EFFECTS OF MAGNESIUM-SULFATE AND LIDOCAINE IN THE TREATMENT OF VENTRICULAR ARRHYTHMIAS IN EXPERIMENTAL AMITRIPTYLINE POISONING IN THE RAT

Objectives: Amitriptyline poisoning is associated with ventricular arr hythmias. Standard treatment is sodium bicarbonate but further interve ntion may be necessary. The present study compared the actions of lido caine and magnesium sulfate on ventricular tachycardia induced by amit ryptiline. Design: Nonrandomized, controlled, intervention trial. Sett ing: University laboratory. Subjects: Thirty male Wistar rats anesthet ized with pentobarbital and mechanically ventilated. Interventions: Af ter pretreatment with norepinephrine, the animals were subjected to a continuous infusion of amitriptyline; After the appearance of ventricu lar tachycardia, they were treated with magnesium sulfate (45 mg/kg 15 mg/kg/min) or Lidocaine (1 mg/kg + 0.5 mg/kg/min) or glucose infusi on as a control. Measurements and Main Results: In the group treated w ith magnesium sulfate, electrocardiogram tracings demonstrated that ni ne of ten animals converted from ventricular tachycardia to sinus rhyt hm compared with one of ten in both the lidocaine- and glucose-treated groups (p < .001). The animals treated with magnesium sulfate also ha d a significantly longer total time in sinus rhythm (10.0+/-1.6 mins) than those rats treated with lidocaine (1.7+/-1.5 mins) or glucose (1. 5+/-1.5 mins). Magnesium sulfate significantly decreased blood pressur e and heart rate, but no severe hemodynamic side effects were observed . Conclusions: Magnesium sulfate is effective in converting ventricula r tachycardia in hyperadrenergic amitriptyline poisoning. In contrast, lidocaine had no effect on arrhythmias.