Study On Different Premedicants On Anesthesia Effect In Isoflurane-anesthetized Cats

In this study, the effects of different premedicants on respiratory, circulatory, electrocardiogram (ECG), electroencephalogram (EEG) and plasma catecholamine were investigated for cats being anaesthetized with propofol-isoflurane. Cats were randomly divided into four groups to receive saline (group A), butorphanol (group B), midazolam (group C), and butorphanol-midazolam (group D) intravenously. Anaesthesia was induced with propofol, and maintained with isoflurane. The cats were monitored in non-invasive way by multifunctional physiologic grapher, Datex respiratory monitor and circulatory monitor.The results showed that the best effects of anesthesia was achieved when the end-tidal isoflurane concentration was 1.93% (group A), 1.39% (group B), 1.44% (group C), and 1.15% (group D), respectively. But recovery time from anesthesia was prolonged in other groups compared with gtoup A.Respiratory monitor showed that isoflurane and midazolam had suppressed effects on respiratory system, and smooth respiration and abundant oxygen with mechanical ventilation were guaranteed in the cats of all groups. Circulatory monitor showed that heart rate, blood pressure and temperatures were reducedagainst time in group D and C, but the heart rate and blood pressure weren't reduced when they reached some degree. In group B and C, there were no effects on cardiorespiratory except blood pressure. Blood oxygen saturation had no obvious changes in all groups. We concluded that different premedicants had suppressed effects on circulatory system, but all the circulatory indexes were in range of physiological tolerance.EEG monitor showed that EEG wave transformed from high frequency, low amplitude and rhythm (α) to low frequency, high amplitude, slow rhythm (δ), and to the reverse during recovery. The recovery time from anesthesia were prolonged in group B and C.Plasma catecholamine monitor showed that the concentrations of epinephrine and norepinephrine were significantly reduced in group B, C and D. It indicated that butorphanol, midazolam and butorphanol-midazolam could inhibit the stress reaction which caused by pain.All of the results in this study showed that the administration of butorphanol, midazolam and butorphanol-midazolam as premedicants before anesthetized with isoflurane in cats had obtained satisfying anesthesia effects and the induction was smooth, which could reduce the dosage of isoflurane, and play an important role on reduction of stress reaction that caused by intubation and extubation. All the results suggested that administration of butorphanol, midazolam and butorphanol-midazolam could produce a good anesthesia and analgesia effect in isoflurane-anesthetized cats, and completely satisfied the need of veterinary clinic.