Effects of hypoxia on endocrine and metabolic responses to anaesthesia in ponies.

The research article studies how low oxygen levels, or hypoxia, during halothane anaesthesia impacts endocrine and metabolic responses in ponies.

Research Subject and Method

• The study involved six ponies, each of which was anaesthetised twice for the purpose of the research.
• During one anaesthesia session, the ponies were subjected to a 20-minute period of hypoxia, where the arterial oxygen tension was between 4.4 and 5.8 kPa. This was done during a 120-minute anaesthesia session
• For the second anaesthesia session, the arterial oxygen tension was maintained above 17 kPa throughout the process.
• Routine cardiovascular monitoring was performed and blood samples were taken for examination.
• These samples were used to measure haematocrit, cortisol, insulin, glucose, and lactate.

Findings

• Low blood pressure, or hypotension, was observed in both groups during anaesthesia.
• A significant fall in arterial blood pH (greater than 7.0 kPa), also known as acidosis, developed in the normoxic group and was more severe than in the hypoxic group.
• Haematocrit or packed cell volume changed little, but was higher in the hypoxic group after the hypoxic period.
• Plasma cortisol levels increased significantly during anaesthesia in both groups, but no significant difference was observed between the two.
• Glucose levels increased in the hypoxic group and was significantly higher than in the normoxic group during the hypoxic period.
• Insulin levels decreased in both groups, but this decrease was significant only in the normoxic group. However, the difference between the groups was not significant.
• Lactacidemia, or the presence of lactic acid in the blood, developed in both groups, but was more severe in the hypoxic group.

Conclusion

• From the findings, it was concluded that a 20-minute period of hypoxia during halothane anaesthesia in ponies did not significantly alter the stress response already induced by anaesthesia.