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Perioperative arrhythmias
An arrhythmia in theatre is first a sign — of hypoxia, a high carbon dioxide, electrolytes, vagal stimulation or light anaesthesia; begin by judging stability, then correct the cause, and only then choose a drug or a shock.
Why it matters in the exam
The exam asks about new atrial fibrillation during surgery, vagal bradycardia, complete heart block, QT prolongation and torsades de pointes, WPW with atrial fibrillation and the drugs that must not be given in it, SVT and adenosine, and the effect of potassium and magnesium on rhythm. Questions also cover anaesthetic drugs that prolong QT and bradycardia in children.
The first step is to check stability: low blood pressure, confusion in an awake patient, chest pain or heart failure. In an unstable patient with tachycardia a synchronised shock is given (for example 120–200 joules biphasic for atrial fibrillation). In a stable patient with atrial fibrillation, oxygen, volume, potassium and magnesium are corrected, anaesthesia is deepened, and the rate is slowed with a beta blocker or diltiazem. If the fibrillation has lasted more than 48 hours, an atrial clot and anticoagulation must be assessed before conversion to sinus rhythm. In narrow-complex SVT vagal manoeuvres are tried and then adenosine 6 mg by rapid injection, and 12 mg if needed.
Bradycardia in surgery usually comes from peritoneal traction, the oculocardiac reflex, laryngoscopy in a child, a high spinal, a second dose of succinylcholine, remifentanil or dexmedetomidine. The stimulus is stopped and atropine 0.5–1 mg is given, repeatable up to 3 mg; in complete block that does not respond, external pacing or adrenaline is started. QT prolongation is caused by low potassium and magnesium and by drugs such as ondansetron, droperidol, haloperidol, methadone and sevoflurane; torsades de pointes is treated with 2 g of magnesium IV. In WPW with atrial fibrillation, drugs that block the node (adenosine, verapamil, digoxin) must not be given, because impulses pass down the accessory pathway and may cause ventricular fibrillation; procainamide or a synchronised shock is given. In ventricular tachycardia with a pulse and stability, amiodarone 150 mg over 10 minutes is given.
Key points
- First stability, then causes, and only then a drug.
- Unstable with tachycardia: synchronised shock.
- Bradycardia: stop the stimulus and give atropine.
- Torsades de pointes: magnesium 2 g.
- WPW with atrial fibrillation: do not block the node.
Summary table
| Disorder | Treatment | Exam point |
|---|---|---|
| New atrial fibrillation | Unstable: synchronised shock; stable: correct causes and slow the rate | More than 48 hours: assess for clot before conversion |
| Narrow SVT | Vagal manoeuvres, adenosine 6 mg then 12 mg | Rapid injection and flush |
| Bradycardia | Stop the stimulus, atropine 0.5–1 mg up to 3 mg | Think of the oculocardiac reflex and peritoneal traction |
| Complete block | External pacing, adrenaline or isoprenaline | Atropine is less effective |
| Torsades de pointes | Magnesium 2 g, correct potassium, stop QT-prolonging drugs | Ondansetron and droperidol prolong QT |
| WPW with atrial fibrillation | Procainamide or synchronised shock | Not adenosine, verapamil or digoxin |
| Ventricular tachycardia with a pulse | Unstable: synchronised shock; stable: amiodarone 150 mg over 10 minutes | Pulseless: the resuscitation protocol |
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Sources
- European Resuscitation Council Guidelines, 2021 — Adult advanced life support: peri-arrest arrhythmias
- Miller's Anesthesia, 9th edition (2020) — Cardiac rhythm disturbances in the perioperative period
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-02. The text may contain errors; when in doubt, check the source.