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Flashcards in Non-protein Nitrogen Compounds Deck (112)
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1

Describe non-protein nitrogen compounds

General term that can be used for different substances that have the element nitrogen in them, but are not proteins

2

Non-protein nitrogen compounds are products of what?

Products from the catabolism of proteins and nucleic acids which includes about 15 different substances (/compounds: NPN fraction)

3

Non-protein nitrogen compounds are used in evaluating

Renal function and excretion (plasma npns increased in renal failure; ordered as blood tests)

4

What are the most important NPNs

• BUN (Blood Urea Nitrogen)
• Creatinine
• Uric acid
• Ammonia

5

Major components of NPN with plasma concenctration (%plasma npn)

• Urea: associated with urine and fertilizer (BUN: 45%)
• Uric acid: increases with intake of protein (20%)
• Creatinine (5%)
• Creatine: component of whey protein (1-5%)
• Amino acids (20%)
• Ammonia (0.2%)

6

What replaced the measurement of NPN?

determination of blood urea nitrogen (BUN)

7

It is the nitrogenous end-product of protein or amino acid and nucleic acid metabolism which constitutes 45-50% of NPN

Urea

8

How is urea synthesized in the liver?

Synthesized in the liver when NH3 is removed and combined with CO2 (Ammonia is very toxic so it is converted to urea)

9

Other characteristics of urea

• Excreted by glomerular filtration and partially reabsorbed through renal tubules
• Rises quickly as compared to creatinine
• Majority excreted in urine
• Most widely used screening test of kidney function

10

Normal value of urea

• Normal value: 10–50 mg/dL

11

Highest concentration of NPN in blood and a major excretory product of protein metabolism (processes which release nitrogen, which is converted to ammonia and synthesized again in the liver from CO2 and ammonia that arises from deamination of amino acids)

Blood urea nitrogen

(BUN=urea determination)

12

BUN is excreted by what organ?

Kidneys
• Filtered by the glomerulus but 40% is reabsorbed by the renal tubules
• <10% of the total are excreted through the gastrointestinal tract and skin

13

Plasma BUN Concentration is determined by:

• Renal function
• Dietary protein intake
• Protein catabolism rate

14

[Clinical significance of BUN)
Measurement of urea is used to:

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

15

Pre-renal causes (ie blood vessels) of Hyperuremia or increased BUN

(Sometimes translates into dehydration)
• ↓ Renal blood flow (e.g. CHF & dehydration)
• ↑ Protein catabolism (as in fever)
• High protein diet
• Corticosteroid drugs

16

Renal/within the kidney causes of hyperuremia have usually what

Co-morbidity with other diseases

17

Renal causes of HYPERUREMIA

• Acute and chronic renal failure (associated with diabetes mellitus)
• Glomerular nephritis
• Tubular necrosis
• Malignant hypertension

18

Post-renal (outside the kidney) causes of HYPERUREMIA are usually associated with

Obstruction:
• Urethral stones
• Tumors of bladder
• Prostate enlargement
• Cervical cancer

19

A decrease in BUN is associated with

Hypouremia

20

Symptoms of hypouremia

• Liver failure or severe liver disease (lack of urea synthesis)
• Severe vomiting and/or diarrhea
• Decreased dietary protein
• Increased protein synthesis (observed in pregnant women and children)
• Malnutrition (e.g. Kwashiorkor)
• Overhydration
• Early and late stages of pregnancy

21

It is the elevated urea concentration in blood (>20mg/dL)

Azotemia

22

T or F: Azotemia is always due to kidney dysfunction

False

23

Very high plasma urea concentration accompanied with renal failure

Uremic Syndrome or Uremia
• Urea crosses the blood-brain barrier which is used by the brain for energy (Leads to confusion, lethargy, and comatose)
• Uremic pericarditis: presence of heart murmurs

24

What is the mechanism of azotemia in pre-renal causes?

Reduced renal blood flow > less blood is delivered to the kidney > less urea filtered
(Anything that causes a decrease in functional blood volume (low blood pressure))

25

Pre-renal causes of AZOTEMIA

• Congestive heart failure
• Shock
• Hemorrhage
• Dehydration
• High-protein diet
• Increased catabolic states (e.g. fever, major illness, stress)

26

Why does decreased renal function (glomerular filtration) lead to increased blood urea?

Poor excretion

27

Renal causes of AZOTEMIA

• Acute & chronic renal failure
• Glomerulonephritis
• Nephrotic syndrome
• Tubular necrosis
• Other intrinsic renal diseases

28

Post-renal causes of AZOTEMIA are usually due to

Obstruction of renal flow (renal calculi/kidney stones)
• Tumors of the bladder or prostate
• Severe infections (UTI)

29

T or F: BUN is more susceptible to non-renal functions

True

30

Reference ranges for BUN

Reference range: 7–18 mg/dL