B5.058 Electrolyte Abnormalities FLIP

Question 1

why does hypokalemia cause muscle weakness?

Answer 1

decreased Ki leads to decreased K+ conductance > cell depolarization is diminished > inactivation of Na+ channels > muscle unexcitability

Question 2

effects of hypokalemia on the heart

Answer 2

U waves on EKG

decreased K+ conductance leads to prolonged ventricular repolarization

Question 3

why does vomiting lead to alkalosis

Answer 3

loss of HCl

Question 4

why does diarrhea cause hypokalemia

Answer 4

loss of K+

Question 5

how to calculate GFR

Answer 5

Ccr = Ucr * V / Pcr

Question 6

how to calculate FEna

Answer 6

FE= (Una/Pna)/(Ucr/Pcr)

Question 7

normal daily excretion of Na and K

Answer 7

around 100 mEq/day

BUT has to be relative to plasma levels (i.e. shouldn’t be losing it if your plasma is depleted)

Question 8

what does an increase in FE suggest

Answer 8

altered tubular function
FEna should be 1%
Fek is variable
BUT
kidney should be reabsorbing in hyponatremia and hypokalemic conditions

Question 9

stimulants of R-A-A system

Answer 9

low BP
high sympathetic activity
decreased Na+ delivery to macula dense

Question 10

factors leading to aldosterone secretion

Answer 10

decrease Na+ in plasma
increased K+ in plasma
R-A-A system
ACTH from pituitary

Question 11

effects of aldosterone

Answer 11

increased Na+ and H2O absorption

increased K= and H+ secretion

Question 12

how do renin and aldosterone levels correlate with renal Na+ and K+ excretion rates in bartters

Answer 12

THEY DONT
increased Na+ and K+ excretion should inhibit renin normally
this shows the abnormal juxtaglomerular apparatus response

Question 13

how does Bartters cause polyuria and polydipsia

Answer 13

malfunction of the NKCC transporters alters the countercurrent mechanism
water cannot be absorbed in distal nephron