Effects of changing body position on oxygenation and arterial blood pressures in foals anesthetized with guaifenesin, ketamine, and xylazine.

This research examines how changing the body position of anesthetized foals (young horses) affects their oxygenation and blood pressure. The findings suggest that lifting the foals can reduce their oxygenation levels, but doesn’t significantly affect their blood pressure or heart rate.

Study Design and Methods

• The study was done on twelve quarter horse foals, aged approximately 5.4 months and with an average weight of 222kg. The foals were anesthetized using a combination of guaifenesin, ketamine, and xylazine.
• The foals were initially positioned in a lateral recumbency (lying on their side) for 40 minutes. They were then divided into two groups, with one group having their body position changed by lifting (Group 1), and the other group remaining in the same position (Group 2).
• Throughout the anesthesia, oxygen was continuously provided into the foal’s windpipe at a rate of 15 liters per minute.
• The researchers measured several parameters at different time intervals: arterial blood pressure, heart rate, respiratory rate, the fraction of oxygen inspired (FIO(2)), and the amount of carbon dioxide at the end of an exhaled breath (PE’CO(2)). The pH levels and gases in the arterial blood, including oxygen (PaO(2)) and carbon dioxide (PaCO(2)), were also measured.

Key Findings

• Statistically, there were no significant differences noted in the time-matched data between the two groups, thus allowed for the results to be combined.
• After hoisting, the arterial partial pressure of oxygen – a measure of the oxygen levels in the blood – significantly decreased. Similarly, there was a significant reduction in the ratio of arterial oxygen partial pressure to fractional inspired oxygen – a common clinical index for assessing the efficiency of gas exchange.
• A noticeable drop was also seen in the end-tidal carbon dioxide (carbon dioxide levels at the end of an exhaled breath). However, there were no significant differences noted for arterial carbon dioxide pressure, blood pressures, and heart rates, even five minutes after the foals were hoisted.

Conclusions and Recommendations

• Lifting the body position in anesthetized healthy foals resulted in a decrease in PaO(2), affecting oxygenation levels. However, it did not have an apparent impact on the blood pressures and heart rates.
• To mitigate the decrease in oxygenation after hoisting, it is recommended to administer supplemental oxygen to the foals.
• For early detection of changes, PaO(2) measurements should be regularly taken.