Sodium and Water Balance Flashcards by Louise Emerson

what hormone controls water balance

anti-diuretic hormone

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what releases ADH

posterior pituitary

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how does ADH work

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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what happens to urine when there is increased ADH

small volume of concentrated urine is produced

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what happen to the urine when there is decreased ADH

large volume of dilute urine is produced

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what is urine osmolality

measure of urine concentration/ dilution

high osmolality= concentrated urine
dilute urine= low osmolality

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what is AVP

arginine vasopressin- another name for ADH

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how can trauma affect ADH secretion

if trauma transects pituitary stalk

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what hormones affect sodium balance

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

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what is mineralocorticoid activity

the effect steroids have in Na+ activity

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what does too much mineralocorticoid activity result in

sodium gain

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how does aldosterone affect sodium

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

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what is the reference interval for sodium concentration

135-145 mmol/L

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what are the two reasons behind decreased sodium concentration

decreased sodium or increased water

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what are the two reasons behind increased sodium concentration

increased sodium, decreased water

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where is there more sodium- intra or extra cellular fluid

more sodium in extracellular fluid

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where is there more potassium- intra or extra cellular fluid

more potassium in intracellular fluid

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where is pure water lost from

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

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where is sodium confined to

extracellular fluid

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what keeps sodium in the extracellular fluid

sodium and potassium ATPase pump

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where is sodium lost from

the extracellular fluid

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what does water follow

sodium

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

lose/ gain water with it

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

excretes sodium which also causes loss of water and ECF

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what causes too much water

water retention- ADH

which changes in sodium and water balance are most serious

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)

what are the features of fluid overload (and cause)

(increased sodium) | oedema, pleural effusion, raised JVP

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

problem with sodium concentration

what can cause decreased sodium concentrations

increased sodium loss- adrenal/ kidney (not producing steroids), gut (D and V, fistula), skin (burns) decreased H2O secretion, increased intake (compulsive water drinking)

what can cause increased sodium

increased sodium intake- some IV meds, near drowning, malicious increased water loss (diabetes insipidus), decreased H2O intake (elderly, young)

what sodium concentration problem can be fatal if you miss it

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

what is the treatment for sodium loss or excess

give sodium- sodium in saline excess- loop diuretic

what sodium concentration problem can be fatal if you miss it

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

what is the treatment for too much water

fluid restriction

how do you replace water

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

where does saline get to

confined to extracellular fluid

what is dextrose

solution with dame tonicity of concentration as blood

when is sodium serious

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

how do you tell if sodium is serious

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

when is sodium in normal range serious

if it has suddenly fallen or risen to that level

what is SIADH

syndrome of inappropriate ADH | inappropriate for the osmolal state

what are the non osmotic stimuli for ADH release

hypovolaemia/ hypertension pain nausea/ vomiting

what are the non osmotic stimuli for ADH release

hypovolaemia/ hypertension pain nausea/ vomiting

does sodium affect ADH secretion

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

what is capillary hydrostatic pressure

when water is pushed out

what is capillary oncotic pressure

water back in

what causes loss of water from the capillaries into the ECF

increased hydrostatic pressure/ too much protein in the blood

what does oedema do to circulating volume

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

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

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

what do loop diuretics do

cause loss of sodium and water

what does an oedematous patient have too much off

water and sodium

what is the main treatment for oedema

loop diuretics

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].

addisons

what causes addisons disease

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

why do you get symptoms of dizziness in addisons

hypotension due to decreased ECF

why do you get excess pigmentation in addisons

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

why do you get increase K in addisons

as it is retained

what is the treatment for addisons

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

what test is used to exclude addisons

synacthen test

what causes diabetes insipidus

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

what are sodium levels like in diabetes insipidus

high- lack of water

what do you give when the pituitary gland cant produce ADJ

exogenous ADH (desmopressin)

Sodium and Water Balance Flashcards

(62 cards)