Cardiac Arrest Medicines

Cardiac arrest medicines support high-quality chest compression and defibrillation, which remain the core of treatment. Drugs add small benefit and are started after compressions, oxygenation and a shock for a shockable rhythm. The key agents are adrenaline and amiodarone, with targeted drugs for reversible causes.

Classification. Vasopressor (adrenaline); antiarrhythmics (amiodarone, lidocaine, magnesium); drugs for reversible causes (calcium, sodium bicarbonate, thrombolytics, naloxone, glucose, fluids); lipid emulsion in local anaesthetic toxicity.

Mechanism. Adrenaline raises coronary and cerebral perfusion pressure through alpha stimulation. Amiodarone prolongs repolarisation in the heart. Lidocaine blocks sodium channels. The others correct a specific cause.

Children. Adrenaline 10 micrograms/kg; amiodarone 5 mg/kg; glucose 2 mL/kg of 10%; fluid bolus 10 mL/kg.

Atropine and vasopressin. Not routinely used in arrest.

Reversible causes. Hypoxia, hypovolaemia, hypo- or hyperkalaemia and other metabolic disturbance, hypothermia, thrombosis, tension pneumothorax, tamponade and toxins.

• First-line. Compressions, oxygen and defibrillation; adrenaline; amiodarone for shockable rhythms.
• Alternative. Lidocaine for shockable rhythms when amiodarone is not available.
• Specialist. Thrombolysis, extracorporeal support, targeted temperature care after return of circulation.
• Emergency. All cases of cardiac arrest.

Selection. Do not delay shocks or compressions to give drugs. Give drugs by the intravenous or intraosseous route; do not use the tracheal route.

Contraindications. None absolute in arrest. Thrombolysis: recent major bleeding or surgery, relative. Amiodarone: severe bradycardia if rhythm returns (after return of circulation).

Serious adverse effects.

• Adrenaline: hypertension, tachyarrhythmia and ischaemia after return of circulation; tissue injury on extravasation.
• Amiodarone: hypotension, bradycardia, phlebitis.
• Bicarbonate: alkalosis, hypernatraemia, hypocalcaemia.
• Thrombolysis: bleeding.

Major interactions. Calcium with digoxin; bicarbonate with calcium in the same line; amiodarone with other QT-prolonging drugs after recovery.

Common prescribing errors.

• Interrupting compressions to give drugs.
• Giving adrenaline too early or too often in shockable rhythms.
• Wrong adrenaline concentration (1 mg in 10 mL versus 1 mg in 1 mL).
• Giving calcium through the same line as bicarbonate.
• Stopping the search for a reversible cause.

Special groups.

• Pregnancy: left uterine displacement; early delivery within 5 minutes if no return of circulation; usual drug doses.
• Breastfeeding: not relevant during the arrest.
• Children: weight-based doses; use paediatric tables.
• Older adults: usual doses.
• Kidney: usual doses; consider hyperkalaemia.
• Liver: usual doses.
• East Africa: adrenaline ampoules are widely available but concentrations differ, so check the label; amiodarone and defibrillators may not be at every site, and lidocaine is a practical alternative; keep calcium chloride and bicarbonate on the arrest trolley.

Monitoring. Rhythm every 2 minutes, end-tidal carbon dioxide, pulse checks, glucose, potassium and blood gas when available.

Referral and escalation. Any return of circulation needs post-arrest care in a high dependency or intensive care area; suspected pulmonary embolism, toxin or cardiac cause needs specialist input.

Comparison with alternative classes. Defibrillation and compressions improve survival most. Adrenaline improves return of circulation but evidence for long-term survival is weaker. Amiodarone and lidocaine are similar for shock-refractory rhythms.