Hemodynamic effects of 6% hydroxyethyl starch infusion in sevoflurane-anesthetized thoroughbred horses.

This research investigates the cardiovascular effects of hydroxyethyl starch (HES) infusion in healthy horses under sevoflurane anesthesia. The study concludes that HES administration increases cardiac output in a dose-dependent manner, without significantly affecting heart rate and arterial blood pressures.

Experimental Design

• The experiment involved administering incremental doses of 6% hydroxyethyl starch (HES) to six healthy thoroughbred horses.
• The horses were initially anesthetized using xylazine, guaifenesin, and thiopental, thereafter, anesthesia was maintained with sevoflurane at 2.8% of end-tidal concentration.
• The horses were positioned on their right sides and received three intravenous doses of 6% HES (5 ml/kg) over 15-minute intervals. This treatment was administered in addition to a constant infusion of a lactated Ringer’s solution (a type of fluid replacement) at 10 ml/kg/hr.

Measurements and Observations

• Hemodynamic parameters such as heart rate, stroke volume, cardiac output, and systemic vascular resistance, among others, were measured before and then every 15 minutes until 90 minutes after the administration of 6% HES.
• No significant changes in heart rate and arterial blood pressures were documented throughout the study.
• The administration of HES resulted in significant increases in the mean right atrial pressure, stroke volume, and cardiac output and a decrease in systemic vascular resistance in a dose-dependent manner.
• Meanwhile, electrolyte levels (Na(+), K(+), Cl(-)) remained steady throughout the study.
• Nonetheless, the concentration of packed cell volume, hemoglobin, total protein, and albumin decreased in a dose-dependent manner following the HES administration.

Conclusions

• This experiment shows that HES administration provides a dose-dependent increase in cardiac output.
• At the same time, HES infusion does not impact arterial blood pressures. This is attributed to a parallel decrease in systemic vascular resistance.
• Further research may expand on these findings, exploring the specific mechanisms that enable the observed cardiovascular effects of HES infusion. It also may be beneficial to assess the longer-term impacts on hemodynamic parameters and other biological markers.