Arterial blood PO2 and PCO2 in horses during early halothane-oxygen anaesthesia.

This research paper examined changes in arterial blood oxygen (PaO2) and carbon dioxide (PaCO2) in horses during the first hour of halothane-oxygen anesthesia. The study outlined the effects of anesthesia on blood oxygen and carbon dioxide levels in different age groups of horses.

Research Methods

• The researchers collected arterial blood from 25 clinically normal horses for this study. Blood samples were collected both just before and at intervals during the first hour of halothane-oxygen anesthesia.
• The horses were divided into two groups based on age: one group was aged between two to seven years (15 horses), and the other consisted of horses over seven years old (10 horses).
• The collected blood was examined for oxygen and carbon dioxide partial pressure (PaO2 and PaCO2 respectively).
• Measurements of the concentration of oxygen inspired during anesthesia were also taken to allow for a direct correlation with the blood gases.

Research Findings

• The researchers found that average blood oxygen and carbon dioxide levels in awake, young horses were 14.1 +/- 1.5 kPa and 5.9 +/- 0.6 kPa respectively, while in older horses the levels were marginally lower at 14.0 +/- 0.7kPa and 5.8 +/- 0.5 kPa respectively.
• Following intravenous anesthetic induction, there was a drop in arterial oxygen tension to 9.3 +/- 1.0 and 8.5 +/- 1.4 kPa in young and older air breathing horses respectively. There was also a corresponding increase in the concentration of carbon dioxide to 6.5 +/- 0.5 and 6.0 +/- 0.7 kPa respectively.
• After 30 minutes of halothane-oxygen anesthesia, they recorded an increase in arterial oxygen levels in both age groups.
• There was a steady increase in arterial carbon dioxide levels during anesthesia. One hour after induction, the concentration had risen to 10.5 +/- 2.4 kPa in the younger horses and 9.2 +/- 1.6 kPa in the older horses.
• The younger horses showed slightly higher oxygen levels at comparable time periods, despite showing a slightly greater degree of hypoventilation (reduced breathing).

Conclusion

• The study showed that halothane-oxygen anesthesia has noticeable effects on the levels of oxygen and carbon dioxide in the arterial blood in horses. The alterations could be key in understanding and managing the impacts of anesthesia in veterinary practice, particularly for horses.
• The changes recorded were age-dependent, with younger horses exhibiting somewhat higher blood oxygen levels during similar time intervals compared to older horses.