Ch04-9781975113285
Useful Formulae 1 3
• FE Na <1% in prerenal states, early acute tubular necrosis, contrast or heme-pigment nephropathy, and acute glomerulonephritis. • Not valid when diuretics have been given. • See “Acute Kidney Injury” section in Chapter 12, Top 10 Workups.
FRACTIONAL EXCRETION OF UREA
FE
= [(U
× P
)/(P
× U
)] × 100
urea
[urea]
[Cr]
[urea]
[Cr]
( all units in mg/dL )
• FE
<35% in prerenal states.
urea
• Not affected by diuretics. • See “Acute Kidney Injury” section in Chapter 12, Top 10 Workups.
MEAN ARTERIAL PRESSURE
Mean arterial pressure = [SBP + (2 × DBP)]/3
MODEL FOR END-STAGE LIVER DISEASE
MELD = (3.78 × Ln[bilirubin]) + (11.2 × Ln INR) + (9.57 × Ln[SCr]) + 6.43 ( [bilirubin] and [Cr] in mg/dL ) • Who remembers what a nature log is? Rhetorical… Only included to provide the interpretation (Table 4-1).
OSMOLALITY (SERUM, ESTIMATED)
Calculated serum osm = (2 × [Na + ]) + ([glucose]/18) + ([BUN]/2.8)
( [Na + ] in mmol/L; [glucose] and [BUN] in mg/dL )
• To correct for methanol + ([MeOH]/3.2). • To correct for ethanol + ([EtOH]/4.6).
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