Electrolytes and physiology

Question 1

Potassium main role

Answer 1

Establish resting membrane potential in nerves and muscles

Little effect on osmotic pressure

Question 2

Major intracellular and extracellular cations?

Answer 2

Intra: Potassium
Extra: Sodium
Chloride and Bicarbonate are anions

Question 3

Hyponatraemia causes?

Answer 3

Excessive sweating
Vomiting/diarrhoea
Acidosis
SiADH

Question 4

Hypernatraemia causes

Answer 4

Hormonal imbalance i.e. Aldosterone and ADH

Question 5

Hypokalaemia causes

Answer 5

Starvation
Vomiting/diarrhoea
Alkalosis
Insulin administration

Question 6

Hyperkalaemia causes

Answer 6

Renal failure
Addison's Disease
Drugs (ACEi, ARBs)
Alcoholism
Rhabdomyolysis

Question 7

Hypocalcaemia causes

Answer 7

Hypoparathyroidism

Vitamin D deficiency

Question 8

Hypercalcaemia causes

Answer 8

Hyperparathyroidism

Malignancy

Question 9

Hypochloraemia causes

Answer 9

Vomiting/diarrhoea
Acidosis
Renal failure

Question 10

Hyperchloraemia causes

Answer 10

Dehydration/high NaCl intake (eg seawater drinking)
Heart failure
Lung disease
CF

Question 11

Hypophosphataemia causes

Answer 11

Excessive antacid use
Alcohol withdrawal
Malnourishment

Question 12

Hyperphosphataemia causes

Answer 12

Renal failure
Acute lymphocytic leukaemia
(and any cell destruction can “dump” phosphate into ECF)

Question 13

Drugs causing hypokalaemia

Answer 13

Loop diuretics (furosemide; bumetanide)
Thiazide diuretics (bendroflumethiazide)

Question 14

Drugs causing hyperkalaemia

Answer 14

K+ sparing diuretics (Amiloride; spironolactone; eplerenone)
ACEi
ARBs
Heparin (due to hypoaldosteronism action)

Question 15

Loop diuretics MOA?

Answer 15

Inhibit Na-K-Cl cotransporter in ascending Loop of Henle
Reduce NaCl absorption
( Can cause hypoelectrolytes)

Question 16

Thiazide diuretic mechanism?

Answer 16

Inhibits Na-Cl cotransporter in distal conv. tubule, water remains in tubule by osmosis

Question 17

Aldosterone MOA?

Answer 17

Low Na+ or high K+ (due to RAA systm)
Upregulates the Na/K ATPase in DCT and collecting duct. (3 Na+/2 K+). Leading to reabsorption of Na and excretion of K+
NB ALDOSTERONE is released directly by adrenals in response to high K+ (zona glomerulosa)

Question 18

When does RAA system kick in?

How does it contribute to change in BP?

Answer 18

Low plasma Na+ levels detected by juxtaglomerular apparatus.

Angiotensin II causes vasoconstriction