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Flashcards in Non-Protein Nitrogens Deck (29)
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1

nitrogen compounds

protein
nucleic acids
non-protein nitrogen plasma concentrations

2

non-protein nitrogens

urea 45-50%
amino acids 25%
uric acid 10%
creatinine 5%
ammonia 0.2%

3

Blood Urea Nitrogen (BUN)

manipulation of ammonia from the break down of protein, conjugated into urea in liver
filtered by renal tubules w/ partial reabsorption
cannot be used in clearance testing bc of reabsorption

4

BUN concentration depends on

renal function - if damaged BUN will be high
perfusion - sluggish blood flow BUN will be high
protein content of the diet
rate of protein catabolism

5

azotemia (BUN increase)

pre-renal conditions
renal conditions
post renal conditions

6

Pre-renal conditions for BUN increase

increased protein degradation - increase protein in diet, stress, fever, major illness, cortisol therapy
decreased blood flow through kidney- dehydration etc

7

renal conditions for BUN increase

kidney diseases
inflammations

8

post-renal conditions for BUN increase

blockages, obstructions
severe infections of kidney
tumors of bladder

9

reasons for BUN decrease

low protein intake
severe liver disease
late in pregnancy
infancy
not as significant as increased BUN

10

BUN/ Creatinine ratios

normal ratio : 10-20
pre-renal BUN/creatinine increase ratio -creatinine is normal & BUN value is elevated
renal BUN/creatinine ratio normal- both markers are elevated but ratio is normal
post-renal BUN/creatinine ratio increased - rise in both but more in BUN
low protein diet - decreased ratio

11

BUN analysis

coupled enzymatic reation - urease
patient's urea + urease enzyme --> ammonia & carboxyl group
ammonia -(GLDH)-> NAD+
NAD is read at 340 nm to get BUN concentration

12

BUN electrode method

urease breaks urea into ammonia & ammonia ions change conductivity of electrod
meter reads change in potential between standard & patient sample
calculates BUN in mg/dL

13

BUN specimens

avoid ammonia, Na-citrate, Na-fluoride in samples
don't need to be fasting
avoid bacterial contamination ( produce urease)
use plasma or serum
urines need to be diluted by 10

14

Uric Acid

nucleic acid breakdown of purines (Adenine & guanine)
eliminated :
70% out kidneys
30% our GI

15

hyperuricemia

elevated uric acid
gout- joint inflammation, uric acid crystals
F-1-PA: fructose 1 phosphate aldolase deficiency will cuase an increase in uric acid
Lesch-nyhan syndrome -missing HGPRT & cannot break down nucleic acids in a way that they can be reuesd

16

hypouricemia

decreased uric acid
fanconi's syndrome- tubule defect in the kidney & cannot reabsorb uric acid
drugs interfere w/ degradation process of nucleic acids & do not allow for uric acid to be formed

17

Uric Acid analyzer methods

enzymatic method using uricase
uric acid from patient + uricase -> allantoin + peroxide+ co2
peroxidase reaction to make color rx
interference for peroxidase :
ascorbic acid, bilirubin etc

18

Uric Acid specimens

use heparinized plasma or serum NO EDTA
drugs like aspirin & thiazides - increase uric acid
lipemia, increased bilirubin, hemolysis etc- decrease uric acid due to interference

19

creatinine

produced from creatine degradation in muscle tissue
creatinine level depends on muscle mass
plasma creatinine is inversely related to GFR

20

eGFR

estimated GFR which accounts for age, gender, ethnicity
better indicator for early kidney disease

21

Creatinine levels (low & high)

low levels are not significant in normal patients
high levels associated w/ increased blood creatinine & decreased GFR
although kidneys can have a 50% loss before any inrease in creatinine levels appear

22

methods for creatinine analysis

kinetic jaffe reaction
colorimetric jaffe reaction
enzymatic reaction -automated methods
IDMS - isotope dilution mass spectroscopy

23

Creatininease reaction

patient's creatinine + creatininase enzyme -> creatine
creatine + CK -> phosphorylated creatine + PK -> pyruvate + LD -> NADP+ which is read at 340 nm

24

Creatinine specimen

use plasma, serum, or urine
avoid hemolysis, icteric (high bilirubin) samples
fasting not required
high protein diet can cause transient increase in creatinine concentration
refrigerate urines - cut bacterial contamination

25

sources of error in creatinine reaction

ascorbate, glucose, alpha keto acids, uric acid
bilirubin - negative bias in reactions
ascorbate interferes w/ peroxidase rx
cephalosporin - increases creatinine levels in jaffe reactions
dopamine & liodcaine - cause positive bias in enzymatic reactions

26

Creatinine clearance calculation

VU/Px1.73/A
V- 24 hour urine volume
U-urine creatinine
P-plasma creatinine
A- body surface in meters2

27

BUN range

7-18 mg/dL

28

Creatinine range

male - 0.9-1.5 mg/dL
female - 0.7-1.3 mg/dL

29

uric acid range

male - 3.5-7.2 mg/dL
female - 2.6-6.0 mg/dL