Postoperative catecholamine response to onychectomy in isoflurane-anesthetized cats. Effects of analgesics.

Twenty-four healthy adult cats were anesthetized with isoflurane in oxygen. Six cats (group 1) served as controls; onychectomy of the forefeet was performed in the other three groups. Saline was administered intravenously to group 1, and morphine, xylazine, and salicylate were administered to groups 2, 3, and 4, respectively. Mixed venous blood samples were drawn for catecholamine analysis before induction of anesthesia, after recovery from anesthesia, and 30 minutes and 60 minutes after administration of the analgesic agent. Plasma catecholamine concentrations were determined by high performance liquid chromatography. Isoflurane anesthesia alone induced a transient increase in epinephrine concentration. Norepinephrine and epinephrine concentrations increased significantly after onychectomy. Morphine and xylazine significantly decreased postoperative norepinephrine and epinephrine concentrations; salicylate did not.