Hypokalaemia
Hypokalaemia is a reduced blood level of potassium<3.5 mmol/L.
Symptoms and Signs
Muscle weakness. Myalgia. Constipation. Paralytic ileus. Cardiac arrhythmia (ranging from ectopics to serious arrhythmias with sudden death at very low levels of potassium).
Investigations
■ Blood bases
Metabolic alkalosis – pH↑HCO3− ↑. Blood glucose. Diabetic ketoacidosis.
■ ECG
Flattened T waves. ST depression. U waves. Prolonged QT intervals.
■ Serum Mg
Mg↓(magnesium is required for adequate processing of K+).
■ Plasma aldosterone
Raised in Conn’s syndrome.
■ Plasma renin
Low in Conn’s syndrome.
■ Plasma cortisol
Diurnal variation lost in Cushing’s syndrome.
■ Plasma aldosterone
Raised in Conn’s syndrome.
■ Urinary free cortisol
Elevated in Cushing’s syndrome.
■ ACTH levels
High in pituitary-dependent cases, low or undetectable with adrenal tumour; may be very high with ectopic ACTH secretion.
