Evaluation of cardiorespiratory effects of combinations of dexmedetomidine and atropine in cats.

The cardiovascular effects of dexmedetomidine alone or in combination with atropine were studied in six cats. Cats underwent four treatments in a randomized crossover design as follows: DEX15, saline+dexmedetomidine 15microg/kg; DEX30, saline+dexmedetomidine 30microg/kg; ADEX15, atropine+dexmedetomidine 15microg/kg; ADEX30, atropine+dexmedetomidine 30microg/kg. Pulse rate (PR) and systolic arterial pressure (SAP) decreased in DEX15 and DEX30. Premedication with atropine was effective in preventing bradycardia (PR<100 beats/min) and resulted in a biphasic effect in blood pressure. Hypertension was followed by a gradual decrease in SAP. Rate pressure product decreased in DEX15 and DEX30 whereas in ADEX15 and ADEX30 it remained within baseline values for at least 60min. Although premedication with atropine in cats sedated with dexmedetomidine prevents bradycardia, it induces hypertension and increases myocardial oxygen consumption. The magnitude of cardiovascular effects produced by dexmedetomidine in cats does not seem to be dose-related.