Download Serum Creatinine Measuring serum creatinine is a useful and

Serum Creatinine
Measuring serum creatinine is a useful and inexpensive method of evaluating
renal dysfunction. Creatinine is a non-protein waste product of creatine
phosphate metabolism by skeletal muscle tissue. Creatinine production is
continuous and is proportional to muscle mass.
Creatinine is freely filtered and therefore the serum creatinine level depends on
the Glomerular Filtration Rate (GFR). Renal dysfunction diminishes the ability
to filter creatinine and the serum creatinine rises. If the serum creatinine level
doubles, the GFR is considered to have been halved. A threefold increase is
considered to reflect a 75% loss of kidney function.
Reference values for serum creatinine:
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Adult males: 0.8 - 1.4 mg/dl: values are slightly higher in males due to
larger muscle mass
Adult females: 0.6 - 1.1 mg/dl: creatinine clearance is increased in
pregnancy, resulting in lower serum levels
Children: 0.2 - 1.0 mg/dl: slight increases with age because values are
proportional to body mass
A panic value for creatinine is 10 mg/dl in nondialysis patients.
Increased serum creatinine levels are seen in:
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Impaired renal function
Chronic nephritis
Urinary tract obstruction
Muscle diseases such as gigantism, acromegaly, and myasthenia gravis
Congestive heart failure
Shock
Decreased creatinine levels may be seen in: the elderly, persons with small
stature, decreased muscle mass, or inadequate dietary protein. Muscle atrophy
can also result in decreased serum creatinine level. If muscle atrophy is
suspected, assessment of serum creatine, an important enzyme necessary for
normal muscle function, is done.
The only important pathological condition that causes a significant increase in
the serum creatinine level is damage to a large number of nephrons. Unlike the
BUN, the serum creatinine level is not affected by hepatic protein metabolism.
Tests to measure serum creatinine, urine creatinine, and creatinine clearance are
all used only to evaluate renal function. Only renal dysfunction changes the
results. The serum creatinine level does not rise until at least half of the
kidney's nephrons are destroyed or damaged. Because creatinine levels rise and
fall more slowly than BUN levels, creatinine levels are often preferred to
monitor renal function on a long-term basis.
Serum creatinine and Blood Urea nitrogen (BUN) are often compared to
evaluate renal function. While serum creatinine increases only with nephron
damage, the BUN is affected by hydration, hepatic metabolism of protein and
reduced GFR. The mean ratio of serum creatinine to the BUN should be
approximately 1:10.
NEPHROTOXIC
DRUG
REDUCE TOXICITY
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ACE inhibitors
ACYCLOVIR
Aminoglycosides
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Avoid bolus dosing
Use IV hydration
Titrate dose to
renal function
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Check levels
Correct potassium
levels
Give only one
daily dose
Titrate to renal
function
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Amphotericin B
Caution in
hypovolemia
Avoid in bilateral
renal artery
stenosis

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Titrate dose to
renal function
IV normal saline
hydration
Liposomal
formulation less
toxic

IV normal saline
hydration

Titrate dose to
renal function
Avoid
erythromycin,
verapamil,
ketoconazole
Cisplatin

Cyclosporin
Indinavir
Interleukin-2
Intravenous
contrast


Hydrate
maintain high urine
output


IV hydration
Possible albumin
infusion

IV normal saline
hydration
Possible
acetylcysteine

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Lithium

Titrate dose to
renal function
Possible Amiloride
The kidney's properties of high blood flow, filtration, reabsorption and
concentration allow nephrotoxins to accumulate. A patient's BUN and
creatinine should always be checked before giving nephrotoxic drugs. If either
level is above the normal range, the drug should be held and the patient's
physician should be contacted.
The commonly prescribed aminoglycoside antibiotics have both potential
nephrotoxic and ototoxic effects. The impaired hearing or dizziness that may
result from ototoxity is more likely if the drug is continued when there is renal
dysfunction. It is also important to keep the patient well hydrated when
aminoglycoside antibiotics are given because they are excreted almost
unchanged in the urine.