4.4 PEA, Asystole, and Reversible Causes
Key Takeaways
- PEA and asystole are nonshockable rhythms.
- Treatment focuses on high-quality CPR, epinephrine, and correction of reversible causes.
- Hs and Ts are a memory framework for causes that may be treatable during arrest.
- A flatline should be confirmed before labeling asystole.
4.4 PEA, Asystole, and Reversible Causes
PEA and asystole require disciplined basics. The team should not shock; it should keep perfusion going, give epinephrine on schedule, confirm rhythm, and look aggressively for reversible causes.
Current official baseline
The adult advanced life support guidance covers cardiac arrest rhythms, defibrillation, airway decisions, drugs, peri-arrest tachycardia and bradycardia, and termination decisions. Use the official AHA 2025 Adult Advanced Life Support Guidelines page when your course materials or training-center instructions differ from third-party summaries: AHA 2025 Adult Advanced Life Support Guidelines.
What you need to know
| Decision point | What to do |
|---|---|
| PEA | Electrical activity is present but there is no pulse. Treat the patient, not the monitor. |
| Asystole | Confirm leads, gain, and connection when the rhythm appears flat. Do not shock confirmed asystole. |
| Reversible causes | Use Hs and Ts to organize the search: hypoxia, hypovolemia, hydrogen ion/acidosis, hypo/hyperkalemia, hypothermia, tension pneumothorax, tamponade, toxins, pulmonary thrombosis, and coronary thrombosis. |
| Team assignment | One person can own reversible causes while another owns CPR quality, another airway, and another medication timing. |
How this shows up on BLS/ACLS questions
BLS and ACLS items usually test priority. Read the patient state first: age, pulse status, breathing status, rhythm, stability, and number of rescuers. Then choose the action that protects perfusion, oxygenation, defibrillation timing, or the correct algorithm branch. If an answer sounds advanced but delays CPR, shock delivery, ventilation, or an urgent stability intervention, it is usually a distractor.
Scenario anchor
A dialysis patient arrests with PEA. The team should continue CPR, give epinephrine, consider hyperkalemia among reversible causes, and prepare appropriate treatment rather than shocking the organized rhythm.
Common traps
- Shocking PEA because the rhythm looks organized.
- Failing to check leads before calling asystole.
- Reciting Hs and Ts without acting on the most likely cause.
Study action
Write this section as a one-line rule in your own words, then test it with mixed questions from the BLS/ACLS practice bank. Do not review only the matching topic. Mix it with nearby branches so you can tell when the rule applies and when it does not. For example, compare respiratory arrest with a pulse against pulseless arrest, or compare unstable tachycardia against VF/pVT arrest. The exam rewards that discrimination more than memorizing isolated facts.
During CPR, a sudden rise in ETCO2 from 15 mmHg to 52 mmHg occurs. What does this MOST LIKELY indicate?
After successful ROSC in a comatose cardiac arrest survivor, what is the recommended target temperature management (TTM) strategy?