Lethal Rhythms: VF, Asystole and PEA
No pulse = start CPR. Then ask one question: shockable or not?
Ventricular fibrillation (VF)
ShockableLooks like: chaotic, irregular waves; no identifiable P, QRS or T; rate cannot be counted. Coarse or fine.
Patient: unresponsive, no pulse, not breathing or only gasping. No cardiac output.
Patient: unresponsive, no pulse, not breathing or only gasping. No cardiac output.
Treatment:
- Start CPR; defibrillate as soon as possible (biphasic 120–200 J per device; monophasic 360 J).
- Resume CPR immediately after each shock for 2 min.
- Epinephrine 1 mg IV/IO every 3–5 min (after 2nd shock).
- Amiodarone 300 mg IV/IO, then 150 mg; or lidocaine 1–1.5 mg/kg, then 0.5–0.75 mg/kg.
Asystole
Not shockableConfirm it: check the patient, the leads and connections, turn up the gain, check a second lead (fine VF can look flat).
Treatment: high-quality CPR + epinephrine 1 mg as soon as possible, then every 3–5 min; look for reversible causes. Never defibrillate asystole.
Pulseless electrical activity (PEA)
The monitor shows an organized rhythm (it may even look normal) but there is no palpable pulse.
Treatment: same as asystole: CPR, epinephrine as soon as possible, find and fix the cause (Hs and Ts). Not shockable.
Memory hook"Shock the chaos, push epi for the flat." VF and pulseless VT get shocks; asystole and PEA get CPR + epinephrine + a search for the cause.
Reversible causes: the Hs and Ts
| Hs | |
|---|---|
| Hypovolemia | Fluids, blood |
| Hypoxia | Airway, oxygen, ventilation |
| Hydrogen ion (acidosis) | Ventilation; bicarbonate in selected cases |
| Hypo-/hyperkalemia | Correct K⁺ (calcium for high K⁺) |
| Hypothermia | Rewarm |
| Ts | |
|---|---|
| Tension pneumothorax | Needle decompression |
| Tamponade (cardiac) | Pericardiocentesis |
| Toxins | Antidote (e.g., naloxone) |
| Thrombosis, pulmonary (PE) | Consider fibrinolytic |
| Thrombosis, coronary (MI) | Cath lab after ROSC |
Priority
During CPR, an end-tidal CO₂ <10 mmHg suggests poor-quality compressions. A sudden rise to 35–45 mmHg suggests return of spontaneous circulation (ROSC).