Evaluation of anesthesia recovery quality after low-dose racemic or S-ketamine infusions during anesthesia with isoflurane in horses.

The research article focuses on comparing the quality of anesthesia recovery in horses, following the use of racemic (R-/S-) or S-ketamine infusions during an isoflurane anesthesia. Results indicated that the anesthesia recovery was better with S-ketamine infusions.

Research Methodology

• The study employed 10 horses for experimentation, all of which underwent arthroscopy.
• Following the administration of xylazine for sedation, each horse received either an R-/S-ketamine (2.2 mg/kg) or an S-ketamine (1.1 mg/kg) – IV, for anesthesia induction.
• Throughout the surgical procedure, anesthesia was maintained with isoflurane in oxygen, together with R-/S-ketamine (1 mg/kg/h) or S-ketamine (0.5 mg/kg/h).
• Progressive measurements were taken on the heart rates, invasive mean arterial pressure, and end-tidal isoflurane concentration. These were monitored before and during the surgical stimulation.
• Every thirty minutes, arterial blood gases in the horses were evaluated and arterial ketamine and norketamine enantiomer plasma concentrations were quantified at 60 and 120 minutes.

Post-Surgery Observation

• After surgery, the horses were kept in a padded recovery box and sedated with xylazine.
• To evaluate the recovery quality, the horses were video-recorded. A visual analogue scale (VAS) and a numeric rating scale were used to assess the recovery.

Research Findings

• Horses that received S-ketamine infusions had better numeric rating scale and VAS values compared to those receiving R-/S-ketamine.
• In the R-/S-ketamine group, a positive correlation was found between the duration of the infusion and the value on the VAS.
• During surgical stimulation, both groups saw significant increases in heart rate and mean arterial pressure. However, values derived from the R-/S-ketamine group were significantly higher than the S-ketamine group.
• The horses in the R-/S-ketamine group required a slightly higher end-tidal isoflurane concentration to maintain the anesthesia.
• Both groups exhibited moderate respiratory acidosis and reduced oxygenation.
• It was observed that the R-norketamine concentrations were significantly lower than the S-norketamine concentrations in the R-/S-ketamine group.

Conclusions

• Results showed that the process of anesthesia recovery was better with S-ketamine infusions compared to R-/S-ketamine infusions.