Serum Creatinine

Definition

A quantitative analysis of serum creatinine levels, the serum creatinine test provides a more sensitive measure of renal damage than do blood urea nitrogen levels because renal impairment is virtually the only cause of creatinine elevation.

Creatinine is a non-protein end product of creatinine metabolism that appears in serum in amount proportional to the body’s muscle mass.

Purpose
  • To assess glomerular filtration.
  • To screen for renal damage.
Procedure
Patient Preparation
  1. Confirm the patient’s identity using two patient identifiers according to facility policy.
  2. Explain to the patient that the serum creatinine test is used to evaluate kidney function.
  3. Tell the patient that the test requires a blood sample.
  4. Explain to the patient that he may experience slight discomfort from the tourniquet and the needle puncture.
  5. Instruct the patient that he doesn’t need to restrict food and fluids.
  6. Notify the laboratory and the practitioner of medications the patient is taking that may affect test results; they may need to be restricted.

Serum Creatinine

Implementation
  1. Perform a venipuncture and collect the sample in a 3 or 4 ml clot activator tube.
  2. Handle the sample gently to prevent hemolysis.
  3. Send the sample to the laboratory immediately.
Nursing Interventions
  1. Send the sample to the laboratory immediately.
  2. Apply direct pressure to the venipuncture site until bleeding stops.
  3. Assess the venipuncture site for hematoma formation; if one develops, apply pressure.
  4. Inform the patient that he may resume his usual medications that were discontinued before the test, as ordered.
Interpretation
Normal Results
  • In men, 0.8 to 1.2 mg/dl (SI, 62 to 115 pmol/L)
  • In women, 0.6 to 0.9 mg/dl (SI, 53 to 97 pmil/L)
Abnormal Results
  • Elevated levels generally indicate renal disease that has seriously damaged 50% or more of the nephrons.
  • Elevated levels may also indicate gigantism and acromegaly.
Interfering Factors
  • Ascorbic acid, barbiturates, and diuretics that may possibly increase.
  • Exceptionally large muscle mass, such as found in athletes that may possibly increase despite normal renal function.
  • Phenolsulfonphthalein given within the previous 24 hours (possible increase, if the test is based on Jaffe’s reaction.
Complications
  • Hematoma to the puncture site.
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