Midazolam in combination with glycopyrrolate and xylazine as a preanaesthetic for general anaesthesia in dogs

Abstract

The anaesthetic study was conducted in 24 female dogs of different breeds subjected to elective surgical procedures (oopherectomies). They were randomly divided into four groups viz., I, II, III and IV, each consisting of six animals and were numbered serially from 1 to 6. Animals of all the groups were administered intramuscularly, glycopyrrolate (0.011mg/kg body weight) followed by xylazine (1.0 mg/kg body weight) at 15 minutes interval. In addition, animals of Group III and IV were also administered intravenously midazolam (0.3 mg/kg body weight) 10 minutes after the administration of xylazine. Fifteen minutes after premedication to all animals ketamine hydrochloride (10 mg/kg body weight) was administered intramuscularly to effect anaesthesia and to the animals of Group II and IV, isoflurane was also administered for the maintenance of anaesthesia. The common clinical signs manifested by the dogs after premedication with glycopyrrolate and xylazine were winking of eyes, yawning, inco-ordination of movement and assumption of sternal recumbency with head down posture. All the dogs were in lateral reccumbency following the administration of midazolam. The other symptoms noticed were vomiting, licking, urination and defecation. Salivation was scanty in all the dogs and the induction of anaesthesia was smooth in all the animals. Endotracheal intubation was easy in animals premedicated with midazolam. During recovery vocalization was not observed in those animals premedicated with midazolam. All the animals had an uneventful recovery, though the dogs showed varying degree of dullness, which lasted for two to six hours. All the dogs had normal food intake from the next day onwards. The induction time of anaesthesia in ketamine/ketamine-isoflurane combination was quicker in dogs premedicated with combination of glycopyrrolate-xylazine-midazolam than with glycopyrrolate-xylazine. The duration of anaesthesia was more or less similar, but prolonged with the supplementation of isoflurane. The muscle relaxation time was prolonged with isoflurane maintenance. The degree of muscle relaxation during anaesthesia was good in animals premedicated with midazolam and excellent with isoflurane supplementation. The depth of anaesthesia achieved with a combination of xylazine-ketamine at the dose rate of 1 mg/kg and 10 mg/kg respectively was found not satisfactory for major surgical procedures like laparotomy. But it was satisfactory with midazolam premedication and good with the supplementation of isoflurane. The recovery time was prolonged in dogs in which midazolam was included for premedication. A marginal decrease in rectal temperature, pulse rate and respiration rate was noticed after premedication and during anaesthesia in all the groups. The colour of mucous membrane was pale roseate throughout the observation. In both ketamine and ketamine –isoflurane anaesthesia, oxygen saturation level and blood coagulation time were increased. Significant increase in systolic, diastolic and mean blood pressures was noticed in all the groups. Electrocardiogram revealed mild to moderate tachycardia following the administration of glycopyrrolate and sinoatrial block, sinoatrial arrest, ST segment depression/elevation, ST coving, increased R amplitude, peaked T wave and ventricular tachycardia following the administration of xylazine. All the abnormalities were observed for a short period of ketamine/ketamine-isoflurane anaesthesia and disappeared during recovery. Significant decrease in haemoglobin concentration, volume of packed red cells and erythrocyte sedimentation rate, and marginal variations in total leukocytes and differential leukocyte counts were noticed after premedication, during anaesthesia and recovery in all the groups. The variations in total protein, creatinine, blood urea nitrogen, aspartate amino transferase, alamine amino transferase, sodium, potassium and chloride parameters were within the normal physiological limits, but the increase in glucose concentration was significant. Arterial blood gas analysis revealed decreased pH with increased partial pressure of oxygen, partial pressure of carbon dioxide and marginal variations in bicarbonate level were observed during anaesthesia. All the dogs had the normal food intake from the next day onwards.