Carbohydrate-electrolyte rehydration protects against intravascular volume contraction during colonic cleansing with orally administered sodium phosphate

Background: Colonic cleansing with sodium phosphate causes intravascular volume contraction in some patients. This study tested the hypothesis that carbohydrate-electrolyte oral rehydration would attenuate the hypovolemic changes associated with administration of sodium phosphate. Methods: Adult outpatients were randomized to ingest either regular clear fluids or a carbohydrate-electrolyte rehydration solution during precolonoscopy purgation by ingestion of aqueous sodium phosphate. Investigators were blinded to the treatment assignment of patients. Clinical hemodynamic measurements and biochemical tests were obtained at baseline and after bowel preparation. Tolerability and colonoscopic visualization were assessed with questionnaires. Results: One hundred sixty-eight patients completed the study (81 clear fluids, 87 rehydration). By comparison with clear fluids, rehydration resulted in significantly less intravascular volume contraction. Changes in estimated central venous pressure and orthostatic pulse were significantly greater in the clear fluid group versus the rehydration group (p < 0.03). Changes in biochemical parameters after purgation also suggested a greater degree of volume contraction in the clear fluid versus rehydration group. Colonoscopic visualization was superior in the rehydration versus clear fluid group (p < 0.01); tolerability of the preparations was similar between groups (p = 0.2). Conclusions: Carbohydrate-electrolyte rehydration protects against intravascular volume contraction during preparation for colonoscopy by ingestion of sodium phosphate. This approach is well tolerated by patients and improves colonic cleansing.