An approach to the patient with severe hypokalaemia: the potassium quiz.

The objective of this teaching session with Professor McCance is to develop an approach to the management of patients with a very low plasma potassium (K(+)) concentration (P(K)). The session begins with a quiz based on six recent medical consultations for a P(K) < 2 mmol/l. Professor McCance outlined how he would proceed with his diagnosis and therapy, using the synopsis that described each patient. This approach was then applied to a new patient, a 69-year-old woman who had a large volume of dependent oedema and developed a severe degree of weakness and hypokalaemia during more aggressive diuretic therapy that included a K(+)-sparing diuretic. The initial challenge for Professor McCance was to deduce why the K(+)-sparing diuretic was not effective in this patient. He also needed to explain why the P(K) was so low on admission.