Antiarrhythmics

Lidocaine

Adult Dosing

• Loading dose = 1-1.5 mg/kg
  • Additional boluses of 0.5-0.75 mg/kg q5-10min up to max of 3mg/kg
  • If effective start infusion of 2mg/min

Contraindications

• High SA or AV block

Indications

• Treatment of ventricular arrhythmias and ectopy
  • Considered 2nd-line to amiodarone for tx of V-fib and pulseless v-tach

Mechanism of Action

• Class Ib
  • Binds to fast Na channels in inactive state thereby inhibiting recovery after repolarization
  • Acts preferentially on ischemic tissue
    • Elevates V-fib threshold
    • Suppresses ventricular ectopy
• Little effect on vascular tone, contractility or cardiac output

Adverse Drug Rxns

• CNS
  • Abrupt change in MS, drowsiness, confusion, sz

Kinetics

• Onset of action = 45-90s
• Duration of action = 10-20min

Isoproterenol

Adult Dosing

2-10mcg/min IV by continuous infusion

Indications

• Refractory torsades
• Refractory symptomatic bradycardia

Mechanism of Action

• Beta agonist

Adverse Drug Rxns

• Dramatic increase in O2 demand
• V-tach (use lowest dose possible)

Kinetics

• Onset of action = 1-5min
• Duration of action = 1-2hr

Magnesium

Adult Dosing

• Loading dose = 1-2gm in 10mL D5W over 1-2min (cardiac arrest)
• Loading dose = 1-4gm in 50-100 D5W over 20-60min (spontaneous circulation)

Indications

• Torsades
• Refractory v-tach/fib (regardless of Mg level)

Mechanism of Action

• Increases vasomotor tone
• Prolongs AV conduction; prolongs refractoriness

Adverse Drug Rxns

• Hypotension (rare)

Kinetics

• Onset of action = Immediate
• Duration of action = 30min

Source

Tintinalli