The effect of dexmedetomidine on the cardiac rhythm in twenty healthy mongrel dogs of both sexes anesthetized with sevofluorane and submitted to increasing doses of adrenaline was evaluated. The animals were randomly allotted to different treatment groups. Animals of placebo group were intravenous injected with 0.9% NaCl solution at 0.3ml/kg/IV. Two moments were considered, M0 and M1, the moments immediately before and after application, respectively. Ten minutes later, the dogs were anesthetized using sevofluorane via face mask until lost of their laringotracheal reflex. Then, orotracheal intubation was performed and maintenance of anesthesia was kept with 1,5MAC sevofluorane using an anesthetic circuit with a rebreathing system. Twenty minutes after anesthesia induction, continuous IV administration of 2% adrenaline solution was given at increasing doses of 1,2,3,4 and 5mg/kg/min., every ten minutes, respectively. The moments M2 to M6 were measured immediately before the next increase of dose. In dexmedetomidine group, the same technique was used replacing 0.9% NaCl by dexmedetomidine hydrochloride at 1mg/kg. Blood pressures were recorded at M0 and M2 to M6. Electrocardiography line in the derivation DII (M2 to M6) was used to observe the number of atrioventricular blocks (AVB) of first and second degrees and ventricular premature complexes (VPC). Statistic evaluation was performed by analysis of variance followed by Tukey's test (P<0.05). Dexmedetomidine significantly altered the atrioventricular conduction resulting in a higher occurrence of AVB. This drug reduced the number of VPC at 2 and 3mg/kg/min of adrenaline. After administration of dexmedetomidine, reduction of arterial blood pressure up to one hour and reduction of cardiac rate were observed.
dog; alpha-2 agonists; cardiac rhythm; inhalatory anesthesia
