Glomerular Filtration Rate

What is it?

Glomerular filtration rate (GFR) is a test used to check how well the kidneys are working. Specifically, it estimates how much blood passes through the glomeruli each minute. Glomeruli are the tiny filters in the kidneys that filter waste from the blood. Normal GFR isĀ greater than 60.

Maintaining GFR

The kidneys have an autoregulation system, which allows renal blood flow to remain stable between systolic blood pressures of 80 mm Hg to 180 mm Hg. Hypotension, when blood pressure falls below 80 mm Hg, can diminish renal perfusion and could potentially precipitate renal failure. Therefore, the most important element in maintaining optimal kidney perfusion is the avoidance of hypotension and the maintenance of adequate hydration.

ACE Inhibitors

ACE inhibitors are most often given for the management of heart failure, for protection of the diabetic kidney, and for blood pressure control. They alter renal perfusion by dilating the efferent arteriole of the glomerulus reducing renal perfusion pressure and decreasing GFR. Diminished filtration can lead to an increase in serum creatinine and a rise in serum potassium. Hypovolemia and hypotension can further compound diminished filtration and lead to renal failure.

NSAIDS

Although engineered to be site specific, they can alter the effects of prostaglandin in the vasculature of the kidney. Prostaglandin allows dilation of the renal vasculature, thus allowing maximal blood flow through the glomerulus. NSAIDS, by inhibiting prostaglandin dilatation, potentiate vasoconstriction and decrease GFR. As with ACE inhibitors, a potential rise in serum creatinine can be seen with the use of NSAIDS, especially when compounded by hypovolemia and hypotension