Bradycardia Medication Protocol

Bradycardia (heart rate under 50 beats each minute) needs treatment when it is causing adverse features: shock, syncope, myocardial ischaemia, heart failure or confusion. A slow rate without these features needs observation and a search for causes.

Causes. Inferior myocardial infarction, beta blockers, calcium channel blockers, digoxin, hyperkalaemia, hypothermia, hypothyroidism, raised intracranial pressure, and sleep or vagal reflexes. Rheumatic carditis and infective endocarditis can cause heart block.

Risk of asystole. Recent asystole, Mobitz type II or complete heart block with a wide QRS, or ventricular pauses over 3 seconds need early pacing.

First line. Atropine intravenously.

If atropine fails or the patient is at risk of asystole. Transcutaneous pacing, or an infusion of adrenaline, dopamine or isoprenaline as a bridge.

Toxins. Calcium for calcium channel blockers and hyperkalaemia, glucagon for beta blockers, digoxin-specific antibody fragments for digoxin, and high-dose insulin with glucose by toxicology direction.

Special groups.

• Children: oxygenation and ventilation first, then adrenaline 0.01 mg/kg intravenously. Atropine 20 micrograms/kg for vagal causes or heart block.

• Heart transplant: atropine is ineffective, so pace.

• Pregnancy: use the usual adult treatment.

• East Africa: check for rheumatic heart disease, endocarditis, and herbal or plant toxins as causes.

• Atropine: 500 micrograms (0.5 mg) intravenously, repeated every 3 to 5 minutes to a maximum of 3 mg.

• Adrenaline infusion: 2 to 10 micrograms/min (about 0.05 to 0.5 micrograms/kg/min).

• Dopamine: 5 to 20 micrograms/kg/min.

• Isoprenaline: 5 micrograms/min, titrated.

• Aminophylline: 100 to 200 mg intravenously slowly, by specialist decision.

• Glucagon (beta blocker toxicity): 3 mg intravenously over 1 minute, then 3 mg/h.

• Calcium chloride 10 percent: 10 mL intravenously for calcium channel blocker toxicity and hyperkalaemia.

Monitoring. Continuous ECG, blood pressure, glucose, potassium, calcium and magnesium, and the response to each step.

Stop rules. Stop atropine after 3 mg. Withdraw the causative drug. Stop infusions when a stable rhythm returns or pacing is established.

Referral and escalation. Seek cardiology for pacing (transcutaneous, then transvenous) and for complete heart block or recurrent pauses, and toxicology advice for drug causes.

Common errors. Giving atropine repeatedly to a patient with complete heart block, delaying pacing, giving doses under 0.5 mg, and ignoring hyperkalaemia.