Page 378 - Critical Care Nursing Demystified

Chapter 8 CARE OF THE PATIENT WITH CRITICAL RENAL NEEDS 363

Blood urea nitrogen (BUN) – Serum level that increases with decreased
blood flow to the kidney, which causes more urea to be absorbed and less to
be excreted in the blood. Value will also rise in high protein diets and prer-
enal failure and is therefore not the best reflection of kidney damage. Normal
value is 5 to 25 mg/dL.
Complete blood cell count (CBC) – Red blood cell (RBC) counts, hemo-
globin, and hematocrit are all low in chronic renal failure due to lack of
erythropoietin stimulation. RBCs are needed to help with oxygenation of
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the tissues. Normal values are RBC (4.2–5.9 million/mm ), hemoglobin
(12–17 g/dL), hematocrit (36%–52%).
White blood cell counts (WBCs) – Needed to fight infection. Elevated with
urinary tract infection (UTI), peritonitis, and transplanted kidney rejection.
Normal value 5,000 to 10,000/mm .
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Creatinine clearance – Most accurate measure of GFR. Values below normal
show 50% loss of nephron functioning. Normal value is 85 to 135 mL/min.
Fractional excretion of sodium (FENa) – Assesses how well kidneys concen-
trate urine and conserve sodium. Normal value is less than 1%.
Glomerular filtration rate (GFR) – Rate at which the urinary filtrate is
formed. Usually 125 mL/min. Downloaded by [ Faculty of Nursing, Chiangmai University 5.62.158.117] at [07/18/16]. Copyright © McGraw-Hill Global Education Holdings, LLC. Not to be redistributed or modified in any way without permission.
Serum calcium – Major components of bone and teeth. Found intravascularly
playing strong roles in blood clotting, muscular contraction, and nerve impulse
transmission. Usually low in patients in acute and chronic renal failure. Con-
trolled by parathyroid and thyroid glands. Normal value 8.5 to 10.5 mg/dL.
Serum chloride – Major anion in the extracellular fluid. Important in acid-base
balance, this level will increase when HCO levels drop. Elevation suggests meta-
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bolic acidosis reflective of chronic renal failure. Normal value 96 to 115 mEq/L.
Serum osmolality – Reflects concentration of solutes in the serum. Normal
value 275 to 295 mOsm/kg. Elevation in osmolality suggests dehydration
while a drop suggests fluid overload.
Serum phosphorus – Found mostly in bone. Assists with ATP and acid-base
balance. Moves the opposite of calcium in the serum so when calcium is low,
phosphorus is high. Regulated by parathyroid-stimulating hormone. Usually
high in renal failure. Normal value 2.5 to 4.5 mg/dL.

Serum potassium – Most common intracellular cation. Liberated with cell
wall rupture. Also retained in renal failure, causing serious cardiac effects.
Normal value 3.5 to 5.0 mEq/L.
Serum magnesium – Important in many enzymatic actions like carbohydrate
and protein synthesis and contraction of muscle tissue. Magnesium and