Effects of Sedation on Rectal Temperature During Equine Dental Procedures Performed in Cold to Warm Ambient Temperatures.

Overview

• This study investigates how sedation affects rectal body temperature in horses during dental procedures performed in a range of cold to warm ambient temperatures.
• The goal was to determine if sedation causes a significant drop in body temperature (hypothermia) when procedures are done in cold weather compared to warm conditions.

Study Background and Importance

• Equine dental procedures often require sedation to ensure the safety and cooperation of the horse.
• Sedation can affect body temperature regulation, potentially increasing the risk of hypothermia, especially in colder climates or months.
• Understanding how sedation interacts with ambient temperature helps veterinarians manage risks during winter or cold-weather procedures.

Research Hypothesis

• Authors hypothesized that sedation for dental work would significantly decrease rectal body temperature more in cold ambient temperatures than in warm ones.

Subjects and Methods

• 246 adult horses undergoing dental equilibration from a private equine dentistry practice were included.
• Horse weights were estimated to dose sedation drugs accurately.
• Combination of sedatives administered:
  • Intravenous: 0.01 mg/kg detomidine and 0.01 mg/kg butorphanol
  • Intramuscular: 0.5 mg/kg xylazine and 0.03 mg/kg acepromazine
• Rectal temperatures were measured at three time points:
  • PRE: Before sedation
  • POST15: 15 minutes after initial intravenous sedation
  • END: At the end of the dental procedure
• Ambient temperature ranged from -7.8°C to 30°C during the procedures.
• Statistical analyses:
  • Shapiro-Wilks test for normality
  • Spearman’s correlation to assess relationship between ambient and body temperature
  • Friedman test with Dunn’s posthoc for temperature comparisons over time
  • Significance threshold set at p < 0.05.

Key Findings

• Median rectal temperatures (with 95% confidence intervals) at each time point:
  • PRE: 37.4°C (37.2 – 37.7°C)
  • POST15: 37.5°C (37.2 – 37.8°C)
  • END: 37.4°C (37.1 – 37.7°C)
• Temperatures 15 minutes after sedation (POST15) were significantly higher than presedation (PRE) and end of procedure temperatures.
• There was no significant difference between the start and end temperatures overall.
• Positive but weak correlations were found between ambient temperature and:
  • POST15 rectal temperatures (r = 0.26, p < 0.001)
  • END rectal temperatures (r = 0.25, p < 0.001)
• Only 7 horses became hypothermic (<36°C), and only 2 of these were in ambient temperatures below 4.44°C.

Interpretation and Implications

• Sedation did not cause a significant or dangerous drop in rectal temperature during dental procedures across a wide temperature range.
• The slight increase in temperature after 15 minutes of sedation could be due to physiological effects of the sedatives or measurement variance.
• Most horses maintain safe body temperature levels even in cold ambient conditions from -7°C to 30°C, minimizing concerns of hypothermia during such procedures.
• Findings support that equine dental work can be safely performed under sedation in cold weather months, with low risk for sedation-induced hypothermia.

Limitations and Considerations

• Weight was estimated rather than accurately measured, which could affect dosing precision.
• The study was limited to a private practice setting and specific sedation protocols, so findings may vary with different settings or sedative combinations.
• Ambient temperatures measured at time of procedure do not account for wind chill or other environmental factors affecting heat loss.

Conclusion

• This research suggests that intravenous and intramuscular sedation for equine dental procedures does not increase the risk of hypothermia, even in cold ambient temperatures.
• Veterinarians can be reassured about maintaining body temperature safety during such procedures from just below freezing to warm temperatures.