CHempath - Sodium + Potassium Flashcards
Causes of hypervolemic hyponatraemia
The failures:
1) kidney
2) heart
3) liver
Hypovolemic hyponatremia - causes?
1) D+V
2) Diuretics
3) Salt losing nephropathy
Euvolemic hyponatremia - causes?
ENDOCRINE:
1) Hypothyroidism
2) SIADH
3) Adrenal insufficiency
Ix for euvolemic hyponatremia
TFTs
Short SynACTHen test
Plasma + urine osmolality
2 stimuli for aldosterone secretion
- Angiotensin II
- High plasma [K]
Aldosterone’s effect on plasma sodium
NO effect: it does increase renal sodium reabsorption but then water follows it
MOA of aldosterone upon binding to mineralocorticoid receptor? (quote specific proteins)
MC receptor activation –> down regulation of Sgk1 activity
Sgk1 usually stimulates Nedd42 protein - this protein degrades the epithelial Na channel
Causes of hyperkalemia
- Reduced GFR
- Reduced Renin (NSAIDS)
- Aldosterone antagonist (spironolactone)
- ACEi
- Rhabdomyolysis
- Acidosis
- Addison’s
What can cause a reduction in renin secretion and thus subsequent hyperkalemia
NSAIDs
Low renin –> low aldosterone
Extra renal/adrenal causes of hyperkalemia? Name two
Rhabdomyolysis
Acidosis
Most common causes of hyperkalemia - top 3?
- Renal failure
- Drugs (NSAIDs/ACEi/spironolactone)
- Addison’s
4 main ECG changes associated with hyperkalemia
Peaked T waves
Flattened P waves
Broad QRS
Sine waves
Management of hyperkalemia - give 3 actions
- 10mL 10% Calcium gluconate
- 50mL 50% dextrose + 10IU insulin
- Nebulised salbutamol
Effect of insulin on plasma {K}
Drives K into cells, thus REDUCES plasma K
How do thiazide diabetics lead to hypokalemia
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
Name a syndrome which affects the distal tubule, associated with hypokalemia?
Gitelman syndrome
3 main groups of causes of hypokalemia?
GI loss
Renal loss - Loop diuretics/thiazides/bartters/gitelman
Metabolic - insulin, alkalosis
Clinical features of hypokalemia?
- Muscle weakness
- Cardiac arrhythmia
- Polyuria/polydypsia (low K makes kidney resistant to ADH)
How does hypokalemia lead to polyuria and polydipsia?
Low K leads to nephrogenic DI (resistance to ADH)
Management of hypokalemia?
If <3, give IV K infusion
If 3-3.5: oral SandoK TDS for 2 days
Max rate of IV K infusion if [K] <3.0?
10mM/hr
Correction of hyponatremia - how?
What must you keep in mind
- Hypertonic 3% saline
do NOT correct >8mM in first 24 hrs due to risk of central pontine myelinolysis
Central pontine myelinolysis - clinical fx?
Dysarthria
Quadriplegia
Dysphagia
Seizures/coma/death
tx of SIADH
Water deprivation –> if ineffective:
- demeclocycline (causes resistance to ADH)
- Tolvaptan (V2 receptor antagonist)
Demeclocycline - MOA?
Induces resistance to ADH –> less water reabsorption
tolvaptan - MOA?
V2 receptor antagonist
3 point management plan for hypernatraemia?
IV 0.9% saline + 5% dextrose
Serial Na measurement every 4-6 hours
