On 58 cats (all ASA III group) the S(+)-isomer of ketamine was compared to its racemic mixture during and until 90 minutes post anaesthesia. Cats received randomly either 5mg/kg S(+)-ketamine (KetS) or 10mg/kg of the racemic ketamine (KetR) in combination with midazolam.
Anaesthesia was maintained with isofluran. Measurements of heart rate (HR), mean arterial blood pressure (BPM) and respiratory rate (RR) were performed. Pain, recovery and sedation scores were assessed as well as the duration of the recovery period. Following a strong surgical stimulus, the HR rose significantly in both groups. The BPM rose significantly with KetR. During the recovery period RR and BPM differed significantly. RR (x±s) with KetS was 53±12/min and 68±12/min with KetR, BPM (x±s) was 69±18mmHg (KetS) and 60±13mmHg (KetR). Cats with KetS had a significantly better analgesia score 60 and 90 minutes after extubation. Sedation and recovery scores were judged significantly better at 30, 60 and 90 minutes after extubation. The first attempt to stand (x±s) after extubation was made 60,7±24,0min (KetS) and 74,2±23,1min (KetR). A sufficient depth of anaesthesia was achieved by the application of this anaesthesia regime. S(+)-ketamine offered a significantly faster and qualitatively better recovery period, with a better post operative analgesia.