Phosphate Abnormalities In ICU

Hypophosphataemia:

• Incidence is 60–80% of septic ICU patients.
• Mortality increases 30% in patients with severe hypophosphataemia (< 0.32 mmol/L).

Clinical presentation of hypophosphataemia can include:

• Confusion, coma, seizure.
• CCF
• Respiratory failure.
• Shift of Hb-dissociation curve left (hypoxia).
• Haemolysis, rhabdomyolysis.

Treatment of hypophosphataemia:

Intravenous replacement is recommended for severe hypophosphataemia.

• Potassium phosphate: 1 mmol/mL phosphate and 2 mmol/mL potassium.
  • 0.15–0.6 mmol/kg/day, IV, over 6 hours.
  • Dilute to ratio 1:4 (potassium phosphate:0.9% sodium chloride).
  • Repeat at 6 hourly intervals until phosphate > 0.6 mmol/L.

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Note:
Rate limiting fact will usually be potassium concentration/rate.

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•  Example: 20 kg child:
  0.15 x 20 kg = 3 mmol/day = 3 mL KP04.
  i.e. add 3 mL KP04 to 12 mL normal saline over 6 hours (3 mL/hour).
  = 0.05 mmol/kg/hour potassium.
  = 0.025 mmol/kg/hour phosphate.

Hyperphosphataemia:

Clinical presentation of hyperphosphataemia:

• Decreased mental status.
• Seizures (secondary to hypocalcaemia).
• Weakness, tetany (secondary to hypocalcaemia).
• ECG changes: prolonged QT, polymorphic VT, Torsade de pointes (secondary to hypocalcaemia).
• Anorexia, nausea, vomiting.
• Soft tissue deposition of calcium-phosphate product – renal dysfunction.
• Metabolic acidosis, hypomagnesaemia.

Management of hyperphosphataemia:

1. Treat the underlying cause.
2. Fluid administration (rhabdomyolysis/tumor lysis).
3. Reduce phosphate intake.
4. Phosphate binders (calcium carbonate).
5. Refer and consult with specialist for consideration for haemodialysis.

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 Standard Treatment Guidelines And Essential Medicines List For South Africa, Hospital Level, Paediatrics, 2023 Edition

Chapter 23: Paediatric Intensive Care,  23.6 Electrolyte Abnormalities,  23.6.5 Phosphate Abnormalities In ICU