Influence of a constant rate infusion of dexmedetomidine on cardiopulmonary function and recovery quality in isoflurane anaesthetized horses.

The research investigated the impact of a constant rate infusion (CRI) of dexmedetomidine on the heart and lung function and the recovery process of horses anesthetized with isoflurane. The study found that the dexmedetomidine CRI caused minor changes in heart and lung function but significantly improved the recovery process.

Study Design

• The research was designed as a prospective, randomized, blinded, clinical study with forty healthy adult horses as subjects.
• Each horse was sedated with dexmedetomidine, induced (put under anesthesia) using midazolam and ketamine, and maintained under isoflurane. This was done in an oxygen/air environment with about 55-60% fraction of inspired oxygen (FiO2).
• If hypoventilation and hypotension occurred, the horses were ventilated and administered dobutamine respectively.
• During anesthesia, the horses were randomly assigned to receive a CRI of either dexmedetomidine or saline.
• Throughout the procedure, variables such as end-tidal isoflurane concentration, cardiopulmonary parameters, and the need for dobutamine and additional ketamine were monitored.
• All horses were given dexmedetomidine for the recovery period.

Data Analysis

• The factors compared between the two groups included: age and weight of horses, duration of anesthesia, amount of additional ketamine and dobutamine required, cardio-pulmonary data, recovery scores, duration of recovery and attempts needed to stand.
• Different statistical tests were used for different variables such as analysis of variance (ANOVA), Wilcoxon Rank Sum Test, t-test and Mann-Whitney test.
• Significance was considered at p-value below 0.05 to ensure any observed differences wasn’t due to chance.

Results

• Horses assigned to the dexmedetomidine group (Group D) had significantly lower heart rate and lower arterial partial pressure of oxygen compared to the saline group (Group S).
• Over time, end-tidal isoflurane concentration and heart rate significantly increased, while packed cell volume, systolic, diastolic and mean arterial pressure, arterial oxygen content, stroke volume index and systemic vascular resistance significantly decreased.
• Recovery scores were significantly better in the dexmedetomidine group compared to saline, with fewer attempts to stand, extended times to sternal (breastbone) position, and first attempt to stand.

Conclusions

• The dexmedetomidine CRI resulted in minor cardiopulmonary effects, but contributed to an improved recovery quality.