Most abundant intracellular cation – as only 2% is extracellular small changes can have major impact. It is a major determinant of intracellular osmolality and plays an important role in nerve impulse conduction.
• decrease in serum potassium concentration – due to a deficit in total body stored or abnormal movement of potassium into cells – from renal loss; GI losses (eg vomiting); transcellular shift, inadequate diet and drugs
• Generally tiredness, palpitations, muscle weakness, parathesia, constipation, nausea, vomiting, abdominal cramps, polyuria, polydipsia, psychoses, hypotension, decreased tendon reflexes
• if severe muscle weakness paralysis
• management – oral or IV K+ salt; prevention (eg diuretics)
• increase in serum potassium concentration – due to an excess in total body stores or abnormal movement out of cells – potentially life threatening
• caused by increased intake (eg IV fluids); tissue breakdown (eg haemolysis); movement of K+ out of cell (eg ischaemia, acidosis, insulin deficiency); impaired excretion (eg renal disease)
• common in diabetic ketoacidosis (treatment with insulin can cause a hypokalaemia)
• clinical features vague and subtle – usually found on laboratory tests.
• may have general fatigue, weakness, paraesthesias or paralysis
• may have diminished deep tendon reflexes
• treatment – identify and treat underlying cause; IV calcium gluconate