Anaesthesia recovery and analgesia qualities were compared in 20 client-owned male cats anaesthetised with intramuscular (IM) medetomidine (0.03 mg/kg) and S-ketamine (S-Ket: 6 mg/kg; n=10) or racemic ketamine (RacKet: 10 mg/kg, n=10). After routine orchiectomy, animals received IM atipamezole (0.15 mg/kg). Heart rate (HR) and respiratory rate (RR) were evaluated pre- and postoperatively. One blinded observer evaluated analgesia using a visual analogue scale (VAS; 0 mm = no pain), 100 mm = worst possible pain) and, by means of four-point scales, sedation, unprovoked behaviour and behavioural reaction to external stimuli 30 and 60 min. after atipemezole administration. Cats with a VAS > 15 mm received butorphanol. Times to sternal (STERNAL) and standing positions (STANDING) were recorded. After 60 min, cats received carprofen (4 mg/kg) subcutaneously.
Anaesthesia with S-Ket, at 50 % of RacKet, provided significantly faster recoveries (STERNAL: S-Ket = 11 +/- 3 min, RacKet = 30 +/- 19 min; STANDING: S-Ket = 22 +/- 6 min, RacKet = 44 +/- 21 min) and increased postoperative RRs. Cats allocated to RacKet had highter HRs postoperatively at 30 and 60 min while those allocated to S-Ket had highter HRs only at 30 min. At 60 min, undisturbed cats in S-Ket had a trend towards fewer behavioural changes. Cats in RacKet were more sedate at 30 min and responded with a lower intensity to external stimulation. Immediate postoperative analgesia was judged adequate for both drugs.