C - Na/Fluid Balance Flashcards
Cause of hyponatraemia
Excess water
What controls fluid balance and how?
ADH - inserts aquaporins into collecting duct
2 stimuli of ADH release
High serum osmolality
Low blood volume / pressure
Receptors for serum osmolality and BP?
SO = hypothalamic osmoreceptors
BP = baroreceptors on carotids / aorta
How do you assess volume status clinically?
Pulse, mucous membranes, lying/standing BP, urine output, skin turgor or confusion
Best indicator of hypovolaemia?
Low urine output <20
What do you need to establish if someone has low sodium?
Fluid status
Causes of hypovolaemic hyponatraemia
D&V
Diuretics
Sodium losing nephropathy
Causes if euvolaemic low Na
Hypothyroid
Adrenal insufficiency
SIADH
Causes of hypervolaemic low Na
Heart failure
Renal failure
Cirrhosis
Describe osmolality findings in SIADH
Low plasma and high urine
Dx of SIADH?
Rule out hypovolaemia and other causes
Plasma osmolality and urine osmolality
Mx of hyovolaemic low Na
Fluid replacement with 0.9% saline
Treatment for severe low Na and warning ?
Saline but do not increase Na by more than 8 to 10mmol /L in first 24 hours
Drugs for SIADH
Demeclocycline
Tovaptan
Define hypernatraemia
> 145
What causes hypernatraemia?
Unreplaced water loss - sweat, GI, renal
Lack of control of water intake - kids/elderly
Ix for hypernatraemia
Check glucose, K, Ca
Plasma/urine osmolality
Water deprivation test
Tx for hypernatraemia
Fluid replacement with 5% dextrose
Treat underlying cause
What Na imbalance does DM cause and why?
Low Na
High glucose draws water out of cells by osmotic diuresis
Which is more common, hypo or hypernatraemia?
Hypo
