01Purpose and principlesWhat the treatment does and how it fits into care.
Cardiac arrest is the absence of effective circulation. Its early appearance can include gasping, brief seizure-like movements or panting, so the task is to identify ineffective breathing in an unresponsive person rather than wait for a textbook appearance. Once arrest is suspected, the interventions with the greatest immediate importance are effective chest compressions and rapid defibrillation when the rhythm is shockable.
Resuscitation is a repeating cycle of perfusion support, rhythm-directed treatment and correction of the precipitating cause. Drugs and airway procedures are important but must be fitted around high-quality compressions. A pulse after resuscitation starts a new phase of care because myocardial dysfunction, recurrent arrhythmia, impaired oxygenation and brain injury may continue after circulation returns.
For initial anterolateral defibrillation, put the right pad below the clavicle beside the sternum and the lateral pad below the left armpit on the mid-axillary line. Use at least 150 J initially for rectilinear or truncated-exponential biphasic waveforms, or 130–150 J for pulsed biphasic devices; increase subsequent energy if available. If the device recommendation is unknown, use its highest adult setting. Clear contact before delivery and resume compressions immediately. After three failed shocks despite correct placement, consider an anteroposterior vector change at the next rhythm check.
Key points
- Call 999 immediately for an unresponsive person in the community, assessing breathing while the call connects.
- Compress the lower half of the sternum at 100–120/min to a depth of 5–6 cm, allowing full recoil.
- Use 30:2 until an effective tracheal tube or supraglottic airway permits continuous compressions with 10 breaths/min; return to 30:2 if supraglottic leakage prevents adequate ventilation.
- VF and pulseless VT require defibrillation; pulseless electrical activity and asystole require CPR and prompt treatment of reversible causes.
- Give adrenaline 1 mg IV as soon as possible in non-shockable arrest, or after the third shock in shockable arrest, then every 3–5 minutes.
- Give amiodarone 300 mg IV after three shocks for VF/pVT, with a further 150 mg after five shocks.
02Indications, selection and cautionsWho may benefit, who needs urgent treatment and important alternatives.
An unresponsive patient with abnormal breathing should receive CPR when circulation is uncertain. A trained clinician who confidently identifies a pulse with absent breathing must provide ventilation and reassess because respiratory arrest can progress rapidly.
Ventricular fibrillation has disorganised electrical activity; pulseless ventricular tachycardia is a fast ventricular rhythm without effective output. Assess the patient and monitor together, since an electrical tracing alone cannot establish whether a pulse exists.
Asystole lacks ventricular activity; pulseless electrical activity describes organised electrical signals without a clinically detectable circulation. Neither benefits from a shock merely because compressions have been unsuccessful.
Seek hypoxia, hypovolaemia, potassium or metabolic disturbance, hypothermia, thrombosis, tamponade, tension pneumothorax and toxins. The pre-arrest history may suggest a cause that can be treated before a formal diagnostic test is available.
03Assessment before treatmentTests and checks that guide safe selection.
Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.
- 01
Rhythm assessment during planned pausesFirst step - Why
- Select the electrical pathway with minimal interruption of compressions.
- Interpretation and limitations
- Analyse the rhythm at scheduled cycle boundaries, normally every two minutes. Check for a pulse only when an organised rhythm and clinical features make circulation plausible; prolonged searching reduces perfusion.
- 02
Waveform capnography - Why
- Confirm tracheal placement and assess ventilation and perfusion during CPR.
- Interpretation and limitations
- A sustained carbon dioxide waveform supports tracheal placement. A sudden rise may accompany return of circulation, but does not alone justify interrupting compressions or making prognostic decisions.
- 03
Point-of-care blood sampling - Why
- Identify immediately treatable metabolic or oxygenation abnormalities.
- Interpretation and limitations
- Obtain glucose, potassium, gas and haemoglobin when feasible without delaying treatment. Severe hyperkalaemia needs specific therapy; routine bicarbonate for every arrest is not supported.
- 04
Focused ultrasound by a skilled operator - Why
- Seek a reversible structural cause without extending a compression pause.
- Interpretation and limitations
- Ultrasound may suggest tamponade or tension pneumothorax. Isolated right ventricular dilatation during arrest cannot establish pulmonary embolism, and absent movement alone must not determine termination.
04Treatment approachPreparation, options, escalation and aftercare.
01Worked casePersisting ventricular fibrillation after three shocksFirst stepA monitored adult collapses into VF and remains pulseless despite three appropriately delivered shocks separated by two-minute CPR cycles.+
- 1Resume compressions immediately after the third shock and check that pad placement, skin contact and delivered energy are appropriate; do not wait to inspect whether a pulse has appeared.
- 2Administer adrenaline 1 mg IV and amiodarone 300 mg IV while CPR continues, assigning one team member to record total shocks and administration times.
- 3Continue two-minute cycles, repeating adrenaline every three to five minutes; if VF/pVT persists after five total shocks, give the additional 150 mg amiodarone dose.
- 4Review potentially correctable causes and ventilation quality throughout; use the next scheduled rhythm assessment to determine whether further defibrillation or a different pathway is needed.
- 5If convincing evidence of circulation returns, verify the rhythm and perfusion, obtain a twelve-lead ECG and begin post-resuscitation physiological support immediately.
02Non-shockable arrestPulseless electrical activity or asystoleThe monitor shows organised electrical activity without a pulse, or confirms asystole during a brief planned assessment.+
- 1Continue high-quality compressions and oxygenation, obtain vascular access and administer adrenaline as soon as possible rather than attempting defibrillation of a non-shockable rhythm.
- 2AlternativeAttempt intravenous access first; if it cannot rapidly be achieved within two attempts, use intraosseous access as a reasonable alternative for resuscitation drug delivery.
- 3Prioritise the likely reversible cause, repeat rhythm checks at cycle boundaries, and move to the shockable pathway immediately if VF or pulseless VT develops.
03After circulation returnsPreventing secondary injury following ROSCA palpable pulse, arterial waveform and clinical findings establish sustained return of spontaneous circulation.+
- 1Maintain a patent airway and effective ventilation; once measurement is reliable, titrate oxygen to SpO2 94–98% and guide ventilation by blood gases toward PaCO2 4.7–6.0 kPa.
- 2Avoid hypotension, aiming for systolic pressure above 100 mmHg or mean arterial pressure above 60–65 mmHg, with support individualised to perfusion. Seek urgent coronary assessment for ST elevation or other strong evidence of acute occlusion.
- 3Arrange critical-care transfer for ongoing coma or instability. In patients remaining comatose, actively prevent fever by targeting temperature at or below 37.5°C, and use appropriately timed multimodal neurological assessment.
05Regimens, contraindications and interactionsTreatment details and the circumstances that modify them.
Adrenaline during adult cardiac arrest
Give 1 mg IV promptly for a non-shockable rhythm or after the third shock for VF/pVT; repeat every 3–5 minutes while ALS continues. Use IO when suitable IV access cannot be rapidly obtained.This cardiac-arrest regimen must not be confused with the 500 microgram IM anaphylaxis regimen in a patient with a circulation. Record dose timing to avoid duplication.
Amiodarone for shock-refractory VF or pulseless VT
Give 300 mg IV after three total shocks and a further 150 mg IV after five total shocks if VF/pVT persists or recurs during the arrest.Do not give it routinely for asystole or PEA. Drug administration must not defer the next required shock or interrupt effective chest compressions.
06Complications, monitoring and follow-upAdverse effects, response and longer-term review.
- Rotate the person delivering compressions approximately every two minutes or sooner if fatigue impairs depth, coordinating changes with existing pauses.
- Assign a recorder to shock number, rhythm, drug timing, reversible-cause treatment and the evidence used to identify return of circulation.
- After ROSC, monitor oxygenation, ventilation, pressure, temperature, glucose and recurrent arrhythmia continuously or at the frequency required by instability.
- Assess survivors for physical, cognitive and emotional impairment and arrange rehabilitation and follow-up; also offer an appropriate team and bystander debrief.
07Special situationsVariants, exceptions and circumstances that change the usual approach.
Airway skill matters
Give each breath over one second with visible chest rise and avoid excessive rate or volume. Confirm tracheal placement with sustained waveform capnography; if ventilation through a supraglottic airway remains inadequate during compressions, use 30:2.
Fluid selection during arrest
Intravenous fluid is indicated when hypovolaemia causes the arrest. An undifferentiated arrest does not justify automatic large-volume infusion, which may worsen congestion without restoring flow.
Cause-specific modifications
Hypothermia, poisoning, pregnancy and arrest after cardiac surgery can require additional interventions or timing changes; identify these circumstances early rather than applying every standard drug interval mechanically.
Contemporaneous decisions
Termination requires an experienced assessment of the overall context and response, including reversible causes; a single low carbon dioxide reading or ultrasound finding is inadequate.
08Common pitfallsFrequent interpretation and management errors.
- 01
Do not delay defibrillation in VF while establishing an advanced airway or searching for venous access.
- 02
Do not perform an immediate prolonged pulse check after each shock; resume compressions and reassess at the planned interval.
- 03
Do not mistake fine VF, disconnected electrodes or low monitor gain for confirmed asystole without checking the tracing and connections.
- 04
Do not continue indiscriminate maximum oxygen after reliable measurements permit titration during post-resuscitation care.