Cardiac arrest is an important medical emergency, where the effective function of the heart ceases without warning, thus resulting in inadequate blood flow to vital organs. It is, therefore, a crucial need to understand the pathophysiology, causes, recognition, and management of cardiac arrest among medical students so that it can be dealt with properly and effectively in a timely manner.
What is Cardiac Arrest?
Cardiac arrest is a situation where the heart fails to pump blood adequately. This condition usually results from an electrical failure. Cardiac arrest is not a heart attack (myocardial infarction) where the flow of blood to the heart muscle is obstructed, but the heart continues to pump.
Key Features:
- Abrupt onset: Symptoms begin suddenly.
- No pulse: No pulse is felt due to ineffective contractions of the heart.
- No response: The patient loses consciousness.
- No breathing or agonal breathing: Gasping in an abnormal or complete cessation of breathing.
Pathophysiology
Cardiac arrest is primarily caused due to an electrical disturbance in the heart, which can lead to:
- Ventricular Fibrillation (VF): Chaotic Electrical activity causing ineffective pumping,
- Pulseless Ventricular Tachycardia (VT): Rapid heart rhythm without blood flow.
- Asystole: Complete absence of electrical activity.
- Pulseless Electrical Activity (PEA): Electrical signals are present but do not result in mechanical contraction.
These conditions result in an abrupt loss of cardiac output, oxygen delivery to tissues, and cellular death if left untreated.
Causes of Cardiac Arrest
Knowing the causes allows one to prevent and control cardiac arrest. Common causes include:
Primary Cardiac Causes:
- Coronary artery disease (CAD)
- Acute myocardial infarction (heart attack)
- Cardiomyopathy
- Congenital heart defects
- Arrhythmias (long QT syndrome, Brugada syndrome)
Non-Cardiac Causes:
- Hypoxia, such as drowning or respiratory failure
- Electrolyte imbalances such as hyperkalemia or hypokalemia
- Drug overdose, such as opioids or cocaine
- Massive pulmonary embolism
- Severe trauma or hemorrhage
- Hypothermia or hyperthermia
The “H and T” Mnemonic:
- H: Hypovolemia, Hypoxia, Hydrogen ion (acidosis), Hyper-/Hypokalemia, Hypothermia
- T: Tension pneumothorax, Tamponade (cardiac), Toxins, Thrombosis (coronary or pulmonary), Trauma
Recognition of Cardiac Arrest
Early recognition is crucial. Evaluate the patient for:
- Unresponsiveness: Shake and shout to check consciousness.
- Breathing: Look for chest rise and fall; check for agonal or absent breathing.
- Pulse: Palpate the carotid or femoral artery for 5-10 seconds.
If all three signs indicate cardiac arrest, intervention is required immediately.
Management of Cardiac Arrest
Cardiac arrest management requires the Chain of Survival:
1. Immediate Recognition and Activation of Emergency Response:
Call for help and activate emergency medical services (EMS).
2. Early Cardiopulmonary Resuscitation (CPR):
Begin high-quality CPR immediately.
- Rate: 100-120 compressions per minute
- Depth: 5-6 cm in adults
- Allow full chest recoil
- Minimize interruptions to chest compressions
Give 2 rescue breaths after every 30 compressions.
3. Rapid Defibrillation:
- Use an Automated External Defibrillator (AED) or manual defibrillator.
- Shock rhythms including VF and pulseless VT.
4. Advanced Life Support (ALS):
Administer medications according to the ACLS guidelines:
- Epinephrine: 1 mg IV/IO every 3-5 minutes
- Amiodarone or Lidocaine for refractory VF/VT
Advance airway management (intubation or supraglottic devices).
5. Post-Cardiac Arrest Care:
- Optimize oxygenation and ventilation.
- Treatment of underlying causes.
- Use targeted temperature management (32°C to 36°C).
- Monitor multi-organ dysfunction.
Prognosis and Outcomes
- Survival depends on the cause, location, and timeliness of intervention.
- Survivors of witnessed arrests with early CPR and defibrillation have better outcomes.
Prevention Strategies
- Primary Prevention:
Manage risk factors like hypertension, diabetes, and high cholesterol.
Lifestyle modifications: healthy diet, exercise, and avoiding smoking. - Secondary Prevention:
Implantable cardioverter defibrillators (ICDs) for high-risk patients.
Regular follow-ups for known cardiac conditions.
Key Take Aways for Medical Students
- Early recognition and intervention are life-saving.
- Master the steps of BLS and ACLS protocols.
- Always consider reversible causes using the “H and T” mnemonic.
- Effective teamwork during resuscitation improves outcomes.
- Stay updated with the latest resuscitation guidelines.
Cardiac arrest is a difficult medical emergency, but proper knowledge, skills, and timely intervention can improve survival rates significantly. As future healthcare providers, your role in managing such emergencies will be pivotal.
