Sedative and echocardiographic effects of dexmedetomidine combined with butorphanol in healthy dogs

Objectives: To evaluate the echocardiographic variables and sedation after two dosages of dexmedetomidine combined with butorphanol in healthy dogs. Animals: Fourteen healthy dogs. Methods: The dogs received dexmedetomidine 5 mcg/kg IM and butorphanol 0.4 mg/kg (low dose (LD), n = 6) or dexmedetomidine 10 mcg/kg IM and butorphanol 0.4 mg/kg (recommended dose (RD), n = 8). Sedation scoring, noninvasive blood pressure measurement, and echocardiography were performed before sedation at baseline, at 20 minutes (T20), and 60 minutes (T60) after drug administration. Results: The median sedation scores were increased at both T20 and T60 in the RD group, and at T60 in the LD group, compared with baseline (p < 0.0001, p = 0.012). At T60, the RD dogs were more sedated than the LD dogs (p = 0.0093). The median cardiac output (CO) decreased at both T20 (63%) and T60 (65%) in the RD group and at T60 (42%) in the LD group, compared with baseline (p = 0.0011, p = 0.0055). The median heart rate (HR) was decreased at both T20 and T60 in the RD group and at T60 in the LD group, compared with baseline (p = 0.0009, p = 0.0001). In both RD and LD dogs, valvular regurgitation developed and was identified by color Doppler imaging. Conclusions: There were significant hemodynamic changes, mainly related to HR and indices of systolic function, following administration of dexmedetomidine in these healthy dogs. The changes also included decreases in systolic function and CO, as well as appearance of 'new' valvular regurgitation. Caution should be used when considering dexmedetomidine for sedation in dogs with, or being screened for, cardiovascular disease. (C) 2015 Elsevier B.V. All rights reserved.