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clinical chem 1 > non protein nitrogen > Flashcards

non protein nitrogen Flashcards

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1
Q

what is the purpose of determining non-protein nitrogen in the blood

A

monitor renal funciton

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2
Q

what causes the formation of most NPN compounds

A

protein catabolism releasing nitrogen which is converted to ammonia

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3
Q

blood urea nitrogen (BUN)

A

highest concentration of NPN
product of protein catabolism
reabsorbed in nephron tubules

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4
Q

where in the liver is BUN at highest concentration

A

collecting duct and ascending arm

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5
Q

what does BUN reabsorption depend on

A

flow rate and hydration in ascending arm

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6
Q

azotemia

A

elevated concentration of urea in blood (high BUN)
- very high associated with uremia or uremic syndrome (renal failure)

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7
Q

three causes of urea plasma elevation

A
  • prerenal: issues with heart (systolic or diastolic) causing less blood flow to kidney
  • renal: issue with kidney itself
  • postrenal: generally urine back up into the kidney
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8
Q

prerenal azotemia

A

less blood to kidney causes less urea filtration

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9
Q

renal azotemia

defintion and disease states related

A

decreased renal function causes increased blood urea due to poor excretion
- acute/chronic failure
- glomerular nephritis (bowmans burst from pressure)
- tubular necrosis (lack if O2)

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10
Q

what can cause decreased urea nitrogen

A

low protein, liver disease, severe vomiting, increased protein synthesis

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11
Q

how is BUN measured

A

urea reported in terms of nitrogen byt measuring NADH-NAD conversion

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12
Q

how are BUN and NADH conversion related

A

inversely proportional

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13
Q

where is creatine synthesized

A

in liver

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14
Q

how are creatine, creatine phosphate and creatinine related

A
  1. creatine can be converted to creatine phosphate via creatine kinase
  2. creatine can be converted to creatinine by loss of water
  3. creatine phosphate can be converted to creatinine by loss of phosphoric acid
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15
Q

what is creatine/creatinine used to measure

A

kidney biomarker

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16
Q

creatinine life cycle

A
  • released in proportion to muscle mass (stable)
  • filtered by glomerulus
  • excreted in urine
17
Q

disease correlations of creatinine

A

elevated creatinine is found with abnormal renal function -> lowered glomerular filtration rate

18
Q

how is glomerular filtration rate (GFR) measured

A

GFR = V/t
V= plasma filtered
t= time

19
Q

what is creatinine clearance

A

measurement of amt creatinine eliminated from blood by kidneys per unit of time
- plasma concentration of creatinine is inversely proportional to clearance
- increased plasma lvls of creatinine decrease GFR

20
Q

creatinine clearence equation

A

(urine creatinine/plasma creatinine)(urine mL/minutes)(1.73/BSA)

21
Q

what is the purpose of BUN:creatinine ratio

A

to determine where azotineal issue is coming from -> both filtered but BUN reabsorbed wherease creatinine is not

22
Q

pre renal BUN:creatinine ratio

A

> 20:1
- BUM reabsorption increased

23
Q

intrarenal BUN:creatinine ratio

A

<10:1
- reduced BUN reabsorption

24
Q

postrenal/normal BUN:creatinine

A

10-20:1
- BUN reabsorption normal

25
Q

uric acid

A
  • a breakdown product of purine metabolism in the liver
  • in plasma as monosodium urate
26
Q

where is uric acid transported to

A

the kidney to be filtered

27
Q

at what concentraiton of plasma monosodium urate do crystals precipitate

A

> 6.8mg/dL

28
Q

urea is formed to neutralize the toxic effect of what waste product

A

ammonia

29
Q

ammonia

A

comes from deamination of amino acids (protein catabolism), digestive biproduct and released from muscles during excerise

30
Q

disease correlations with ammonia

A
  • severe liver disease (not enough urea to convert to BUN to remove)
  • encephalopathy: elevated ammonia
  • reye’s syndrome: ammonia deposition from infants taking aspirin

clinical chem 1 (23 decks)

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