Q J Med 2005; 99:181–192 Advance Access publication 9 February 2006 doi:10.1093/qjmed/hcl011 Masterclasses in medicine Unusual causes of hypokalaemia and paralysis M. ALAZAMI 1 , S.-H. LIN 2 , C.-J. CHENG 2 , M.R. DAVIDS 3 and M.L. HALPERIN 1 From the 1 Division of Nephrology, St. Michael’s Hospital, University of Toronto, Toronto, Canada, 2 Renal Division, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan (ROC), and 3 Nephrology Unit and Department of Internal Medicine, Stellenbosch University, Cape Town, South Africa Summary We demonstrate how the application of physiologi- cal principles may help to identify unusual causes of a very low plasma potassium (K þ ) concentration (P K ) and paralysis. In the two patients described, the short time course of the illness suggested that there was an acute shift of K þ into cells. The combination of a low rate of excretion of K þ , the absence of a metabolic acid-base disorder, and the fact that the clinical findings occurred very soon after a large intake of carbohydrate supported this impression. Surprisingly, the P K remained low for many hours after these stimuli to shift K þ into cells had abated. The missing link in this story was eventually provided by the attending medical team with the help of their mentor, Professor McCance. Introduction In this teaching exercise, the central (imaginary) figure is Professor McCance, based on a real consultant who practiced medicine 70 years ago. The overall objective is to demonstrate how apply- ing principles of integrative physiology at the bedside and relying on a quantitative analysis can be extremely helpful in revealing the pathophysiol- ogy of disease, making more accurate clinical diagnoses, and in planning optimal therapy. When these principles of physiology are combined with recent discoveries at the molecular and genetic levels, the features responsible for many disorders can be better understood. The consultation After their recent teaching session with Professor McCance, the medical team was confident that they would be able to work up the next patient with hypokalaemia and paralysis. 1 They were therefore extremely disappointed to find themselves faced with two patients where they could not determine the cause of a very low plasma potassium (K þ ) concentration (P K ) and paralysis. As was their custom in this situation, they asked their favourite consultant, Professor McCance, to join them on rounds and assist them in analysing the information. The two patients in question, 45- and 35-year- old Asian males, had similar clinical Address correspondence to Professor M.L. Halperin, University of Toronto, St Michael’s Hospital Annex, Lab #1, Research Wing, 38 Shuter Street, Toronto, Ontario, M5B 1A6, Canada. email: mitchell.halperin@utoronto.ca ! The Author 2006. Published by Oxford University Press on behalf of the Association of Physicians. All rights reserved. For Permissions, please email: journals.permissions@oxfordjournals.org Downloaded from https://academic.oup.com/qjmed/article-abstract/99/3/181/2261044 by guest on 18 June 2020