Some kidney-specific figures
Renal blood flow
= 25% of cardiac output
= 1250mLs/min
Renal oxygen consumption
= 7.2% of body oxygen consumption
= 18mLs O2/min
Oxygen extraction ratio
= 7.2%
This is coincidental because
Oxygen flux
= 250mLs O2
= body oxygen consumption
However,
Using slightly different numbers,
Blood flow is 24% of cardiac output
= 1200mL
Oxygen flux
= 240mL O2/min
Oxygen extraction ratio
= 18/240
= 7.5%
Renal blood flow is measured using para-aminohippurate (PAH)
Renal plasma flow
= PAH uptake / [PAH] difference in renal arterial and venous blood
But because clearance is not 100%, therefore...
Effective plasma flow
= Urinary [PAH] x urine volume per unit time / venous [PAH]
Extraction of PAH is about 90%
--> Plasma flow x 0.9 = Effective plasma flow
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Reviewed | 20050816 |