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Endocrinology > Sodium and Water Balance > Flashcards

Sodium and Water Balance Flashcards

1
Q

what hormone controls water balance

A

anti-diuretic hormone

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2
Q

what releases ADH

A

posterior pituitary

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3
Q

how does ADH work

A

causes water to be re absorbed from the renal tubules

stimulate the insertion of aquaporins into the membranes of kidney tubules

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4
Q

what happens to urine when there is increased ADH

A

small volume of concentrated urine is produced

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5
Q

what happen to the urine when there is decreased ADH

A

large volume of dilute urine is produced

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6
Q

what is urine osmolality

A

measure of urine concentration/ dilution

high osmolality= concentrated urine
dilute urine= low osmolality

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7
Q

what is AVP

A

arginine vasopressin- another name for ADH

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8
Q

how can trauma affect ADH secretion

A

if trauma transects pituitary stalk

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9
Q

what hormones affect sodium balance

A

steroids released from the adrenals- aldosterone (main one) + others e.g. cortisol

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10
Q

what is mineralocorticoid activity

A

the effect steroids have in Na+ activity

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11
Q

what does too much mineralocorticoid activity result in

A

sodium gain

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12
Q

how does aldosterone affect sodium

A

usually released in response to low BP, causes sodium reabsorption, increases the osmolarity in the extracellular fluid

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13
Q

what is the reference interval for sodium concentration

A

135-145 mmol/L

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14
Q

what are the two reasons behind decreased sodium concentration

A

decreased sodium or increased water

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15
Q

what are the two reasons behind increased sodium concentration

A

increased sodium, decreased water

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16
Q

where is there more sodium- intra or extra cellular fluid

A

more sodium in extracellular fluid

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17
Q

where is there more potassium- intra or extra cellular fluid

A

more potassium in intracellular fluid

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18
Q

where is pure water lost from

A

as water can move between all body compartments it is lost from the whole body

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19
Q

where is sodium confined to

A

extracellular fluid

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20
Q

what keeps sodium in the extracellular fluid

A

sodium and potassium ATPase pump

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21
Q

where is sodium lost from

A

the extracellular fluid

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22
Q

what does water follow

A

sodium

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23
Q

what happens to water if you lose/ gain sodium from the ECF

A

lose/ gain water with it

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24
Q

what happens when the body senses its ECF to be too high

A

excretes sodium which also causes loss of water and ECF

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25
Q

what causes too much water

A

water retention- ADH

26
Q

which changes in sodium and water balance are most serious

A

when it is loss or gain of sodium causing the problem (not too mch or too little water as this is distributed across all body and cell compartments)

27
Q

what are the features of fluid overload (and cause)

A

(increased sodium)

oedema, pleural effusion, raised JVP

28
Q

what must you always think when you see signs of dehydration or fluid overload

A

problem with sodium concentration

29
Q

what can cause decreased sodium concentrations

A

increased sodium loss- adrenal/ kidney (not producing steroids), gut (D and V, fistula), skin (burns)

decreased H2O secretion, increased intake (compulsive water drinking)

30
Q

what can cause increased sodium

A

increased sodium intake- some IV meds, near drowning, malicious

increased water loss (diabetes insipidus), decreased H2O intake (elderly, young)

31
Q

what sodium concentration problem can be fatal if you miss it

A

increased sodium loss causing dehydration (adrenal failure, kidney, gut, skin losses)

32
Q

what is the treatment for sodium loss or excess

A

give sodium- sodium in saline

excess- loop diuretic

33
Q

what sodium concentration problem can be fatal if you miss it

A

increased sodium loss causing dehydration (adrenal failure, kidney, gut, skin losses)

34
Q

what is the treatment for too much water

A

fluid restriction

35
Q

how do you replace water

A

give dextrose as will reach into all extra and intra cellular areas

36
Q

where does saline get to

A

confined to extracellular fluid

37
Q

what is dextrose

A

solution with dame tonicity of concentration as blood

38
Q

when is sodium serious

A

if very low or very high (<120mmol/L or >160 mmol/L)

39
Q

how do you tell if sodium is serious

A

if patients have symptoms from it: altered consciousness, confusion, nausea, vomiting, fitting, etc.

40
Q

when is sodium in normal range serious

A

if it has suddenly fallen or risen to that level

41
Q

what is SIADH

A

syndrome of inappropriate ADH

inappropriate for the osmolal state

42
Q

what are the non osmotic stimuli for ADH release

A

hypovolaemia/ hypertension
pain
nausea/ vomiting

43
Q

what are the non osmotic stimuli for ADH release

A

hypovolaemia/ hypertension
pain
nausea/ vomiting

44
Q

does sodium affect ADH secretion

A

high serum sodium (high osmolality) can stimulate posterior pituitary to cause re-absorbtion water (by secretion of ADH)

45
Q

what is capillary hydrostatic pressure

A

when water is pushed out

46
Q

what is capillary oncotic pressure

A

water back in

47
Q

what causes loss of water from the capillaries into the ECF

A

increased hydrostatic pressure/ too much protein in the blood

48
Q

what does oedema do to circulating volume

A

is depleted, due to altered balance of starling forces at capillary level

49
Q

what hormones are secreted in oedema in attempt to restore circulating volume- why does this create a viscous circle

A

ADH and aldosterone

these cause water retention in an attempt to increase volume but much of this fluid is retained in interstitial fluid

50
Q

what do loop diuretics do

A

cause loss of sodium and water

51
Q

what does an oedematous patient have too much off

A

water and sodium

52
Q

what is the main treatment for oedema

A

loop diuretics

53
Q

what is this disease:
A 24 year-old student presents with a six month history of malaise, tiredness, poor appetite and one stone weight loss. She has developed a craving for salty foods – crisps in particular. She has had a number of dizzy spells particularly while in warm places.

She is thin. She has low BP which falls further on standing. You have the impression that she is tanned, and you find increased pigmentation in her mouth and hand creases.

Her bloods show low sodium [122 mmol/L] and high potassium [5.8 mmol/L].

A

addisons

54
Q

what causes addisons disease

A

adrenal insufficiency- cant make enough steroids, don’t have mineralocorticoid activity meaning you cant retain sodium in the kidneys - results in a loss of sodium (and water) from the ECF

55
Q

why do you get symptoms of dizziness in addisons

A

hypotension due to decreased ECF

56
Q

why do you get excess pigmentation in addisons

A

ACTH from pituitary- ACTH contains MSH within it and this is exposed when proteases degrade ACTH

57
Q

why do you get increase K in addisons

A

as it is retained

58
Q

what is the treatment for addisons

A

sodium replacement (saline) + can give hydrocortisone shot to replace steroids they are not making

59
Q

what test is used to exclude addisons

A

synacthen test

60
Q

what causes diabetes insipidus

A

disruption of hormone axis where patients cant secrete ADH or there is renal resistance to it

61
Q

what are sodium levels like in diabetes insipidus

A

high- lack of water

62
Q

what do you give when the pituitary gland cant produce ADJ

A

exogenous ADH (desmopressin)

Endocrinology (46 decks)

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