Measurement of cardiac output in standing horses by Doppler echocardiography and thermodilution.

This research tested the accuracy of Doppler echocardiography in measuring cardiac output in horses, comparing the results against the thermodilution method. The Doppler method’s effectivity was observed under various conditions, and it was found to have a strong correlation with thermodilution, making it a viable non-invasive procedure for cardiac output assessment.

Doppler Echocardiography versus Thermodilution

• The experiment involved direct comparison of cardiac output measurements through Doppler echocardiography and thermodilution in nine conscious horses. The Doppler measurements involved recording mean blood flow velocities from the aorta and pulmonary artery.
• In addition, the flow area of each vessel was calculated using the vessel’s diameter from a 2D ultrasound image. Differences in the site and method of measuring the vessel diameter resulted in variation in cardiac output estimation via the Doppler method.

Cardiac Output Modification

• The researchers manipulated cardiac output using the intravenous (IV) administration of various drug doses. The drugs used were dopamine, dobutamine, detomidine, and butorphanol.
• The results showed that Doppler measurements of cardiac output closely correlated with thermodilution measurements. Notably, measurements from the aortic outflow correlated more closely than those from the pulmonary artery.

Evaluation of Doppler Echocardiography

• The researchers hence determined that Doppler echocardiography is a reliable non-invasive method for measuring cardiac output in horses.
• The data revealed no significant bias between the Doppler and thermodilution techniques when Doppler flow velocities were recorded using a particular method. However, the differences between the two methods increased as cardiac output increased.
• The study found an agreement between Doppler echocardiography and thermodilution measurements, similar to those reported in human studies.

In conclusion, this study points to the large potential of Doppler echocardiography as a safe, non-invasive, and accurate method for measuring cardiac output in horses. However, it does note that the differences between this technique and the thermodilution method may increase with higher cardiac outputs.