Context: When is bradycardia an emergency?
The decisive factor is not the heart rate alone but whether the circulation tolerates the bradycardia. The bradycardia algorithm of the ERC Guidelines 2025 therefore focuses on two questions:
- Are there signs of instability? These include shock (hypotension, cool peripheries, impaired consciousness), syncope, myocardial ischaemia and heart failure.
- Is there a risk of asystole? Indicators are high-grade AV block (particularly Mobitz II or third-degree AV block with broad QRS complexes), recently documented asystole or ventricular pauses.
Asymptomatic bradycardia without a risk of asystole usually does not require emergency treatment. It does, however, require monitoring and investigation of the underlying cause.
Initial management using ABCDE
Basic measures precede any specific treatment:
- Structured assessment using ABCDE, oxygen in the presence of hypoxaemia
- Continuous ECG monitoring, 12-lead ECG as soon as feasible
- Secure IV access
- Apply defibrillation/pacing pads early so that transcutaneous pacing is immediately available if the patient deteriorates
- Systematic search for reversible causes
Typical reversible causes
- Hypoxia: the most common cause in children, but also relevant in adults
- Acute coronary syndrome: particularly inferior myocardial infarction
- Electrolyte disturbances: especially hyperkalaemia
- Drugs and poisoning: e.g. beta-blockers, calcium channel blockers, digitalis glycosides, organophosphates
- Iatrogenic causes: Magnesium sulfate can also cause bradycardia and hypotension if given too rapidly, and AV block progressing to asystole in overdose.
- Hypothermia and raised intracranial pressure
In poisoning, specific antidote therapy should follow the relevant summary of product characteristics and toxicological recommendations.
Atropine in bradycardia: dosing and limitations
According to ERC 2025, atropine is the first-line drug for unstable bradycardia in adults.
| Parameter | Adults (ERC 2025 ALS) |
|---|---|
| Single dose | 0.5 mg IV |
| Repeat | every 3–5 min |
| Maximum dose | 3 mg in total |
| Volume | at 0.5 mg/ml = 1 ml |
Practical points:
- Check the concentration: Depending on the manufacturer, 0.5 mg/ml or 1 mg/ml preparations are available. Check the ampoule before each administration.
- Avoid underdosing: Doses below 0.5 mg can cause paradoxical bradycardia in adults.
- Ineffective after heart transplantation: The denervated heart does not respond to atropine. Escalate directly in these patients.
- Infranodal block: In AV block with broad QRS complexes, the effect is often insufficient. Preparations for pacing should then be made early.
- Contraindications: There are no absolute contraindications in the emergency indication. In angle-closure glaucoma, tachyarrhythmia and myocardial ischaemia, weigh benefits against risks.
- Organophosphate poisoning: Considerably higher doses are required here. Dosing follows toxicological recommendations and not the bradycardia regimen.
Adrenaline as pharmacological escalation
If atropine fails, the compendium – in line with ERC 2025 – provides for an adrenaline infusion via syringe driver or transcutaneous pacing as the next step. Both options are often prepared in parallel.
Important: The dose of the continuous adrenaline infusion for bradycardia should follow the current ERC guideline, the summary of product characteristics and local protocols. It is titrated to heart rate and blood pressure.
Risk of confusion: The bolus of 1 mg IV/IO every 3–5 min (dilution 0.1 mg/ml; 1 mg = 10 ml) applies exclusively to resuscitation in cardiac arrest. This dose is not indicated in a patient with a preserved circulation.
Adverse effects and handling:
- Tachycardia, arrhythmias, hypertension and myocardial ischaemia may occur. Close monitoring is therefore essential.
- Adrenaline is inactivated when mixed with alkaline solutions (e.g. sodium bicarbonate). Flush the line beforehand and ideally use a separate lumen.
The ERC algorithm lists further alternatives for pharmacological escalation. Their use depends on the guideline, the underlying cause and local availability.
Transcutaneous pacing: application and settings
In the emergency setting, transcutaneous pacing is a bridging measure until transvenous or definitive pacing can be provided. It is indicated when there is no response to drug therapy or when the risk of asystole is high.
Preparation
- Apply pads: Place the electrodes in the anterior–posterior or anterior–lateral position according to the manufacturer's instructions on dry skin; remove hair if necessary.
- Connect the device's ECG leads: This is the only way the pacemaker can detect intrinsic beats in demand mode.
- Plan analgosedation: Pacing is painful. Choice of agent and dosing according to local protocols, with airway management readily available.
Settings
- Select the mode: Usually demand mode, so that intrinsic beats are not overpaced.
- Set the pacing rate: according to the device instructions, the guideline and the clinical target.
- Increase the current: Increase the output current stepwise until each pacing spike is followed by a broad QRS complex with a subsequent T wave (electrical capture). Then set the current moderately above the threshold.
- Check mechanical capture: Confirm a palpable pulse synchronous with pacing; additionally use blood pressure, the pulse oximetry waveform and, where available, capnography.
Typical pitfalls
- Muscle twitching mistaken for a pulse: Palpate the pulse preferably at the femoral artery, as contractions of the chest wall muscles can confound carotid palpation.
- Electrical without mechanical capture: This is functionally equivalent to PEA and requires resuscitation according to the ALS algorithm.
- Artefacts: Large pacing artefacts can mask the underlying rhythm. Assess the rhythm regularly with pacing briefly paused, provided this is clinically justifiable.
- Early consultation: Involve cardiology or intensive care early for transvenous pacing.
On the evidence: robust outcome data for transcutaneous pacing are limited. Its role is based largely on physiological plausibility and expert consensus.
Overview of the bradycardia algorithm (adults)
- ABCDE, monitoring, 12-lead ECG, IV access, apply pads
- Identify and treat reversible causes
- Instability? → Atropine 0.5 mg IV, repeat every 3–5 min up to a maximum of 3 mg
- Inadequate response or high risk of asystole → adrenaline infusion via syringe driver (titrated according to guideline and summary of product characteristics) and/or transcutaneous pacing
- Request expert help for transvenous pacing
- In cardiac arrest → resuscitation according to the ALS algorithm
Special considerations in children
In children, bradycardia is usually the result of hypoxia or circulatory failure. Treatment therefore differs fundamentally:
- Oxygenation and ventilation first: Secure the airway, oxygenate, ventilate.
- Bradycardia with poor perfusion despite adequate oxygenation and ventilation: According to ERC 2025, this is treated as cardiac arrest, with chest compressions (15:2). The ERC does not specify a fixed heart rate threshold for this. Other algorithms, e.g. RCUK, give a heart rate < 60/min as a guide.
- Adrenaline: 0.01 mg/kg (10 µg/kg) IV/IO, maximum 1 mg. In non-shockable rhythms as early as possible (within 3 min), then every 4 min. At a dilution of 0.1 mg/ml, this corresponds to 0.1 ml/kg.
- Vascular access: Intraosseous immediately if IV access appears difficult or fails.
- Fluids if hypovolaemia is suspected: 10 ml/kg balanced crystalloid solution, repeat after reassessment.
Practical conclusion
Unstable bradycardia is recognised by clinical signs, not by a heart rate threshold. Atropine at the correct dose is the first step. An adrenaline infusion via syringe driver and transcutaneous pacing are the escalation options and should be prepared early. When pacing, confirming mechanical capture determines success. In children, oxygenation and ventilation take priority.
References
- Soar J, Böttiger BW et al. European Resuscitation Council Guidelines 2025 Adult Advanced Life Support. Resuscitation 2025;215 Suppl 1:110769 (Korrigendum 2026).
- Djakow J, Turner NM, Skellett S et al. European Resuscitation Council Guidelines 2025 Paediatric Life Support. Resuscitation 2025;215 Suppl 1:110767.
- Resuscitation Council UK. Paediatric advanced life support algorithm – 2025 Resuscitation Guidelines (Fassungen 10/2025 und V2 11/2025) sowie Paediatric Life Support Guideline 2025, Tabelle 1 „Approximate normal values" (Wiedergabe in Medscape: Paediatric Life Support – RCUK 2025 Guideline Summary).
This article does not replace clinical judgement in the individual case or the current summary of product characteristics and guidelines.
