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HYPOPHOSPHATEMIA & HYPERPHOSPHATEMIA
Hypophosphatemia is recognized most often in critically-ill patients, decompensated diabetics, alcoholics or other malnourished persons, and acute infectious or pulmonary disorders.
A decrease in serum phosphate should be distinguished from a decrease in total body storage of phosphate.
Hypophosphatemia may be transient and reflect intracellular shift with minimal clinical consequences.
Most symptoms of acute hyperphosphatemia are due to secondary hypocalcemia.
The significant level of hyperphosphatemia in adults is 5 mg/dL.

Principles of Therapy

Hypophosphatemia:
  • Presence of signs & symptoms suggestive of phosphate deficiency
    • Most important consideration 
  • Estimated severity of cellular phosphate deficit
  • Overall clinical status of the patient
  • Renal insufficiency, simultaneous administration of intravenous (IV) glucose or hyperalimentation solutions
  • Risk of aggravating coexistent hypocalcemia
Hyperphosphatemia
  • Resolve underlying cause
  • Resolution of symptoms
  • Serum Ca level w/in the low reference range

Pharmacotherapy

Hypophosphatemia

Phosphate intravenous (IV)

  • In patients w/o severe renal insufficiency or hypocalcemia, IV phosphate at a rate of 2-8 mmol/hour of elementalphosphorous over 4-8 hours often corrects hypophosphatemia w/o inducing hyperphosphatemia or hypocalcemia
  • Monitor serum Ca & phosphate every 6-12 hours during & after phosphate therapy
  • Recurrent hypophosphatemia w/in 24-48 hours of apparently successful replacement may require additional infusions

Hyperphosphatemia

Oral binders

  • Administered to decrease gastrointestinal (GI) absorption of phosphorous
  • Ca-containing phosphate binders may increase Ca-phosphate product & induce vascular calcium deposition
  • Resin binders promote excretion of phosphorous w/o affecting Ca
  • Avoid aluminum-containing phosphate binders in patients w/ renal failure

Diuretics

  • Those that act on the proximal tubules (eg Acetazolamide) may be considered to promote renal phosphate excretion

Non-Pharmacological Therapy

Hypophosphatemia

  • In most asymptomatic patients, serum phosphate level spontaneously normalizes w/in several days when factors that trigger hypophosphatemia are corrected
  • Dairy products supply absorbable Ca that help avoid hypocalcemia that may result from more aggressive replacement therapies

Hyperphosphatemia

Dialysis

  • Hemodialysis or peritoneal dialysis is indicated for severe refractory cases & for patients w/ renal failure

Gastric lavage

  • May be performed in toxic ingestions
  • Oral phosphate binders are given to prevent further absorption
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