The effect of dobutamine and bolus crystalloid fluids on the cardiovascular function of isoflurane-anaesthetised horses
C.M. Loughran, A.L. Raisis, G. Hosgood, C.J. Secombe and G.D. Lester
This study asked whether providing concurrent fluid support improved cardiovascular status in horses given dobutamine under anaesthesia. Six horses were anaesthetised on two separate occasions at least 3 weeks apart and received either intravenous infusion of dobutamine alone or dobutamine infusion with a 20 ml/kg bwt bolus of Hartmanns solution.
The treatments were targeted to achieve a mean arterial blood pressure of 80 mmHg within 30 minutes of the start of the infusion. There was no significant increase in cardiac index between the treatments. During treatment with dobutamine, there was a significant increase in arterial oxygen content and haemoglobin concentration, to values that were significantly higher than those measured during the combined dobutamine and fluids treatment, during which there was no significant change in these factors.
There was also a significant increase in oxygen delivery index during dobutamine treatment. However, there was no significant difference in femoral blood flow measurements (a proxy measurement of peripheral perfusion) when dobutamine only was administered. During the combined treatment, femoral blood flow in the upper and lower (dependent) limbs increased significantly over time.
In isoflurane-anaesthetised horses, dobutamine administration alone causes an increase in cardiac index and oxygen delivery index, but a combination of dobutamine and crystalloid fluid bolus achieves significant improvements in femoral blood flow, providing evidence that this approach improves peripheral perfusion.