Why is it inappropriate to estimate GFR in AKI with CG or MDRD?

The eGFR estimation formulas [(such as Cockcroft-Gault or MDRD)] were derived using patients at steady states, whose renal function was stable; can only be used in patients with stable creatinines.

EXAMPLE: A patient goes for surgery and has a baseline creatinine of 125. They sustain a very severe renal injury => their GFR will fall suddenly (let’s just say to near zero) but their creatinine will lag behind (remain @125) initially when you run bloodwork post surgery. The following day their creatinine will begin rising to ~200, yet their GFR would still be near zero. This lag demonstrates why you can’t use this estimation in the setting of AKI.

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Dr. C Humphreys

Internal Medicine

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Dr. C Humphreys

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