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Cardiac arrest

Specialties > Child health

Background knowledge 🧠

Definition

  • Cardiac arrest is the sudden cessation of cardiac mechanical activity resulting in loss of effective circulation.
  • Characterised by an absence of pulse, unresponsiveness, and apnoea (or gasping).
  • Requires immediate intervention to prevent death.

Epidemiology

  • Leading cause of death worldwide.
  • Approximately 60,000 out-of-hospital cardiac arrests (OHCA) occur annually in the UK.
  • Survival rates for OHCA are around 8-10% in the UK.
  • Incidence higher in older adults, males, and those with a history of cardiovascular disease.

Aetiology and Pathophysiology

  • Most common cause is ischemic heart disease, particularly acute myocardial infarction.
  • Other causes include arrhythmias (e.g., VF, VT), heart failure, and structural heart abnormalities.
  • Pathophysiology involves a sudden failure of the heart’s electrical system, leading to ineffective pumping and cessation of blood flow.
  • Hypoxia, acidosis, electrolyte imbalances, and myocardial ischemia exacerbate the condition.

Types

  • Ventricular Fibrillation (VF): chaotic electrical activity leading to quivering of the ventricles.
  • Pulseless Ventricular Tachycardia (VT): rapid heart rate without effective output.
  • Asystole: absence of electrical activity and heart contractions.
  • Pulseless Electrical Activity (PEA): organised electrical activity without a pulse.

Clinical Features 🌡️

Symptoms

  • Preceding symptoms may include chest pain, palpitations, shortness of breath, and syncope.
  • Often occurs suddenly without warning.
  • Patients are typically unresponsive and may appear cyanotic.

Signs

  • No palpable pulse (central or peripheral).
  • Absence of normal breathing (apnoea) or agonal respirations.
  • Loss of consciousness.
  • Pupils may be fixed and dilated.
  • Signs of poor perfusion, such as cyanosis and cool extremities.

Investigations 🧪

Tests

  • ECG to identify rhythm (VF, VT, asystole, PEA).
  • Blood tests: ABGs, electrolytes, cardiac enzymes, and glucose levels.
  • Imaging: chest X-ray and echocardiography post-resuscitation to assess for underlying causes.
  • Coronary angiography if myocardial infarction is suspected.
  • Post-mortem examination in cases of sudden unexplained cardiac arrest.

Management 🥼

Immediate Management

  • Call for help and initiate cardiopulmonary resuscitation (CPR) immediately.
  • Defibrillation for shockable rhythms (VF, pulseless VT) using an automated external defibrillator (AED).
  • Administration of adrenaline (epinephrine) every 3-5 minutes during resuscitation.
  • Consider reversible causes (4 Hs and 4 Ts): hypoxia, hypovolemia, hypo/hyperkalaemia, hypothermia, tension pneumothorax, tamponade, toxins, and thrombosis.
  • Advanced airway management (e.g., intubation) if required.

Post-Resuscitation Care

  • Transfer to a coronary care unit or intensive care unit (ICU).
  • Targeted temperature management (TTM) to 32-36°C for neuroprotection.
  • Continuous ECG monitoring to detect arrhythmias.
  • Treat underlying cause (e.g., PCI for myocardial infarction).
  • Neurological assessment and imaging to evaluate for hypoxic brain injury.

Complications

  • Hypoxic brain injury leading to cognitive impairment or coma.
  • Multi-organ failure due to prolonged hypoperfusion.
  • Recurrent arrhythmias and risk of subsequent cardiac arrest.
  • Post-resuscitation syndrome (systemic inflammatory response).
  • Rib fractures and pneumothorax from CPR.

Prognosis

  • Survival depends on early defibrillation, quality of CPR, and cause of arrest.
  • Better outcomes associated with witnessed arrest, bystander CPR, and early advanced care.
  • Poor prognosis if prolonged downtime before resuscitation or severe hypoxic injury.
  • Post-resuscitation survival ranges from 5-20% depending on various factors.

Key Points

  • Early recognition and prompt initiation of CPR are critical.
  • Defibrillation within minutes can significantly improve survival.
  • Identify and treat reversible causes (4 Hs and 4 Ts).
  • Post-resuscitation care and neuroprotection are essential to optimise outcomes.

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