Effects of perzinfotel, butorphanol tartrate, and a butorphanol-perzinfotel combination on the minimum alveolar concentration of isoflurane in cats

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To determine the effects of perzinfotel, butorphanol, and their combination on the minimal alveolar concentration (MAC) of isoflurane in cats. 7 healthy sexually intact cats (4 males and 3 females), aged 12 to 17 months and weighing 2.8 to 4.6 kg. In a crossover design, saline (0.9% NaCl) solution, perzinfotel (2.5 to 15 mg/kg; IV, IM, and SC), butorphanol tartrate (0.2 mg/kg, IM), or a combination of 5 mg of perzinfotel/kg and 2 mg of butorphanol tartrate/kg (both IM) was administered to 6 cats before 7 separate episodes of anesthesia with isoflurane in oxygen. Heart rate, arterial blood pressure, bispectral index (BIS), and inspiration and expiration concentrations of isoflurane were continuously monitored. The isoflurane MAC was determined twice during anesthesia. IV, IM, and SC administration of perzinfotel at 2.5 to 15 mg/kg resulted in a significant decrease in mean isoflurane MAC by 43.3% to 68.0%. The BIS significantly increased after perzinfotel administration via the same routes at 2.5 to 15 mg/kg and after perzinfotel-butorphanol administration IM. Blood pressure was significantly higher after perzinfotel was administered at 5 mg/kg, IM; 10 mg/kg, IV; and 10 mg/kg, SC than after saline solution administration. Perzinfotel administration decreased the isoflurane MAC and increased several BIS and blood pressure values in anesthetized cats. Administration of perzinfotel prior to isoflurane anesthesia may improve anesthetic safety by reducing inhalant anesthetic requirements and improving cardiovascular function during anesthesia.