Synchronized Cardioversion in the Field
Objective: Pick synchronized cardioversion for unstable tachyarrhythmia with a pulse, confirm sync marks, and switch to unsync if they become pulseless.
Why This Is Hard
They are hypotensive and the rate is 180. Crews push adenosine while the BP is 60 because “sync is scary.” AHA 2025: instability is a perfusion judgment. Unstable + pulse + tachyarrhythmia → cardioversion per protocol.
- Sedate if they are awake and protocol allows — this site does not publish the drug or the joules.
- See the sync marks on the R waves before you charge. If it will not sync, you may be in VF or the gain is wrong.
- If they lose pulses, unsynchronized defibrillation. Do not keep hunting for sync on a pulseless patient.
Field Rules (Education)
- Unstable signs: shock, severe AMS, ischemic pain, acute heart failure — not “the number is 150.”
- Do not cardiovert sinus tach that is compensatory (fever, bleed, PE). Treat the cause.
- Pre-excited AF: avoid AV-nodal blockers; unstable → cardioversion per protocol, not adenosine.
- Clear, shock, pulse/rhythm check, then the algorithm you are actually in.
Field Pitfalls
- Adenosine into crashing wide-complex tachycardia from habit.
- Forgetting to turn SYNC on.
- Cardioverting a talking sinus tach from sepsis.
Practice
60-second drill
Partner: (1) regular narrow 190, BP 50, diaphoretic; (2) sinus 130, febrile GI bleed; (3) pulseless VT. Sync, unsync, or no shock.
Related: Stable vs unstable, SVT.
Sources & Further Study
Named guidelines for further study. They are not clinical orders and do not replace your protocol or medical direction.
- NASEMSO National Model EMS Clinical Guidelines (2022) — U.S. EMS model language; protocol still wins
- AHA 2025 Part 9: Adult ALS — unstable tachycardia with a pulse: synchronized cardioversion; protocol owns energy
Education only. Apply learning within your protocols and medical direction. This is not clinical care guidance.
Check Your Understanding
Street decisions from this lesson only. After you check, the key is highlighted. Education practice — not a certification exam.