Clinical

• Laboratory tests

  Can provide useful information for clinicians for the diagnosis of a medical condition and for the monitoring of drug therapy
• Laboratory values


  Can help select the most safe and appropriate therapy for patients, in addition to aid in the monitoring of the selected therapy
• Although laboratory errors are fairly uncommon, they do occur
• Potential causes of laboratory errors could include technical errors, sample contamination, timing in which the lab value was taken, and medication interference
• Values shown in mmol/L units


  Are equivalent to mEq/L units for some ions when valence is 1, like Hydrogen and Potassium
• Always treat the patient, never the laboratory value
• Electrolytes and blood chemistries

  • Sodium
  • Potassium
  • Chloride
  • Calcium
  • Magnesium
  • Phosphate
• Sodium


  The most prevalent extracellular cation in the body, regulates serum osmolality, fluid balance, and acid-base balance
• Normal sodium values


  • 135-145 mEq/L
• Hyponatremia


  Serum sodium of less than 135 mEq/L
• Causes of hyponatremia


  • Replacement of lost solute with water
  • Edema from a relative increase in free body water
  • Certain drugs
• Hypernatremia


  Serum sodium of >145 mEq/L
• Potassium


  The main intracellular cation, plays a key role in nerve excitability, acid-base balance, and muscle function
• Normal potassium values


  • 3.5-5 mEq/L

  
• Hypokalemia


  K+ concentration < 3.5 mEq/L
• Causes of hypokalemia


  • Severe diarrhea
  • Alkalosis
  • Loop and thiazide diuretics
  • Insulin
  • β-agonist
  • Osmotic diuretics
• Hyperkalemia


  K+ concentration >5 mEq/L
• Causes of hyperkalemia


  • Acidosis
  • Renal failure
  • Certain drugs
• Chloride


  The principal extracellular anion which functions to serve a passive role in the maintenance of fluid balance and acid-base balance
• Normal chloride values


  • 96 -106 mEq/L
• Calcium

  Normal serum 8.5 - 10.5 mg/dL (includes ionized calcium and calcium bound to protein, primarily albumin, and ions)
• Ionized calcium


  4.4-5.3 mg/dL

  
• Hypocalcemia


  Serum calcium <8.5 mg/dL; ionized Ca2+ <4.4 mg/dL
• Causes of hypocalcemia


  • Hypoalbuminemia
  • Hypoparathyroidism
  • Hypomagnesemia
  • Renal failure, renal tubular necrosis
  • Vitamin D deficiency or impaired metabolism
• Hypercalcemia


  Serum calcium >10.5 mg/dL; ionized Ca2+ >5.3 mg/dL
• Causes of hypercalcemia


  • Hyperparathyroidism
  • Some malignancies
  • Medications
  • Immobilization
  • Hyperthyroidism
• Corrected calcium


  (0.8 x (4 – plasma albumin in g/dL)) + Serum Calcium
• Phosphorus


  Major intracellular anion; 85% of body stores found in bone
• Normal phosphorus values


  • 2.5 ‐ 4.5 mg/dL
• Hypophosphatemia


  Serum phosphate < 2.5 mg/dL
• Causes of hypophosphatemia


  • Impaired absorption
  • Medications
  • Alcoholism
  • Intracellular shifts
  • Refeeding syndrome
  • Increased losses
• Hyperphosphatemia


  Serum phosphate >4.5 mg/dL
• Causes of hyperphosphatemia


  • Decreased renal excretion
  • Hypoparathyroidism
  • Increased cellular release
  • Increased exogenous phosphorus load or absorption
  • Acidosis
• Magnesium


  Normal range 1.7–2.3 mg/dL
• Hypomagnesemia


  Serum magnesium concentration less than 1.7 mg/dL
• Causes of hypomagnesemia


  • Decreased absorption
  • Renal losses
  • Alcoholism malnutrition
  • Intracellular shift
  • Refeeding syndrome
• Hypomagnesemia is commonly associated with hypokalemia caused by increased renal loss of K+; correction of plasma potassium requires simultaneous correction of serum magnesium
• Hypermagnesemia


  Serum magnesium greater than 2.3 mg/dL
• Causes of hypermagnesemia


  • Acute or chronic renal failure
• Acidosis


  Any pH less than 7.35 indicates a primary acidosis