Doxapram infusion during halothane anaesthesia in ponies.

The research investigated the effect of doxapram, a respiratory stimulant, on ponies under halothane anaesthesia. It found that doxapram lowered the levels of carbon dioxide in the blood and increased pH and blood pressure, but did not affect pulse rate or oxygen levels. While the doxapram did lighten the anaesthesia, requiring an increase in the vapouriser setting, it did not affect recovery from the anaesthesia.

Objective of the Study

• The study aimed to investigate the impact of administering doxapram, a respiratory stimulant, to ponies under halothane anaesthesia. Halothane is a general anesthetic that can lead to respiratory depression, where breathing becomes inadequate.

Research Methodology

• Six ponies were selected for the study. They were all subjected to two hours of halothane anaesthesia.
• In two ponies, the researchers infused them with doxapram during the second hour of anaesthesia. Doxapram was given at a rate of 0.05 mg/kg body weight per minute.
• On a second occasion, these two ponies also served as controls, where they were given 5% dextrose instead of doxapram.

Observations and Findings

• As expected, the ponies experienced respiratory depression typical to halothane anaesthesia in the first hour.
• The control animals, which only received dextrose, continued to show signs of respiratory depression in the second hour.
• However, the ponies that were given the doxapram infusion showed a decrease in arterial carbon dioxide tension and an increase in blood pH. These changes indicate that the doxapram was effective in stimulating respiration to some extent.
• Additionally, the doxapram also led to an increase in arterial blood pressure. However, the infusion did not alter the ponies’ pulse rate, the electrocardiogram readings, or the arterial oxygen tension.
• The doxapram infusion lightened the anaesthetic effect, meaning it made the ponies less sedated. Therefore, an increase in the vapouriser setting was required to prevent them from waking up from the anaesthesia.
• Despite these changes, the doxapram did not appear to affect the ponies’ recovery from the anaesthesia. That is, it did not cause any noticeable extended effects in the ponies’ post-anaesthesia state.

Conclusion

• The study concludes that doxapram, when used during halothane anaesthesia, can stimulate respiration in ponies, as evidenced by the decrease in arterial carbon dioxide levels and increase in pH. A rise in arterial blood pressure was also observed, though pulse rate and arterial oxygen tension remained unaltered.
• However, due to its effect of lightening the anaesthesia, adjustments in the vapouriser settings were necessary. Despite this, doxapram did not affect the recovery process from anaesthesia.