Antiarrhythmic drugs in broad complex tachycardia



Procainamide

Dosage:

  • 20-30 mg per minute by intravenous infusion to a maximum dose of 1g. (Usually no more than 500 mg is required)
  • Stop loading infusion if the dysrhythmia is controlled, the QRS widens by more than 50%, the QT becomes prolonged, or the maximum dose has been given. 
  • If VT is successfully treated, infuse at 2 - 6 mg/min to maintain the suppression.

Principal side effects

  • Hypotension and heart failure due to myocardial depression. 
  • ECG abnormalities .. especially QRS prolongation, QT prolongation, VF and torsades de pointes.

Contraindications

  • Relative: Renal and hepatic impairment
  • Absolute: Hypotension, heart failure, heart block, prolonged QT syndrome, Torsades de Pointes, amide allergy, SLE, breast feeding

All antiarrhythmic drugs can also cause arrhythmias. These notes are orientated towards emergency usage and are not comprehensive


Lidocaine (lignocaine)

Dosage:

  • 50 - 100mg bolus over 1-2 minutes.
  • This should be followed by an infusion at 4 mg/minute for 30 minutes, 2 mg/minute for 2 hours, then 1 mg/minute.
  • If an infusion cannot be set up immediately following the 1st bolus the dose can be repeated once or twice at intervals of 10 minutes, to a maximum dose of 200 mg.

Principal side effects:

  • CNS effects are the principal problem, and are mainly seen if administration is too rapid.
  • Hypotension and bradycardia can occur.

Contraindications:

  • Relative: Reduce doses in congestive cardiac failure, hepatic failure, and in the elderly
  • Absolute: Sinoatrial disorders, all grades of atrioventricular block, severe myocardial depression, amide sensitivity, porphyria.

All antiarrhythmic drugs can also cause arrhythmias. These notes are orientated towards emergency usage and are not comprehensive


Flecainide

Dosage

  • 2 mg/kg over 10 -30 minutes. Maximum dose 150 mg. 
  • Can be followed by an infusion at 1.5 mg/kg/hour for the first hour, then 100-250 micrograms/kg/hour for up to 24 hours. Maximum dose in 24 hours 600 mg.

Principal side effects:

  • Can cause heart failure, myocardial infarction, hypotension, bradycardia, and convulsions.
  • There may be paraesthesia and visual disturbance. 
  • On the ECG there may be prolongation of the PR interval and widening of the QRS complex.

Contraindications:

  • Relative: Sinus node dysfunction and heart blocks, hepatic and renal impairment, patients with pacemakers
  • Absolute: Heart failure, previous MI, haemodynamically significant valvular heart disease

All antiarrhythmic drugs can also cause arrhythmias. These notes are orientated towards emergency usage and are not comprehensive


Amiodarone

Dosage

  • In VF / pulseless VT: 300 mg diluted to 20 ml with 5% dextrose, as an iv bolus
  • In arrhythmias with a pulse: 150 mg diluted to 20 ml with 5% dextrose over 10 min iv Can be repeated.
  • Alternatively give 300 mg diluted to100 ml with 5% dextrose over 1 hour. 
  • Follow by an infusion of 1 mg/min for 6 hours, thereafter reducing to 0.5 mg/min. 
  • BNF recommends maximum dose of 1.2g over 24 hours. Resuscitation Council recommends maximum dose of 2g over 24 hours.
  • Give via central line whenever possible

Principal side effects:

  • Hypotension is common with parenteral use, and bradycardia may occur.
    • if this occurs slow the rate of drug infusion, and consider iv fluids, pressors, chronotropic agents, or pacing.

Contraindications

  • Hypotension, bradycardia, sino-atrial heart block or conduction disturbances, pregnancy and breast feeding.
  • Avoid bolus use in congestive cardiac failure or cardiomyopathy.

All antiarrhythmic drugs can also cause arrhythmias. These notes are orientated towards emergency usage and are not comprehensive


Sotalol

Dosage:

  • 20 -120 mg over 10 minutes. Can be repeated at 6 hour intervals.

Principal side effects:

  • Hypotension, bradycardia ( treat with atropine ), heart failure, conduction disturbance, bronchospasm, peripheral vasoconstriction. 
  • QT prolongation and Torsades de Pointes. 
  • Can reduce responsiveness to epinephrine

Contraindications:

  • Hypotension, bradycardia, heart failure, heart block, asthma or chronic obstructive airways disease, severe peripheral arterial disease, phaeochromocytoma, prolonged QT syndromes, Torsades de Pointes, renal failure

All antiarrhythmic drugs can also cause arrhythmias. These notes are orientated towards emergency usage and are not comprehensive



Content by Dr Ian Higginson, Dr Íomhar O' Sullivan 11/07/2003.   Reviewed by Dr ÍOS 11/07/2004, 11/07/21005, 24/04/2007, 14/09/2010. Last review Dr ÍOS 4/12/18.