The effects of a long-duration intravenous infusion of detomidine, with and without vatinoxan, on equine energy metabolism and urine composition

OBJECTIVE: To assess the effects of a 4 hour detomidine constant rate infusion (CRI) with and without a vatinoxan CRI on energy metabolism and urine composition. STUDY DESIGN: Randomized, blinded, crossover study. ANIMALS: Eight Finnhorses, 587 (550-620) kg [median (range)] and 13 (4-16) years old. METHODS: Horses were administered an intravenous (IV) detomidine loading dose (0.01 mg kg-1) followed by 240 minutes CRI (0.015 mg kg-1 hour-1) (DET) and the same detomidine protocol combined with an IV vatinoxan loading dose (0.15 mg kg-1) and CRI (0.05 mg kg hour-1) (DET+VAT). Blood samples for glucose, insulin, non-esterified fatty acid (sNEFA), and β-hydroxybutyrate (sBHB) concentrations were collected during and for 240 minutes after CRI. Urine samples for glucose and sodium concentrations were collected at the end of CRI. Data were analysed using repeated measures ANCOVA and Wilcoxon signed-rank test. RESULTS: Blood glucose concentrations were significantly higher during CRI with DET compared with DET+VAT (all p < 0.001). Median insulin concentration was significantly lower during CRI with DET compared with DET+VAT (p = 0.012-0.018) and peaked at the end of follow-up period. With DET+VAT CRI, sBHB and sNEFA were significantly higher compared with DET (p < 0.001-0.002, p < 0.001-0.007). Urination was more frequent during DET CRI than with DET+VAT (p = 0.020). Glucosuria was more profound with DET [6.3 (2.4-11.1) mmol L-1] than with DET+VAT [0.1 (0.0-3.1) mmol L-1] (p = 0.012). More sodium was excreted into urine with DET [49.0 (22-66) mmol L-1] than with DET+VAT [27.0 (8-43) mmol L-1] (p = 0.012). CONCLUSIONS AND CLINICAL RELEVANCE: Vatinoxan alleviated detomidine-induced hypoinsulinaemia and hyperglycaemia and diminished urination frequency, glucosuria, and natriuresis during and after a 4 hour CRI. Vatinoxan may be beneficial during standing sedation with alpha2-adrenoceptor agonists.