Effects of a highly concentrated hypertonic saline-dextran volume expander on cardiopulmonary function in anesthetized normovolemic horses.

This research investigates the effects of a concentrated solution of hypertonic saline-dextran on the heart and lung functions of anesthetized horses. The study found that this solution quickly expands blood volume and improves cardiac performance, offering a potential alternative for fluid delivery in equine surgical emergencies.

Study Design and Procedure

• The study was conducted on seven horses that were anesthetized with halothane and lying on their sides (laterally recumbent). They were breathing naturally (spontaneously ventilating) and had normal blood volumes (normovolemic).
• The horses were treated with a 25% sodium chloride (NaCl) – 24% dextran 70 solution, known as HSD. This was administered intravenously at a dose of 1.0 ml/kg of the horse’s body weight and infused over a period of 10 minutes.
• The effects of the HSD solution were measured for two hours (120 minutes) after infusion.

Results and Findings

• The results showed that the plasma volume in the horses’ blood quickly and significantly expanded, from 36.6 ml/kg of body weight to 44.9 ml/kg, and remained enlarged throughout the experiment.
• This volume expansion led to significant decreases in packed cell volume, total blood hemoglobin, and plasma protein concentrations, demonstrating that the blood was being diluted (hemodilution) rapidly and enduringly.
• The cardiac index and stroke index – measures of cardiac function – also increased immediately and remained high for the entire study. For example, the cardiac index increased from 69.6 ml/min/kg to 106.6 ml/min/kg, and the stroke index rose from 1.88 ml/beat/kg to 2.50 ml/beat/kg.
• Systemic vascular resistance, another parameter of cardiovascular function, decreased significantly after the HSD infusion and stayed decreased throughout the experiment.
• While oxygen content in both arterial and venous blood dropped (due to hemodilution), the actual oxygen transport in the body temporarily increased at the 10-minute measurement before returning toward the baseline level.

Conclusion and Implications

• The results of this study suggest that a small volume of a highly concentrated hypertonic saline-dextran solution could be a beneficial alternative to conventional fluid resuscitation in equine surgical emergencies.
• Hypertonic saline-dextran solution appears to provide rapid and lasting expansion of blood volume and improves cardiac performance.
• This could potentially allow for quicker stabilization of horses in emergency surgical cases, where currently, the amount of fluids required often cannot be administered rapidly enough.
• However, more research is needed on the safety, efficacy, and clinical application of this experimental approach.