythms with symptoms):
  • Synchronised DC cardioversion -up to 3 attempts (sedation or anaesthesia if conscious).
  • If unsuccessful -amiodarone 300 mg IV over 10–20 minutes, then repeat cardioversion; amiodarone 900 mg over 24 hours.
• Stable -no adverse features -is the QRS narrow (under 0.12 s) or broad? Regular or irregular?

  Rhythm	Treatment
  Broad, regular (VT or uncertain)	Amiodarone 300 mg IV over 10–60 minutes (or as directed by experts); if known SVT with bundle branch block, treat as narrow complex
  Broad, irregular	AF with bundle branch block (treat as AF); pre-excited AF (WPW -avoid AV node blockers -no adenosine, digoxin, verapamil, diltiazem -consider cardioversion or flecainide); polymorphic VT / torsades -magnesium 2 g IV over 10 minutes
  Narrow, regular (SVT -AVNRT, AVRT)	Vagal manoeuvres (modified Valsalva -blow into a syringe, then lie flat with legs raised); adenosine 6 mg rapid IV bolus (large vein, flush), then 12 mg, then 18 mg; continuous ECG. If adenosine fails or is contraindicated (severe asthma) -verapamil or a beta-blocker. Atrial flutter -adenosine reveals flutter waves -rate control
  Narrow, irregular (usually AF)	Rate control -beta-blocker (or diltiazem; digoxin or amiodarone in heart failure); consider anticoagulation; rhythm control (cardioversion) if onset under 48 hours (see the Cardiology chapters)

• Adenosine -very short half-life; warn the patient (transient chest discomfort, flushing, feeling of impending doom); avoid in asthma; reduce dose with dipyridamole, after heart transplant, or via central line; dipyridamole and carbamazepine enhance; theophylline blocks.

Paediatric and Newborn Life Support

• Paediatric arrests are usually respiratory or from shock (hypoxia) -not primary cardiac.
• Paediatric BLS (RCUK):
  • Open the airway; give 5 initial rescue breaths.
  • If no signs of life -15 compressions : 2 breaths (healthcare providers).
  • Compress at least one-third of the chest depth (about 4 cm infants, 5 cm children); rate 100–120/minute.
  • Infants -two thumbs encircling (two rescuers) or two fingers; children -one or two hands.
• Paediatric ALS doses -adrenaline 10 micrograms/kg IV/IO (maximum 1 mg); amiodarone 5 mg/kg after the 3rd and 5th shocks; shock 4 J/kg; fluid bolus 10 mL/kg; glucose 2 mL/kg of 10%.
• Newborn life support (at birth):
  • Dry and stimulate, keep warm (cover the head), start the clock.
  • Assess tone, breathing and heart rate.
  • If not breathing -open the airway and give 5 inflation breaths (2–3 seconds each); reassess.
  • If chest moving but heart rate under 60 after 30 seconds of effective ventilation -chest compressions 3:1 with ventilation.
  • Start with air in term babies (21%) -increase oxygen if needed.

Resuscitation at a Glance

Spot the Rhythm or Action

Exam-style Scenarios

1. A 64-year-old man on the cardiology ward with chest pain collapses. He is unresponsive and not breathing normally. The monitor shows VF.
Answer: Witnessed, monitored VF cardiac arrest.

• Call for help (2222); give up to three quick successive shocks (rhythm check after each), then CPR 30:2.
• Continue the shockable algorithm -if VF persists, adrenaline 1 mg and amiodarone 300 mg after the third shock (stacked shocks count as the first); minimise interruptions; airway and capnography.
• Likely coronary occlusion -after ROSC, 12-lead ECG and emergency angiography and PCI.

2. A 78-year-old woman on dialysis who missed a session is found in cardiac arrest. The rhythm is a broad, slow, bizarre complex with no pulse.
Answer: PEA arrest, likely from hyperkalaemia.

• CPR, adrenaline 1 mg as soon as possible, then every 3–5 minutes.
• IV calcium chloride 10% 10 mL, insulin 10 units with glucose, consider sodium bicarbonate; check potassium on a blood gas.
• Consider dialysis during CPR in specialist settings; check DNACPR status if not yet known.

3. A 70-year-old man has dizziness and BP 78/50. ECG shows complete heart block with broad QRS complexes, rate 32. He takes bisoprolol and digoxin.
Answer: Bradycardia with adverse features (shock).

• ABCDE; atropine 500 micrograms IV, repeat to 3 mg; check potassium and digoxin level.
• If no response -isoprenaline or adrenaline infusion, transcutaneous pacing (with analgesia); consider DigiFab if digoxin toxicity and glucagon for beta-blocker toxicity.
• Expert help for transvenous pacing; stop bisoprolol and digoxin; look for ischaemia.

4. A 25-year-old woman has palpitations. HR 190, regular narrow complex tachycardia, BP 118/76, no chest pain. She has no asthma.
Answer: Stable SVT (likely AVNRT).

• Modified Valsalva manoeuvre first (strain then lie flat with legs raised).
• If unsuccessful -adenosine 6 mg rapid IV bolus with flush and continuous ECG, then 12 mg, then 18 mg; warn her about brief unpleasant sensations.
• If still unresolved -verapamil or a beta-blocker; refer to cardiology (ablation for recurrent episodes).

5. After 15 minutes of CPR and two cycles of adrenaline, a 58-year-old man has ROSC after a VF arrest. He remains comatose. SpO₂ 100% on 15 L/min, BP 85/50. ECG shows ST elevation in V1–V4.
Answer: Post-resuscitation care after STEMI-related arrest.