Decide if the patient is unstable (shock, syncope, ischaemia, heart failure). Unstable tachycardia: synchronised cardioversion. Unstable bradycardia: atropine, then adrenaline infusion or pacing.
At the bedside
Timed steps- 1
ABCDE, O2, IV, 12-lead ECG, monitor
0 minTreat the patient, not the monitor. Ask: is the arrhythmia the cause of instability or a response to it (sepsis, bleeding, hypoxia)?
- 2
Adverse features
AssessShock (SBP < 90 or MAP < 65, cold, confused), syncope, myocardial ischaemia, severe heart failure. Any = unstable.
- 3
Synchronised cardioversion
Unstable tachycardiaSedate if conscious (e.g. ketamine or small-dose propofol/midazolam). AF or flutter: start ≥ 200 J biphasic (AHA 2025). Regular narrow or monomorphic VT: 100-200 J, escalate. Up to 3 attempts, then amiodarone 300 mg over 10-20 min and repeat.
- 4
Vagal then adenosine
Stable regular narrowModified Valsalva (blow into a 10 mL syringe for 15 s then lie flat with legs raised), then adenosine 6 mg → 12 mg rapid push. See module 10 for full tachycardia care.
- 5
Atropine
Unstable bradycardiaAHA: 1 mg IV every 3-5 min (max 3 mg). ERC: 500 mcg repeated to 3 mg. Indian ampoule 0.6 mg/mL.
- 6
Adrenaline infusion or pacing
Atropine failsAdrenaline 2-10 mcg/min (or isoprenaline/dopamine) while arranging transcutaneous then transvenous pacing. Mobitz II, complete heart block with wide QRS, or asystole risk: pace early.
- 7
Magnesium
Torsades2 g IV over 10-15 min; correct K+; stop QT-prolonging drugs; overdrive pacing or isoprenaline if bradycardia-dependent.
First-line for unstable bradycardia
Atropine
- Dose
- AHA 1 mg every 3-5 min (max 3 mg); ERC 500 mcg every 3-5 min (max 3 mg)
- Preparation
- 0.6 mg/mL ampoule: 1 mg ≈ 1.7 mL
Bradycardia not responding to atropine
Adrenaline (epinephrine)
- Dose
- 2-10 mcg/min
- Preparation
- 4 mg in 50 mL (80 mcg/mL)
- Worked example
- 5 mcg/min × 60 = 300 mcg/h ÷ 80 = 3.75 mL/h
Stable regular narrow-complex tachycardia
Adenosine
- Dose
- 6 mg, then 12 mg
3 mg via central line or after heart transplant.
After failed cardioversion, or stable VT
Amiodarone
- Dose
- 300 mg over 10-20 min (ERC) or 150 mg over 10 min (AHA), then 900 mg over 24 h
- Preparation
- In 5% dextrose only
Torsades de pointes
Magnesium sulfate
- Dose
- 2 g over 10-15 min
- Preparation
- 4 mL of 50% in 20-100 mL NS
Calculators for this topic
References
- 1
- 2
Peri-arrest rhythm decision
Step 1 of ~4
Decision: Adverse features? (shock, syncope, ischaemia, heart failure)
Based on Part 9: Adult Advanced Life Support: 2025 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care; Soar J, Böttiger BW, Carli P, et al. Educational use; follow local protocol.
Evidence
- AHA 2025 ALS: stability assessment drives therapy. Synchronised cardioversion for unstable wide- or narrow-complex tachycardia. ≥ 200 J initial energy for AF and atrial flutter cardioversion. Adenosine for regular narrow-complex tachycardia; may be considered for stable regular monomorphic wide-complex tachycardia; never for unstable, irregular or polymorphic wide-complex tachycardia. Verapamil and diltiazem must not be given for wide-complex tachycardia.
- ERC 2025: atropine 500 mcg boluses for bradycardia; second-line drugs include isoprenaline and adrenaline; pacing for high-risk bradycardia.
Controversies
- Atropine dose difference (AHA 1 mg vs ERC 500 mcg). The app should state one unit protocol.
🇮🇳 India notes
- Atropine ampoules are 0.6 mg/mL in most Indian hospitals, so "1 mg" means 1.7 mL; mistakes are common.
- Isoprenaline availability varies; adrenaline infusion is the practical second line in most Indian ICUs.
References
- 1
- 2
Test yourself
Module quiz · score 70% to complete the module
Educational reference for trained clinicians. Check doses against your hospital protocol and the patient in front of you.