[2S] UNIT 4 Non-Protein Nitrogen Compounds: Urea & Uric Acid Flashcards
(133 cards)
1
Q
Nitrogen-containing substances found in blood that are not proteins.
A
Non-Protein Nitrogen Compounds
2
Q
For the assessment and monitoring of renal function
A
Non-Protein Nitrogen Compounds
3
Q
Prior to the current analytical methods available, nitrogen content was measured with the removal of proteins before analysis
A
Protein Free Filtrate
4
Q
Most Abundant NPN
A
Urea
4
Q
Least Abundant NPN
A
Ammonia
5
Q
Derived from the catabolism of protein and amino acids
A
Urea
5
Q
Major NPN found in the blood (45-50% of total NPN)
A
Urea
6
Q
Synthesized in the liver from CO2 + ammonia
A
Urea
7
Q
Filtered freely by the glomerulus
○ 40% Reabsorbed
○ 50% Excreted in the Urine
○ <10% Excreted through GI tract and skin
A
Urea
7
Q
Arising from the deamination of the amino acids by means of the Krebs-Henseleit Cycle or Ornithine Pathway
A
Urea
8
Q
T/F: The concentration of urea is dependent on renal function and perfusion, the protein content of the diet, and the amount of protein catabolism
A
T
9
Q
CLINICAL APPLICATION
● Assess nitrogen balance
● Aid in the diagnosis of renal disease
● Verify the adequacy of dialysis
A
Urea
9
Q
CLINICAL APPLICATION
● Evaluate renal function
● Determine hydration status
A
Urea
10
Q
PATHOPHYSIOLOGY OF UREA
Fatal if not treated by dialysis or transplantation
A
Uremia / Uremic Syndrome
11
Q
PATHOPHYSIOLOGY OF UREA
Very high levels of plasma urea accompanied by renal
failure
A
Uremia / Uremic Syndrome
12
Q
AZOTEMIA (BASED ON THE DYSFUNCTION OR SITE OF ABNORMALITY)
↑ Creatinine ↑ B.U.N. ↑ Osm.
A
Pre-Renal
12
Q
PATHOPHYSIOLOGY OF UREA
An elevated concentration of urea in the blood
A
Azotemia
13
Q
AZOTEMIA (BASED ON THE DYSFUNCTION OR SITE OF ABNORMALITY)
Decreased blood flow to the kidneys
A
Pre-Renal
14
Q
AZOTEMIA (BASED ON THE DYSFUNCTION OR SITE OF ABNORMALITY)
Impaired Perfusion: (Commonly seen in patients with)
○ Cardiac Failure (Congestive Heart Failure)
○ Sepsis (Shock)
○ Blood Loss (Hemorrhage)
○ Dehydration
○ Vascular Occlusion
A
Pre-Renal
15
Q
AZOTEMIA (BASED ON THE DYSFUNCTION OR SITE OF ABNORMALITY)
Level of protein metabolism
■ High protein diet
■ Increased protein catabolism
A
Pre-Renal
16
Q
AZOTEMIA (BASED ON THE DYSFUNCTION OR SITE OF ABNORMALITY)
● Occurs in the kidneys
● Decreased renal function
A
Renal / Intrinsic
17
Q
AZOTEMIA (BASED ON THE DYSFUNCTION OR SITE OF ABNORMALITY)
● Small-vessel Vasculitis
● Acute Tubular Necrosis
A
Renal / Intrinsic
17
Q
AZOTEMIA (BASED ON THE DYSFUNCTION OR SITE OF ABNORMALITY)
● Acute / Chronic Renal Failure
● Glomerulonephritis
A
Renal / Intrinsic
18
Q
AZOTEMIA (BASED ON THE DYSFUNCTION OR SITE OF ABNORMALITY)
● Prolonged Hypotension
● Interstitial Nephritis
A
Renal / Intrinsic
19
AZOTEMIA (BASED ON THE DYSFUNCTION OR SITE OF ABNORMALITY)
Happens after reaching the kidneys
Post-Renal
20
High urea: Normal Creatinine
Pre-Renal
21
AZOTEMIA (BASED ON THE DYSFUNCTION OR SITE OF ABNORMALITY)
Urinary Tract Obstruction
○ Causes:
■ Renal calculi
■ Tumors of the bladder/prostate
■ Severe infection like UTI
Post-Renal
22
High urea: High Creatinine
Renal
23
Normal urea: High Creatinine
Post-Renal
24
Urea Nitrogen (B.U.N.) : Creatinine
10:1 to 20:1
25
Determination of urinary concentration is of value in the assessment of nitrogen balance for nutritional
management
BUN
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Chemical Formula of Urea
CO(NH2)2
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B.U.N. to Urea
2.14
28
B.U.N.. in mg/dL to mmol/L
0.357
29
Urea to B.U.N
0.467
30
UREA DETERMINATION
Measures urea as a whole without isolating nitrogen
Direct Method
31
UREA DETERMINATION
Measures the nitrogen content of urea (B.U.N.)
Indirect Method
32
UREA DETERMINATION
Uses:
○ Evaluate renal function
○ Assess hydration status
○ Determine nitrogen balance
○ Verify adequacy of dialysis
Indirect Method
33
UREA METHODS OF DETERMINATION
● Fearon’s Reaction
● Also known as Friedman’s Method or Xanthydrol Method
Condensation with Diacetyl Monoxime Method
34
UREA METHODS OF DETERMINATION
Reagents: strong acid, oxidizing agent, ferric ions,
thiosemicarbazide
Condensation with Diacetyl Monoxime Method
35
UREA METHODS OF DETERMINATION
Product of Condensation with Diacetyl Monoxime Method
Yellow Diazine Derivative
36
UREA METHODS OF DETERMINATION
Direct or Indirect?
Condensation with Diacetyl Monoxime Method
Direct
37
UREA METHODS OF DETERMINATION: ADVANTAGES
● Ammonia does not interfere in the measurement
● Used in auto analyzers
Condensation with Diacetyl Monoxime Method
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UREA METHODS OF DETERMINATION: DISADVANTAGES
● Non-specific
● Uses toxic substances
Condensation with Diacetyl Monoxime Method
39
UREA METHODS OF DETERMINATION
DAM + water === (H+) diacetyl
Diacetyl + urea === (Fe+3) diazine
Condensation with Diacetyl Monoxime Method
40
UREA METHODS OF DETERMINATION
Urea + o-phthalaldehyde (H+) → isoindoline + naphthylethylene diamine (H+) → colored product
Reaction w/ O-phthalaldehyde and Naphthylethylene Diamine
41
UREA METHODS OF DETERMINATION
Product of Reaction w/ O-phthalaldehyde and Naphthylethylene Diamine
Chromogen / Colored Product
42
UREA METHODS OF DETERMINATION
Reaction w/ O-phthalaldehyde and Naphthylethylene Diamine
43
UREA METHODS OF DETERMINATION: ADVANTAGES
● No ammonia interference
○ Measure entire urea and do not isolate the nitrogen content
● Used in automation
Reaction w/ O-phthalaldehyde and Naphthylethylene Diamine
44
UREA METHODS OF DETERMINATION: DISADVANTAGES
Sulfa containing drugs
interfere
Reaction w/ O-phthalaldehyde and Naphthylethylene Diamine
45
UREA METHODS OF DETERMINATION
It is a 2-step procedure wherein we need to digest urea first; this allows the isolation of nitrogen component
Micro-Kjeldahl Method
45
UREA METHODS OF DETERMINATION
Direct or Indirect?
Micro-Kjeldahl Method
Indirect
46
UREA METHODS OF DETERMINATION
Digestion: urea (H2SO4 + H3PO4) → NH4+
○ Digestion is done by adding strong acids, eg.
sulfuric acid and phosphoric acid
○ Isolated content: ammonium
Micro-Kjeldahl Method
46
UREA METHODS OF DETERMINATION
NH4 + (alkalinized) → NH3↑ + K2HgI → NH2Hg2I3
Micro-Kjeldahl Method
46
UREA METHODS OF DETERMINATION
Urea (urease) → HCO3 + NH4+ + Gum Ghatti
(alkaline) + Nessler’s reagent → NH2Hg2I3 (yellow)
ENZYMATIC: Urease-Nessler’s method
47
UREA METHODS OF DETERMINATION
Product of Micro-Kjeldahl Method
yellow compound (diamino mercuric iodide)
48
UREA METHODS OF DETERMINATION
Urea in the sample will be reacted upon urease, which will hydrolyze urea, resulting to bicarbonate and ammonium → Gum Ghatti is added to prevent bubble formation → add
Nessler’s reagent → di amino mercuric iodide (measure spectrophotometrically)
ENZYMATIC: Urease-Nessler’s method
48
UREA METHODS OF DETERMINATION
Direct or Indirect?
Urease-Nessler’s method
Indirect
49
Systematic name of urease
urea amidohydrolase
50
UREA METHODS OF DETERMINATION
Urea (urease) → HCO3- + NH4+ + sodium
nitroprusside (alkaline) phenol hypochlorite →
indophenol blue + NaCl + H2O
ENZYMATIC: Urease-Berthelot’s method
50
UREA METHODS OF DETERMINATION
Disadvantages:
○ Not specific
○ Very sensitive to interference from
endogenous ammonia
ENZYMATIC: Urease-Berthelot’s method
51
UREA METHODS OF DETERMINATION
Coupled enzymatic method; combining L-glutamate dehydrogenase and urease
ENZYMATIC: Urease-L-Glutamate Dehydrogenase Method (GLDH method)
52
UREA METHODS OF DETERMINATION
● First reaction is to utilize urease to hydrolyze ammonia to form ammonium and bicarbonate
● Secondary reaction involves utilizing
glutamate dehydrogenase
○ We monitor the reaction or oxidation of NADH to NAD+
ENZYMATIC: Urease-L-Glutamate Dehydrogenase Method (GLDH method)
53
UREA METHODS OF DETERMINATION
The conductivity of ammonium is measured
ENZYMATIC: Urease-Conductometric method
54
UREA METHODS OF DETERMINATION
● Quantification of result using isotopically labeled
compound
● Proposed reference method of urea
Istotope Dilution Mass Spectrometry
54
UREA METHODS OF DETERMINATION
Detection of characteristic fragments following
ionization
Istotope Dilution Mass Spectrometry
55
SPECIMEN REQUIREMENT FOR UREA
T/F: If plasma will be used, any anticoagulant maybe used including sodium fluoride/sodium citrate.
F; EXCEPT sodium fluoride/sodium citrate, which interferes with urease and ammonium ions
56
SPECIMEN REQUIREMENT FOR UREA
T/F: Urine is susceptible to bacterial decomposition: urine sample should be refrigerated
T
57
SPECIMEN REQUIREMENT FOR UREA
T/F: Protein content of diet influences urea but minimal: no fasting requirement
T
58
Product of catabolism of purines bases (adenine and
guanine)
Uric Acid
59
Readily filtered by glomerulus, but undergoes
reabsorption and secretion
Uric Acid
60
98-100%:reabsorbed in the PROXIMAL tubules
Uric Acid
61
<1%: excreted in the distal tubules
○ Renal excretion: 70% of UA
○ GI excretion: 30%
Uric Acid
62
Relatively insoluble in plasma as monosodium urate at pH 7
Uric Acid
63
URIC ACID
At concentrations >6.8 mg/dL), plasma is saturated, _______ _____ may form in the tissues
urates crystals
64
URIC ACID
At pH ____, uric acid crystals may form
<5.75
65
High concentrations accumulate in the joints and tissue resulting in inflammation (gouty arthritis)
Uric Acid
66
CLINICAL APPLICATION
○ Assess inherited disorders of purine metabolism
○ Detect kidney dysfunction
Uric Acid
67
CLINICAL APPLICATION
Assist in the diagnosis of renal calculi (kidney
stones)
Uric Acid
68
CLINICAL APPLICATION
Confirm diagnosis and monitor treatment of
gout
Uric Acid
69
CLINICAL APPLICATION
Assess and prevent uric acid during chemotherapeutic management (Chemotherapy)
Uric Acid
70
URIC ACID: PATHOPHYSIOLOGY
● In males between 30 and 50 years of age
● In female they appear after menopause
HYPERURICEMIA: Gout
71
URIC ACID: PATHOPHYSIOLOGY
Px (patient) pain and inflammation of the joints caused by precipitation of sodium urates
HYPERURICEMIA: Gout
72
URIC ACID: PATHOPHYSIOLOGY
Increased: hyperuricemia (___ mg/dL)
○ Hyperuricemia – in 25% to 30% of patients
○ Result of overproduction of uric acid
○ Formation of renal calculi
>6.0
73
URIC ACID: PATHOPHYSIOLOGY
Treatment for Increased Nuclear Breakdown
Allopurinol
74
URIC ACID: PATHOPHYSIOLOGY
● Seen in patients undergoing chemotherapy for leukemia, lymphoma, multiple myeloma, polycythemia
● UA monitoring to avoid nephrotoxicity
HYPERURICEMIA: Increased Nuclear Breakdown
75
URIC ACID: PATHOPHYSIOLOGY
inhibit xanthine oxidase and stop formation of uric acid
Allopurinol
76
URIC ACID: PATHOPHYSIOLOGY
● Impaired filtration and secretion
● Not a good indicator of renal function
○ For renal: BUN, creatinine
HYPERURICEMIA: Kidney Diseases
77
URIC ACID
X-linked genetic disorder (seen only in males)
Lesch-Nyhan Syndrome
78
URIC ACID
Lack of this enzyme prevents the reutilization of purine bases in the nucleotide salvage pathway
Lesch-Nyhan Syndrome
79
URIC ACID
Caused by the complete deficiency of hypoxanthine–guanine phosphoribosyltransferase (HPRT)
Lesch-Nyhan Syndrome
80
URIC ACID
Too much secretion of AMP/AMV → uric acid increases
Lesch-Nyhan Syndrome
81
URIC ACID
It consequently results in INCREASED concentrations of uric acid (plasma and urine)
Lesch-Nyhan Syndrome
82
URIC ACID
Neurologic symptoms, mental retardation, and
self-mutilation characterize this extremely rare disease
Lesch-Nyhan Syndrome
83
URIC ACID
Increasing purine synthesis; increases the degradation
product
Lesch-Nyhan Syndrome
84
URIC ACID: DISEASE CORRELATION
Increased or Hypouricemia?
Secondary to severe liver disease
Hypouricemia
84
URIC ACID: DISEASE CORRELATION
Increased or Hypouricemia?
Mutation on phosphoribosylpyrophosphate synthetase
Increased
85
URIC ACID: DISEASE CORRELATION
Increased or Hypouricemia?
Toxemia of pregnancy
Increased
86
URIC ACID: DISEASE CORRELATION
Increased or Hypouricemia?
Lactic acidosis (competition for binding sites in renal tubules)
Increased
87
URIC ACID: DISEASE CORRELATION
Increased or Hypouricemia?
Defective tubular reabsorption (Fanconi’s Syndrome)
Hypouricemia
88
URIC ACID: DISEASE CORRELATION
Increased or Hypouricemia?
Chemotherapy with 6-mercaptopurine
or azathioprine (inhibits de novo purine synthesis)
Hypouricemia
89
URIC ACID: DISEASE CORRELATION
Increased or Hypouricemia?
Overtreatment with allopurinol
Hypouricemia
90
CAUSES OF HYPER OR HYPOURICEMIA?
Increased dietary intake of purine-rich food
Hyperuricemia
91
CAUSES OF HYPER OR HYPOURICEMIA?
Catabolic pathways enzyme defects
Hyperuricemia
91
CAUSES OF HYPER OR HYPOURICEMIA?
Increased URATE production (postmenopausal women,
increased tissue metabolism such as in starvation
Hyperuricemia
92
CAUSES OF HYPER OR HYPOURICEMIA?
DECREASED excretion
Hyperuricemia
93
CAUSES OF HYPER OR HYPOURICEMIA?
Increased METABOLISM of cell nuclei (lymphoma,
leukemia, multiple myeloma, polycythemia, hemolytic and megaloblastic anemia)
Hyperuricemia
94
CAUSES OF HYPER OR HYPOURICEMIA?
Inherited disorders with ENZYME deficiency
(Lesch-Nyhan Syndrome)
Hyperuricemia
95
CAUSES OF HYPER OR HYPOURICEMIA?
Decreased uric acid excretion (preeclampsia, lactic acidosis)
Hyperuricemia
96
ANALYTICAL METHODS – URIC ACID
Uric acid + phosphotungstic acid + O2 → NaCO3/OH →
tungsten blue + allantoin + CO2
DIRECT REDOX METHOD: Caraway's / Henry Method
97
CAUSES OF HYPER OR HYPOURICEMIA?
Chronic renal disease (impaired filtration and secretion)
Hyperuricemia
98
ANALYTICAL METHODS – URIC ACID
Based on the oxidation of UA in PFF (protein-free filtrate) and reduction of PTA
DIRECT REDOX METHOD: Caraway's / Henry Method
99
ANALYTICAL METHODS – URIC ACID
Interferences (false +/ increase) – turbidity, aspirin and metabolite, acetaminophen, caffeine, and theophylline
DIRECT REDOX METHOD: Caraway's / Henry Method
100
ANALYTICAL METHODS – URIC ACID
Uses ferric ion for the presence of uric acid produces
Iron Reduction Method
101
ANALYTICAL METHODS – URIC ACID
Develop color formation; Darker the color→ higher
concentration of uric acid
Iron Reduction Method
102
ANALYTICAL METHODS – URIC ACID
Reduced in the presence of Uric Acid
Iron Reduction Method
103
ANALYTICAL METHODS – URIC ACID
● Most commonly used in the laboratory
● Allantoin is measured and is the final/end product
ENZYMATIC: Uricase Method (Blaunch & Koch)
104
ANALYTICAL METHODS – URIC ACID
Measurement of the differential absorption of UA and allantoin at 290-293 nm
ENZYMATIC: Uricase Method (Blaunch & Koch)
105
ANALYTICAL METHODS – URIC ACID
More specific
ENZYMATIC: Uricase Method (Blaunch & Koch)
106
ANALYTICAL METHODS – URIC ACID
Disadvantage: Bilirubin and ascorbic acid are interfering
substances that may destroy peroxide
Coupled Enzyme
106
ANALYTICAL METHODS – URIC ACID
● Proteins cause high
background absorbance
● Negative interference due to Hb and Xanthine
ENZYMATIC: Uricase Method (Blaunch & Koch)
107
ANALYTICAL METHODS – URIC ACID
● Uses the enzymes peroxidase and catalase.
● Color production is proportional to the uric acid
concentration
Coupled Enzyme
108
ANALYTICAL METHODS – URIC ACID
Remedy for coupled enzyme
Addition of potassium ferricyanide and ascorbate oxidase
109
ANALYTICAL METHODS – URIC ACID
● Uses ion exchange and reverse phase column
● Detects ratio
HPLC
110
ANALYTICAL METHODS – URIC ACID
● Detection of characteristic fragments after ionization
● Quantification using isotopically labeled compound
● Proposed reference method but not routinely used
IDMS
111
Specimen used for Uric Acid
Heparinized plasma, serum, or URINE
112
SPECIMEN REQUIREMENT FOR URIC ACID
T/F: Diet may affect uric acid concentration
T
113
SPECIMEN REQUIREMENT FOR URIC ACID
T/F: Gross lipemia should be used
F; Gross lipemia should be avoided
114
SPECIMEN REQUIREMENT FOR URIC ACID
Hemolysis, with concomitant glutathione release, may result in ___ values
low
115
SPECIMEN REQUIREMENT FOR URIC ACID
Serum samples may be stored refrigerated for ___ days
3 to 5
116
SPECIMEN REQUIREMENT FOR URIC ACID
Salicylates and thiazides = ________ values for uric acid
INCREASED
117
SPECIMEN REQUIREMENT FOR URIC ACID
T/F: EDTA or fluoride SHOULD NOT BE be used
T
118
SPECIMEN REQUIREMENT FOR URIC ACID
Urine specimen pH
alkaline (pH 8)
