ICM - Viva - Phosphate

Question 1

Is phosphate a cation or anion

Answer 1

Anion - most abundant in the body

Question 2

How much of total body weight is phosphate

Answer 2

1%

Question 3

Intracellular or extracelluar

Answer 3

Intracellular, 100x more than in plasma

Question 4

What is phosphate?

Answer 4

Phosphate is an intracellular anion, which is the most abundant in the body, occupying 1% of Total body weight.

Question 5

Normal serum phosphate

Answer 5

0.85 to 1.4 mmol/l

Question 6

Total body phosphate

Answer 6

700g (1%)

Question 7

Average requirement

Answer 7

20mg/kg of phosphorous

Question 8

Where is PO3 absorbed

Answer 8

Small intestine

Question 9

What increases absorption of phosphate and calcium

Answer 9

1,25 dihydroxy vitamin D3

Question 10

Where is phosphte

Answer 10

85% in bone complexed with Ca
14% in soft tissue
1% in ECF

Question 11

Which organ regulates homoestasis of phosphate?

Answer 11

Kidney

Question 12

What hormone acts on phosphate reguation

Answer 12

PTH - causes PO3 resoprtion from bone and decreases reabsoprtion in the PCT

Question 13

How is phosphate excreted

Answer 13

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)

Question 14

Role of phosphate

Answer 14

Energy production ATP
Membrane as part of the phospholipid bilayer
RBC - 2,3, DPG
Phosphorylation
Buffer
Bone mineralisation

Question 15

Define hyperphosphataemia

Answer 15

Serum phosphate > 1.4 mmol/L

Question 16

Causes of hyperphos

Answer 16

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

Question 17

Major concern of hyper phos

Answer 17

Phosphate complexes with calcium. May precipitate hypocalcaemia and tetany if rate of rise is rapid

May be nephrocalcinosis, renal calculi and ectopic calcification

Question 18

Tx of hyper phos

Answer 18

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

Question 19

What is hypophosphataemia

Answer 19

Serum PO3 less than 0.85mmol/L

Question 20

Causes of hypophos

Answer 20

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

Question 21

Features of hypophosphataemia

Answer 21

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

Question 22

Tx of hypophos

Answer 22

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