Makindo Medical Notes

Related Subjects: | Calcium Physiology | Hypophosphataemia | Hyperphosphataemia

About

• Phosphorus, primarily present in the body as phosphates or esters, plays a crucial role in various biological functions.
• It is an essential component of key molecules such as DNA, RNA, and certain vitamins.
• Phosphates are integral to energy production processes like glycolysis and oxidative phosphorylation.
• The concentration of phosphate in the body is tightly regulated by:
  • Calcium levels
  • Parathyroid hormone (PTH)
  • Vitamin D
  • Renal function
• Nutritionally depleted individuals have an increased phosphate requirement and are at a higher risk of developing clinically significant hypophosphataemia.

Management of Hypophosphataemia

• When to Replace Phosphate:
  • Serum phosphate < 0.32 mmol/L: Immediate replacement is required, as this level is considered severe and can lead to complications such as muscle weakness, respiratory failure, or cardiac dysfunction.
  • Serum phosphate 0.32–0.8 mmol/L: Replace phosphate in symptomatic patients or those with risk factors (e.g., malnutrition, alcoholism, critical illness).
  • Serum phosphate > 0.8 mmol/L: Replacement is usually not required unless the patient is symptomatic.
• Oral Replacement:
  • First-line treatment in mild to moderate hypophosphataemia.
  • Common preparations include:
    • Phosphate supplements (e.g., sodium phosphate, potassium phosphate).
    • Dosage: 30–60 mmol/day, divided into 2–3 doses.
  • Encourage dietary intake of phosphate-rich foods such as dairy products, meats, nuts, and whole grains.
• Intravenous Replacement:
  • Indicated for severe hypophosphataemia (<0.32 mmol/L), symptomatic patients, or those unable to tolerate oral supplementation.
  • Common IV formulations include potassium phosphate or sodium phosphate.
  • Typical dose: 0.08–0.16 mmol/kg over 6–12 hours, adjusted based on severity and renal function.
  • Administer slowly to avoid complications such as hypocalcaemia, hyperkalaemia, or hyperphosphataemia.

Monitoring and Precautions

• Regularly monitor serum phosphate, calcium, potassium, and magnesium during replacement therapy.
• Be cautious in patients with renal impairment, as they are at higher risk for hyperphosphataemia and associated complications.
• Consider stopping phosphate replacement once serum levels normalize to prevent overcorrection.