Cardiac Arrest and Advanced Life Support (ALS)
Resuscitation Council UK Adult Advanced Life Support Guidelines (2021)
Changes made to this article:
- Link to the latest 2025 Resuscitation Guidelines updated
- New emphasis on mechanical chest compression devices (e.g. LUCAS device): “Consider mechanical chest compressions only if high-quality manual chest compression is not practical or compromises provider safety.“
There were no major changes in the 2025 Resuscitation Council UK guidelines that affect UKMLA-relevant content
Date: 24/11/25
Background Information
Definition
Cardiac arrest is defined as the abrupt cessation of cardiac mechanical activity, resulting in the absence of signs of circulation (triad of consciousness, breathing and detectable pulse)
Recognition
BLS guidelines:
- Identify cardiac arrest and start CPR in any unresponsive person with absent or abnormal breathing
- Slow, laboured breathing (agonal breathing) should be considered a sign of cardiac arrest
The presence of an unpalpable central pulse is not required to identify cardiac arrest or to initiate CPR, especially in lay rescuers.
For healthcare providers, a pulse check may be performed, but it should not take more than 10 seconds, and CPR should be initiated if a pulse is not definitely felt or if there is any doubt about the presence of a pulse.
Classification
The rhythm-based classification is critical, as it directly guides resuscitation:
| Type | Rhythm | ECG features |
|---|---|---|
| Shockable rhythm | Pulseless ventricular tachycardia (pVT) | Regular wide QRS complexes with a rate of >100 bpm |
| Ventricular fibrillation (VF) | Rapid, chaotic, and grossly irregular electrical activity with no identifiable QRS complexes, P waves, or T waves | |
| Non-shockable rhythm | Asystole | Flat or nearly flat line (due to complete absence of ventricular electrical activity) |
| Pulseless electrical activity (PEA) | The presence of organised electrical activity (including sinus rhythm, atrial rhythms or ventricular rhythms), but without a palpable pulse (or effective cardiac output)
(The heart’s electrical system is functioning to produce coordinated electrical signals, but the cardiac muscle fails to contract effectively enough to generate effective cardiac output) |
Be aware that ventricular tachycardia (VT) can present with or without a pulse. Note that they have distinctly different management:
- f there is no pulse → follow the ALS algorithm (CPR + defibrillation)
- If there is a pulse → follow the peri-arrest tachycardia algorithm (see the Tachycardia (Peri-Arrest) Management article)
Reversible Causes
4Hs and 4Ts
- Hypoxia
- Hypovolaemia
- Hyperkalaemia (hypokalaemia, hypoglycaemia, hypocalcaemia, acidaemia and other metabolic disorders)
- Hypothermia
- Tension pneumothorax
- Tamponade (cardiac)
- Thrombosis (coronary or pulmonary thrombosis) (i.e. acute coronary syndrome and pulmonary embolism, respectively)
- Toxins
Bedside ultrasound plays a crucial role in identifying reversible causes of cardiac arrest. It can help detect or exclude:
- Tension pneumothorax – suggested by the absence of lung sliding
- Cardiac tamponade – suggested by pericardial effusion with chamber collapse
- Pulmonary embolism – suggested by a dilated right ventricle and signs of right ventricular strain
- The leading cause of cardiac arrest in adults is cardiac problems (e.g. myocardial infarction)
- While the leading cause in children is hypoxia (respiratory-related problems)
Management
ALS interventions take absolute priority in cardiac arrest. It is also important to check for reversible causes and treat them accordingly, but should not interrupt or delay ALS interventions.
Cardiac Arrest Management (ALS Algorithm)
- Call for help (“Cardiac Arrest Call” telephone number: 2222)
- Start CPR immediately
The following things should be carried out simultaneously by the resuscitation team:
- Attach defibrillator and assess rhythm
- Gain IV access, if not possible IO access
- Airway management
- High flow oxygen via bag valve mask ventilation
Subsequent management depends on whether the rhythm is shockable or non-shockable.
Shockable Rhythm Algorithm
Use of drugs in the shockable rhythm algorithm:
- Adrenaline is only given after 3rd shock / cycle. Once adrenaline has been given, repeat every 3-5 minutes or alternating cycles (i.e. after 3rd, 5th, 7th, 9th shock and so on…).
- Amiodarone is only given TWICE MAXIMUM throughout the ALS, after 3rd and 5th shock. (300mg and 150mg, respectively). Unlike adrenaline, amiodarone should not be repeated further after 2 times.
If amiodarone is not available, lidocaine is an alternative (a class Ib antiarrhythmic): 100mg to be given after the 3rd shock, and 50mg after the 5th shock.
Once a shockable rhythm is identified on monitor / defibrillator
- Deliver 1 shock (1st shock)
- No drugs given here
- Resume CPR immediately for 2 minutes
- After 2 minutes, pause for <5 sec to reassess the rhythm
Shockable rhythm persists (2nd cycle)
- Deliver 1 shock (2nd shock)
- No drugs given here
- Resume CPR immediately for 2 minutes
- After 2 minutes, pause for <5 sec to reassess the rhythm
Shockable rhythm persists (3rd cycle)
- Deliver 1 shock (3rd shock)
- Resume CPR immediately for 2 minutes AND administer 1mg of 1:10,000 adrenaline and 300mg of amiodarone
- After 2 minutes, pause for <5 sec to reassess the rhythm
- Shockable rhythm persists
Shockable rhythm persists (4th cycle)
- Deliver 1 shock (4th shock)
- No drugs given here
- Resume CPR immediately for 2 minutes
- After 2 minutes, pause for <5 sec to reassess the rhythm
Shockable rhythm persists (5th cycle)
- Deliver 1 shock (5th shock)
- Resume CPR immediately for 2 minutes AND administer 1mg of 1:10,000 adrenaline AND 150 mg of amiodarone
- After 2 minutes, pause for <5 sec to reassess the rhythm
- Shockable rhythm persists
If there is a combination of clinical and physiological signs of ROSC such as waking, purposeful movement, arterial waveform or sharp rise in ETCO2, consider stopping chest compressions for rhythm analysis, and if appropriate a pulse check.
Non-shockable Rhythm Algorithm
Once a non-shockable rhythm is identified, adrenaline is given immediately
- Once adrenaline has been given, repeat every 3-5 minutes or alternating cycles (i.e. after 3rd, 5th, 7th shock and so on…)
- Amiodarone (or lidocaine) should NOT be given in the non-shockable algorithm
As suggested in its name, do not give shocks (i.e. defibrillation) in non-shockable rhythms
Non-shockable rhythm identified on monitor / defibrillator
- Resume CPR immediately for 2 minutes AND administer 1mg of 1:10,000 adrenaline
- After 2 minutes, pause for <5 sec to reassess the rhythm
Non-shockable rhythm persists: (2nd cycle)
- Resume CPR immediately for 2 minutes
- No drugs given here
- After 2 minutes, pause for <5 sec to reassess the rhythm
Non-shockable rhythm persists: (3rd cycle)
- Resume CPR immediately for 2 minutes AND administer 1mg of 1:10,000 adrenaline
- After 2 minutes, pause for <5 sec to reassess the rhythm
Down the line, adrenaline will be given in the 5th cycle, 7th cycle and so on…
If there is a combination of clinical and physiological signs of ROSC such as waking, purposeful movement, arterial waveform or sharp rise in ETCO2, consider stopping chest compressions for rhythm analysis, and if appropriate a pulse check.
Components of ALS
Cardiopulmonary Resuscitation (CPR)
CPR is made up of:
- Chest compression
- Depth: 5-6 cm (adults), 5 cm (children), 4 cm (infants)
- Rate: 100-120 compressions/min (across all ages)
- Rescue breaths
- If trained → 2 rescue breaths after every 30 compressions (compression: rescue breaths ratio = 30:2) (ratio may change if a supraglottic airway or definitive airway is in situ, see below)
- If unable or unwilling to do so → give continuous chest compression
The 2025 guideline states: “Consider mechanical chest compressions only if high-quality manual chest compression is not practical or compromises provider safety.”
This is consistent with American ALS guidance, which does not recommend the routine use of mechanical compression devices and instead emphasises high-quality manual chest compressions as the standard of care.
Do not mix up the CPR ratios in various age groups:
- Neonates (0-28 days): 3:1
- Children (1 month – puberty): 15:2
- Adults: 30:2
Defibrillation
Strategy
Antero-lateral pad position is the position of choice for initial pad placement.
- First pad: below the right clavicle, next to the sternum
- Apical (lateral) pad position: mid-axillary line, level with V6 ECG electrode position or female breast (i.e. below the axilla)
- Click to view alternative positions.
Continue chest compression when:
- The defibrillator is being retrieved
- Pads are being applied
- The defibrillator is charging
- Aim for a < 5 sec interruption in chest compression during the pre-shock and post-shock pause
- Immediately resume chest compressions after shock delivery
Energy Levels and Shocks
- If shockable rhythm is identified on monitor, give a single shock and resume the 2-minute chest compression cycle
- Three-stacked shocks may be considered if a shockable rhythm occurs during a witnessed, monitored cardiac arrest with a defibrillator immediately available (e.g. during cardiac catheterisation or in a high-dependency area)
- Initial shock energy level: 120-360 J. Increase energy level for subsequent shocks using a fixed or escalating strategy up to maximum output of the defibrillator
Safety Precautions
- To minimise risk of fire:
- Take off all oxygen delivery devices and place ≥1 m away from the patient’s chest
- Ventilator circuits should remain attached
- If the patient has an implantable device: place the pad >8 cm away from the device or use an alternative pad position.
- During manual chest compressions, ‘hands-on’ defibrillation, even when wearing clinical gloves, is a risk to the rescuer. (check what this means)
Airway and Ventilation
Airway
During CPR, start with basic airway techniques and progress stepwise according to the skills of the rescuer. Hierarchy of airway techniques:
| Hierarchy | Technique / device |
|---|---|
| Basic airway manoeuvres |
|
| Airway adjuncts |
|
| Supraglottic airways (SGA) |
|
| Definitive airway |
|
If ETT is indicated:
- Only rescuers with a high tracheal intubation success rate should use tracheal intubation
- Aim for < 5 sec interruption in chest compression for tracheal intubation.
- Use waveform capnography to confirm tracheal tube position.
Ventilation
- Give the highest feasible inspired oxygen during CPR
- Give each breath over 1 sec to achieve a visible chest rise
Ventilation when an ETT or SGA is placed:
- Ventilate at a rate of 10 breaths/min (i.e. 1 breath every 6 sec)
- Continue chest compressions without pausing during ventilations
- With a SGA, if gas leakage results in inadequate ventilation, pause compressions for ventilation using a compression-ventilation ratio of 30:2
Drugs and Fluids
Vascular access
- First attempt IV access
- If unfeasible or unsuccessful → consider IO access
Drugs
Adrenaline (Vasopressor)
Adrenaline dose in ALS: 1mg (10mL of 1 in 10,000) to be given via IV/IO route
Give adrenaline in:
- Non-shockable rhythm: immediately once identified
- Shockable rhythm: after the 3rd shock
Once adrenaline has been given, repeat every 3-5 minutes or at alternative cycles whilst ALS continues (this applies to both shockable and non-shockable rhythms)
Do not mix up the doses of adrenaline in ALS vs anaphylaxis:
- ALS: always 1mg of 1:10,000 adrenaline (IV/IO route)
- Anaphylaxis (adults): 0.5mg of 1:1,000 adrenaline (IM route) (other age group has different doses, but still use 1:1,000 adrenaline)
To be clear, ALS uses one in ten-thousand adrenaline, and anaphylaxis uses one in one-thousand adrenaline.
Pharmacology:
- Adrenaline is a non-selective alpha- and beta-adrenergic agonist – causes vasoconstriction, +ve inotrophic effect + bronchodilation
- Noradrenaline is a predominantly alpha-adrenergic agonist – which causes mainly vasoconstriction
Antiarrhythmic Drugs
Both amiodarone and lidocaine are only given in a shockable rhythm:
- Amiodarone:
- 300 mg IV (IO) after the 3rd shock for patients in a shockable rhythm
- 150 mg IV (IO) after the 5th shock for patients in a shockable rhythm
- Lidocaine:
- 100 mg IV (IO) may be used as an alternative to amiodarone
- An additional bolus of lidocaine 50 mg IV (IO) can also be given after the 5th shock if patient is in a shockable rhythm
Unlike adrenaline, which is repeated indefinitely every 3-5 minutes / or at alternating cycles. Amiodarone is only given twice maximum in patients in a shockable rhythm, such that after the 7th shock, 9th shock… amiodarone should not be given.
Pharmacology:
- Amiodarone: class III antiarrhythmic (potassium channel inhibitor) (However, amiodarone has additional channel blockage effects; it’s technically a mixed class with predominant class III property)
- Lidocaine: class IB antiarrhythmic (sodium channel blocker)
Thrombolytic Drugs
Thrombolytic drugs are tissue plasminogen activators (e.g. alteplase)
- Consider when pulmonary embolus is suspected or confirmed as the cause of cardiac arrest.
- Continue CPR for an extra 60-90 minutes after administration of thrombolytic drugs.
Fluids
IV (IO) fluids should only be given where the cardiac arrest is caused by hypovolaemia.