Fluid and electrolyte

Question 1

3 main categories that determine water balance

Answer 1

intake
output
redistribution

Question 2

2 main categories of water losses

Answer 2

obligatory

controlled

Question 3

2 examples of obligatory losses

Answer 3

skin

lungs

Question 4

3 controlled losses of water

Answer 4

renal function
gut
vasopressin

Question 5

3 things that stimulate ADH secretion

Answer 5

Increase in plasma osmolality (v. sensitive 1-2% change)

Pain, stress, nausea, drugs, lung and CNS lesions, ectopic

Decrease in plasma volume (>5-8%)

Question 6

3 things that decrease ADH secretion

Answer 6

Decrease in plasma osmolality (plasma dilution)

Increase in plasma volume

Ethanol (resulting in diuresis

Question 7

Describe the physiological responses to water deficiency

Answer 7

stimulation of ADH release

stimulation of hypothalamic thirst centre

redistribution of water from ICF

Question 8

what controls the amount of fluid excreted?

Answer 8

intravascular fluid volume

Question 9

Describe RAAS

Answer 9

renin is released from the adrenal gland. this converts angiotensinogen to angiotensin 1. ACE released from the lungs then converts angiotensin 1 to angiotensin which acts on the adrenal gland to stimulate aldosterone release. This promotes sodium reabsorption, and hence increases water retention.

Question 10

What two things sense BP?

Answer 10

Baroreceptors

renal perfusion pressure

Question 11

2 affects of aldosterone

Answer 11

Na reabs

H+/K loss

Question 12

4 key aspects of a hx for fluid/electrolyte balance

Answer 12

fluid intake/output
vomiting/diarrhoea
past hx
medication

Question 13

5 examinations for volume status assessment

Answer 13

o	Lying and standing BP
o	Pulse
o	Oedema
o	Skin turgor/Tongue
o	JVP / CVP

Question 14

Key lab Ix

Answer 14

paired serum and urine osmolality and electrolytes

urea:cr

serum osmolality

urinary sodium

urine osmolality

urine:serum osmolality

Question 15

how do you calculate serum osmolality?

Answer 15

2 x Na + urea + glucose (+/- 10)

Question 16

where is most K found?

Answer 16

Intracellularly

Question 17

What happens to K levels in acidosis?

Answer 17

Hyperkalaemic

Question 18

What happens to K levels in alkalosis

Answer 18

hypoK

Question 19

2 categories of causes of hypoK and 2 examples of each

Answer 19

Increased loss- diarrhoea, diuretics, Mg def

Decreased intake- alcohol anorexia

Question 20

2 categories of causes of hyperK and examples of each

Answer 20

Increased intake- usually parenteral

Decreased loss- reduced GFR, K sparing diuretics, ACEi

Question 21

requirements for the diagnosis of SIADH (7)

Answer 21

• Euvolaemia ie. no evidence of volume depletion or oedema
• Hyponatraemia and hypo-osmolality
• Inappropriately high urine osmolality & excessive renal excretion of Na
• Normal renal, adrenal, pituitary, thyroid
• Not on any drugs (diuretics, antidiuretics)
• DIAGNOSIS OF EXCLUSION !!
• Clinical and biochemical improvement with fluid restriction

Question 22

5 drug groups associated with hypoNa

Answer 22

anticonvulsants
antineoplastics
hypoglycaemics
narcotics
thiazies
frusemide
tricyclics
SSRIs
paracetamol

Question 23

complication of over rapid correction of hypoNa

Answer 23

central pontine myelinolysis

Question 24

complication of over rapid correction of hyperNa

Answer 24

cerebral oedema

Question 25

rate for sodium correction

Answer 25

no more than 10mmol/L per 24h sodium change