Effect of splenectomy on exercise-induced pulmonary and systemic hypertension in ponies.

The research article evaluates the effects of splenectomy on exercise-induced changes in systemic and pulmonary pressures in ponies. The study suggests that the increase in blood viscosity induced by an increase in PCV (packed cell volume) due to exercising may significantly contribute to the heightened pulmonary and systemic blood pressures in healthy ponies.

Methodology and Research Parameters

• The study was conducted on nine healthy ponies which underwent a procedure called splenectomy (removal of the spleen) four to nine weeks prior to the start of the research.
• The subjects’ systemic and pulmonary pressures were measured using catheter-tip micromanometers, along with their indicator dilution cardiac output. These measurements were taken both at rest and during suboptimal and maximal exercise regimes (10.5 to 11.0 mph for submaximal and 14 to 15 mph for maximal).

Results and Discussion

• Post-splenectomy, the PCV of the ponies increased only by 4 vol% during maximal exercise. The cardiac output of the ponies post-splenectomy reached levels similar to that of healthy ponies that hadn’t undergone the procedure.
• Interestingly, despite a similar cardiac output, the systemic and pulmonary arterial pressures of the exercising ponies post-splenectomy increased to significantly lower levels as compared to the healthy control group.
• Additionally, the total pulmonary vascular resistance and total peripheral resistance in the splenectomized ponies dropped to lower levels than in the healthy ponies.

Conclusion

• Based on the results, the researchers put forth the theory that the increase in PCV caused by exercise might have a notable contribution toward exercise-induced pulmonary and systemic hypertension in healthy ponies. This is inferred from the fact that post-splenectomy, when the increase in PCV is limited, the pressures are significantly lower despite a similar cardiac output.