Effects of detomidine alone or combined with butorphanol on oxygenation status, F-shunt and sedation level in healthy sheep.

This study evaluated the effects of detomidine alone or combined with butorphanol on arterial oxygenation, gas exchange indices, estimated shunt fraction (F-shunt) and sedation level in healthy sheep. A prospective, randomized, blinded, experimental study was conducted on twenty-seven Merino sheep allocated to three groups (9 sheep/group): 5 μg/kg detomidine +200 μg/kg butorphanol (Deto5But), 10 μg/kg detomidine + 200 μg/kg butorphanol (Deto10But), or 10 μg/kg detomidine (Deto10) administered intravenously. Following arterial and venous catheter placement, arterial blood samples were collected to determine oxygenation status and F-shunt at baseline (fraction of inspired oxygen, FiO₂: 21%), 5 min after sedation (FiO₂: 21%), and at 5 and 30 min after propofol induction (FiO₂: 100%). Sedation was evaluated by a blinded observer at 5, 10, and 15 min after drug administration using two numerical scales. Sedation produced a significant deterioration in oxygenation parameters, gas exchange indices, and F-shunt (15.36%: 95% CI 10.07-20.65; p = 0.001) compared with baseline, without significant differences between treatment groups. However, five minutes after induction of anaesthesia, the Deto5But group presented better oxygenation, gas exchange efficency, and F-shunt values compared with Deto10But (10.30%: 95% CI 0.86-19.76; p = 0.029) and Deto10 (13.93%: 95% CI 2.94-24.92%; p = 0.008). Sedation scores did not differ significantly between treatment groups or across time points. Combination of detomidine at 5 μg/kg with 200 μg/kg of butorphanol provided adequate sedation and was associated with a milder impact on oxygenation and F-shunt at 5 min post-induction.