C - Na/Fluid Balance

Question 1

Cause of hyponatraemia

Answer 1

Excess water

Question 2

What controls fluid balance and how?

Answer 2

ADH - inserts aquaporins into collecting duct

Question 3

2 stimuli of ADH release

Answer 3

High serum osmolality
Low blood volume / pressure

Question 4

Receptors for serum osmolality and BP?

Answer 4

SO = hypothalamic osmoreceptors
BP = baroreceptors on carotids / aorta

Question 5

How do you assess volume status clinically?

Answer 5

Pulse, mucous membranes, lying/standing BP, urine output, skin turgor or confusion

Question 6

Best indicator of hypovolaemia?

Answer 6

Low urine output <20

Question 7

What do you need to establish if someone has low sodium?

Answer 7

Fluid status

Question 8

Causes of hypovolaemic hyponatraemia

Answer 8

D&V
Diuretics
Sodium losing nephropathy

Question 9

Causes if euvolaemic low Na

Answer 9

Hypothyroid
Adrenal insufficiency
SIADH

Question 10

Causes of hypervolaemic low Na

Answer 10

Heart failure
Renal failure
Cirrhosis

Question 11

Describe osmolality findings in SIADH

Answer 11

Low plasma and high urine

Question 12

Dx of SIADH?

Answer 12

Rule out hypovolaemia and other causes
Plasma osmolality and urine osmolality

Question 13

Mx of hyovolaemic low Na

Answer 13

Fluid replacement with 0.9% saline

Question 14

Treatment for severe low Na and warning ?

Answer 14

Saline but do not increase Na by more than 8 to 10mmol /L in first 24 hours

Question 15

Drugs for SIADH

Answer 15

Demeclocycline
Tovaptan

Question 16

Define hypernatraemia

Answer 16

> 145

Question 17

What causes hypernatraemia?

Answer 17

Unreplaced water loss - sweat, GI, renal
Lack of control of water intake - kids/elderly

Question 18

Ix for hypernatraemia

Answer 18

Check glucose, K, Ca
Plasma/urine osmolality
Water deprivation test

Question 19

Tx for hypernatraemia

Answer 19

Fluid replacement with 5% dextrose
Treat underlying cause

Question 20

What Na imbalance does DM cause and why?

Answer 20

Low Na
High glucose draws water out of cells by osmotic diuresis

Question 21

Which is more common, hypo or hypernatraemia?

Answer 21

Hypo