Measurement of cardiac output by transoesophageal Doppler echocardiography in anaesthetized horses: comparison with thermodilution.

This study researches the effectiveness of transoesophageal Doppler echocardiography as a non-invasive method for measuring cardiac output in anaesthetized horses, by comparing it to the commonly used thermodilution method.

Research Methodology

• The study was conducted on eight healthy adult thoroughbred horses that were anaesthetized.
• Cardiac output was measured using two methods: Transoesophageal Doppler Echocardiography and thermodilution.
• Within the echocardiography method, measurements of aortic blood flow velocity were made using two techniques: High Pulse Repetition Frequency (HPRF) and Continuous Wave (CW) Doppler echocardiography. These measurements were made using a 3.5-MHz transoesophageal probe.
• The cardiac output of the horses was increased during the study by administering dobutamine. This gave a range of cardiac output measurements by thermodilution from 15.0 to 64.4 liters per minute.

Research Findings

• Estimations of cardiac output derived from CW Doppler were found to overestimate cardiac output compared to thermodilution, by a bias of 4.0 liters per minute.
• Estimations from HPRF Doppler echocardiography more closely reflected measurements obtained by thermodilution, with a smaller bias of 0.7 liters per minute.
• The limits of agreement between the techniques (CW and HPRF) and thermodilution were similar for both modes, despite the different biases.
• Significant differences in the biases between both Doppler techniques and thermodilution were observed for individual horses. As such, when measured per individual horse, the limits of agreement between the techniques were narrower.

Conclusion

• From this study, it can be inferred that transoesophageal echocardiography, despite some differences, can provide an effective and non-invasive alternative for measuring cardiac output in anaesthetized horses.