See also

Electrolyte abnormalities
Hypophosphataemia
Intravenous fluids

Key points

1. Hyperphosphataemia may be an asymptomatic laboratory finding
2. Cease any oral or intravenous products that contain phosphate
3. Assess for renal impairment (acute or chronic) in the presence of severe hyperphosphataemia
4. Specialist advice should be sought for symptomatic children with hyperphosphataemia

Background

• Approximately 85% of body phosphate is located in bones and teeth, 14% in cells and <1% in extracellular fluid
• Phosphate requirements depend on bone formation and growth rate. They are higher in childhood, especially in premature infants
• The terms serum phosphate and serum phosphorus are often used interchangeably. It is the phosphorus content of anionic plasma phosphate (PO₄^3-) that is measured
• Phosphate balance is closely related to calcium homeostasis
• Pseudo-hyperphosphataemia may result from ex vivo haemolysis eg due to difficult blood sampling/tourniquet

Causes of hyperphosphataemia

Assessment

Assess renal function (urine output, serum urea, electrolytes and creatinine) and check serum calcium and albumin levels. Severe hyperphosphataemia can lead to symptomatic hypocalcaemia

Identify underlying cause and correct where possible

• May be an asymptomatic laboratory diagnosis finding
• May relate to renal impairment
• Check timing of blood sampling in relation to recent intravenous phosphate infusions and whether the sample was taken from the same intravenous access as where the infusion was administered
• Repeat test if there is a clinical suspicion of sample haemolysis related to difficult blood sampling
• Ask about medications and supplements that may contain phosphate, including enemas

Assess for signs/symptoms

• Hyperphosphataemia in isolation is often asymptomatic
• Gastrointestinal: anorexia, nausea, vomiting
• Renal: acute or chronic kidney failure
• Cardiac: tachycardia, arrhythmias, ECG changes
• Neuromuscular: muscle weakness or spasms, hyperreflexia, soft tissue and vascular calcifications
• Endocrine: secondary hyperparathyroidism, chronic hyperphosphataemia may be associated with skeletal changes on x-rays from osteodystrophy

Management

Investigations

Serum phosphate levels should be monitored, with frequency depending on the degree of the abnormality and whether the child is symptomatic

Treatment

Treatment should be directed at the underlying cause with an aim to return serum phosphate levels to the normal range. Monitor closely with clinical and biochemical (serum phosphate and calcium levels) parameters

• Cease any phosphate containing medications or intravenous solutions
• In significant acute hyperphosphataemia, renal phosphate excretion can be encouraged by extracellular volume expansion with intravenous sodium chloride 0.9% or use of loop diuretic agent (Use caution if acute or chronic renal impairment is present. Discuss with local nephrology or PICU team)
• Children with severe or symptomatic hyperphosphataemia, particularly those with acute or chronic kidney injury, may require dialysis. Discuss with local nephrology or PICU team
• Chronic hyperphosphataemia may require dietary phosphorus restriction and/or use of phosphate binding agents eg calcium carbonate

Consider consultation with local paediatric team when

The child is symptomatic or there is a significant abnormality

Consider consultation with renal team when

Renal dysfunction is present

Consider transfer when

The child is symptomatic or requires close monitoring not available in your centre

For emergency advice and paediatric or neonatal ICU transfers, see Retrieval Services

Last updated January 2023