Influence of catecholamines at different dosages on the function of the LiDCO sensor in isoflurane anesthetized horses.

The focus of this research is to investigate how different doses of certain cardiovascular drugs known as catecholamines influence the readings given by an instrument called the LiDCO sensor, which is used to measure cardiac output in horses under general anaesthesia.

Objective and Methodology

The study was conducted in order to:

• Compare two methods for measuring cardiac output from anesthetized horses – the lithium dilution method (LiDCO) and the bolus-thermo-dilution (BTD)
• Assess how these measurements are influenced by the administration of various doses of four different catecholamines: dobutamine, dopamine, phenylephrine, or noradrenaline.
• Examine whether there is a correlation between measurement errors and readings from the LiDCO sensor, specifically comparing voltages recorded when the sensor is exposed to saline versus blood.

The research took the form of a prospective experimental study, conducted at a university teaching hospital involving nine Warmblood horses. After a 90-minute equilibration period, the horses were infused with three different doses of the catecholamines over a 15-minute period, and cardiac output was measured with both the LiDCO and BTD methods at the lowest and highest doses. Sensor voltages were also recorded at the beginning and end of each infusion.

Results and Conclusions

The results highlighted a discrepancy between the measurements provided by the LiDCO and BTD methods, with biases – that is, systematic discrepancies – noted. The presence and degree of these biases depended on the particular catecholamine being infused and its dosage, with larger biases recorded after administration of higher catecholamine doses.

Furthermore, the research found a correlation between the difference in sensor voltages (between those exposed to saline and those exposed to blood) and the size of the discrepancies in cardiac output measurements. This suggests that monitoring changes in these sensor voltage discrepancies could be a clinically valuable way of predicting errors in LiDCO measurements?

In conclusion, the study demonstrated that the administration of catecholamines can result in an overestimation of cardiac output when measured by the LiDCO monitoring system. Therefore, consideration of the doses of these drugs being administered is important when interpreting LiDCO measurements. This has implications for veterinary practice, as an awareness of these potential discrepancies could improve the reliability of cardiac output measurements, thus improving patient management.