Synopsis
Deliver synchronised cardioversion safely, choose rhythm-specific energy and use emergency antiarrhythmics in their correct licensed or resuscitation context.
- Synchronised cardioversion times the shock to the R wave to avoid energy delivery during ventricular repolarisation.
- A conscious patient needs carefully titrated sedation or anaesthesia, but instability must not be allowed to worsen while waiting.
- RCUK 2025 energies: AF at maximum defibrillator output; flutter/regular narrow tachycardia 70-120 J; VT with a pulse 120-150 J.
Key red flags
Shock, syncope with severe or ongoing hypotension, myocardial ischaemia, severe pulmonary oedema or immediately post-ROSC favours immediate electricity.
Investigation priorities
Define rhythm, regularity, QRS width, QT, pre-excitation and ischaemia.
Management branches
A perfusing tachyarrhythmia causes a life-threatening adverse feature.
- Call expert and anaesthetic help, perform ABCDE assessment, attach pads, monitor continuously and obtain IV access.
- Sedate or anaesthetise a conscious patient with careful haemodynamic planning when feasible without dangerous delay.
QRS is under 120 ms, rhythm regular and no adverse feature is present.
Key medicines
AdenosineRCUK March 2026: 6 mg, then 12 mg, then 18 mg by very rapid IV bolus, each followed by a rapid flush. This algorithm-specific sequence differs from the cited product SmPC's licensed 3 mg, 6 mg, then 12 mg sequence.
Procainamide10-15 mg/kg IV over 20 minutes, maximum 1 g.