Effects of norepinephrine and combined norepinephrine and fenoldopam infusion on systemic hemodynamics and indices of renal function in normotensive neonatal foals.

This research assesses how the drug norepinephrine, alone or combined with fenoldopam, affects blood pressure, heart activity, and kidney function in healthy young horses. The study suggests that norepinephrine can successfully increase systemic vascular resistance (SVR) without causing harm to the kidneys, and that the addition of fenoldopam doesn’t offer extra benefits to kidney performance.

Study Parameters and Methodology

• The experiment was designed to assess the effects norepinephrine, either in isolation or combined with another drug fenoldopam, on the systemic hemodynamics and renal function in healthy neonatal horses (foals).
• A total of five conscious foals were chosen as subjects, each receiving different dosage levels and combinations of norepinephrine (0.3 microg/kg/min), combined norepinephrine and fenoldopam (0.04 microg/kg/min), and a placebo control dose of saline.
• The drugs’ impacts on heart rate (HR), arterial blood pressure, cardiac output, and other physiological parameters such as systemic vascular resistance (SVR), stroke volume, cardiac index (CI), and stroke volume index were examined.
• The researchers also tracked urine output, creatinine clearance (as a measure of kidney function), and fractional electrolyte excretion.

Key Findings

• In the studied neonatal foals, norepinephrine alone or paired with fenoldopam triggered an increase in arterial blood pressure, SVR, urine output, and creatinine clearance. This effect was measured in comparison to the control saline infusion.
• In addition to increased blood pressure, the combination of norepinephrine and fenoldopam led to higher heart rates and lower arterial blood pressure than what was observed with norepinephrine alone.
• Both the norepinephrine-only and combined drug regimen resulted in a decline in heart rate and the cardiac index, compared to the foals receiving the saline control.

Conclusions and Implications

• The results suggest that, at the studied dosage level, norepinephrine might be beneficial for treating hypotensive (low-blood-pressure) conditions in young horses. This is due to its capacity to enhance SVR while not negatively affecting kidney health, as suggested by an observed increase in creatinine clearance.
• The study found that the addition of fenoldopam to the norepinephrine infusion did not provide any additional benefits regarding kidney function.
• In summary, the researchers recommend further exploration of these findings, to better understand the potential use of norepinephrine for managing hypotensive conditions in foals and possibly in other equine subjects.