The study aimed to evaluate the applicability and repeatability of cold stimulation in dogs.
10 healthy Beagle dogs were used in a blinded cross-over experiment.
Measurements were performed in triplicate at 4 skin locations. The probe was manually placed, and temperature decreased (32 to 10 °C) at different cooling rates (0.5, 1, and 5 °C second−1) and latency was measured (11 °C for 60 seconds). Stimulations were discontinued when avoidance reactions were detected. Thermal threshold or time-to-reaction were recorded. Experiments were performed 3 times per animal in weeks 1 (Exp1), 2 (Exp2), and 5 (Exp3). Feasibility of cold stimulation was scored (0–5). Data were analyzed with mixed logistic regression.
No significant differences in number of avoidance reactions between cooling-rates were detected. Significantly more reactions (P < .001) were observed during Exp1 compared to Exp2 and Exp3. Thermal thresholds were 13 ± 2.6 °C, 17.7 ± 4 °C and 16.3 ± 4.6 °C for 5, 0.5 and 1 °C second−1, respectively. Latency to the reaction was determinable in 37% of measurements. The mean time-to-reaction was 13 ± 11 seconds. In 85% of measurements, a feasibility score of 0 (best feasibility) was assigned.
The method is easily applicable and well tolerated, but habituation could not be excluded. Overall, the aversiveness of cold stimulation in healthy dogs is limited and it is not possible to recommend a specific protocol. In future studies, it needs to be determined if the aversiveness of cold stimulation is increased in diseased dogs.
OBJECTIVE To determine global and peripheral perfusion and oxygenation during anesthesia with equipotent doses of desflurane and propofol combined with a constant rate infusion of dexmedetomidine in horses.
ANIMALS 6 warmblood horses.
PROCEDURES Horses were premedicated with dexmedetomidine (3.5 μg•kg−1, IV). Anesthesia was induced with propofol or ketamine and maintained with desflurane or propofol (complete crossover design) combined with a constant rate infusion of dexmedetomidine (7 μg•kg−1 •h−1). Microperfusion and oxygenation of the rectal, oral, and esophageal mucosa were measured before and after sedation and during anesthesia at the minimal alveolar concentration and minimal infusion rate. Heart rate, mean arterial blood pressure, respiratory rate, cardiac output, and blood gas pressures were recorded during anesthesia.
RESULTS Mean ± SD minimal alveolar concentration and minimal infusion rate were 2.6 ± 0.9% and 0.04 ± 0.01 mg•kg−1 •min−1, respectively. Peripheral microperfusion and oxygenation decreased significantly after dexmedetomidine administration for both treatments. Oxygenation returned to baseline values, whereas tissue microperfusion remained low during anesthesia. There were no differences in peripheral tissue microperfusion and oxygenation between treatments. Cardiac index was significantly higher and systemic vascular resistance was significantly lower for desflurane treatment than for propofol treatment. For the propofol treatment, Pao2 was significantly higher and there was less dead space and venous admixture than for the desflurane treatment.
CONCLUSIONS AND CLINICAL RELEVANCE Dexmedetomidine decreased blood flow and oxygen saturation in peripheral tissues. Peripheral tissues were well oxygenated during anesthesia with desflurane and propofol combined with dexmedetomidine, whereas blood flow was reduced.