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HYPOPHOSPHATEMIA & HYPERPHOSPHATEMIA

Hypophosphatemia is an electrolyte imbalance where there is a decrease in the serum phosphate level that is less than the normal range.

It is recognized most often in critically-ill patients, decompensated diabetics, alcoholics or other malnourished persons, and acute infectious or pulmonary disorders.

It may be transient and reflect intracellular shift with minimal clinical consequences.

Hyperphosphatemia is an electrolyte disturbance in which an increase in the serum phosphate level of more than the normal range is present.

Most symptoms of acute hyperphosphatemia are due to secondary hypocalcemia.

The significant level of hyperphosphatemia in adults is >6 mg/dL.

Introduction

Hypophosphatemia is recognized most often in:
  • Critically-ill patients
  • Decompensated diabetics
  • Alcoholics or other malnourished persons
  • Acute infectious or pulmonary disorders
  • Patients who are in IV hyperalimentation without phosphate supplementation
  • Patients w/ urinary phosphate-wasting syndromes (eg Fanconi syndrome or tumor-induced osteomalacia)

Hyperphosphatemia

  • Defined as an electrolyte disturbance in which an increase in the serum phosphate level of more than the normal range is present

Etiology

Hypophosphatemia 

  • More pronounced when there is underlying phosphate depletion (eg hyperparathyroidism,vitamin D deficiency, alcoholism & glycosuria)
  • Mechanisms that may cause hypophosphatemia:
    • Increased urinary losses due to impaired intestinal absorption
    • Redistribution of phosphate from extracellular fluid into the intracellular space or the mineral phase of bone
    • Severe & selective deprivation of dietary phosphate that rarely occurs

Hyperphosphatemia

  • Decreased Renal Phosphate Excretion
    • Renal failure
    • Hypoparathyroidism
    • Pseudohypoparathyroidism
    • Familial tumoral calcinosis
    • Bisphosphonate therapy
    • Vitamin D intoxication
    • Acromegaly
    • Mg deficiency
  • Others
    • Acid-base disorders
    • Crush injuries
    • Fulminant hepatitis
    • Rhabdomyolysis
    • Artifactual due to hemolysis
    • Extracellular shift from intracellular compartment
    • Chronic Heparin therapy

Signs and Symptoms

Hypophosphatemia
Mild
  • Usually asymptomatic
Moderate-Severe
  • Confusion
  • Irritability
  • Apprehension
  • Fatigue
  • Myalgia & myopathy
  • Muscle weakness
  • Numbness
  • Paresthesia
  • Rhabdomyolysis
  • Seizures
  • Coma
  • Reversible respiratory failure
  • Impairment of cardiac contractility
  • Cardiomyopathy
  • Hemolysis
  • Thrombocytopenia
  • Impaired phagocytosis
  • Metabolic encephalopathy
  • Rickets & osteomalacia
Hyperphosphatemia
Acute - 
Most symptoms are due to secondary hypocalcemia
  • Hypocalcemia
  • Neuromuscular irritability/muscle cramps
  • Tetany
  • Paresthesias
  • Seizures
  • Hypotension
  • Cardiac arrhythmia

Chronic - Persistent hyperphosphatemia (>12 hours) that usually occurs in patients w/ chronic renal failure & familial tumoral calcinosis

  • Normocalcemia
  • Nephrocalcinosis
  • Soft tissue or vascular calcification
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