Haemodynamic effects of change in position and respiration mode during a standard halothane anaesthesia in ponies.

This paper examines how changes in position and the way of breathing during regular anaesthesia usage with halothane affects the functioning of the cardiovascular (heart and blood vessels) system in ponies. It found that certain positions and respiratory methods significantly impacted the cardiovascular state of the anaesthetised animal.

Objective of the Research

• This study intended to understand how orientation changes and different .respiration modes during halothane anesthesia influenced essential cardiovascular parameters such as mean arterial blood pressure, cardiac output, stroke volume and left ventricle work in ponies.

Research Methodology

• Five ponies were subjected to halothane anesthesia under standard conditions.
• Their respiration and positions during the anesthesia were modified, and the cardiovascular responses were observed and recorded in each scenario.

Key Findings

• Recumbency or lying down spontaneously lead to notable cardiovascular depression, most pronounced when the ponies were lying on their back (dorsal recumbency).
• The difference in cardiovascular effect between lying on the right or left was not significant.
• Being in a sternally recumbent position (lying on the chest and stomach) was slightly better in terms of maintaining systemic blood pressure and arterial oxygenation.
• Peripheral resistance, the opposition to blood flow in the vessels, decreased in the lateral positions but increased slightly when the ponies were positioned dorsally.
• A significant decrease in the mean pulmonary artery pressure was also observed in the dorsal position.
• There was a minute increase in pulmonary resistance, suggesting pulmonary vessel constriction, in laterally and sternally recumbent positions, while it decreased in dorsal recumbency.
• Arterial oxygenation consistently decreased during anesthesia but never fell below the level of standing control subjects.
• All positions showed an increase in arterial carbon dioxide, indicating hypoventilation.

Effects of Controlled Intermittent Positive Pressure Ventilation (I.P.P.V.)

• Applying I.P.P.V. resulted in further reduction of all cardiovascular parameters, although the cardiac indexes didn’t show significant differences when compared to ponies breathing naturally.
• In situations with ventilation, the highest cardiovascular depression was again observed in dorsal positioning.
• Peripheral resistance saw a slight uptick in sternally-positioned and ventilated ponies.
• Pulmonary resistance saw a gradual time-dependent increase.
• Interestingly, arterial oxygenation experienced a slight improvement across all positions with the application of I.P.P.V., with the most noticeable improvement happening in the sternally recumbent position.

The results from this study provide valuable insights into how positions and ways of breathing during anaesthesia can impact the cardiovascular system in ponies, which could have implications for their anaesthesia management in veterinary medicine.