Plasma concentrations at two dexmedetomidine constant rate infusions in isoflurane anaesthetized horses: a clinical study.

The research article discusses a study carried out to determine the plasma concentrations of dexmedetomidine in horses anesthetized with isoflurane at two different infusion rates, and how these rates affect cardiovascular effects and anesthetic recovery.

Study Overview

• The study is a prospective, randomized, and masked clinical trial involving healthy adult horses, presented for castration. It was designed to explore the variations in dexmedetomidine plasma concentrations during isoflurane anaesthesia at two different infusion rates.
• The two rates used are 0.5 μg/kg/hr and 1.75 μg/kg/hr which formed the two treatment groups: ‘treatment DL’ and ‘treatment DH’ respectively.
• Premedication for the horses included acepromazine, romifidine and morphine and anesthesia was induced with ketamine and midazolam. Dexmedetomidine was then administered at the respective doses for 90 minutes of isoflurane anesthesia at an end-tidal concentration of 1.2%.
• Plasma concentrations were determined using liquid chromatography-electrospray-ionization-tandem mass spectrometry.

Methods and Data Collection

• Both arterial and jugular venous blood samples were taken for analysis at the start and end of infusion to monitor changes in cardiovascular variables.
• 14 adult male horses aged between 2-6 years and weighing 325-536kg were included in the trial.
• For both treatment groups, the dexmedetomidine plasma concentrations were recorded at 30 minutes, 60 minutes, and 90 minutes post-administration.
• The recovery parameters of the horses following the procedure were also assessed and compared between treatment groups.

Results

• Findings showed that dexmedetomidine plasma concentrations had low variations in both infusion rates, reaching a stable level after 75 minutes of infusion.
• The mean plasma concentrations for DL and DH treatments at 30, 60 and 90 minutes have been quantified. For treatment DL, it was observed to be relatively lower than for the DH treatment.
• Significant cardiovascular changes were noticed in the DH treatment group, where the heart rates demonstrated substantial decrease from the beginning to the end of the infusion when compared to DL group.
• No other significant differences were found in the cardiovascular and recovery parameters between these two treatment groups.

Conclusions

• The results concluded that, irrespective of the dexmedetomidine infusion rate, the quality of recovery and cardiovascular variables didn’t show considerable changes.
• However, the rates did affect heart rate, especially in the higher-dose DH treatment group, with a significant decrease observed during the procedure. This is a factor worth considering in future studies or clinical procedures.