Electrolyte Imbalances Flashcards
Hyperkalaemia causes
Acute kidney injury Drugs Metabolic acidosis Addison's disease Rhabdomyolysis Massive blood transfusion
Drugs causing hyperkalaemia
Potassium sparing diuretics ACE inhibitors Angiotensin 2 receptor blockers Spironolactone Ciclosporin Heparin
Regulation of plasma potassium levels
Aldosterone
Acid-base balance
Insulin levels
Why is hyperkalaemia associated with metabolic acidosis?
Hydrogen and potassium ions compete with each other for exchange with sodium ions across cell membranes and in the distal tubule
Treatment of hyperkalaemia (acute)
Calcium infusion is given to rapidly REVERSE conduction abnormalities
Insulin to stimulate the sodium/potassium pump, promoting INTRA-cellular shift
Hemodialysis to remove potassium
Treatment of hyperkalaemia (mild or moderate with no ECG changes)
Ion exchange resin (eg. sodium polystyrene sulphonate exchanges sodium for potassium in the colon)
Effects of hyperkalaemia
Chronic - kidneys adapt by excreting more potassium
Acute - systemic symptoms, irregular heartbeat/palpitations
How does hyperkalaemia cause VF?
As potassium levels INcrease in the EXTRAcellular space, the MAGNITUDE of potassium gradient across the cell membrane is REDUCED, and so is the ABSOLUTE value of the resting membrane potential. Membrane voltage becomes less negative, moving closer to the threshold potential, making it EASIER to initiate an action potential. While initial changes seem to increase myocyte excitability; further rise of potassium has the OPPOSITE effect. This is because the value of membrane potential at the onset of an action potential DETERMINES the number of voltage-gated sodium channels activated during depolarization. As this value becomes less negative in hyperkalemia, the number of available sodium channels DEcreases, resulting in a SLOWER influx of sodium and subsequently SLOWER impulse conduction.
Hypokalaemia causes (with acidosis)
Diarrhoea
Renal tubular acidosis
Acetazolamide
Partially treated diabetic ketoacidosis
Hypokalaemia causes (with alkalosis)
Vomiting
Thiazide and loop diuretics
Cushing’s syndrome
Conn’s syndrome (primary hyperaldosteronism)
Hypokalaemia treatment
Discontinue causative drugs
Use potassium sparing diuretics
Hypercalcaemia causes
Primary hyperparathyroidism
Malignancy
Sarcoidosis
Vitamin D intoxication
Acromegaly
Thyrotoxicosis
Milk-alkali syndrome
Drugs: thiazides, calcium containing antacids
Dehydration
Addison's disease
Paget's disease of the bone
Hypercalcaemia treatment
Calcitonin
Hypocalcaemia causes
Vitamin D deficiency Chronic kidney disease Hypoparathyroidism Pseudohypoparathyroidism Rhabdomyolysis Magnesium deficiency Massive blood transfusion Acute pancreatitis
Hypocalcaemia management
IV replacement - preferred method => IV calcium gluconate
ECG monitoring is recommended
Further management depends on the underlying cause
