Influence of dopamine and dobutamine on the cardiovascular depression during a standard halothane anaesthesia in dorsally recumbent, ventilated ponies.

This research investigates the effects of dopamine and dobutamine on cardiovascular depression that occurs during standard halothane anesthesia in managed ventilated ponies. The results show that low doses of dobutamine are effective in counteracting the cardiovascular depression.

Research Methodology

• The study was conducted in dorsally recumbent, ventilated ponies undergoing standard halothane anesthesia.
• Cardiac output, mean systemic, and pulmonary artery pressure were assessed using thermodilution technique and direct intravascular method respectively.
• Blood analysis was performed to examine blood gases and packed cell volume.

Findings: Stabilization Period

• After a stabilization period of 30 minutes, the authors observed notable cardiopulmonary depression characterized by decreases in cardiac output, cardiac index, systemic and pulmonary artery pressure, and other cardiovascular parameters.

Impact of Dopamine

• Dopamine was administered to the ponies at two different infusion rates (2.5 and 5.0 micrograms/kg/min). This induced minor changes of the cardiopulmonary parameters, with insignificant increases in systemic pressure, cardiac index, left ventricular work, stroke volume, and a trivial decrease in total peripheral resistance.
• There were also a number of minor time-related changes observed, such as increases in pulmonary artery pressure and total pulmonary resistance.
• The level of arterial blood gases remained constant during the different dopamine infusions.

Impact of Dobutamine

• Low doses of dobutamine (1.25 micrograms/kg/min) were found to effectively combat the cardiovascular depression with significant increases in CO, CI, systemic and pulmonary artery pressure and stroke volume observed.
• Total peripheral resistance and total pulmonary resistance tended to decrease, although not significantly. Heart rate and blood gases remained unchanged.
• Higher doses of dobutamine (2.5 and 5.0 micrograms/kg/min) intensified these changes. However, along with those, a significant increase in heart rate and an increase of the packed cell volume were noticed. At times, periods of severe tachycardia (rapid heart rate) were also observed.

Conclusion

• Based on the study’s observations, low doses of dobutamine could potentially be used to manage cardiovascular depression during anesthesia in the dorsally recumbent ventilated horse.