Sodium & Water Balance Flashcards
what hormone is water balance controlled by?
ADH
what releases ADH?
posterior pituitary
ADH makes you pee more/less
ADH makes you pee LESS
ADH causes water to be ____________ from the renal tubules
ADH causes water to be REABSORBED from the renal tubules
high ADH = ______ volume of _____________ urine
low ADH = ______ volume of _______ urine
high ADH = SMALL volume of CONCENTRATED urine
low ADH = LARGE volume of DILUTE urine
what do we measure urine concentration/dilution as?
urine osmolarity
concentrated urine = low/high osmolarity
dilute urine = low/high osmolarity
concentrated urine = high osmolarity
dilute urine = low osmolarity
mineralocorticoid activity:
name the main steroid and 1 other involved
too much MA = sodium gain/loss
too little MA = sodium gain/loss
mineralocorticoid activity:
ALDOSTERONE (MAIN)
CORTISOL
too much MA = sodium GAIN
too little MA = sodium LOSS
state the important equation for water balance
[Na+] = Na+/H2O
what can cause low [Na+]?
low sodium OR high water
what can cause high [Na+]?
high sodium OR low water
intra/extracellular:
(a) high fluid and low sodium
(b) low fluid and high sodium
(a) high fluid and low sodium - INTRACELLULAR
(b) low fluid and high sodium - EXTRACELLULAR
wherever sodium goes, what follows?
water
what can cause too little sodium?
increased Na loss OR decreased Na intake
what can cause too much water?
reduced water excretion OR increased intake
what can cause too much sodium?
increased Na intake OR decreased Na loss
what can cause too little water?
increased water loss OR decreased water intake
what condition causes increased water loss?
DM
what condition causes reduced water excretion?
SIADH - syndrome of inappropriate antidiuretic hormone secretion
whats the very very common cause of reduced sodium?
reduced water excretion - SIADH
whats the uncommon but fatal if you miss it cause of reduced sodium?
increased sodium loss
treatment:
(a) too little sodium =
(b) too much water =
(c) too much sodium =
(d) too little water =
treatment:
(a) too little sodium = GIVE SODIUM
(b) too much water = FLUID RESTRICT
(c) too much sodium = REMOVE SODIUM
(d) too little water = GIVE WATER AS DEXTROSE
why give dextrose?
can enter the intracellular compartment
name some stimuli for ADH release
osmotic
non-osmotic in disease
hypo/hypertension
pain
nausea/vomiting
oedema treatment?
loop diuretic
patient with oedema has too much what?
water and sodium
low sodium in a well patient diagnosis?
pseudohyponatraemia
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].
diagnosis?
Addisons disease
too little sodium
primary adrenal insufficiency
adrenal not making aldosterone
A 29 year-old man is admitted to ITU following a cycling accident in which he sustained a severe head injury. During his ITU stay his urine output is in excess of 12 litres daily; his IV fluid requirement is correspondingly large.
Serum sodium is 167 mmol/L on admission to ITU and slowly falls as fluid replacement ‘catches up’. He is in addition commenced on desmopressin (exogenous ADH) which produces a sharper fall in sodium.
diagnosis?
DM
those with too little sodium will look what?
dehydrated
