The aim of this work was to compare the antiarrhythmogenic effects of levomepromazine and acepromazine, in dogs anesthetized with halothane, receiving increasing doses of epinephrine. For this purpose, 19 male and female healthy adult mixed breed dogs were divided in two groups, one with 10 (G1) and other with 09 (G2) animals. G1 received intravenously, 1mg/kg of levomepromazine, followed, 15 minutes later, by anesthetic induction with propofol (5 ± 1.3mg/kg). The intubation was proceeded, followed by imediate administration of halothane at 3 MAC (2.5 V%) through a semi-closed anesthetic circuit. After 50 minutes of the anesthetic induction, administration of 4% epinephrine solution had begun, with increasing doses of 4, 5, 6, 7 and 8mug/kg/min. The increment of the doses occurred at 10 minutes intervals. For G2 the same methodology was used, except that levomepromazine was replaced with 0.1mg/kg of acepromazine. Electrocardiography and arterial blood pressure (systolic, diastolic and mean) were continuously evaluated, starting immediately before the administration of the drugs and going on until the end of the experimental period. The measurements were made immediately before the administration of the drugs (M1), followed by new measurements related with the increasing doses of epinephrine (4, 5, 6, 7 and 8mug/kg/min; M2, M3, M4, M5 and M6 respectively). The electrocardiographic values obtained were referent to the total number of ventricular premature complexes, coincident with each epinephrine dose. Only one animal of each group presented sustained ventricular arrhythmia, and the animal pretreated with acepromazine died. These results allowed the conclusion that levomepromazine and acepromazine minimizes ventricular epinephrine-induced arrhythmia in dogs anesthetized with halotane. In addiction, the risk of death by epinephrine use in dogs anesthetized with halotane and pretreated with levomepromazine seems to be even lower.
anesthesia; phenothiazines; antiarrhythmics
