Sodium haemostasis and osmolality Flashcards
What is normal serum osmolality?
282-295mOsm/L
Difference between CSW and SIADH
CSW volume depletion with Na loss, SIADH - euvolaemic or hypervolaemic
Note both can have high urinary Na
SIADH seen in particular with which disease?
Small cell lung Ca
What percentage of head injuries affected by SIADH?
4.6%
Drugs used in neurosurgery that cause SIADH
Carbemazepine/oxycarbemazepine
NSAIDS
antipsychotics
DDAVP
What is the risk of over rapid correction of Na?
Osmotic demyelination (including cerebral pontine myelinolysis)
2 causes of acute hyponatraemia outside of hospital
ecstasy
marathoners
What type of hyponatraemia does mannitol cause?
Hypertonic hyponatraemia (pseudohyponatraemia)
Addisons gives what picture of hyponatraemia?
same as CSW - Low Na, Low Serum osmo, volume depleted, high urinary Na
What is Schwartz-Bartter syndrome?
SIADH first described with small cell lung Ca
Essential features of diagnosing SIADH?
Low Na, paired serum (low) and urinary (high) osmos
clinically euvolaemic
Normal thyroid function and no diuretic use
Definitive test for SIADH?
Water load test - consume 20ml/kg water up to 1.5L, 65% should be excreted within 4 hours
Note this should not be done in patients with severe or symptomatic hyponatraemia!
What is Conivaptan?
Type V1A and V2 vasopressin receptor blocker used in severe hyponatraemia
What is the treatment of CSW?
Postive salt balance
fluid replacement
What medications can be used to help treat CSW?
Fludrocortisone
Urea can be used in CSW and SIADH