The effect of body position on intraocular pressure in anesthetized horses.

This research examines how different recumbent body positions affect intraocular pressure (IOP) in anesthetized horses, suggesting that changes in body position can significantly increase IOP.

Research Design and Methodology

• The study involved ten mature horses that weren’t suffering from glaucoma. The initial IOP reading was taken with the horses standing and mildly sedated, serving as the baseline for later comparisons.
• The IOP of the horses was then tracked under general anesthesia in four randomly assigned recumbent positions: Trendelenburg position (head down at a 15-degree angle), reverse Trendelenburg position (head up at a 15-degree angle), dorsal position (lying on the back), and lateral position (lying on the side). During the lateral position phase, only the eye facing upwards was measured.
• At each position, three separate IOP readings were recorded, with a minimum of two-minute intervals for the horse to adapt to the change in position before the measurements were taken. The average of the three readings was used as the IOP data for each position.
• Statistical methods like Repeated Measures Analysis with Newman-Keuls Multiple Comparison Post hoc were used for comparing the IOP readings in different positions, while linear regression was applied to examine any correlations between IOP and the horses’ age and weight.

Research Findings

• Compared to the baseline, the most substantial rise in IOP was observed in the Trendelenburg position, with an average increase of about 25.63 millimeters of mercury (mmHg).
• When comparing all recumbent positions to the baseline, the IOP increased significantly in three out of the four body positions, with no notable difference identified between the reverse Trendelenburg position and the baseline.
• The greatest difference in IOP was seen when comparing the Trendelenburg and reverse Trendelenburg positions − an overall increase of roughly 26.95 mmHg.
• Further, the study found no correlation between the horses’ age or weight and their IOP in any position.

Conclusions

• The results highlighted that the recumbent body position could significantly raise the IOP in horses under anesthesia. This finding could have important implications in veterinary ophthalmology and anesthesiology. It prompts the need for careful monitoring of IOP in equine patients undergoing surgery, as the changes in body position associated with general anesthesia might cause significant increases in IOP.