Severe metabolic acidosis induced in a patient during fasting by KCl administration

The purpose of this study was to determine the cause of an acute metabolic acidosis of the normal anion gap type which developed during a 3 day period when 64 mmol of KCl was administered daily to an obese but otherwise healthy subject fasted for 2 weeks (called the index case). She had typical ketoacidosis of fasting for the first 13 days of fasting; since the plasma [K] was 3.6 mmol/l, she was given 64 mmol of KCl daily for 3 days. On day 3 of KCl treatment, the plasma [HCO₃] was 13 mmol/l with no change in the plasma anion gap or 3-hydroxybutyrate concentration; the plasma [K] had risen to 4.3 mmol/l. The cause of the acidosis was a reduction of urine ammonium excretion by 42 mmol/day without a parallel fall in the rate of 3-hydroxybutyrate excretion. Since renal ammonium production can be inhibited by K administration, 5 other obese subjects were studied in a similar fashion to gain insight into the problem. They had a similar reduction in the daily rate of ammonium excretion (41 mmol) after KCl; however, their daily 3-hydroxybutyrate excretions declined by a similar amount (47 mmol) and thus metabolic acidosis did not develop.