CHempath - Sodium + Potassium

Question 1

Causes of hypervolemic hyponatraemia

Answer 1

The failures:

1) kidney
2) heart
3) liver

Question 2

Hypovolemic hyponatremia - causes?

Answer 2

1) D+V
2) Diuretics
3) Salt losing nephropathy

Question 3

Euvolemic hyponatremia - causes?

Answer 3

ENDOCRINE:

1) Hypothyroidism
2) SIADH
3) Adrenal insufficiency

Question 4

Ix for euvolemic hyponatremia

Answer 4

TFTs
Short SynACTHen test
Plasma + urine osmolality

Question 5

2 stimuli for aldosterone secretion

Answer 5

• Angiotensin II

- High plasma [K]

Question 6

Aldosterone’s effect on plasma sodium

Answer 6

NO effect: it does increase renal sodium reabsorption but then water follows it

Question 7

MOA of aldosterone upon binding to mineralocorticoid receptor? (quote specific proteins)

Answer 7

MC receptor activation –> down regulation of Sgk1 activity

Sgk1 usually stimulates Nedd42 protein - this protein degrades the epithelial Na channel

Question 8

Causes of hyperkalemia

Answer 8

• Reduced GFR
• Reduced Renin (NSAIDS)
• Aldosterone antagonist (spironolactone)
• ACEi
• Rhabdomyolysis
• Acidosis
• Addison’s

Question 9

What can cause a reduction in renin secretion and thus subsequent hyperkalemia

Answer 9

NSAIDs

Low renin –> low aldosterone

Question 10

Extra renal/adrenal causes of hyperkalemia? Name two

Answer 10

Rhabdomyolysis

Acidosis

Question 11

Most common causes of hyperkalemia - top 3?

Answer 11

• Renal failure
• Drugs (NSAIDs/ACEi/spironolactone)
• Addison’s

Question 12

4 main ECG changes associated with hyperkalemia

Answer 12

Peaked T waves
Flattened P waves
Broad QRS
Sine waves

Question 13

Management of hyperkalemia - give 3 actions

Answer 13

• 10mL 10% Calcium gluconate
• 50mL 50% dextrose + 10IU insulin
• Nebulised salbutamol

Question 14

Effect of insulin on plasma {K}

Answer 14

Drives K into cells, thus REDUCES plasma K

Question 15

How do thiazide diabetics lead to hypokalemia

Answer 15

Thiazide diuretics reduce Na reabsorption in the distal tubule, thus more Na is in the collecting duct lumen

In the collecting duct, Na and K are swapped and K is excreted

Question 16

Name a syndrome which affects the distal tubule, associated with hypokalemia?

Answer 16

Gitelman syndrome

Question 17

3 main groups of causes of hypokalemia?

Answer 17

GI loss
Renal loss - Loop diuretics/thiazides/bartters/gitelman
Metabolic - insulin, alkalosis

Question 18

Clinical features of hypokalemia?

Answer 18

• Muscle weakness
• Cardiac arrhythmia
• Polyuria/polydypsia (low K makes kidney resistant to ADH)

Question 19

How does hypokalemia lead to polyuria and polydipsia?

Answer 19

Low K leads to nephrogenic DI (resistance to ADH)

Question 20

Management of hypokalemia?

Answer 20

If <3, give IV K infusion

If 3-3.5: oral SandoK TDS for 2 days

Question 21

Max rate of IV K infusion if [K] <3.0?

Answer 21

10mM/hr

Question 22

Correction of hyponatremia - how?

What must you keep in mind

Answer 22

• Hypertonic 3% saline

do NOT correct >8mM in first 24 hrs due to risk of central pontine myelinolysis

Question 23

Central pontine myelinolysis - clinical fx?

Answer 23

Dysarthria
Quadriplegia
Dysphagia
Seizures/coma/death

Question 24

tx of SIADH

Answer 24

Water deprivation –> if ineffective:

• demeclocycline (causes resistance to ADH)
• Tolvaptan (V2 receptor antagonist)

Question 25

Demeclocycline - MOA?

Answer 25

Induces resistance to ADH –> less water reabsorption

Question 26

tolvaptan - MOA?

Answer 26

V2 receptor antagonist

Question 27

3 point management plan for hypernatraemia?

Answer 27

IV 0.9% saline + 5% dextrose

Serial Na measurement every 4-6 hours