Fluid and electrolytes- sodium and water

Question 1

is there a greater conc of K+ in ICF or ECF

Answer 1

ICF

Question 2

is there a greater conc of Na+ in ICF or ECF

Answer 2

ECF

Question 3

how can you check for ECF clinically

Answer 3

plasma- bp, HR, jvp. interstitial fluid- skin turgor, muscous membranes, oedema

Question 4

how can you check for ICF clinically

Answer 4

neuro status- cerebral oedema or dehydration

Question 5

what is osmolality

Answer 5

ionic concentration of a fluid mOsm/kg

Question 6

what is osmolality important for

Answer 6

determining the vol of a fluid compartment

Question 7

what is tonicity

Answer 7

decription of osmolality compared to another solution, dependent on osmotically active components that do not cross the cell membrane

Question 8

how much of total body water is ICF and ECF

Answer 8

2/3 and 1/3

Question 9

how much of ECF is plasma

Answer 9

1/4

Question 10

where is ADH released from

Answer 10

post pituitary

Question 11

where does the ADH originate from

Answer 11

hypothalamic, supraventricular and supra orbital nuclei

Question 12

what triggers ADH release

Answer 12

plasma osmolality increasing (thirst reflex), low bp (baroreceptors)

Question 13

what does ADH bind to and what is the sequence of events

Answer 13

vasopressin 2 receptors in collecting duct, opens aquaporin channels leads to reabsorption of water from the urine into the plasma

Question 14

what is isotonic fluid

Answer 14

fluid with the same osmlolality as plasma

Question 15

what happens in isotonic depletion

Answer 15

decrease in ECF but no change in osmolality so no fluid shift

Question 16

what happens in sodium depletion

Answer 16

decrease Na+, affects ECF so osmolality is higher in ICF thus leading to fluid shift into the ICF

Question 17

what triggers renin release

Answer 17

decrease BP or Na+

Question 18

what are the actions of angiotensin 2

Answer 18

acts on adrenal cortex to secrete aldosterone, and release ADH

Question 19

what does aldosterone act on

Answer 19

tubular- for the reabsorption of Na+ and water; and the excretion of K+

Question 20

what is hypertonic (referring to plasma)

Answer 20

decrease in plasma Na+

Question 21

what is hypotonic (referring to plasma)

Answer 21

increase in plasma Na+ - so losing more water than sodium

Question 22

what happens in water excess

Answer 22

Na+ decreases

Question 23

what happens in sodium excess

Answer 23

osmolality higher in ECF than ICF so water shifts from here to ECF. however if driven by low circulating blood volume or decrease in BP, ADH is released which may result in further water retention and hyponatraemia

Question 24

what is most fluid loss in the body

Answer 24

hypotonic

Question 25

what lab investigations can be done

Answer 25

plasma/serum sodium, osmolality, plasma glucose, serum urea and creatinine, urine osmolality and sodium, urine vol, serum cortisol, serum TFTs