ACID-BASE STATUS AND CARDIOVASCULAR FUNCTION IN MINK (MUSTELA-VISON) ANESTHETIZED WITH KETAMINE MIDAZOLAM/

Heart rate, arterial blood pressure and blood acid-base status were de termined in 18 adult female mink (mean (+/-SEM) body weight 1052+/-34 g) during long-term anaesthesia with either controlled ventilation (n= 12) or spontaneous respiration (n=6). Surgical anaesthesia was induced by intramuscular injection of ketamine hydrochloride (Ketaminol Vet(R ), 40.0+/-1.7 mg/kg) and midazolam hydrochloride (Dormicum(R) 2.8+/-0. 1 mg/kg) and maintained for at least 5 h by continuous intravenous inf usion of this drug combination in 0.9% saline. For all animals, the me an rates of infusion of ketamine and midazolam were 48.4+/-1.6 and 1.6 1+/-0.12 mg/h, respectively. Following continuous infusion of the anae sthetics in isotonic saline, at a rate of 20 ml/h, a moderate 'dilutio n acidosis' developed, which could be corrected by replacement of part of the saline with sodium bicarbonate to a final concentration of app roximately 25 mmol NaHCO3 per Litre. However, when the animals were al lowed to breathe spontaneously, an increase in heart rate and a combin ed respiratory and metabolic acidosis occurred, due to severe respirat ory depression. Apart from these effects and a few cases of increased salivation, no adverse effects over time were observed on the arterial blood acid-base status and cardiovascular function of the animals dur ing ketamine/midazolam anaesthesia. It is concluded that the procedure described for long-term anaesthesia in mink is convenient and safe fo r acute physiological experiments in this species, provided normal bod y temperature and pulmonary gas exchange is sufficiently maintained. T hus, the need for an adequately controlled artificial ventilation is s trongly emphasized. Finally, a proposal for the composition of an intr avenous solution, containing ketamine and midazolam hydrochloride, and sodium bicarbonate in saline, suitable for long-term anaesthesia in a dult mink is presented.