Because of the need to avoid pain and suffer for ethical reasons in animal experimetns, anesthesics use is a must in these cases. To improve this , we have used 12 weeks old mice, 35 males and 35 females that were injected by IP route with ketamine (100 mg/kg) added with acepromazine (5 mg/kg) or diazepam (5 mg/kg) or medetomidine (1 mg/kg) or midazolam (5 mg/kg) or xylazine (10 mg/kg). The aim of this study was to analyze respiratory rate (10, 20, 40, and 60 minutes after injection), pulse rate and blood oxygen saturation (5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 75, and 90 minutes after injection) in each association and comparison among them.

Respiratory rate was within normal values, but differences between associations had been found. The most similar and the lowest values were for xylazine and medetomidine association in females ([asymp]110 rpm) and in males ([asymp]140 rpm) but for acepromazine association was higher (> 200 rpm) in both sexes. Pulse rate was more variable than respiratory rate. The alpha2-agonists/ketamine associations were the lowest, a mild bradycardia near to 300 ppm for females and a little higher for males. The most variability was found for diazepam/ketamine association.The highest values for oxygen saturation were for acepromazine/ketamina association. These values were about 90%. The lowest values were for alpha2-agonists/ketamine associations, wich are according the values for respiratory and pulse rates.Nevertheless,anaesthetic parameters shown that the best association was for alpha2-agonists/ketamine.