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Saturn Medic

Clinical Subject Page

Cardiac Arrest

Also called

Sudden cardiac arrest

ICD-10

I46.9

Specialty

Cardiology

Onset

Acute

Reviewed

July 2026
On This Page

Overview

Cardiac arrest is the sudden cessation of cardiac function and blood circulation, resulting in loss of consciousness, apnea (or abnormal gasping), and absence of a pulse. It is a medical emergency requiring immediate CPR and, if indicated, defibrillation to improve survival.

Etiology & Risk Factors

Cardiac Causes

  • Coronary artery disease (most common in adults)

  • Acute myocardial infarction

  • Malignant arrhythmias (VF, pulseless VT)

  • Cardiomyopathy

  • Severe heart failure

Noncardiac Causes (Reversible Causes)

5 Hs

  • Hypovolemia

  • Hypoxia

  • Hydrogen ion (acidosis)

  • Hyperkalemia/Hypokalemia

  • Hypothermia

5 Ts

  • Tension pneumothorax

  • Cardiac tamponade

  • Toxins

  • Thrombosis (pulmonary embolism)

  • Thrombosis (coronary)

Other causes include:

  • Hypoglycemia

  • Hypocalcemia

  • Hypomagnesemia

  • Anaphylaxis

  • Severe asthma

Pathophysiology

Cardiac arrest occurs when the heart suddenly stops pumping blood effectively, causing cessation of systemic circulation.

Mechanism

  • Loss of effective cardiac mechanical activity
  • No cardiac output
  • No blood flow to vital organs
  • Rapid cerebral hypoxia and ischemia
  • Irreversible brain injury begins within minutes if circulation is not restored

Simple Flow

Underlying cardiac/noncardiac cause → Heart stops pumping effectively → No cardiac output → No oxygen delivery to organs → Brain ischemia → Organ failure → Death (without prompt CPR/defibrillation)

Clinical Presentation

Symptoms/Signs

  • Sudden collapse
  • Unresponsiveness
  • No normal breathing (or gasping)
  • No palpable pulse
Cardiac Arrest Overview
Cardiac Arrest Overview

Recognition of Cardiac Arrest (Initial Assessment)

Step 1: Ensure Scene Safety

  • Make sure the environment is safe for you and the patient.

Step 2: Check Responsiveness

  • Tap the patient’s shoulders.

  • Shout: “Are you okay?”

  • If there is no response, suspect cardiac arrest.

Step 3: Call for Help

  • Activate the emergency response system.

  • Ask someone to bring an AED/defibrillator immediately.

Step 4: Check Breathing

  • Look for normal breathing.

  • Agonal gasps are NOT normal breathing and should be treated as cardiac arrest.

Step 5: Check Pulse (Healthcare Providers)

  • Check a central pulse (carotid or femoral).

  • Spend no more than 10 seconds checking.

  • If no pulse or unsure → start CPR immediately.

Step 6: Start High-Quality CPR

  • Begin chest compressions immediately.

  • Attach an AED/defibrillator as soon as it is available.

Signs Suggesting Cardiac Arrest

  • Sudden collapse

  • Unresponsiveness

  • No normal breathing or only gasping

  • No palpable central pulse

  • Pale or cyanotic skin

  • Dilated pupils (late sign)

Investigations

Laboratory

  • CBC

  • Electrolytes

  • Renal & liver function

  • Troponin

  • BNP/NT-proBNP

  • Arterial blood gas

  • Serum lactate

  • Coagulation profile

ECG

  • Acute MI changes

  • Arrhythmias

Imaging

  • Echocardiography (first-line)

  • Chest X-ray

  • Coronary angiography (if ACS suspected)

Hemodynamic Monitoring

  • Arterial line

  • Central venous access

  • Pulmonary artery catheter (selected patients)

Diagnosis

Diagnosis is based on:

  • Clinical evidence of shock
  • SBP <90 mmHg (or need for vasopressors)
  • Signs of end-organ hypoperfusion
  • Elevated lactate
  • Echocardiographic evidence of severe cardiac dysfunction
  • Identification of the underlying cardiac cause
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Management

1. Basic Life Support (BLS)

  • Recognize cardiac arrest and activate the emergency response system.

  • Start high-quality CPR immediately.

  • Apply an AED (Automated External Defibrillator) as soon as available.

  • Defibrillate immediately if a shockable rhythm is detected.

2. Advanced Cardiac Life Support (ACLS)

Step 1

  • Continue high-quality CPR.

  • Attach a cardiac monitor/defibrillator.

  • Obtain IV/IO access.

Step 2: Identify the Rhythm

A. Shockable Rhythms

  • Ventricular fibrillation (VF)

  • Pulseless ventricular tachycardia (pVT)

Management

  • Immediate defibrillation

  • Resume CPR for 2 minutes

  • Epinephrine 1 mg IV/IO after the second unsuccessful shock, then every 3–5 minutes

  • Amiodarone 300 mg IV/IO (or lidocaine) after the third unsuccessful shock

B. Nonshockable Rhythms

  • Pulseless electrical activity (PEA)

  • Asystole

Management

  • Do NOT defibrillate

  • Continue CPR

  • Epinephrine 1 mg IV/IO immediately, then every 3–5 minutes

  • Search for and treat reversible causes (5 Hs & 5 Ts)

3. Airway Management

  • Minimize interruptions to CPR.

  • Consider advanced airway (endotracheal tube or supraglottic airway) if needed.

  • Confirm placement with continuous waveform capnography.

  • Once an advanced airway is in place:

    • Continue continuous chest compressions.

    • Give 1 breath every 6 seconds.

4. Post-Resuscitation Care (After ROSC)

  • Secure the airway and optimize oxygenation/ventilation.

  • Maintain hemodynamic stability.

  • Consider PCI if a cardiac cause (e.g., STEMI) is suspected.

  • Temperature control.

  • Treat seizures if present.

  • Monitor for organ dysfunction and neurological recovery.

Complications

  • Anoxic-ischemic encephalopathy (brain injury) (most important complication)
  • Neurological dysfunction
  • Ischemic cardiomyopathy
  • Acute kidney injury (AKI)
  • Shock liver
  • Multiorgan dysfunction syndrome (MODS)
  • Seizures
  • Coma, persistent vegetative state, or brain death (in severe cases)

Prognosis

  • Prognosis depends mainly on:
    • Time to CPR
    • Time to defibrillation (for shockable rhythms)
    • Duration of anoxia
    • Presence of return of spontaneous circulation (ROSC)
  • Early CPR and early defibrillation significantly improve survival and neurological outcomes.
  • Anoxia lasting >3–5 minutes is commonly associated with permanent brain injury.
  • Patients who achieve ROSC require comprehensive post-resuscitation care to optimize recovery.

Key Points / Clinical Pearls

  • Cardiac Arrest is the sudden cessation of effective cardiac mechanical activity, causing loss of consciousness and absence of normal breathing.
  • In an adult who is unresponsive and not breathing normally or only gasping, assume cardiac arrest.
  • A healthcare professional should check for a pulse for no more than 10 seconds; if no definite pulse is felt, start CPR.
  • Activate the emergency response system and obtain an AED/defibrillator immediately.
  • Start high-quality CPR immediately.
  • Adult CPR uses 30 chest compressions : 2 breaths.
  • Compression rate: 100–120/minute.
  • Compression depth in adults: 5–6 cm.
  • Allow complete chest recoil and minimize interruptions.
  • Use an AED/defibrillator as soon as available.
  • Shockable rhythms: ventricular fibrillation (VF) and pulseless ventricular tachycardia (pVT).
  • Non-shockable rhythms: pulseless electrical activity (PEA) and asystole.
  • If the rhythm is shockable → 1 shock → immediately resume CPR for 2 minutes