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Emergency Medicine Advanced Cardiac Life Support (ACLS) Intermediate
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Reversible Causes of Cardiac Arrest: 5 H's & 5 T's

5
H's
&
5
T's
The ACLS checklist of reversible physiological insults causing pulseless electrical activity (PEA) and asystole.

During CPR for non-shockable rhythms (PEA/asystole), identifying and treating the underlying reversible etiology is the ONLY path to achieving return of spontaneous circulation (ROSC).

Systematic Breakdown

H1

Hypovolemia

Most common cause of PEA. Treat with rapid IV/IO crystalloid fluid resuscitation or blood products.

H2

Hypoxia

Ensure patent airway, effective ventilation, and 100% oxygen delivery.

H3

Hydrogen Ion (Acidosis)

Severe metabolic or respiratory acidosis; optimize ventilation, consider sodium bicarbonate if indicated.

H4

Hypo- / Hyperkalemia

Hyperkalemia treated with IV calcium gluconate, insulin + dextrose, and sodium bicarbonate.

H5

Hypothermia

Core temp < 30°C; patient is not dead until warm and dead (active rewarming required).

T1

Tension Pneumothorax

Immediate needle thoracostomy (2nd intercostal space midclavicular or 5th ICS anterior axillary line) followed by chest tube.

T2

Tamponade (Cardiac)

Ultrasound-guided emergent pericardiocentesis or thoracotomy.

T3

Toxins

Accidental or deliberate overdose (TCAs, opioids, beta-blockers, CCBs, organophosphates); administer specific antidotes.

T4

Thrombosis (Pulmonary)

Massive pulmonary embolism; consider emergency IV fibrinolytic (Alteplase) during ongoing CPR.

T5

Thrombosis (Coronary)

Massive acute myocardial infarction causing pump failure; emergent transport for cath lab intervention.

High-Yield Clinical Pearls & Exam Tips
  • Point-of-care ultrasound (POCUS) during rhythm checks (< 10 seconds) can rapidly confirm tamponade, pneumothorax, massive PE (RV strain), or hypovolemia.
  • Narrow-complex PEA is most commonly caused by hypovolemia or mechanical obstruction (tamponade/tension pneumothorax).
Related Pharmaceuticals
Epinephrine Amiodarone Calcium Gluconate Sodium Bicarbonate
Related Clinical Conditions
Pulseless Electrical Activity Asystole Massive Pulmonary Embolism
Authoritative Sources: AHA Guidelines for CPR and ECC 2020 · ERC Resuscitation Guidelines 2021

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System Notice

Confirm Action