The rate of rise of intraventricular pressure as an index of myocardial contractility in conscious and anaesthetised ponies.

The research article discusses an investigation on the impact of different types of anesthesia on heart function in ponies, specifically looking at the rate of increase of left ventricular blood pressure.

Objective and Experiment Setup

• The primary aim of the research was to understand the influence of different types of anaesthesia on myocardial contractility—the ability of the heart muscle to contract—in ponies. This was studied through measurements of the rate of rise of left ventricular blood pressure (dP/dt), in both conscious and anaesthetised states.
• Alongside the dP/dt, other concurrent measurements were taken such as heart rate, mean arterial pressure and left ventricular pressure. These would help evaluate their relationship with the dP/dt values.

Types of Anaesthesia Used

• Two combinations of anaesthesia were used for this study: Thiopentone-halothane and Thiopentone-ether anesthesia.
• Both combinations resulted in a decrease in the rate of rise of intraventricular pressure (dP/dt max) from the level when the ponies were conscious.

Results and Observations

• After adjusting the results for changes in loading conditions of the heart muscle, the researchers still saw the depressant effect of the halothane anaesthesia but not of the ether anaesthesia. Here, “depressant effect” refers to a decrease in heart muscle functionality or contractility.
• The research concluded that the negative impact on myocardial contractility by halothane in ponies was greater than the ether, possibly due to a lack of compensatory sympathoadrenal stimulation that usually occurs during ether anesthesia. “Sympathoadrenal stimulation” refers to the response of the sympathetic nervous system and the adrenal gland, which can affect heart function.