Six dogs weighing 17.9 ±3.9 kg were anesthetized on two occasions, at least 7 days apart, in randomized blinded manner. Anesthesia was induced and maintained with isoflurane in mechanical ventilation. After instrumentation, the end-tidal isoflurane was maintained at 1,3%V throughout the study. After a 30 minutes stabilization period (M -15), baseline hemodynamic parameters and arterial blood gases were recorded and atropine (atropine group) or 0.9% NaCl (saline group) were administered. Fifteen minutes later, data were recorded again (M0) and a chlorpromazine- dexmedetomidine (Chlor-Dex) combination was administered. Variables were measured for an additional 65 minutes after Chlor-Dex. A one-way ANOVA-Student-Newman-Keuls was used for comparisons within groups, while a paired t test was used for comparisons between groups (P<FONT FACE=Symbol>£</FONT>0,05). Heart rate was higher in atropine group after Chlor-Dex administration. Cardiac index (CI) was reduced from baseline after Chlor-Dex in both treatments. Although mean CI values tended to be higher in atropine group, CI did not differ between groups. Chlor-Dex administration caused increased arterial blood pressure in dogs treated with atropine. Mean arterial pressure (MAP) was significantly higher in the atropine group from 5 to 65 min after Chlor-Dex. The systemic vascular resistance index (SVRI) increased from baseline in both groups after Chlor-Dex administration. No significant differences were observed for arterial blood gases. Atropine administration prior to Chlor-Dex resulted in increased arterial blood pressure. Bradycardia induced by the administration of these drugs was prevented by the anticholinergic given, however decrease in cardiac output was not prevented.
atropine; dexmedetomidine; chlorpromazine; dogs
