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49 Cards in this Set

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What is a normal GFR for adults?
men 125 +/- 15/1.73m2
women 110 +/- 15 /1.73m2
What is normal GFR for newborns?
50% of normal adjusted for body surface area
How does GFR change?
decreases 1%/year above age 40
What things increase GFR?
afternoon, pregnancy, increased dietary ptoein intake
What decreases GFR?
nighttime, exercise
Why do you use inulin to measure GFR?
filtred by glomerulus, not secreted/reabsorbed in tubules
GFR rate equivalent to inulin clearance
How do you measure clearance of inulin?
infuse inulin IV to steady state, measure plasma and urine inulin levels simultaneously
How do you calculate GFR from Cin?
Uin x V = Cin = GFR
What should you use instead of inulin?
iohexol
Why do you use creatinine clearance?
released from muscle at a constant rate, filtered completely by glomerulus, not reabsorbed by tubules, minimally secreted by tubules
excretion is equal to creatinine filtered
How do you calculate GFR from creatinine clearance?
Ccr = (UcrV) /PCr
What is UcrV
creatinine excretion, equal to creatinine production, dependent on muscle mass
What does higher serum creatinine mean?
worse kidney function
What is a normal creatinine?
.6 - 1.2
What is the relationship between serum creatinine and GFR?
inverse curvilinear
How do you determine serum creatinine?
24h urine collection
What is normal serum creatinine?
.6 - 1.2 mg/dl
How much creatinine would be expected to be excreted in women?
15-25 mg/kg/d
How much creatinine would be expected to be excreted in men?
20-30 mg/kg/d
How much creatinine would be expected to be excreted in the elderly?
10 mg/kg/d
How much creatinine would be expected to be excreted in children?
14.7 + (0.45 x age) mg/kg/d
What decreases muscle mass (and creatinine excretion)?
corticosteroids, inactivity, old age
What is the Cockroft-Gault formula?
GFR = ((140-age) x lean body weight in kg) / (72 x serum creatinine)
x .85 for women
What's wrong with MDRD formula?
underestimates GFR when near normal
What is normal BUN?
7-21 mg/dl
What does BUN do in kidney failure?
increases
Upon what is BIUN dependent?
protein intake, catabolism, liver function, volume status
What increases BUN?
increased protein intake, catabolism, low volume states
What decreases BUN?
cirrhosis, high volume states
What is normal VUN?
60% of creatinine or inulin clearance
Why do you use BUN?
assess dietary protein intake, catabolism, volume status, renal perfusion, GFR
How do lab values change in AKI?
GFR falls, creatinine excretion decreases, serum creatinine and BUN rise, not in steady state
When do lab values normalize with AKI?
at about 14 days, GFR improves, creatinine plateaus and falls to normal
What do you not use to measure GFR with AKI?
24h urine, Cockroft-Gault, MDRD
Why do you use fractional excretion?
determine parts of renal function
How do you calculate fractional excretion?
clearance of substance/clearance of ideal GFR marker
What do you test for with urinalysis?
specific gravity, pH, glucose, ketones, blood, protein, bilirubin, urobilinogen, nitrite, leukocytes, cells, casts, formed elements
What is specific gravity?
dependent on the number, size, density of particles in the urine
What is omsolality?
depends on number of particles in the urine
What is normal urine pH?
4.5 - 8
What pH comes with calcium phosphate stones?
high
What pH comes with urea splitting organisms?
high pH
What pH comes with uric acid stones?
low pH
How do you determine proteinuria?
add 20% sulfasalicylic acid to urine, makes urine look cloudy
measure protein with 24h urine
What values give you microalbuminuria?
30 mg/g creatinine - 300 mg/d, early diabetic nephropathy
What constitutes nephrotic proteinuria?
> 3g/d of proteinuira
What do you see in obstructive jaundice?
increased urobilinogen
What do you see in non-obstructive jaundice?
increaesd urinary urobilinogen
Why do you test for nitrite?
gram negative bacteria, will not test for enterococcus or organisms that don't produce nitrite