C12 Non-Protein Nitrogens

Question 1

What are NPNs?

Answer 1

Increased in renal failure and are commonly ordered as blood tests to check renal function

Question 2

Most important NPNs?

Answer 2

BUN, Creatinine, Uric Acid, and Ammonia

Question 3

BUN

Answer 3

Blood Urea Nitrogen, 50% of NPNs, urea, filtered by glomerulus but also aborbed by renal tubules (40%), some is lost through the skin and GI tract (<10%)

Question 4

Urea

Answer 4

by product of protein catabolism which produces ammonia

Question 5

Ammonia

Answer 5

very toxic- converted to urea by the liver

Question 6

Liver converts ammonia and CO2 into?

Answer 6

urea

Question 7

Plasma BUN is affected by?

Answer 7

renal function, dietary protein, and protein catabolism

Question 8

Azotemia

Answer 8

elevated plasma BUN

Question 9

Prerenal (increased) BUN- not related to renal function

Answer 9

low bp, decreased flow to kidney, increased dietary protein or protein catabolism
increased BUN/normal creatinine

Question 10

Prerenal (decreased) BUN- not related to renal function

Answer 10

decreased dietary protein, increased protein synthesis (pg women and children)

Question 11

Renal causes of (increased) BUN

Answer 11

renal disease with decreased glomerular filtration (glomerular nephritis, renal failure from DM)

Question 12

Post renal cause of (increased) BUN-not related to renal function

Answer 12

obstruction of urine flow- kidney stones, tumors, UTIs

increased BUN/increased creatinine

Question 13

Renal decreased BUN

Answer 13

low dietary protein or severe liver disease

decreased BUN/normal creatinine

Question 14

Creatinine

Answer 14

formed at a constant rate by the muscles as a function of muscle mass, removed from plasma by glomerular filtration, not secreted/absorbed by the renal tubules

Question 15

Liver

Answer 15

Amino acids>creatinine

Question 16

Muscles

Answer 16

Creatinine>phosphoscreatinine

phosphocreatinine>creatinine

Question 17

Plasma creatinine?

Answer 17

function of glomerular filtration, unaffected by other factors, its a very good test to evaluate renal function

Question 18

delta check

Answer 18

significant change from previous results

Question 19

Jaffee Method

Answer 19

creatinine analytical technique
Creatinine+Picrate Acid>colored chromogen
Specimen-plasma/serum
elevated bilirubin and hemolysis causes falsely decreased results (everyone uses this technique)

Question 20

Uric Acid

Answer 20

breakdown product of purines (nucleic acid/DNA), converted from liver, filtered by glomerulus (98-100% reabsorbed)

Question 21

Elevated plasma uric acid?

Answer 21

can promote formation of solid uric acid crystals in joints and urine

Question 22

Uric acid diseases?

Answer 22

Gout (increased plasma uric acid, acid crystals in joints, associated with alcohol consumption, may also form kidney stones)
Leukemias and lymphomas
Megaloblastic anemias
renal disease

Question 23

Uric acid absorbs light at?

Answer 23

293 nm, rate of decreased absorption is proportional to the uric acid concentration

Question 24

Ammonia

Answer 24

produced from the deamaination of amino acids, bacterial enzymatic conversion of GI tract protein, muscle catabolism

Question 25

Causes of increased ammonia

Answer 25

liver disease, Reye's syndrome, sever renal disease, genetic enzyme dificiencies of the urea cycle, Valproic acid (anti-seizure medications)

Question 26

Ammonia analytical technique

Answer 26

decreasing absorbance @340 nm proportional to the ammonia concentration EDTA/Heparinized whole blood on ice, delayed testing causes false increase values

Question 27

Creatinine clearance

Answer 27

calculated measurement of the rate at which creatinine is removed from the plasma by the kidneys, measurement of glomerular filtration

Question 28

Creatinine is?

Answer 28

an endogenous substance (not affected by diet), filtered by glomerulus but not secreted or reaborbed by renal tubules

Question 29

Creatinine clearance specimens?

Answer 29

24 hr urine specimen | plasma/serum creatinine collected during the urine collection

Question 30

Creatinine Clearance Formula

Answer 30

(UV//P)(1.73/A) U=creatinine concentration of the 24 hr urine (mg/dl) V=24 hr urine volumes, V=V/1440=ml/min P=plasma creatinine concentration (mg/dl) A=correction factor accounts for differences in BMI