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nonprotein nitrogen
SCC chemistry
Question | Answer |
---|---|
List the NPN constituents found in the blood (4) | Urea, creatinine, uric acid and ammonia |
How are NPN compounds formed? | The majority of them arise from the breakdown of proteins and nucleic acids. |
Which of the NPN makes up the largest fraction? | Urea |
In which organ of the body are NPN synthesized? | Liver |
5. What term is given to urea plasma measurements? | BUN |
6. What does BUN stand for? | Blood Urea Nitrogen |
7. Define azotemia | an ELEVATED level of urea in the blood |
7. Define Uremia | VERY HIGH levels of urea accompanied by renal failure |
Prerenal azotemia is caused by what? | Reduced renal blood flow. Less blood to the kidneys means less urea is filtered anything that causes decrease in blood volume contributes to this: heart failure, shock hemmorrage, dehydration |
Decreased renal function causes what? | Causes an increase in plasma urea concentration due to compromised urea excretion |
what is the reference interval (normal pat. reference range) for BUN/Creatinine? | Normally 10:1 to 20-1 |
What analytical methods are used to measure BUN levels? | enzymatic method, indicator dye, conductimertric |
what is the enzymatic methods that are used to measure BUN levels | urease reaction coupled wit L-glutamate dehydrogenase (GLDH) to quantify ammonium ions |
what is the indicator dye method to measure BUN levels | urese +pH indicator, this is used in instruments using liquid reagents, a multilayer film format and reagent strips |
what is the conductimetric method that is used to measure BUN levels | an electrode that is used to measure the amount of ammonium ions that are produced from urea |
11. What is the reference interval (normal patient reference range) for BUN? | 7-18 mg/dL |
Where does creatinine come from? | Creatine is synthesized in the liver, and broken down to form creatinine. |
13. Plasma creatinine levels are related to three sources. What are they? | Plasma levels of creatinine are related to the relative muscle mass, the rate of creatine turnover, and renal function. |
14. What is the creatinine test that measures renal function (glomerular filtration)? | creatinine clearance |
What does "clearance of a substance" mean? | The clearance of a substance is “the volume of plasma from which that substance is cleared per unit time.” |
What is the creatinine clearance formula | CrCl = UCr x VU / PCr x t |
What are the reported units of measure for creatinine clearance tests? | - mL/minute and is corrected for body surface |
17. Why are creatinine clearance test results corrected for muscle mass? | Creatinine levels are related to muscle mass men have more (typically) then men, the more fit the more mass vs. obese....etc |
18. What is the most common analytical method used to measure plasma creatinine levels? | Jaffe reaction |
What is the Jaffe reaction | In this reaction creatinine reacts with picric acid. |
19. What is the reference interval (normal patient reference range) for creatinines? | • Males: 0.9-1.3 mg/dL • Females: 0.6-1.1 mg/dL |
20. Where does uric acid come from? | Uric acid is formed from the breakdown of purines. |
21. Where do purines come from? | Purines come from the breakdown of nucleic acids or from tissue destruction. Purines are converted to uric acid in the liver. |
22. What three major disease states are associated with elevated uric acid levels? | • gout, • increased catabolism of nucleic acids, and • renal disease |
23. Define hyperuricemia. | Increased level of uric acid in the plasma |
24. What analytical methods are used to measure uric acid? | • Uricase (enzymatic method) • Coupled enzymatic method using either catalase or peroxidase |
25. What is the reference interval (normal patient reference range) for uric acid? | • Male: 3.5-7.2 mg/dL • Female: 2.6-6.0 mg/dL |
26. Where does ammonia come from? | The breakdown of amino acids (proteins) |
27. What two clinical conditions are associated with elevated ammonia levels? | Hepatic failure and Reye's syndrome |
28. What is the special handling requirement for ammonia levels? | placed IMMEDIATELY on ice to prevent brkdown of amino acids which would cause ammonia levels to rise. Seperate plasma and assayed ASAP or frozen. |
29. What is the reference interval (normal patient reference range) for ammonia? | 19-60 μg/dL |