NPNs Flashcards
what is the kidney’s function?
excrete undesirable end products of metabolism such as NPNs: urea (BUN), creatinine, uric acid, and also excrete organic acids and amino acids. It also maintains body homeostasis and has an endocrine function.
How does the kidney maintain body homeostasis?
electrolyte balance
acid base balance
water balance
What is the kidney’s endocrine function?
primary: renin, erythopoeitin, and prostaglandins
secondary: produce vit d3
what are NPN compounds?
catabolism of proteins and nucleic acids result in the formation of so-called NPN compounds. Some of these metabolic products are derived from exogenous or endogenous proteins.
What does catabolism of proteins form?
urea
What does catabolism of purines form?
uric acid
What does catabolism of creatine and creatine phosphate form?
creatinine
What is Urea?
Blood urea nitrogen, >75% of NPN excreted in urine is urea
what is the greatest type of NPN that is excreted in urine?
urea, it accounts for more than 75%
Where is biosynthesis of urea carried out?
in the liver
Production of urea is dependent on several variables, what are they?
hight protein diet, hepatic function, increased protein catabolism (like muscle wasting–starvation), over hydration = urea excretion is increased, post renal obstruction. bacteria in urine causes decreased urea.
What is urea considered a measurement of?
renal function.
What are the expected values for urea?
plasma= 5-20, critical is over 100
What can cause increased BUN levels?
CHF, shock, hemorrhage, dehydration, renal impairment, renal failure, stones, tumors of bladder or prostate, severe infection, fever, stroke, major illness.
What causes decreased BUN levels?
low protein diet, malnutrition, newborn, severe hepatic insufficiency, severe vomiting or diarrhea, over hydration.
What are the normal ranges for BUN and what do they correlate with?
<8-10= overhydration 5-20= normal 20-26= dehydration 50-150 = implies impairment of GFR 150-250= extreme impairment
What is creatinine?
creatine is synthesized mainly in the liver and then transported in blood to other organs such as muscle and brain where it is phosphorylated to phosphocreatine, a high energy compound. A portion of creatine is muscle spontaneously and irreversibly converts to creatinine.
does the amount of creatinine vary greatly from day to day?
no, based on muscle mass
clinical application of creatinine: a test of renal function.
creatinine levels are a useful index of renal function, primarily GFR
What are CrCl tests used for?
to eval the GFR and to eval when administering nephrotoxic drugs.
As renal function decreases, what happens to GFR?
it decreases, and then the CrCl decreases.
What is normal GFR? what is end stage renal failure?
125-152, less than 5
What is Uric Acid?
it is the the major end product of purine nucleotide catabolism The conversion of purine nucleotides occurs in the liver.
What do plasma uric acid levels vary with?
dietary intake, renal disease, excess purine synthesis
