Hemodynamic responses to intravenous maropitant in anesthetized dogs depend on premedication protocol

OBJECTIVE: To evaluate the hemodynamic effects of intravenous maropitant in dogs under general anaesthesia premedicated with dexmedetomidine or acepromazine. STUDY DESIGN: Prospective randomized clinical study. ANIMALS: Twenty-six healthy Spanish Greyhounds. METHODS: Dogs were randomly premedicated with dexmedetomidine (DEX; 4μg/kg) or acepromazine (ACP; 20μg/kg), both combined with methadone (0.3mg/kg) administered intramuscularly. Anesthesia was induced with propofol and midazolam and maintained with sevoflurane. Once a stable anesthetic plane was achieved, maropitant (1mg/kg IV) or saline was administered, resulting in four groups: DEX-M, ACP-M, DEX-C, and ACP-C. Invasive arterial blood pressure (systolic, diastolic, mean) and heart rate were recorded at baseline and for 20minutes after administration. Changes over time were analyzed and compared with baseline values using the Friedman test (p < 0.05). RESULTS: In the DEX-M group, diastolic arterial pressure decreased significantly at 2minutes, accompanied by a transient increase in heart rate. In the ACP-M group, systolic, diastolic and mean arterial pressures decreased significantly at 2minutes, also with an increase in heart rate. Clinically relevant hypotension (mean arterial pressure 51 ± 7mmHg) occurred only in ACP-M dogs. All changes were transient. CONCLUSIONS: Intravenous maropitant administration appears to be hemodynamically well tolerated in healthy dogs under general anesthesia premedicated with dexmedetomidine. In contrast, when acepromazine is used for premedication, maropitant administration results in more pronounced hemodynamic effects, including clinically relevant hypotension. These findings suggest that alternative routes of administration should be considered in the perioperative setting.