Calcium, Magnesium and Phosphate Flashcards
What percentage of Ca is found in skeleton?
99%
How much serum Ca is bound to plasma proteins
50%
Remainder is Ionised Ca
How is calcium measurement linked to proteins?
Falls and rises with protein
Therefor take blood sample without tourniquet as this will increase the protein content
How is calcium level adjusted for protein content? (recognise equation)
Increase Ca by 0.02 mmol for every 1 g fall in albumin below 40g/L
(Decreased by 0.02 for every 1 g when albumin is ABOVE 40g/L)
How does PTH increase calcium?
Increased bone resorption
Increased gut resorption
Increased renal absorption
Increased activated D synthesis
EXCRETES MORE PHOSPHATE
Summarise Vit D metabolism
UV light converts cholesterol to vit D
Converted in liver to 25 Vit D in liver
Converted to activated 1,25 vit D in kidneys
Drug causes of hypercalcaemia
Thiazides
Endocrine causes of hypercalcaemia
PTH excess
Hyperthyroidism
Addisons
Familial hypocalciuric hypercalcaemia
Investigation of hypercalcaemia?
Take UNCUFFED, FASTING sample
Look at phosphate lvl (will be low)
ALP for bone disease
PTH and Vit D levels
CXR for sarcoid
Plasma protein electrophoresis (myeloma)
Urine calcium
Management of hypercalcaemia?
Rehydration (4-6 L in 24 hours) Monitor urine output Loop diuretic Monitor K+ Bisphosphonates to bind Ca Hydrocortisone for myeloma or sarcoid
Causes of Hypocalcaemia
Lack of Vit D Renal failure (increased phosphate)
Vit D deficiency
BISPHOSPHONATES
Hypoparathyroidism
Clinical features of hypocalcaemia
Tetany
Chvosteks sign
Trousseaus sign
Prolonged QT interval
Management of (1) mild and (2) severe hypocalcaemia
Mild: oral calcium, vit D
Severe: IV calcium gluconate
Where is phosphate sotred in body?
85% in bone, mainly intracellular
Required for ATP, and DNA
Causes of hypophosphatemaia?
Decreased intake Decreased absorption(low vit D
Shift into cells:
RESPIRATORY ALKALOSIS
INSULIN
Increased urinary excretion:
HYPERPARATHYROIDISM
Renal tubular defects
What condition is hypophosphataemia most often linked to?
REFEEDING SYNDROME
Lots of glucose causes phosphate to quickly shift into the cells
Causes respiratory alkalosis
Also linked to alcohol abuse
Adverse affects of hypophosphataemia eg in refeeding syndrome?
Rhabdomyolysis
Cardiomyopathy
ARDS
Erythrocyte and WC dysfunction
Treatment of hypophosphataemia?
MILK/oral supplements
IV over 12 hours
EXCESS PHOSPHATE CAN CAUSE HYPOCALCAEMIA!!
When is hyperphosphataemia seen? (1)
Renal failure
Where is magnesium stored?
67% in bones
30% in cells
When dietary Mg is low, the loops of Henle are v efficient at retaining Mg
Causes of hypomagnaesia?
Poor intake or malabsorption
Diarrhoea
REFEEDING SYNDROME
Alcohol withdrawal
Features of hypomagnesia
Same as hypocalcaemia
Treatment of hypomagnesia? (just recognise)
Oral or IV Mg
30mmol in first 24 hrs and the 20mmol per 24 hours
Causes of raised ALP?
Childhood, pregnancy
Bone damage or malignancy
Liver disease
