A comparison of rectal versus fetlock temperatures in dorsally recumbent horses during general anesthesia.

This research study examined the effect of isoflurane anesthesia on thermoregulation and peripheral heat loss in horses lying on their backs under general anesthesia. The researchers measured temperatures in different parts of the body at regular intervals and found evidence of heat redistribution during anesthesia.

Research Methods and Procedure

• The study involved seven adult horses (averaging 2.6 years old and weighing around 455 kg).
• These horses underwent elective surgical procedures while lying dorsally (on their backs) under general anesthesia, induced and maintained with isoflurane in oxygen.
• The rectal temperature (T), intranasal temperature (T) and fetlock surface temperature (T) of the horses were measured at 10-minute intervals for the first 80 minutes following the induction of general anesthesia. The room temperature (T) was also monitored throughout the study.
• Statistical analysis was used to determine differences in temperature measurement locations and techniques, as well as any differences over time. These analyses used a mixed-effects model and included Tukey’s multiple comparison or Dunnett’s multiple comparison testing where needed.

Results of the Study

• The rectal temperature of the anesthetized horses increased significantly compared to baseline, particularly from 40 to 80 minutes post-anesthesia induction.
• There were no significant differences detected in the intranasal and room temperatures at any time point compared with the baseline.
• The fetlock surface temperature was significantly lower than both the rectal temperature and the intranasal temperature at various points throughout the study, providing evidence of body heat redistribution in the anesthetized horses.
• There were no significant differences between the rectal and intranasal temperature measurements at any time.

Conclusions of the Study

• The findings of this research indicate that during isoflurane-induced general anesthesia, horses’ rectal temperatures increase, suggesting peripheral heat loss, likely due to vasodilation.
• There was a clinically significant decrease in intranasal temperature over time.
• The results suggest that heat redistribution occurs within the body of horses undergoing general anesthesia while lying on their backs.
• This study supports the use of thermographic imaging of horses’ peripheral limbs, alongside monitoring of intranasal and rectal temperatures, as a way to detect this heat redistribution in anesthetized horses.
• The peripheral heat loss in anesthetized horses could lead to hypothermic complications, and understanding this process may provide insights into how to improve thermoregulation in these animals.