Sodium & Water Balance

Question 1

what hormone is water balance controlled by?

Answer 1

ADH

Question 2

what releases ADH?

Answer 2

posterior pituitary

Question 3

ADH makes you pee more/less

Answer 3

ADH makes you pee LESS

Question 4

ADH causes water to be ____________ from the renal tubules

Answer 4

ADH causes water to be REABSORBED from the renal tubules

Question 5

high ADH = ______ volume of _____________ urine

low ADH = ______ volume of _______ urine

Answer 5

high ADH = SMALL volume of CONCENTRATED urine

low ADH = LARGE volume of DILUTE urine

Question 6

what do we measure urine concentration/dilution as?

Answer 6

urine osmolarity

Question 7

concentrated urine = low/high osmolarity

dilute urine = low/high osmolarity

Answer 7

concentrated urine = high osmolarity

dilute urine = low osmolarity

Question 8

mineralocorticoid activity:

name the main steroid and 1 other involved

too much MA = sodium gain/loss

too little MA = sodium gain/loss

Answer 8

mineralocorticoid activity:

ALDOSTERONE (MAIN)
CORTISOL

too much MA = sodium GAIN

too little MA = sodium LOSS

Question 9

state the important equation for water balance

Answer 9

[Na+] = Na+/H2O

Question 10

what can cause low [Na+]?

Answer 10

low sodium OR high water

Question 11

what can cause high [Na+]?

Answer 11

high sodium OR low water

Question 12

intra/extracellular:

(a) high fluid and low sodium
(b) low fluid and high sodium

Answer 12

(a) high fluid and low sodium - INTRACELLULAR

(b) low fluid and high sodium - EXTRACELLULAR

Question 13

wherever sodium goes, what follows?

Answer 13

water

Question 14

what can cause too little sodium?

Answer 14

increased Na loss OR decreased Na intake

Question 15

what can cause too much water?

Answer 15

reduced water excretion OR increased intake

Question 16

what can cause too much sodium?

Answer 16

increased Na intake OR decreased Na loss

Question 17

what can cause too little water?

Answer 17

increased water loss OR decreased water intake

Question 18

what condition causes increased water loss?

Answer 18

DM

Question 19

what condition causes reduced water excretion?

Answer 19

SIADH - syndrome of inappropriate antidiuretic hormone secretion

Question 20

whats the very very common cause of reduced sodium?

Answer 20

reduced water excretion - SIADH

Question 21

whats the uncommon but fatal if you miss it cause of reduced sodium?

Answer 21

increased sodium loss

Question 22

treatment:

(a) too little sodium =
(b) too much water =
(c) too much sodium =
(d) too little water =

Answer 22

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

Question 23

why give dextrose?

Answer 23

can enter the intracellular compartment

Question 24

name some stimuli for ADH release

Answer 24

osmotic

non-osmotic in disease

hypo/hypertension
pain
nausea/vomiting

Question 25

oedema treatment?

Answer 25

loop diuretic

Question 26

patient with oedema has too much what?

Answer 26

water and sodium

Question 27

low sodium in a well patient diagnosis?

Answer 27

pseudohyponatraemia

Question 28

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?

Answer 28

Addisons disease

too little sodium

primary adrenal insufficiency

adrenal not making aldosterone

Question 29

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?

Answer 29

DM

Question 30

those with too little sodium will look what?

Answer 30

dehydrated