Clinical problem solving: electrolytes, acid-base

Question 1

in lean adults, body fluids constitute what % of the female body? male body?

Answer 1

• female: 55%

- male: 60%

Question 2

what proportion of the body fluid is intracellular fluid?

Answer 2

2/3

Question 3

what % of the ECF is interstitial fluid? plasma?

Answer 3

• interstitial fluid: 80%

- plasma: 20%

Question 4

where is the thirst center located?

Answer 4

hypothalamus

Question 5

what is the main factor that determines body fluid volume?

Answer 5

extent of urinary SALT loss

Question 6

what is the main factor that determines body fluid osmolarity?

Answer 6

extent of urinary WATER loss

Question 7

how does ANP affect fluid homeostasis?

Answer 7

promotes natriuresis, excretion of Na and Cl followed by water excretion to decrease blood volume

Question 8

what is the major hormone regulating water loss?

Answer 8

ADH

Question 9

ADH promotes insertion of aquaporin-2 into what cells? in what part of the nephron?

Answer 9

• principal cells

- collecting duct

Question 10

what are the 4 general functions of electrolytes?

Answer 10

• control water osmosis
• acid-base balance
• carry electrical current
• cofactors

Question 11

what are the major cation of the ECF?

Answer 11

Na

Question 12

what is the major anion of the ECF?

Answer 12

Cl

Question 13

what is the major cation of the ICF?

Answer 13

K

Question 14

what are the major anions of the ICF?

Answer 14

proteins, phosphates

Question 15

how does PTH affect phosphate homeostasis?

Answer 15

• stimulates resorption of bone by osteoclasts
• calcium released, phosphate released
• inhibits reabsorption of phosphate in kidneys

Question 16

ammonium is produced from the metabolism of what amino acid?

Answer 16

glutamine

Question 17

each glutamine produces how many ammonium ions? what about bicarbonate?

Answer 17

2 ammonium, 2 bicarbonate

Question 18

how can you differentiate between the etiologies of hypokalemic alkalosis?

Answer 18

BP

Question 19

in what situations (GI, GU) will you see a low-normal BP in hypokalemic alkalosis?

Answer 19

GI:

• vomiting
• NG suction

GU:

• diuretics
• bartter’s
• gitelman’s

Question 20

what will the BP be in the hypokalemic, alkalotic state of bartter’s and gitelman’s syndromes?

Answer 20

low-normal

Question 21

what will the BP be in the hypokalemic, alkalotic state of liddle’s syndrome?

Answer 21

high