Energy Imbalance and Physiological Changes During Detomidine Hydrochloride Constant Rate Infusion in Standing Horses

Detomidine is an alpha-2-adrenergic agonist widely used in horses. To evaluate changes in muscular energy metabolism caused by detomidine continuous rate infusion in standing horses, six adult animals were submitted to 1 hour 20 μg/kg/hr IV constant rate infusion detomidine. Heart rate, respiratory rate (RR), mean arterial blood pressure, systolic blood pressure, diastolic blood pressure, capillary refill time, rectal temperature, plasma glucose, blood lactate, total plasma protein, packed cell volume (PCV), hemoglobin (Hb), partial arterial pressure of oxygen, partial arterial pressure of carbon dioxide (PaCO2), arterial oxygen saturation, bicarbonate (HCO3−), sodium, potassium, ionized calcium (iCa), arterial oxygen content (CaO2), muscle glycogen, and muscle lactate were recorded before the infusion, after 20, 40, and 60 minutes, when it was discontinued. One last sample was obtained 1 hour after infusion was finished. Four animals were submitted to 1 hour saline infusion as a control group. Constant rate infusion detomidine resulted in significant decrease in HR, RR, PCV, Hb, iCa, CaO2, and muscle glycogen in comparison with both baseline and control groups and significant increase in PaCO2, blood lactate, and HCO3−. Detomidine 20 μg/kg/hr produces minimal clinically significant changes in horses, and it does interfere with energy metabolism through mobilization of muscle glycogen and increase in blood lactate.