Correction of severe hypokalemia in decompensated pyloric stenosis: a case report

Severe hypokalemia, defined as a serum potassium concentration below 2.5 mmol/L, is a relatively uncommon but clinically significant condition. It is often associated with a poorer prognosis in hospitalized patients. Potassium replacement in severe hypokalemia may be challenging. A major contributing factor is substantial underestimation of the deficiency when standard calculation methods are used.

A 64-year-old woman with decompensated pyloric stenosis due to gastric cancer and displacement of a previously installed stent developed severe hypokalemia following persistent vomiting. Despite potassium replacement according to the British Dietetic Association’s Clinical Nutrition Guidelines commonly used for hypokalemia, both hypokalemia and symptoms of severe potassium deficiency continued to worsen. The patient was transferred to the intensive care unit with progressive weakness, muscle cramps, and gastrointestinal paresis, where a simplified protocol for rapid potassium replacement was used. Normokalemia and resolution of severe manifestations of potassium deficiency were achieved within 2 days.

In cases of severe potassium deficiency, it is essential to diagnose hypokalemia and monitor serum potassium concentrations during correction and also to accurately estimate the potassium dose required to replenish the deficiency. Standard potassium deficiency calculations used for mild or moderate hypokalemia substantially underestimate the actual deficiency in severe hypokalemia, resulting in inadequate correction. Existing nomograms for potassium repletion that take into account current acid–base balance are complex to use. They do not offer any advantages in clinical practice, as minor calculation errors are compensated by repeated serum potassium measurements and subsequent therapy adjustments. In severe hypokalemia, for the initial general estimation of potassium deficiency, it is convenient to consider that that each decrease in potassium concentration by 0.3 mmol/L with serum potassium below 3.5 mmol/L corresponds to a total body potassium deficit of approximately 10 mmol per 10 kilograms of body weight.