Comparison of cardiac output determined by an ultrasound velocity dilution cardiac output method and by the lithium dilution cardiac output method in juvenile horses with experimentally induced hypovolemia.

The research aims to compare and assess the accuracy of an ultrasound velocity dilution cardiac output (UDCO) method to the lithium dilution cardiac output (LiDCO) method in determining cardiac output (CO) in juvenile horses subjected to experimentally induced hypovolemia.

Methodology

• The researchers conducted their study on 12 anesthetized juvenile horses aged from 2 to 6 months.
• Each horse had their cardiac output (CO) determined by both LiDCO and UDCO methods at four different hemodynamic states – the baseline state, low CO state (after withdrawing about 40% of the horse’s blood volume), high CO state (maintenance of hypovolemia and infusion of norepinephrine until mean arterial blood pressure equals to the baseline value), and post-transfusion state (further norepinephrine infusion and back-transfusion of withdrawn blood).
• For each state, CO and calculated cardiac index (CI) values were obtained twice using each method, thus creating 8 pairs of measurements per horse.
• Mean values for each horse and overall mean values across all horses were then calculated.
• The agreement between the CI values obtained by each method from the 96 paired values was assessed via Bland-Altman analysis – a statistical method used to compare two measurement techniques that measure the same variable.

Findings

• The UDCO method’s mean ± SD bias was found to be -4 ± 11.3 mL/kg/min (with 95% limits of agreement, from -26.1 to 18.2 mL/kg/min), and the mean relative bias was -10.4 ± 21.5% (with 95% limits of agreement, from -52.6% to 31.8%).
• The bias values indicate how much the UDCO method deviated from the LiDCO method.

Conclusion

• Based on the results, the study concluded that the UDCO method can be considered clinically acceptable in determining cardiac output in young horses, relative to the LiDCO method.