Cardiac Arrest: Advanced Life Support

Introduction

Cardiac arrest is the abrupt loss of effective cardiac output, causing immediate cessation of cerebral and coronary perfusion. Without intervention, consciousness is lost within seconds and irreversible neurological injury begins within minutes.

Around 30,000 out-of-hospital cardiac arrests are attended by the emergency services in the UK each year, with overall survival to hospital discharge of roughly one in ten. In-hospital arrest is somewhat more survivable, in part because it is witnessed and treated earlier, though the underlying condition is often more advanced.

Three interventions determine outcome more than anything that happens later: early recognition, early high-quality CPR, and early defibrillation. Survival from a shockable rhythm falls by approximately 10% for every minute that defibrillation is delayed, which is why bystander CPR and public access defibrillators matter so much.

Recognition

Cardiac arrest is a clinical diagnosis. In an unresponsive patient who is not breathing normally, start CPR - do not delay for a prolonged pulse check.

• Unresponsive to voice and to a firm shake of the shoulders
• Absent or abnormal breathing - agonal gasping is present in up to 40% of arrests in the first minutes and is frequently mistaken for breathing by both bystanders and clinicians. Slow, laboured, noisy gasps are a sign of cardiac arrest, not of life.
• Absent central pulse - carotid or femoral, checked for no more than 10 seconds, and only by someone trained to do so. Pulse checks are unreliable even among experienced clinicians.
• Sudden collapse, sometimes preceded by seizure-like activity from cerebral hypoperfusion - another common source of misdiagnosis

In hospital, most arrests are preceded by hours of physiological deterioration. Recognising and acting on a rising early warning score prevents more deaths than any resuscitation skill, and this is the reasoning behind track-and-trigger systems and critical care outreach teams.

Basic life support

1. Ensure safety for yourself, the patient and bystanders
2. Check responsiveness - shake and shout
3. Open the airway with a head tilt and chin lift, and look, listen and feel for normal breathing for up to 10 seconds
4. Call for help - dial 2222 in hospital or 999 in the community, and send for a defibrillator
5. Start chest compressions - 30 compressions, then 2 rescue breaths, continuing at 30:2
6. Attach a defibrillator or AED as soon as it arrives and follow its prompts

The advanced life support algorithm

Once the rhythm is known, the algorithm divides into two branches. The critical difference is not only whether a shock is given, but when adrenaline is given.¹

Shockable rhythms: VF and pulseless VT

1. Defibrillate immediately - 150 J biphasic for the first shock (or per the manufacturer's guidance), escalating with subsequent shocks
2. Resume chest compressions immediately for 2 minutes without checking the rhythm or the pulse. The heart rarely produces an effective output straight after a shock, and pausing wastes perfusion time.
3. Reassess the rhythm after 2 minutes; if still shockable, deliver a second shock and resume compressions
4. After the third shock, give adrenaline 1 mg IV and amiodarone 300 mg IV, then resume compressions
5. Continue in 2-minute cycles, giving adrenaline 1 mg every 3-5 minutes (in practice, every other cycle)
6. After the fifth shock, give a further amiodarone 150 mg IV
7. Throughout, seek and treat reversible causes

Non-shockable rhythms: PEA and asystole

1. Give adrenaline 1 mg IV as soon as possible - unlike in shockable rhythms, it is not delayed
2. Continue CPR in 2-minute cycles, reassessing the rhythm at the end of each
3. Repeat adrenaline 1 mg every 3-5 minutes
4. Amiodarone has no role in non-shockable arrest
5. Concentrate on reversible causes - the yield here is far higher than in shockable rhythms, and identifying one is usually the only route to survival
6. If the rhythm changes to a shockable one, switch to that branch of the algorithm

Reversible causes

Considering these is a mandatory part of every arrest, and should be spoken aloud during the resuscitation. They matter most in PEA and asystole, where treating the cause is often the only path to survival.

Point-of-care ultrasound by a competent operator can identify tamponade, right heart strain suggesting massive pulmonary embolism, hypovolaemia and cardiac standstill. It must be used during the 10-second rhythm check without prolonging the pause in compressions.

During CPR

• Ensure high-quality compressions with minimal interruption - this outranks every other consideration
• Airway - a bag-valve-mask with an oropharyngeal airway is acceptable. A supraglottic airway or tracheal tube allows continuous compressions. Tracheal intubation should only be attempted by someone competent, and only with a pause of under 5 seconds.
• Oxygen - give the highest concentration available during the arrest itself
• Waveform capnography - continuous end-tidal CO2 monitoring confirms tracheal tube placement, gives real-time feedback on compression quality, and a sudden rise in ETCO2 is often the first indicator of return of spontaneous circulation. A persistently low value (under 1.3 kPa) after 20 minutes of ALS is a poor prognostic sign, though it must never be used alone to stop.
• Vascular access - intravenous first; if not obtained quickly, use the intraosseous route. The tracheal route is no longer recommended.
• Consider extracorporeal CPR (eCPR) in selected patients with a reversible cause in centres where it is available

Post-resuscitation care

Return of spontaneous circulation is the beginning of treatment, not the end of it. Post-cardiac arrest syndrome comprises hypoxic brain injury, myocardial dysfunction, a systemic ischaemia-reperfusion response resembling sepsis, and the persisting effects of the precipitating illness.

• Airway and breathing - titrate oxygen to saturations of 94-98%; hyperoxia after arrest worsens neurological injury. Aim for normocapnia (PaCO2 4.5-6.0 kPa), since hypocapnia causes cerebral vasoconstriction. Use lung-protective ventilation.
• Circulation - a 12-lead ECG immediately. Arrange urgent coronary angiography if there is ST elevation, and consider it in any arrest with a likely cardiac cause even without ST elevation. Target a mean arterial pressure sufficient for adequate urine output and lactate clearance.
• Disability - control seizures, maintain normoglycaemia, and avoid fever aggressively. Targeted temperature management with active prevention of fever (keeping temperature below 37.7 degrees) is recommended for at least 72 hours.
• Exposure and everything else - identify and treat the precipitating cause, correct electrolytes, insert a urinary catheter, and admit to intensive care
• Neuroprognostication - should be deferred for at least 72 hours after normothermia is restored and sedation has cleared, and must use a multimodal approach combining clinical examination, EEG, somatosensory evoked potentials, neuron-specific enolase and imaging. No single test is sufficient to withdraw treatment.

When not to start, and when to stop

These decisions are difficult, frequently examined in ethics stations, and best approached through a small number of clear principles.

Withholding resuscitation

• A valid DNACPR decision is in place. This records a clinical decision that CPR would not be successful or would not be in the patient's best interests. It applies only to CPR and must never restrict any other treatment.
• A valid and applicable advance decision to refuse treatment covering CPR
• Injuries incompatible with life - decapitation, hemicorporectomy, rigor mortis, hypostasis, or incineration
• CPR would be futile - where the patient is dying of an irreversible condition and cardiac arrest represents the expected end of that process

Stopping resuscitation

The decision rests with the team leader and is based on the overall clinical picture rather than any single factor. Considerations include the presenting rhythm and any change in it, the duration of the arrest, whether it was witnessed and whether bystander CPR was given, the response to treatment, the identification and correction of reversible causes, end-tidal CO2 values, and the patient's condition before the arrest.

Red flags

Prognosis

Overall survival to hospital discharge after out-of-hospital cardiac arrest in the UK is approximately 8-10%, though this conceals enormous variation. Survival exceeds 50% in a witnessed arrest with a shockable rhythm and immediate bystander CPR and defibrillation, and approaches zero in an unwitnessed asystolic arrest with no bystander intervention.

The determinants of outcome, in approximate order of importance, are: whether the arrest was witnessed, whether bystander CPR was given, the initial rhythm (shockable rhythms carry a far better prognosis), the time to defibrillation, and the presence of a reversible cause. Every one of the first four is influenced by public education and by the availability of defibrillators, which is why community resuscitation training is a genuine public health intervention.

In-hospital cardiac arrest has a survival to discharge of roughly 15-20%, better where arrest occurs in a monitored area and worse where it follows a prolonged deterioration on a general ward. Much of that gap is preventable through earlier recognition of the deteriorating patient.

Among survivors, neurological outcome dominates quality of life. The majority of those who survive to discharge have a good or moderate neurological recovery, but hypoxic brain injury is the commonest cause of death after successful initial resuscitation. This is why post-resuscitation care - oxygen targets, temperature control, avoidance of fever, and careful multimodal prognostication - is as much a part of resuscitation as the compressions themselves.