| Abstract: | The effects of xylazine given to cats before anesthetization was induced with pentobarbital were determined. Cardiac hemodynamic variables and regional blood flow rates in the heart and other organs were measured, using radiolabeled microspheres. Two groups, each of 10 cats, were included in the study: one group (group 1) was anesthetized with pentobarbital given intraperitoneally and subsequently given xylazine; the other group (group 2) was first given 1 mg of xylazine/kg, IM, and then anesthetized with pentobarbital given IV. Anesthesia was maintained in both groups with nitrous oxide. The preanesthetic administration of xylazine decreased the amount of pentobarbital used for surgical anesthesia by approximately 50%. It also resulted in decreased heart rate, cardiac contractility, and cardiac output and increased left ventricular end-diastolic pressure, compared with those values in cats given pentobarbital (group 1). After the latter cats (anesthetized with pentobarbital) were given xylazine, heart rate, cardiac contractility, and cardiac output decreased and left ventricular end-diastolic pressure increased to values similar to those found in group 2 (given xylazine before anesthetization). Myocardial tissue blood flow rates in the left and right ventricles were lower in the cats of group 2. In group 1 cats, myocardial blood flow rates decreased when xylazine was subsequently added. Blood flow rates in the kidneys and gastrointestinal tract were generally decreased by xylazine. Xylazine profoundly changed cardiac hemodynamic function and perfusion in the heart, as well as several other organ systems, because of marked cardiodepression. |
