sodium and water balance Flashcards
what secretes steroids?
adrenal glands
what secretes ADH?
-posterior pituitary gland
what effect does ADH have on peeing?
ADH makes you pee less (anti diuretic hormone) as it causes water to be reabsorbed into the renal tubules
what effect does increased ADH have?
it causes you to have a small volume of concentrated urine (high osmalarity)
what effect does decreased ADH have?
it causes a large volume of dilute urine (low osmolality))
what is urine concentration/ dilution measured?
using urine osmolality
does concentrated urine suggest high or low osmolality?
-high osmolality
does dilute urine suggest high or low osmolality?
low osmolality
what controls sodium balance?
steroids
what is mineralocorticoid activity?
- the effect of steroids on Na+ balance
- this refers to Na+ reabsorption in renal tubules in exchange for K+/H+
what steroids have mineralocorticoid activity?
- aldosterone (the main one)
- other steroids such as cortisol
what effect does too much mineralocorticoid activity have ?
-sodium gain
what effect does too little mineralocorticoid activity have?
-sodium loss
what causes a sodium concentration to be low?
-too little sodium or too high water concentration
is there more water intracellularly (inside cells) or extracellularly (outwith of cells)?
more water intracellularly (double)
is there more sodium intracellularly (inside cells) or extracellularly (outwith of cells)?
more sodium extraceullar due to less water extracellularly
when you gain/lose water, which compartment does it go to?
loss/gain of water goes to the whole body (intracellular and extracellular compartments)
when you gain/lose sodium, which compartment does it go to?
it only goes to the ECF (extracellular fluid compartment)
if you lose sodium from the ECF what occurs to the water?
you lose water with it
if you gain sodium from the ECF what occurs to the water?
you gain water with it
what do the kidneys do if the blood volume is too high?
-kidneys will excrete sodium, causing water to go with it, decreasing blood volume
what do the kidneys do if the blood volume is too low?
-kidneys will reabsorb sodium, reabsorbing water with it and increasing blood volume
what effect does primary adrenal insufficiency have on sodium and water levels?
- they can’t make the steroid hormones that control sodium balance
- so will not reabsorb sodium from the kidneys as they would normally do
- meaning you would lose sodium and water with it
what affect does vomiting have on sodium/water levels?
-vomiting would make you lose sodium for gut and water along with it
whats more common hypernatreamia due to too much water or due to too little sodium?
too much water
are the changes or hyponatremia/hypernatraemia more dramatic in sodium loss/gain or water loss/gain?
sodium loss/gain as it is only lost/gained in ECF whereas water is lost from everywhere
clinical signs of hyponatraemia due to too much sodium?
- clinical dehydration
- hypotension
- tachycardia
- small volume concentrated urine
- decreased skin elactisity
clinical signs of hypernatraemia due to too much sodium?
- clinical signs of extracellular fluid compartment
- raised JVP
- pleural effusion
- ascites
- bibasal crepitaitions
clinical signs of hyponatraemia/ hypernatraemia due to water loss/excess?
not always obvious due to water loss occuring in both intracellular and extracellular compartments
what causes hyponatramia due to sodium?
- There may be Na+ loss in adrenal insufficiency losing sodium from kidneys
- sodium lost from the gut due to vomiting/diarrhoea
- it may be lost from the skin from third degree burns
what causes hyponatramia due to water?
- most common is decreased H20 excretion due to SIADH (syndrome of inappropriate antidiuretic hormone secretion) where too much ADH is made
- or increased intake of water from drinking too much
what causes hypernatramia due to sodium?
- if there is increased H20 loss in diabetes insipidus as ADH is disrupted
- decreased H20 intake in very young or very old
what causes hypernatramia due to water?
increase sodium intake from IV meds and near drowning
what is treatmeant for hyponatraemia due to too little sodium?
-give sodium replacement
what is treatmeant for hyponatraemia due to too much sodium?
remove sodium by giving loop diuretics
how would water be removed in hyponatraemia?
-fluid restrict
how would water be given in hypernatraemia?
- give dextrose IV
- dextrose contains glucose so it can be metabolised in a controlled way and release H20 into the body
what may a patient experience if sodium level is very high or very low?
- altered consciousness
- confusion
- nausea
- vomiting
- fitting
what are the two kidns of stimuli for ADH release?
- osmotic (in health)
- non osmotic (in disease)
what are examples of non osmotic stimuli?
- hypovolaemia
- pain
- nausea/vomiting
what does an oedema suggest?
too much water in interstitial fluid
does oedematous patient have too much water or sodium?
-too much water and sodium
how is an oedematous patient treated?
with loop diuretics as it causes a loss of sodium and so also water
