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MT 6317 LEC: CLINICAL CHEMISTRY > Unit 4.1 - NPN (Urea) > Flashcards

Unit 4.1 - NPN (Urea) Flashcards

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1
Q

Nitrogen containing substances found in blood that are not proteins.

A

Nonprotein Nitrogen Compounds

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2
Q

For assessment and monitoring of renal function.

Ex: Urea, BUN, Creatinine, Ammonia, Uric Acid

A

Nonprotein Nitrogen Compounds

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3
Q

Before the current analytical methods available, this method is used to remove the proteins before analysis in measuring the nitrogen content.

A

Protein Free Filtrate (PFF)

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4
Q

What are the clinically significant Nonprotein Nitrogen Compounds?

A
  • Urea
  • Amino acids
  • Uric acids
  • Creatinine
  • Creatine
  • Ammonia
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5
Q

What is the approximate plasma concentration of Urea?

A

45-50%

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6
Q

What is the approximate plasma concentration of Uric acid?

A

10%

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7
Q

What is the approximate plasma concentration of Creatinine?

A

5%

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8
Q

What is the approximate plasma concentration of Creatine?

A

1-2%

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9
Q

What is the approximate plasma concentration of Ammonia?

A

0.2%

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10
Q

What is the approximate urine concentration of Urea?

A

86.0%

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11
Q

What is the approximate urine concentration of Uric acid?

A

1.7%

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12
Q

What is the approximate urine concentration of Creatinine?

A

4.5%

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13
Q

What is the approximate urine concentration of Creatine?

A

No!

char wala

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14
Q

What is the approximate urine concentration of Ammonia?

A

2.8%

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15
Q

This NPN is found in the blood, and the major excretory product from protein metabolism.

A

Urea

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16
Q

Urea is synthesized in what organ during the protein catabolism?

A

Liver

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17
Q

Renal or liver disease

Increase in ammonia, and decrease in urea would lead to?

A

Renal disease

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18
Q

Renal or liver disease:

Decrease in ammonia = low protein in-take would lead to?

A

Liver disease

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19
Q

This cycle takes places in hepatocytes and is a compartmentalized process between the mitochondria and cytosol.

A

Urea Cycle

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20
Q

Other name of Urea Cycle:

A

Krebs Henseleit Cycle

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21
Q

In mitochondria during urea cycle, what are the two molecules formed?

A
  1. Carbamoyl phosphate
  2. Citrulline
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22
Q

What are the important enzymes in cytosol during urea cycle?

A
  1. Arginase enzyme
  2. Argininosuccinate synthetase
  3. Argininosuccinate lyase
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23
Q

This enzyme located in the cytosol forms & release the urea.

A

Arginase enzyme

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24
Q

NPN that is filtered freely by the glomerulus.

A

Urea

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25
Q

% of urea that is re-absorbed.

A

40-60%

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26
Q

% of excreted urine in the urea.

A

50%

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27
Q

% of urea excreted through GI tract & skin.

A

<10%

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28
Q

Concentration of urea is dependent on: (3)

A
  1. Renal function
  2. Protein content of diet
  3. Amount of protein metabolism
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29
Q

Determination of urinary concentration is of value in the assessment of nitrogen balance for nutritional management.

A

Blood Urea Nitrogen

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30
Q

Molecular weight of Urea:

A

60 mg/mmol

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31
Q

Conversion of BUN to UREA:

A

BUN x 2.14

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32
Q

Conversion of UREA to BUN:

A

UREA X 0.467 or UREA/(1/2.14)

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33
Q

What are the clinical applications of Urea? (5)

A
  • Evaluate renal function
  • Determine hydration status
  • Assess nitrogen balance
  • Aid in the diagnosis of renal disease
  • Verify adequacy of dialysis
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34
Q

Urea pathophysiology:

An elevated concentration of urea in the blood.

A

Azotemia

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35
Q

Urea pathophysiology:

Mainly due to laboratory findings, patient can have an asymptomatic condition.

A

Azotemia

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36
Q

Urea pathophysiology:

Has very high levels of plasma urea accompanied by renal failure.

A

Uremia/Uremic Syndrome

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37
Q

Urea pathophysiology:

A condition where the urine is deposited through the skin.

A

Uremic frost

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38
Q

Urea pathophysiology:

3 phases of Azotemia

A
  1. Pre-renal
  2. Renal/Intrinsic
  3. Post-renal
39
Q

Identify if pre, renal, post azotemia:

  • Decreased blood flow to the kidney
  • Decreased filtration = resulting to increased urea in the blood
  • Increased reabsorbtion of water
A

Pre-renal Azotemia

40
Q

Identify if pre, renal, post azotemia:

Directly damages the kidney, cannot remove NPNs

A

Renal/Intrinsic Azotemia

41
Q

Identify if pre, renal, post azotemia:

  • Increase NPNs, waste substances
  • Obstruction in urinary tract
  • Example: Kidney Stones
A

Post-renal azotemia

42
Q

Identify if pre, renal, post azotemia:

Impaired perfusion:
* Cardiac failure
* Sepsis
* Blood loss
* Dehydration
* Vascular occlusion

A

Pre-renal Azotemia

43
Q

Identify if pre, renal, post azotemia:

  • Glomerulonephritis
  • Small-vessel vasculitis
  • Acute tubular necrosis
  • Interstitial nephristis
A

Renal/Intrinsic Azotemia

44
Q

Identify if pre, renal, post azotemia:

  • Urinary calculi
  • Retroperitoneal fibrosis
  • Benign prostatic enlargement
  • Prostate cancer
  • Cervical cancer
  • Urethral stricture/valves
  • Meatal stenosis/phimosis
A

Post-renal Azotemia

45
Q

Identify if pre, renal, post azotemia:

  • Decreased blood flow to the kidney
  • Congestive heart failure
  • Shock, haemorrage
  • Dehydration
A

Pre-renal Azotemia

46
Q

What are the other causes of Pre-renal Azotemia?

A
  • Level of protein metabolism
  • High protein diet
  • Increased fever catabolism
47
Q

Pre-renal azotemia:

Causes of increased protein catabolism (6):

A
  1. Fever
  2. Mental illness
  3. Stress
  4. Burns
  5. Corticosteroid therapy
  6. GI Bleeding
48
Q

What are the 3 causes of Acute Renal Failure?

A
  1. Prerenal
  2. Intrarenal
  3. Postrenal
49
Q

T/F:

The basis of identifying the causes/types of Azotemia is Urea.

A

FALSE!!!!!!

Dapat blood :D

50
Q

Identify if pre-renal, renal, post-renal:

High urea: Normal creatinine

A

Pre-renal azotemia

51
Q

Identify if pre-renal, renal, post-renal:

High urea: High creatinine

A

Renal azotemia

52
Q

Identify if pre-renal, renal, post-renal:

Normal urea: High creatinine

A

Post-renal azotemia

53
Q

Normal value of a normal BUN:

A

6-20 mg/dL

54
Q

Urea Nitrogen: Creatinine Normal ratio?

A

10:1 - 20:1

55
Q

Normal value of normal creatinine:

A

0.5-1 mg/dL

But still varies to gender (as creatinine of male is higher than female)

56
Q

The following conditions could be linked to renal azotemia except:

a. High urea, high creatinine
b. Glomerulonephritis
c. Direct damage to the kidneys due to reduced blood supply
d. High urea and normal creatinine
e. Uremic syndrome
f. “Normal” BUN/Creatinine ratio

A

d. High urea and normal creatinine

Associated with pre-renal azotemia

57
Q

What are the conditions with decreased levels of plasma urea? (6)

A
  1. decreased protein intake
  2. poor nutrition
  3. high fluid intake, overhydration
  4. sever liver disease
  5. severe vomiting & diarrhea
  6. increased protein synthesis
58
Q

2 types of Urea Determination?

A
  1. Direct method
  2. Indirect method
59
Q

Direct/Indirect:

Measures urea as a whole:

A

Direct Method

60
Q

Direct/Indirect:

Measures the nitrogen contect of uea (BUN)

A

Indirect

61
Q

Urea determination (chemical method):

Also known as Friedman’s Method or Xanthydrol Method

A

Condensation with Diacetyl Monoxime Method

62
Q

Urea determination (chemical method):

What are the reagents used in Condensation with Diacetyl Monoxime Method?

A
  • strong acid
  • oxidizing agent
  • ferric ions
  • thiosemicarbazide
63
Q

Urea determination (chemical method):

Product of Condensation with Diacetyl Monoxime Method:

A

yellow diazine derivative

64
Q

Urea determination (chemical method):

DAM + water ===(H+) diacetyl
Diacetyl + urea === (Fe3+) diazine

A

Condensation with Diacetyl Monoxime Method

65
Q

Urea determination (chemical method):

Disadvantages of Friedman’s Method or Xanthydrol Method: (2)

A
  1. non-specific
  2. uses toxic substances
66
Q

Urea determination (chemical method):

Advantages of Friedman’s Method or Xanthydrol Method: (2)

A
  1. ammonia does not interfere
  2. used in autoanalyzers
67
Q

Urea determination (chemical method):

Urea + o-pthalaldehdyde (H+) -> isoindoline + naphthylethylene diamine (H+) -> colored product

A

Reaction w/ o-pthalaldehdyde and naphthylethylene

68
Q

Urea determination (chemical method):

Product of Reaction w/ o-pthalaldehdyde and naphthylethylene?

A

chromogen or colored product

69
Q

Urea determination (chemical method):

Advantages of Reaction w/ o-pthalaldehdyde and naphthylethylene? (2)

A
  1. no ammonia interference
  2. used in automation
70
Q

Urea determination (chemical method):

Disadvantages of Reaction w/ o-pthalaldehdyde and naphthylethylene? (1)

A
  1. sulfa containing drugs interfere
71
Q

Urea determination (chemical method):

NH4+ (alkalinized) → NH3 ↑ + K2HgI4 → NH2Hg2I3

A

Micro-Kjeldahl Nessler Method

72
Q

Urea determination (chemical method):

Digestion of Micro-Kjeldahl Nessler Method

A

Urea to Ammonium (NH4+)

73
Q

Urea determination (chemical method):

Product of Micro-Kjeldahl Nessler Method

A

yellow compound

74
Q

Urea determination (enzymatic method):

Urea (urease) → HCO3- + NH4+ + Gum Ghatti (alkaline) + Nessler’s reagent → NH2Hg2I3 (yellow)

A

Urease-Nessler’s Method

75
Q

Urea determination (enzymatic method):

Optimal temperature of Urease-Nessler Method:

A

37 degree

76
Q

Urea determination (enzymatic method):

Urea (urease) → HCO3- + NH4+ + sodium nitroprusside (alkaline) + phenol hypochlorite → indophenol blue + NaCl + H2O

A

Urease-Berthelot’s Method

77
Q

Urea determination (enzymatic method):

Disadvantages of Urease-Berthelot’s Method: (2)

A
  1. not specific
  2. very sensitive to interference from endogenous ammonia
78
Q

Urea determination (enzymatic method):

  • Best to perform in kinetic method
  • Most common method in automation
A

Urease-L-Glutamate Dehydrogenase Method (GLDH Method)

79
Q

Urea determination (enzymatic method):

2 enzymes used in GLDH method:

A
  1. Urease
  2. GLDH
80
Q

Urea determination (enzymatic method):

Absorbance in measuring the GLDH method

A

340 nm

81
Q

Urea determination (enzymatic method):

Urea + 2H2O → 2NH4+ CO23-

A

Urease Conductimetric Method

82
Q

Urea determination (enzymatic method):

Conductivity of ammonium is measured.

A

Urease Conductimetric Method

83
Q

Analytical methods:

  • Proposed reference method of urea
  • Confirmatory purpose
  • Debatable results
  • Not used in routine
  • Sensitive & specific
A

Isotope Dilution Mass Spectrometry (IDMS)

84
Q

Analytical methods:

Detecion of characteristic fragments following ionization; quantification using isotopically labaled compound

A

IDMS

85
Q

Specimen requirements for measuring Urea:

A

Non-hemolyzed sample (plasma/serum) or urine

86
Q

If plasma is used, any additive is used except _ & _ which interferes w/ urease and ammonium ions.

A
  1. Light blue top (sodium citrate)
  2. Gray top (sodium fluoride)
87
Q

Urea is suspectible to bacterial composition, urine sample should be _

A

refrigerated

88
Q

T/F:

Protein content of diet influences urea but minimal: has fasting requirement.

A

False

89
Q

T/F:

A reference method for measuring Urea is Micro-Kjeldahl Nessler method.

A

False.

Should be IDMS

90
Q

T/F:

Sodium citrate & fluoride are the recommended collection additive when measuring Urea concentration.

A

False

not recommended.

91
Q

T/F:

Increased concentrations of Urea could be seen in low protein intake, liver disease, and severe vomiting and diarrhea.

A

False.

decreased

91
Q

T/F:

Urea measurement will come out elevated in azotemia, uremic syncrome, and prerenal conditions.

A

True

92
Q

Reference interval of urea nitrogen for adult in plasma/serum:

A

6-20 mg/dL or 2.1-7.1 mmol/L

93
Q

Reference interval of urea nitrogen for adult in 24-hour urine:

A

12-20 g/day or 0.43-0.71 mol urea/day

MT 6317 LEC: CLINICAL CHEMISTRY (3 decks)

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