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2 ENDOCRINE > Sodium and water balance > Flashcards

Sodium and water balance Flashcards

1
Q

what hormones control water and sodium balance

A

ADH
(anti-diuretic hormone)

aldosterone and steroids (mineralocorticoid)

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2
Q

what does ADH do

A

makes you pee less

causes water to be reabsorbed by the renal tubules

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3
Q

what happens to urine when there’s an increase in ADH

A

Small volume of concentrated urine

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4
Q

what happens to urine when theres a low secretion of ADH

A

large volume of dilute urine

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5
Q

how do you measure urine concentration/dilution

A

urine osmolarity
(concentrated urine - high osmolarity)
(dilute urine - low osmolarity)

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6
Q

where is ADH released from

A

posterior pituitary

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7
Q

how does ADH cause water reabsorption in the kidneys

A

watch video linked in slide

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8
Q

what controls sodium balance

A

steroid hormones from the adrenals

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9
Q

what is the effect of steroids on Na+ balance called

A

mineralocorticoid activity

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10
Q

how do steroids affect Na+ balance

A

cause Na+ reabsorption in renal tubules in exchange for K+/H+

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11
Q

what is the main steroid with mineralocorticoid activity

A

aldosterone

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12
Q

what happens if theres too much mineralcoritcoid activity

A

sodium gain

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13
Q

too little mineralcorticoid activity

A

sodium loss

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14
Q

how much sodium is there inside cells

A

4mmol/L

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15
Q

how much sodium is in extracellular fluid

A

140 mol/L

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16
Q

where do you loose water from

A

the WHOLE BODY

water can move between all the body compartments

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17
Q

what body compartment is sodium confined to

A

extracellular fluid

sodium potassium pump makes sure the concentrations of sodium and potassium in and out the cells is kept

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18
Q

what does water follow by osmosis

A

solute

therefore water follows sodium

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19
Q

what happens to water if you loose sodium

A

you loose water too

water follows sodium

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20
Q

low sodium concentration with a unremarkable volume status

A

too much water?

21
Q

high sodium with unremarkable volume status

A

too little water??

22
Q

what happens clinically if theres not enough sodium

A

clinical dehydration

dry mucus membranes

23
Q

clinical picture of too much sodium

A 
water overload 
raised JVP
oedema 
plural effusion 
swelling
24
Q

what are the scenarios where you would loose sodium

A

diarrhoea and vomiting
fistulae - loos gut fluid from body
from skin -burns
if adrenals aren’t working - steroid hormones aren’t causing sodium uptake

rare but can be fatal

25
Q

what scenarios would you have too much water

A

decreased H2O secretion (common)

increased H2O intake (compulsive water drinking)- rare

26
Q

what are the scenarios when theres too much sodium

A

increased sodium intake

  • Some IV meds
  • Near-drowning
  • Malicious (child being given salt maliciously)

decreased sodium loss

rare but fatal

27
Q

what scenarios is there too much sodium due to water

A

increased water loss (not very common)

decreased water intake (v common)

28
Q

how do you treat too much sodium

A

loop diuretic causes loss of sodium and water

just replace the water

29
Q

how do you treat patient with not enough water

A

give water as dextrose (glucose as a concentration similar to that of blood)

30
Q

how do you treat too little sodium

A

give sodium

31
Q

how do you treat too much water

A

fluid restriction

32
Q

if you give dextrose what body compartment will it go into

A

all of them (its water)

33
Q

if you give saline what body compartment will it go into

A

plasma and interstitial fluid

34
Q

if you give plasma/blood what body compartment does it go into

A

plasma

35
Q

when is sodium concentration normal

A

135-145

36
Q

when is a low sodium v serious

A

<120

37
Q

when is a high sodium v serious

A

> 160

38
Q

what are the symptoms of life threatening hypo/hypernatraemia

A 
altered consciousness 
confusion 
nausea 
vomiting 
fitting
39
Q

what are the two stimuli for ADH release

A

osmotic (high Na so osmolarity is high which stimulates more ADH to reabsorb more water and dilute the blood)

Non-osmotic (in disease, eg. hypovolaemia, hypotension, pain, nausea and vomiting)

40
Q

what does oedema signify

A

excess fluid in interstitial space so circulating vascular volume is depletes

41
Q

what does an oedemas patient have

A

too much water and sodium

treat with loop diuretics

42
Q

why is oedema a vicious circle

A

because the vascular volume is depleted
this causes ADH and aldosterone secretion
these cause water and sodium retention
this causes hyponatramiea

43
Q

what is pseudohyponatraemia

A

check with serum osmolarity

whether theres low sodium or normal sodium just in less?? idk

44
Q

what does Addisons disease cause

A

adrenal indeficiency so steroid hormones aren’t being made so theres no mineralocorticoid activity so patient can’t hold onto sodium and therefore cant hold on to water decreasing the ECF and giving rise to clinical dehydration

45
Q

symptoms of Addisons disease

A

dizziness reflects hypotension from decreased ECF

excess pigmentation reflects excess ACTH from anterior pituitary

46
Q

why does excess ACTH cause tanned skin

A

ACTH is broken down by proteases releasing MSH from within it which causes excess pigmentation in skin

47
Q

what is the typical presentation of someone who has too much water

A

patient often in hospital with other illness
routine biochem shoes decreased Na
volume status unremarkable (do to loss of water being distributed everywhere)
Addisons disease tests negative
most patients have inappropriate ADH secretion
often no symptoms

48
Q

cause of too much water in someone who is already ill

A

ADH secreted in response to a non-osmotic stimulus
causes water retention distributed all over body compartments so patients volume status seems unremarkable
first noticed when U&Es done
often diagnosis of exclusion

49
Q

how does diabetes insidious cause too little water

A

patient cant secrete ADH from the posterior pituitary due to disruption of pituitary stalk
No ADH to act on kidneys to cause water reabsorption
so LOTS of pure water lost in urine
Patients Na is high reflecting water deficit

treat with exogenous ADH

2 ENDOCRINE (32 decks)

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