What are the causes of Pulseless Electrical Activity (PEA) arrest?

Causes of Pulseless Electrical Activity (PEA) Arrest

Pulseless Electrical Activity (PEA) arrest is most commonly caused by potentially reversible conditions summarized as the "H's and T's," including hypovolemia, hypoxia, hydrogen ion (acidosis), hypo/hyperkalemia, hypothermia, toxins, cardiac tamponade, tension pneumothorax, thrombosis (coronary or pulmonary), and trauma. 1

Primary Causes of PEA Arrest

The Traditional "H's and T's"

Hypovolemia

• Identified by BCU findings of small, hyperdynamic left ventricle and collapsed IVC 2
• Common causes include severe blood loss, dehydration, and sepsis 1
• Management includes rapid IV/IO fluid administration and blood transfusion for hemorrhage 2

Hypoxia

• One of the most frequent causes (23.6% of PEA cases) 3
• Identified by low SpO₂ and low PETCO₂ despite adequate CPR 2
• Management includes ensuring proper airway management and ventilation with 100% oxygen 2

Hydrogen ion (Acidosis)

• Identified using arterial blood gas showing pH <7.2 2
• Management involves treating the underlying cause and ensuring adequate ventilation 2

Hypo/Hyperkalemia and other electrolyte abnormalities

• Hyperkalemia can directly cause cardiac arrest 1
• Identified using ECG findings and serum potassium levels 2
• Management for hyperkalemia includes calcium, insulin/glucose, and sodium bicarbonate 2, 4
• Severe hyperkalemia can develop rapidly and be asymptomatic until cardiac arrest occurs 4

Hypothermia

• Identified using clinical indicators such as cold skin and history of environmental exposure 2
• Management includes active internal rewarming and continuing resuscitation until core temperature >32°C 2

Toxins

• Identified through history of ingestion, medication overdose, and specific toxidromes 2
• Management includes specific antidotes when available and supportive care 2

Cardiac Tamponade

• Identified using BCU findings of pericardial effusion with right atrial/ventricular diastolic collapse 2
• Management includes pericardiocentesis (echocardiography-guided if available) 2

Tension Pneumothorax

• Identified using BCU/chest ultrasound findings of absence of lung sliding, absence of B-lines, and lung point sign 2
• Management includes immediate needle decompression followed by chest tube placement 2

Thrombosis - Coronary

• Identified using ECG findings of ST-segment elevation and new LBBB, and BCU findings of regional wall motion abnormalities 2
• Management includes fibrinolytic therapy or immediate coronary intervention after ROSC 2

Thrombosis - Pulmonary (Pulmonary Embolism)

• Identified using BCU findings of right ventricular dilation and dysfunction, and McConnell's sign 2
• In patients with confirmed PE as the cause of cardiac arrest, thrombolysis, surgical embolectomy, and mechanical embolectomy are reasonable emergency treatment options 1
• Low-dose systemic thrombolysis (50 mg tPA) has shown promising results with 87% survival at 22 months in one study 5

Trauma

• Significant cause (12.5% of PEA cases) 3
• Management depends on specific injury but may include immediate surgical intervention 3

Additional Important Causes (Beyond Traditional H's and T's)

Acute Coronary Syndrome

• Second most common cause (12.5% of PEA cases) 3
• Identified by ECG changes, cardiac biomarkers, and regional wall motion abnormalities on BCU 2
• Management includes early coronary angiography and revascularization 2

Nonischemic Cardiac Disorders

• Account for 8.3% of PEA cases 3
• Include cardiomyopathies, valvular disease, and conduction disorders 3
• Identified using BCU 2

Intracranial Hemorrhage

• Accounts for 6.9% of PEA cases 3
• Identified using CT imaging when patient is stabilized 2

Pathophysiology of PEA

PEA represents a late phase in the clinical dying process, characterized by continued electrical activity without effective mechanical contraction 6. Echocardiographic studies show a continuous process from pseudo-PEA (with ineffective contractions) to true PEA and then asystole 6.

The underlying mechanism involves profound cardiovascular insult leading to tissue hypoxia and metabolic substrate depletion 6. This can be caused by any of the reversible conditions listed above.

Diagnostic Approach

1. Immediate BCU: Should be performed during cardiac arrest to rapidly identify potentially reversible causes 1, 2

   • Minimal interruption to chest compressions (≤10 seconds)
   • Views should include subcostal four-chamber, parasternal long-axis, and apical four-chamber

2. Differentiate true PEA from pseudo-PEA:

   • True PEA: Organized electrical activity without mechanical cardiac activity
   • Pseudo-PEA: Organized electrical activity with some mechanical cardiac activity but insufficient to generate a palpable pulse 1

3. Laboratory tests:

   • Arterial blood gas, electrolytes, lactate, and toxicology screening 2
   • Cardiac biomarkers to assess for myocardial injury 2

4. ECG analysis:

   • Evaluate for signs of ischemia, electrolyte abnormalities, or other specific patterns 7

Management Considerations

1. Continue high-quality CPR while searching for and treating the underlying cause 1

2. Administer vasopressors as soon as feasible to increase myocardial and cerebral blood flow 1

3. Treat identified reversible causes according to specific protocols 1, 2

4. Consider empiric treatments when high suspicion exists:

   • Fibrinolytic therapy when pulmonary embolism is suspected 1
   • IV fluids for suspected hypovolemia 2
   • Needle decompression for suspected tension pneumothorax 2

5. Post-ROSC care if successful resuscitation:

   • Targeted temperature management for comatose patients 2
   • Early coronary angiography for suspected cardiac etiology 2
   • Continued monitoring and support of organ systems 2

Special Considerations

• Increasing incidence: PEA as a cardiac arrest rhythm has been increasing over the past 10-20 years with a corresponding decrease in "shockable" rhythms 7

• Prognosis: Generally poor compared to shockable rhythms, but can be improved with rapid identification and treatment of the underlying cause 7

• Bedside ultrasound: Critical tool for rapid diagnosis of many PEA causes and should be incorporated into resuscitation efforts when available 1

• Specific patient populations: Patients with conditions like amyotrophic lateral sclerosis may be at higher risk for PEA during procedures like general anesthesia 8