An editorial in the British Medical Journal recently advocated that people should increase their intake of potassium. Its benefits include lowering blood pressure in both hypertensive and normotensive people. But, scientists C J Doorenbos and C G Vermeij, warned in a recent issue of the BMJ that in the high risk population that may benefit most from an increased consumption of potassium, several medical conditions predispose to the development of hyperkalaemia through impairing renal excretion of potassium.
Such conditions include renal failure, diabetes mellitus with hyporeninaemic hypoaldosteronism, and obstructive uropathy.
The risk of hyperkalaemia, which can lead to cardiac arrhythmias and cardiac arrest, is further increased by the frequent prescription in these patients of angiotensin converting enzyme inhibitors, angiotensin II receptor blockers, and potassium sparing diuretics, say the authors.
Elderly patients with osteoarthritis may also use non-steroidal anti-inflammatory drugs, which also may contribute to increased plasma potassium values.
They write that salt substitutes that contain potassium may cause hyperkalaemia with life threatening consequences in susceptible patients. The researchers illustrated their paper with a case report.
They continue that consumption of fruit and vegetables is the preferred source of potassium, but the use of a salt substitute also increases the intake of potassium at the same time as reducing the use of sodium.
Patients are often not aware that their medical condition may reduce potassium excretion or of the potassium content of the salt substitute they may use to reduce their sodium intake. Carers may not always know of a patient's use of a salt substitute.
They recommend that patients with impaired renal potassium excretion due to renal disease, especially those taking angiotensin converting enzyme inhibitors, angiotensin II receptor blockers, potassium sparing diuretics, or non-steroidal anti-inflammatory drugs, should be warned by their doctors and dieticians about the danger of hyperkalaemia. Prescribers of these drugs to such patients should inquire about their use of potassium-containing salt substitutes.