Reversible Causes of PEA and Asystole
The correct answer is D: Hypokalemia, hypothermia, hydrogen ion acidosis, and cardiac tamponade are all potentially reversible causes of pulseless electrical activity (PEA) and asystole.
The "H's and T's" Framework
The American Heart Association emphasizes that PEA and asystole are often caused by reversible conditions that can be successfully treated if identified and corrected promptly. During each 2-minute CPR cycle, providers should systematically recall the complete list of reversible causes 1, 2:
The 4 H's:
- Hypovolemia - Requires IV/IO crystalloid administration or blood transfusion for severe blood loss 1, 3
- Hypoxia - Demands adequate oxygenation through advanced airway management and ventilation 1, 3
- Hydrogen ion (acidosis) - Needs identification and correction of metabolic abnormalities 1, 3
- Hypo/Hyperkalemia - Requires immediate treatment of electrolyte abnormalities, particularly high potassium levels which can cause cardiac arrest 1, 3
- Hypothermia - Treated by preventing further heat loss and active rewarming techniques 3
The 4 T's:
- Tension pneumothorax - Requires immediate needle decompression at 2nd intercostal space, mid-clavicular line 1, 3
- Tamponade (cardiac) - Treated with pericardiocentesis guided by echocardiography 1, 3
- Toxins - Requires identification of specific toxin and appropriate antidote administration 1, 3
- Thrombosis (coronary or pulmonary) - May require fibrinolytic therapy, percutaneous intervention, or mechanical thrombectomy 1, 3
Why the Other Options Are Incorrect
Option A is incorrect because "tetany" is not part of the standard reversible causes framework 1.
Option B is incorrect because "hypernatremia" is not included in the established H's and T's mnemonic 1.
Option C is incorrect because "hypervolemia" is not a recognized reversible cause—the actual cause is hypovolemia (not hypervolemia) 1, 3.
Clinical Application During Resuscitation
Bedside cardiac ultrasound should be performed immediately in PEA to accurately diagnose true PEA arrest, evaluate for reversible causes (such as tamponade, tension pneumothorax, and pulmonary embolism), and differentiate pseudo-PEA states with wall motion 1, 2. However, the examination should not interrupt chest compressions for more than 10 seconds 2.
Point-of-care ultrasound has demonstrated high sensitivity and specificity for cardiac tamponade (100%), pulmonary embolism (100% sensitivity, 97% specificity), and myocardial infarction (86% sensitivity, 94% specificity) when performed by experienced personnel 3.
Common Pitfalls to Avoid
- Do not delay treatment while searching for causes—continue high-quality CPR with minimal interruptions while systematically evaluating for reversible causes 1, 2
- Avoid prolonged interruptions in chest compressions for diagnostic procedures, as any pause reduces coronary perfusion pressure and decreases likelihood of ROSC 1, 4
- Do not overlook less common causes: Research shows that intracranial hemorrhage and nonischemic cardiac disorders represent significant causes of PEA, with prevalence equaling or exceeding some classical H's and T's etiologies 5