Prevalence of hypokalemia before and after bowel preparation for colonoscopy in high-risk patients

BACKGROUND AND AIMS: Bowel preparation for colonoscopy should not cause significant shifts in systemic electrolyte concentrations. We recently encountered 2 cases of severe postcolonoscopy hypokalemia with fatal consequences, prompting us to conduct a study to explore the magnitude of and risk factors for hypokalemia associated with bowel preparation. We paid specific attention to higher-risk subgroups, in particular, diuretic users, hospitalized patients, and patients estimated to be at high risk by the gastroenterologist.

METHODS: From January 1 to December 31, 2014, we included all patients at risk for hypokalemia (diuretic users, hospitalized patients, and patients estimated at high risk by the gastroenterologist) who underwent colonoscopy at our institution. We measured serum potassium levels before low-volume polyethylene glycol bowel preparation for colonoscopy. In a subset of patients who had normal serum potassium levels before bowel cleansing, serum potassium levels after bowel cleansing also were measured.

RESULTS: In total, 5515 colonoscopies were performed, including 1822 procedures in diuretic users or hospitalized patients. Of these, 77 (4.2%) patients had hypokalemia before bowel cleansing. A logistic regression model showed that hospitalized patients were more likely to have hypokalemia than non-hospitalized patients. 301 patients with normal potassium levels had potassium controls after bowel cleansing, of whom 71 (23.6%) developed hypokalemia. A logistic regression model showed that diuretic users were more likely to develop hypokalemia than those who did not use diuretics.

CONCLUSIONS: Hypokalemia is frequently encountered after low-volume polyethylene glycol bowel cleansing in high-risk patients. Additional large-scale studies are needed on the prevalence of hypokalemia in unselected populations undergoing bowel cleansing and on the occurrence of potentially very serious side effects in order to decide on screening of high-risk groups in daily clinical practice. (Clinical trial registration number: NTR5400.).