The clinical effects of a low dose dexmedetomidine constant rate infusion in isoflurane anesthetized cats.

The aim of this study was to evaluate the effects of a low dose dexmedetomidine constant rate infusion (CRI) on cardiopulmonary function, inhalant anesthetic concentration and recovery in isoflurane anesthetized cats. In a prospective, randomized, blinded, controlled design, 12 cats undergoing anesthesia for ovariohysterectomy were administered hydromorphone (0.1mg/kg) intramuscularly, propofol (4.3-7.8mg/kg) intravenously and maintained with isoflurane. During isoflurane anesthesia, the cats were administered either a dexmedetomidine loading dose (0.5μg/kg) followed by a dexmedetomidine CRI (0.5μg/kg/h) (group LDD), or a saline loading dose followed by a saline CRI (group SAL). Heart rate (HR), respiratory rate, blood pressure, temperature, oxygen saturation (SpO2 ), end tidal carbon dioxide concentration (ETCO2 ), end tidal isoflurane concentration (ETISO ) and anesthetic depth were recorded at nine time points (T0-T8). Overall effects (T1-8) and individual time point results were compared between groups. There were no significant differences in baseline variables (T0), age, weight, propofol dose, anesthesia and surgery time, time to extubation or recovery score between groups. Among the physiological variables measured, significant differences were observed in respiratory rate, ETCO2 , and mean and diastolic blood pressure, between groups at individual time points. Systolic blood pressure, HR, SpO2 , ETISO and temperature were not significantly different between groups at individual time points. Overall, ETCO2 and ETISO were significantly lower and respiratory rate was significantly higher for LDD compared to SAL. At the doses administered, a CRI of dexmedetomidine reduced isoflurane requirements in anesthetized cats undergoing ovariohysterectomy. The utility of a low dose dexmedetomidine CRI in the perioperative setting requires further investigation, since intraoperative cardiopulmonary values during dexmedetomidine infusion were not different from those receiving saline.