Uncovering the basis of a severe degree of acidemia in a patient with diabetic ketoacidosis

Abstract

In this teaching exercise, the goal is to demonstrate how an application of principles of physiology can reveal the basis for a severe degree of acidaemia (pH 6.81, bicarbonate <3 mmol/l (PHCO3), PCO2 8 mmHg), why it was tolerated for a long period of time, and the issues for its therapy in an 8-year-old female with diabetic ketoacidosis. The relatively low value for the anion gap in plasma (19 mEq/l) suggested that its cause was both a direct and an indirect loss of NaHCO3. Professor McCance suggested that ileus due to hypokalaemia might cause this direct loss of NaHCO3, and that an excessive excretion of ketoacid anions without NH4 in the urine accounted for the indirect loss of NaHCO3. In addition, he suspected that another factor also contributing to the severity of the acidaemia was a low input of alkali. He was also able to explain why there was a 16-h delay before there was a rise in the PHCO3 once therapy began. The missing links in this interesting story, including a possible basis for the hypokalaemia, emerge during the discussion between the medical team and Professor McCance. © The Author 2007. Published by Oxford University Press on behalf of the Association of Physicians. All rights reserved.