Cardiac performance was evaluated in 9 healthy cats sedated with
xylazine. Each cat was evaluated echocardiographically before and after the administration of
xylazine or
xylazine and
glycopyrrolate. Each cat was echocardiographically evaluated during manual restraint only (control value), after IM administration of 0.55 mg of
xylazine/kg of
body weight, after IM administration of 2.2 mg of
xylazine/kg, and after IM administration of 0.011 mg of
glycopyrrolate/kg followed 10 minutes later by IM administration of 2.2 mg of
xylazine/kg. Echocardiographic indices of cardiac performance (fractional shortening, left ventricular wall amplitude, aortic amplitude, mitral valve E point septal separation) indicated a significant decrease (P less than 0.05) in the left ventricular function and heart rate after the small (0.55 mg/kg) and large (2.2 mg/kg) dosages of
xylazine. With the administration of
glycopyrrolate, the
bradycardia was minimized, but cardiac performance was not improved. After administration of
glycopyrrolate, cardiac performance decreased, but the decrease was not significant when compared with the ventricular performance of the cats after administration of the large dosage of
xylazine. Compared with control values, the reduction in left ventricular function values associated with administration of
xylazine or
xylazine and
glycopyrrolate was independent of the heart rate. Therefore, the alpha-2
adrenergic agonist xylazine has a marked depressive effect on cardiac performance in the cat, and
premedication with
glycopyrrolate may not completely alleviate the undesirable
bradycardia, but may actually be detrimental to the cardiovascular system.