Objectives: Oral sodium phosphate (NaP), a colonic cleansing agent for colonoscopy that is superior to standard polyethylene glycol-based lavage solutions because of greater patient acceptance, effectiveness, and significantly less cost, causes intravascular volume depletion and hyperphosphatemia. To determine whether these changes may be near the threshold for inducing clinically serious side effects, these parameters were studied in patients receiving two doses of NaP over 5 h rather than the conventional 12-h duration.
Methods: 50 patients (27 outpatients, 23 inpatients) drank 45 ml of NaP at 1700 and 2200 h the night before colonoscopy. Patients with renal failure, active heart disease, ileus, or gross ascites were excluded.
Results: Serial blood tests and hemodynamic measurements demonstrated signs of intravascular volume depletion in less than 10% of outpatients but up to 40% of inpatients. None of the patients complained of postural dizziness or presyncope. All patients became hyperphosphatemic (maximum 3.72; normal < 1.30 mmol/L). Measurements of ionized calcium were significantly lower compared with baseline values (mean values 1.19 vs 1.23 mmol/L, respectively). In 44% of patients, these values were below the lower limits of normal (1.19 mmol/L) but these changes were minor (lowest value 1.07 mmol/L) and none of the patients were symptomatic.
Conclusions: This study suggests that oral NaP is a safe agent in most patients for colonic cleansing, even when given using a 5-h regimen.