Blood glucose, acid-base and electrolyte changes during loading doses of alpha2-adrenergic agonists followed by constant rate infusions in horses

The aim of the present study was to investigate changes in blood glucose concentration ([Glu]B), acid-base status and electrolyte concentrations during constant rate infusions (CRI) of two alpha2-adrenergic agonists in seven horses treated in a blinded, randomised, crossover design with xylazine or romifidine. An intravenous (IV) bolus of xylazine (1 mg/kg) or romifidine (80 μg/kg) was administered followed by an IV CRI of xylazine (0.69 mg/kg/h) or romifidine (30 μg/kg/h) for 2 h. Blood samples were collected from the pulmonary artery before and after loading doses, during the CRI, and for 1 h after discontinuing drugs.Blood glucose, base excess (BE), pH, partial pressure of carbon dioxide (Pv¯CO2), strong ion difference (SIDest) and bicarbonate concentration ([HCO3std-]B) increased significantly during the CRI with both alpha2-adrenergic agonists. Chloride concentration ([Cl−]B) and anion-gap (AG) decreased significantly compared to baseline. The decrease in sodium concentration ([Na+]B) was only significant with xylazine. From 1 h after starting the CRI onwards, [Glu]B was significantly higher with romifidine compared to xylazine. Except [Glu]B, SIDest, and Pv¯CO2, all variables returned to normal values 1 h after discontinuing xylazine. After stopping romifidine, all variables except pH remained altered for at least 1 h.It was concluded that loading doses of alpha2-adrenergic agonists followed by CRIs produce [Glu]B, acid-base and electrolyte changes. The clinical significance of the reported changes remains to be investigated and absolute values should be interpreted with caution, as fluid boli were used for cardiac output measurements, but may become important during prolonged infusion and in critically ill patients.