phosphate
Table of Contents
phosphate
see also:
high phosphate diets probably not good for you
- there is concern that high intake of phosphate containing beverages such as Diet Coke may lead to increased calcium excretion and thus increase risk of osteoporosis.
- there is no evidence for this currently, but one may theorise that high levels of phosphate will result in increased parathyroid hormone (PTH) secretion due to the fall in free ionised calcium levels, this may then result in:
- increased phosphate excretion
- mobilisation of calcium from bones and thus risk of osteoporosis but the rise in serum calcium will then reduce parathyroid hormone (PTH) secretion returning system to normal
- increased 1,25 dihydroxycholecalciferol production but this may be minimised by inhibition by raised phosphate levels
- renal calcium excretion will only increase if the rise in serum calcium is sufficient to cause increased calcitonin secretion
- thus as long as dietary calcium intake is reasonable, additional risk of osteoporosis may be marginal
phosphate physiology
- phosphate has an essential role in bone structure, where it gives rigidity to the bone.
- it is also important in many metabolic and enzymatic pathways.
- it is involved in energy storage and transfer, the utilisation of B complex vitamins, the buffering of body fluids, and in the renal excretion of hydrogen ions
- see also calcitonin and parathyroid hormone (PTH)
hypophosphataemia
- may be caused by:
- transient intracellular shifts
- increased urinary losses
- decreased intestinal absorption
- increased cellular use
phosphate replacement Rx
- if the patient has renal impairment or a renal transplant any replacement should be discussed with the Nephrology Consultant on call.
- use cautiously in hypocalcaemia, due to the close relationship between hypocalcaemia and hyperphosphataemia.
- use cautiously in hyperkalaemia since the potassium in the solution may exacerbate the condition. Therefore consider using sodium dihydrogen phosphate.
- use cautiously in conditions where high phosphate levels may be encountered, such as hypoparathyroidism, chronic renal disease, rhabdomyolysis, acute dehydration, pancreatitis, severe renal insufficiency and extensive tissue damage (such as severe burns)
- if the patient has had nil oral intake or has been poorly nourished for a period of seven days or more they are at risk of “Re-feeding syndrome”. If this is the case serum levels of phosphate, magnesium, potassium and calcium should be checked daily & a referral made to the unit’s dietician.
C/I to phosphate replacement Rx
- severe renal impairment
- hyperphosphataemia
- hypocalcaemia
- hyperkalaemia
- Addison’s disease
- urolithiasis
oral phosphate tablets
indications
- serum level 0.5-0.79 mmol/L, or
- serum level 0.32-0.49 mmol/L and IV phosphate not indicated
example form and dosing
- Phosphate-Sandoz Tablets:
- phosphorus 500mg, sodium 469mg, potassium 123mg, sucrose 136mg.
- each effervescent tablet contains 16.1 mmol of phosphate ions.
- dosage should be adjusted to suit the requirements of individual patients.
- up to six tablets a day in divided doses according to condition and response.
- the tablets must be dissolved in a 1/3 to 1/2 a glass of water.
iv phosphate
indications
- serum phosphate < 0.32mmol/L (urgent if <0.30mmol/L)
- symptomatic and serum phosphate 0.32-0.5mmol/L
formulations
- 13.6% (1.36g) potassium dihydrogen phosphate in 10ml
- each vial of potassium dihydrogen phosphate contains 10mmol of potassium and 10mmol of phosphate ions.
- 15.6% (1.56g) sodium dihydrogen phosphate in 10ml
- each vial of sodium dihydrogen phosphate contains 10mmol of phosphate and 10mmol of sodium ions.
administration
- IV infusion into large peripheral vein for severe hypophosphataemia:
- dilute up to 10 mmol (10 mL) of phosphate in 250 mL sodium chloride 0.9% or glucose 5% given over 2-6hrs
- CVC infusion for severe hypophosphataemia:
- dilute up to 10 mmol (10 mL) of phosphate in 100 mL sodium chloride 0.9% or glucose 5% infuse over at least ONE hour. If more than 10 mmol is required, give subsequent infusions over 2 to 6 hours
- phosphate level of <0.3mmol/L:
- serum phosphate levels checked 20 minutes after a maximum of 20mmols intravenously administered
- phosphate level of >0.3mmol/L:
- serum phosphate level checked 20 minutes after a maximum of 10mmols intravenously administered.
- rapid IV infusion may precipitate hypotension
- IV site should be monitored for signs of phlebitis
- monitor patient for signs of tetany indicating serum calcium levels have dropped due to serum phosphate levels sudden increase.
- monitor patient for signs of soft tissue calcification (if patient develops hyperphosphataemia)
- serum sodium, potassium, phosphate and calcium concentrations and renal function should be monitored at least every 24 hours during therapy
- in ICU, phosphate level is checked daily unless otherwise specified by the ICU consultant
- if the patient complains of severe pain or burning around the intravenous site or in the limb, check the access site, halve the infusion rate and consult a Medical Officer
phosphate.txt · Last modified: 2025/03/12 01:04 by wh