C - K and Electrolytes

Question 1

what is the most abundant intracellular cation

Answer 1

K

Question 2

give normal range of K

Answer 2

3.5 to 5 mmol/L

Question 3

what regulates K

Answer 3

angiotensin 2
aldosterone

Question 4

describe the ang / ald / K pathway

Answer 4

angiotensinogen –> angiotensin 1 (via renin from JGA)
angiotensin 1 –> angiotensin 2 (via ACE in lungs)
angiotensin 2 stimulates aldosterone in adrenals
aldosterone increases K and decreases N in kidney

Question 5

which cells does aldosterone act on to increase K

Answer 5

principal cells in cortical collecting duct of kidney

Question 6

what 2 things stimulate aldosterone production

Answer 6

K+ and ang 2

Question 7

what electrical change causes K+ excretion

Answer 7

if LUMEN of principal cells in kidney is more negative then K+ is lost into lumen down electrical gradient

Question 8

what R does aldosterone act on

Answer 8

mineralocorticoid R

Question 9

are K and Na transported on the same transporter in the kidney

Answer 9

NO - separate transporters but their passage is linked by the electrical gradient equillibrium

Question 10

describe the mechanism of how aldosterone increases K excretion

Answer 10

aldosterone increases the number of open Na channels –> more Na resorption –> lumen becomes more negative –> more K secreted out of cells into lumen

Question 11

list 4 main causes of high K in order of commonness

Answer 11

1.) renal impairment
2.) drugs
3.) low aldosterone eg Addisons
4.) release of K from cells - rhabdomyolysis / acidosis

Question 12

name 3 drug classes to cause high K

Answer 12

ACEi
ARBs
spironolactone

Question 13

what ECG finding is seen with high K

Answer 13

peaked T waves

Question 14

give the Mx of high K (inc doses)

Answer 14

10ml 10% calcium gluconate
100ml of 20% dextrose + 10 units of insulin
nebulised salbutamol
treat underlying cause

Question 15

give causes of low K

Answer 15

GI loss - vomitting
renal loss - osmotic diuresis, high ald/cortisol, more Na to distal nephron
redistribution into cells - insulin / beta agonists / alkalosis
rare = renal tubular acidosis or low magnesium

Question 16

what drugs cause low K & how

Answer 16

loop diuretics / Bartters syndrome –> block ascending limb of LoH
thiazdie diuretics / Gitelman syndrome –> block distal tubule
xs aldosterone - Conn.s / hyperplasia

Question 17

Sx of low K

Answer 17

weakness
cardiac arrhythmias
polyuria, polydipsia –> nephrogenic DI

Question 18

if someone presents with low K and HTN, what Ix would you do?

Answer 18

aldosterone renin ratio

Question 19

Mx of low K inc doses

Answer 19

If K 3-3.5 mmol (mild)
- oral KCl (2 sandok tabs tds for 48hrs)
- recheck K
If K < 3mmol (sev)
- IV KCl max 10mmol/hr

Question 20

give the equation for blood osmolality

Answer 20

2 (Na + K) + Urea + Glucose

Question 21

what is the normal blood osmolality

Answer 21

276 - 296

Question 22

give the equation for anion gap

Answer 22

Na + K - Cl - Bicarb

Question 23

what is the normal anion gap

Answer 23

18

Question 24

what causes large anion gap

Answer 24

extra anions - ketones, lactate, poison, methanol/ethanol
xs metformin - lactic acidosis

Question 25

defining ranges for DM

Answer 25

fasting >7 or 2hr >11.1 after OGTT

Question 26

raised ALP in jaundice. cause?

Answer 26

obstructive

Question 27

raised ALT in jaundice. cause?

Answer 27

hepatitis