Hypokalaemia Flashcards
what is the definition of hypokalaemia?
Hypokalaemia is defined as a serum potassium level <3.5 mmol/L (<3.5 mEq/L). Moderate hypokalaemia is defined as serum potassium levels of 2.5 to 3 mmol/L (2.5 to 3 mEq/L) and severe hypokalaemia defined as a serum potassium level <2.5 mmol/L (<2.5 mEq/L)
what is the aetiology of hypokalaemia?
Hypokalaemia is most commonly due to urinary or GI losses
Increased potassium excretion:
Renal (renal tubular acidosis, diuretics, elevated mineralocorticoids, elevated cortisol), GI (vomiting, villous adenoma, VIPoma), skin (burns, eczema, psoriasis, sweating)
Decreased potassium intake :
Anorexia, diuretics, hypocaloric protein diets
Increased potassium entry to cells:
Elevated extracellular pH, increased beta-adrenergic activity, increased availability of insulin
what is the pathophysiology of hypokalaemia?
The ratio of intracellular to extracellular potassium determines, in part, the cellular membrane potential. Therefore small changes in the extracellular potassium level can have large effects on the function of the cardiovascular and neuromuscular systems.
A fall in serum potassium from 4 to 3 mmol/L (4 to 3 mEq/L) represents an approximate loss of 200 to 400 mmol (200 to 400 mEq) of potassium. However, these estimates do not always apply to patients with transcellular potassium redistribution. Clinical manifestations of hypokalaemia are typically seen only if the serum potassium is <3.0 mmol/L (<3.0 mEq/L).
what are the key presentations of hypokalaemia?
Common acute manifestations are muscle weakness and ECG changes. More prolonged and profound hypokalaemia may cause rhabdomyolysis, renal abnormalities, and cardiac arrhythmias.
what are the signs of hypokalaemia?
ECG changes
Rhabdomyolysis
Renal abnormalities
Cardiac arrhythmias
what are the symptoms of hypokalaemia?
Frequently asymptomatic
Muscle weakness
what are the first line and gold standard investigations for hypokalaemia?
History to determine cause
Basic metabolic panel
BP measurements
Urine potassium and calcium (differentiating renal or non-renal cause)
ABG - metabolic acidosis
ECG - depression of ST segment, decrease in T wave amplitude, increase amplitude of U waves
what are the differential diagnoses for hypokalaemia?
Vomiting, severe diarrhoea, laxative use, bulimia, anorexia, drug use, alcoholism
how is hypokalaemia managed?
The rapidity and method of potassium repletion depends on:
The severity of hypokalaemia
The presence of associated conditions
The presence or absence of signs and symptoms
The expectation of continued losses
