Stay informed with the latest updates on coronavirus (COVID-19). Find out more >>

Hyperphosphataemia

  • See also

    Electrolyte abnormalities
    Hypophosphataemia
    Intravenous fluids guideline

    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

    Increased exogenous phosphate load

    Increased endogenous phosphate load or
    internal redistribution between body compartments

    Decreased renal phosphate excretion

    Increased renal phosphate reabsorption

    • phosphate supplements
    • phosphate containing laxatives/enemas
    • excessive vitamin D intake
    • dietary (meat especially organ meat, dairy)

     

    • lactic acidosis
    • diabetic ketoacidosis
    • malignancy
    • chemotherapy
    • tumour lysis syndrome
    • rhabdomyolysis
    • acute or chronic kidney failure
    • dehydration
    • hypoparathyroidism
    • FGF 23 deficiency or resistance
    • bisphosphonate use
    • hypoparathyroidism

    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 0.9% normal saline 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 

  • Reference List

    • Canada TW, et al.  ASPEN Fluids, Electrolytes, and Acid-Base Disorders Handbook. 2015. American Society for Parenteral and Enteral Nutrition. U.S.A.
    • Sydney Children’s Hospital Electrolyte Replacement Prescribing – SCH. Guideline no. 2018-036 v1. 27 March 2018.