Evaluation of anesthesia recovery quality after low-dose racemic or S-ketamine infusions during anesthesia with isoflurane in horses.
OBJECTIVE
To compare anesthesia recovery quality after racemic (R-/S-) or S-ketamine infusions during isoflurane anesthesia in horses.


METHODS
10 horses undergoing arthroscopy.


METHODS
After administration of xylazine for sedation, horses (n = 5/group) received R-/S-ketamine (2.2 mg/kg) or S-ketamine (1.1 mg/kg), IV, for anesthesia induction. Anesthesia was maintained with isoflurane in oxygen and R-/S-ketamine (1 mg/kg/h) or S-ketamine (0.5 mg/kg/h). Heart rate, invasive mean arterial pressure, and end-tidal isoflurane concentration were recorded before and during surgical stimulation. Arterial blood gases were evaluated every 30 minutes. Arterial ketamine and norketamine enantiomer plasma concentrations were quantified at 60 and 120 minutes. After surgery, horses were kept in a padded recovery box, sedated with xylazine, and video-recorded for evaluation of recovery quality by use of a visual analogue scale (VAS) and a numeric rating scale.


RESULTS
Horses in the S-ketamine group had better numeric rating scale and VAS values than those in the R-/S-ketamine group. In the R-/S-ketamine group, duration of infusion was positively correlated with VAS value. Both groups had significant increases in heart rate and mean arterial pressure during surgical stimulation; values in the R-/S-ketamine group were significantly higher than those of the S-ketamine group. Horses in the R-/S-ketamine group required slightly higher end-tidal isoflurane concentration to maintain a surgical plane of anesthesia. Moderate respiratory acidosis and reduced oxygenation were evident. The R-norketamine concentrations were significantly lower than S-norketamine concentrations in the R-/S-ketamine group.


CONCLUSIONS
Compared with R-/S-ketamine, anesthesia recovery was better with S-ketamine infusions in horses.
Larenza
M Paula
MP
Equine Department, Vetsuisse-Faculty, University of Zürich, Winterthurerstrasse 260, CH-8057 Zürich, Switzerland.
Ringer
Simone K
SK
Kutter
Annette P N
AP
Conrot
Aude
A
Theurillat
Regula
R
Kummer
Martin
M
Thormann
Wolfgang
W
Bettschart-Wolfensberger
Regula
R
D000700:Analgesics / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology; D000758:Anesthesia / Q000662:veterinary*; D000762:Anesthesia Recovery Period; D018685:Anesthetics, Inhalation / Q000494:pharmacology; D000818:Animals; D005260:Female; D006736:Horses; D007530:Isoflurane / Q000494:pharmacology*; D007649:Ketamine / Q000008:administration & dosage* / Q000737:chemistry / Q000494:pharmacology*; D008297:Male
D000700:Analgesics; D018685:Anesthetics, Inhalation; D007649:Ketamine; D007530:Isoflurane