When a patient collapses in cardiac arrest, the first minutes decide whether they survive. Nurses are usually first on scene and often lead the response until a resuscitation team arrives. Basic life support (BLS) and early defibrillation save the most lives, but knowing how advanced life support (ALS) works helps nurses anticipate the next steps, prepare drugs and equipment, and keep the team focused.
This guide summarises the adult ALS algorithm used by the Resuscitation Council UK and European Resuscitation Council, which closely matches American Heart Association ACLS. Always follow your local protocol and complete accredited training.
Start with high-quality CPR
Everything in ALS rests on good basic life support:
- Confirm cardiac arrest: unresponsive and not breathing normally. Call for help and the arrest team, and get the defibrillator.
- Start chest compressions at 100 to 120 per minute, depth 5 to 6 cm, allowing full recoil.
- Ratio of 30 compressions to 2 breaths until the airway is secured.
- Minimise interruptions. Change the person compressing every 2 minutes to prevent fatigue.
Attach the defibrillator and assess the rhythm
Apply self-adhesive pads (one below the right clavicle, one in the left mid-axillary line at the V6 position) while CPR continues. Pause compressions briefly to check the rhythm. The algorithm then splits into two paths.
Shockable rhythms: VF and pulseless VT
Ventricular fibrillation (VF) is chaotic electrical activity with no organised complexes. Pulseless ventricular tachycardia (pVT) shows broad, fast complexes but no pulse. Both respond to defibrillation, and the earlier the shock, the better the chance of survival.
- Deliver one shock (energy per your device: often 150 to 200 J biphasic for the first shock, escalating if needed).
- To shock safely: continue compressions while the defibrillator charges, ensure oxygen is moved away, give a clear warning (“Stand clear, oxygen away”), check nobody is touching the patient, then shock.
- Immediately resume CPR for 2 minutes without checking the pulse.
- Reassess the rhythm after 2 minutes.
- After the third shock, give adrenaline 1 mg IV/IO and amiodarone 300 mg IV/IO.
- Repeat adrenaline 1 mg every 3 to 5 minutes (every alternate cycle).
- Consider a further dose of amiodarone 150 mg after the fifth shock.
For a witnessed arrest in a monitored patient (for example in a cardiac unit), up to three quick successive shocks may be given before starting compressions.
Non-shockable rhythms: PEA and asystole
Pulseless electrical activity (PEA) means there is organised electrical activity on the monitor, but no pulse. Asystole is a near-flat line. Shocks don’t help these rhythms.
- Continue CPR at 30:2.
- Give adrenaline 1 mg IV/IO as soon as access is obtained.
- Repeat adrenaline every 3 to 5 minutes.
- Reassess the rhythm every 2 minutes.
- Search for and treat reversible causes.
With asystole, check the leads are attached and the gain is turned up, because fine VF can look like asystole.
Reversible causes: the 4 Hs and 4 Ts
Survival from PEA and asystole depends largely on finding and fixing the cause:
4 Hs
- Hypoxia: ensure effective ventilation with high-concentration oxygen.
- Hypovolaemia: bleeding or severe dehydration; give fluids or blood and stop the bleeding.
- Hypo/hyperkalaemia and other metabolic causes: check potassium, glucose, calcium; treat high potassium urgently.
- Hypothermia/hyperthermia: check temperature and correct it.
4 Ts
- Thrombosis: coronary (heart attack) or pulmonary (massive pulmonary embolism); consider thrombolysis.
- Tension pneumothorax: needs needle or finger decompression.
- Tamponade: fluid around the heart; needs drainage.
- Toxins: drug overdose or poisoning; specific antidotes may help.
Point-of-care ultrasound, if available and used by a trained clinician, can help identify several of these causes.
Airway and access
- Start with simple airway manoeuvres and bag-valve-mask ventilation with high-flow oxygen.
- A supraglottic airway (such as an i-gel) or tracheal tube may be placed by trained staff. After an advanced airway is in place, give continuous compressions with about 10 breaths per minute.
- Use waveform capnography if available; a sudden rise in end-tidal CO2 may signal return of spontaneous circulation.
- Get IV access; if that fails, intraosseous (IO) access is a fast alternative.
The nurse’s roles during an arrest
- Compressions: the most important job. Take turns, and say if you’re tiring.
- Defibrillator operator: pads, charging, safe shocks.
- Airway assistant: suction, bag-valve-mask, oxygen.
- Drugs: prepare and give adrenaline and amiodarone as instructed, flush each drug with 20 mL saline, and call out what was given.
- Scribe/timekeeper: record times of arrest, shocks, rhythm checks and drugs, and remind the leader when 2-minute cycles end and when adrenaline is due.
- Runner: fetch equipment, blood gas, notes and allergy information.
- Family support: a staff member should stay with relatives. Many guidelines support offering family members the chance to be present.
After return of spontaneous circulation (ROSC)
If a pulse returns, the work is not over:
- Use an ABCDE approach.
- Target oxygen saturation of 94 to 98% (avoid both hypoxia and excess oxygen).
- Record a 12-lead ECG; the patient may need urgent coronary intervention.
- Maintain blood pressure and treat the cause.
- Monitor glucose and temperature, and avoid fever.
- Arrange transfer to critical care.
After the event
Cardiac arrests are stressful, whatever the outcome. A short team debrief helps everyone learn and process what happened. Check on colleagues, especially new nurses and students. Document clearly and complete any incident or audit reports required.
Key points
- Good CPR and early defibrillation save lives.
- Shockable rhythms: shock, then 2 minutes of CPR; adrenaline and amiodarone after the third shock.
- Non-shockable rhythms: adrenaline as soon as possible, then every 3 to 5 minutes.
- Always look for the 4 Hs and 4 Ts.
- Every nurse has a role in the team.