Hypophosphataemia

1. Is the patient unwell?

• ABCDE approach 

2. Is the result a true value?

• Could the sampling method have affected the result?
• Is there a previous level?

3. Does the patient have any symptoms or signs?

• May indicate the significance and rapidity of electrolyte change
• Muscle weakness, dysphagia, ileus, respiratory failure, haemolysis, impaired phagocytosis, irritability, confusion, coma

4. Are there culprit drugs? - consider stopping them

• Adrenaline, alcohol, phosphate binders, thiazide diuretics, IV Iron

5. Causes? - treat them

• Alcoholism and malnutrition, chronic diarrhoea, malnutrition, sepsis, hyperparathyroidism, vitamin D deficiency, refeeding syndrome, haemodialysis and renal replacement therapy

Note - do not give at same time as calcium replacement - risk of calciphylaxis

Severe (PO₄^3- <0.3 mmol/L OR symptoms)

• 50 mmol (500 ml) phosphate polyfusor at 22 ml per hour (each polyfusor contains 81mmol phosphate)
• Check other electrolytes- often associated with other electrolyte derangement
• Recheck phosphate and calcium after infusion
• If malnutrition is the cause – risk refeeding syndrome – do not start feeding until hypophosphataemia corrected

Moderate (PO₄^3- 0.3-0.59 mmol/L)

• Phosphate Sandoz 1-2 tablets three times daily for 3 days (note each tablet contains 16.1 mmol phosphate and 20.4 mmol sodium)
• Check other electrolytes- often associated with other electrolyte derangement
• Recheck phosphate after 3 days
• If malnutrition is the cause – risk refeeding syndrome – do not start feeding until hypophosphataemia corrected

Note - oral phosphate can worsen diarrhoea - consider IV phosphate in patients with diarrhoea, malnutrition, or ileostomies

Mild (PO₄^3- 0.6-0.79 mmol/L)

• No treatment required

Seek senior advice if concerns and in particular if:

• Renal impairment (acute or chronic) - phosphate replacement needs to be undertaken with caution in this patient group
• Sodium >150 mmol (phosphate polyfusors contain a significant amount of sodium)

Cardiac monitoring or HDU review?

• Cardiac monitoring is not needed specifically for hypophosphataemia. HDU review needed only if clinical concern and ONLY if patient a candidate for escalation of care