Adrenocortical and metabolic responses to dobutamine infusion during halothane anaesthesia in ponies.

The research explored the relationship between hypotension caused by halothane anaesthesia in ponies and stress response in the adrenal cortex, by using dobutamine infusion to maintain normal blood pressure. It found that hypotension is not the only trigger for adrenocortical activity during halothane anaesthesia in ponies.

Study Design and Methodology

• Two groups of six ponies each were used in the study. The ponies were premedicated with acepromazine and anaesthetised using thiopentone.
• In one group (referred to as the AN group), halothane was used to maintain anaesthesia for 120 minutes, and dobutamine was infused in doses varying from 1.1-4.4 micrograms/kg/min to maintain normal arterial pressure.
• The second group (referred to as the CON group) was prepared the same way as the AN group but only received a dobutamine infusion of 1.0 microgram/kg/min for 120 minutes without halothane.
• The researchers measured various parameters at different intervals, including blood pressure, pH levels, oxygen and carbon dioxide tension, pulse rate, haematocrit levels, as well as plasma cortisol, glucose, and lactate concentrations.

Results and Findings

• The blood pressure remained close to the control levels in both groups throughout the study.
• The AN group showed signs of hypercapnia and acidosis, indicating an increase in carbon dioxide in the blood and an upset in the body’s acid-base (pH) balance. Their pulse rate and haematocrit levels also increased.
• The cortisol levels in the AN group increased more than two fold, while the plasma glucose and lactate levels remained unchanged.
• In the CON group, the most notable changes were small increases in haematocrit levels and decreases in pulse rate. Most other parameters remained at control levels, indicating less stress response.

Conclusion of the Research

• The research concluded that normally maintaining blood pressure during halothane anaesthesia with dobutamine infusion does not mitigate the adrenocortical response to anaesthesia in ponies.
• Additionally, it was found that administering the same dose of dobutamine without the anaesthesia does not increase the cortisol levels in the blood.
• Finally, the study concluded that while hypotension is a factor, it is not the only stimulus for adrenocortical activity during anaesthesia with halothane in ponies.