ICM - Viva - Phosphate Flashcards
Is phosphate a cation or anion
Anion - most abundant in the body
How much of total body weight is phosphate
1%
Intracellular or extracelluar
Intracellular, 100x more than in plasma
What is phosphate?
Phosphate is an intracellular anion, which is the most abundant in the body, occupying 1% of Total body weight.
Normal serum phosphate
0.85 to 1.4 mmol/l
Total body phosphate
700g (1%)
Average requirement
20mg/kg of phosphorous
Where is PO3 absorbed
Small intestine
What increases absorption of phosphate and calcium
1,25 dihydroxy vitamin D3
Where is phosphte
85% in bone complexed with Ca
14% in soft tissue
1% in ECF
Which organ regulates homoestasis of phosphate?
Kidney
What hormone acts on phosphate reguation
PTH - causes PO3 resoprtion from bone and decreases reabsoprtion in the PCT
How is phosphate excreted
85-90% of flitered phopshate is reabsorbed in the PCT
Renal excretion influences:
PTH - increased excretion
Calcitonin - Increased
Bicarb - Increased
Magnesium - increased
Vitamin D3, decreased Sodium absorbtion (decreased exretion of PO3, co-transported with Na)
Role of phosphate
Energy production ATP Membrane as part of the phospholipid bilayer RBC - 2,3, DPG Phosphorylation Buffer Bone mineralisation
Define hyperphosphataemia
Serum phosphate > 1.4 mmol/L
Causes of hyperphos
Reduced excretion - Renal failure
Hypoparathyoid
Hypomagnesaemia
Bisphosphonate use
Exogenous load - Vit D intoxication, enteral and paretnral use,
Incresed production or release - Rhabdo, TLS, LH, Haemolysis, Acidosis
Major concern of hyper phos
Phosphate complexes with calcium. May precipitate hypocalcaemia and tetany if rate of rise is rapid
May be nephrocalcinosis, renal calculi and ectopic calcification
Tx of hyper phos
STOP PHOSPHATE
Aluminium hydroxide is a binder
Mg/Ca also used
Remove phosphate - RRT, dieurtetics, volume repletion
Monitor PO and Ca
Prevent recurrents
Ca may rise due to mobilisation of abnormal soft tissue Ca/PO deposits
What is hypophosphataemia
Serum PO3 less than 0.85mmol/L
Causes of hypophos
Increased renal losses
Hyperaldosteronism, Hyperparathyoidism Low Vit D RTA Alcohol Acetazolamide
GI loss - antacid abuse, vit D, diarrhoea
Altered balance - cause glycolysis which drives phosphate intracellulary
Refeeding, resp alkalosis, reovery from DKA Sepsis Glucagon Cortisol Adrenaline
Features of hypophosphataemia
Mild - found on bloods
Clinical when below 0.3, often with low K, Low Mg
Neuromuscular disturbance (prox myopathy, weakness, and resp failure)
Smooth muscle dysfucntion - dysphagia, ileus
Rhabdo complicates cases
Cardiomyopathy
Tx of hypophos
Stop phosphate wasting drugs
Supplement - if less than 0.32 or malnutiriton, refeeding
1-3g/day
10mmol of phosphate as Potassium Diphosphate over 1 hour
Phopshate polyfusor
Correct co-existing electrolyes (beware Ca in TLS)
Regular monitor of PO and Ca