Hypokalemia Following Polyethylene Glycol–Based Bowel Preparation for Colonoscopy in Older Hospitalized Patients with Significant Comorbidities

BACKGROUND: Polyethylene glycol-based bowel preparations (PEGBPs) are widely perceived as safe and effective alternatives to oral sodium phosphate for bowel cleansing prior to colonoscopy. Most studies supporting this belief involve young patients with few comorbidities. OBJECTIVE: To characterize the incidence of electrolyte disturbances following PEGBPs administered prior to colonoscopy among elderly inpatients and hypothesize that PEGBP would be associated with hypokalemia in this setting. METHODS: This retrospective chart review, conducted at 3 tertiary care teaching hospitals in Toronto, Canada, from 2005 to 2007, included 96 consecutive patients aged 65 or older who were admitted to the hospital and given PEGBP prior to their first inpatient colonoscopy. Patients were excluded if they received additional cathartics, underwent colonoscopy while admitted to a critical care unit, or were admitted for a complication arising from an outpatient colonoscopy. The primary outcome was hypokalemia (serum potassium < or =3.2 mEq/L) within 48 hours of PEGBP. RESULTS: Of 96 patients, 73 had serum electrolytes measured at baseline and within 48 hours following PEGBP administration. Hypokalemia was identified in 4 patients (5.5%) prior to PEGBP and in 15 patients (20.5%) after PEGBP (p < 0.001). The incidence of significant hypokalemia, defined as serum potassium < or =3.0 mEq/L, in this group was 9.6% (p = 0.008). We found consistent results among patients with and without concomitant diuretic treatment. CONCLUSIONS: Among older patients, administration of PEGBP is commonly complicated by the development of hypokalemia, which is occasionally severe. Monitoring of electrolytes may be necessary following colonoscopy, particularly in patients with cardiac or renal disease.