Oral sodium phosphate is used for colon preparation prior to colonoscopy or barium enema. However, sodium phosphate induces hyperphosphatemia, hypocalcemia, and hypokalemia.
Elderly patients have an increased risk of phosphate intoxication, due to decreased glomerular filtration rates, medication use, and systemic and gastrointestinal diseases.
In this study, researchers from Israel assessed electrolyte disorders and their correlation with creatinine clearance, coexistent diseases, medications, and functional status.
The research team included 36 hospitalized patients in the study.
|Hypocalcemia was present in 58% of patients.|
|Archives of Internal Medicine|
On day 1, the team administered 2 doses of oral sodium phosphate to the patients.
They then obtained venous blood samples to determine electrolyte levels, on days 1, 2 (the procedure day), and 3. In addition, urine samples were obtained from 10 patients.
The researchers found that increased serum phosphorus levels were correlated with decreased creatinine clearance (R = -0.52).
Hypocalcemia and hypokalemia were present in 58% and 56% of patients, respectively.
The determined that patients with a serum potassium concentration of ≤ 3.5 mEq/l on day 2 had a lower concentration on day 1, compared to those with a concentration > 3.5 mEq/l on day 2. Overall, 5 patients had a serum potassium concentration of 3 mEq/l or less, and 2 had severe diarrhea, necessitating treatment.
In addition, the team found that there were more demented patients with hypokalemia, compared with normokalemic patients.
They also found that urinary fractional excretion of phosphorus tripled on day 2, while potassium and sodium fractional excretion remained unchanged.
Dr Yichayaou Beloosesky's team concluded, "Sodium phosphate induces serious electrolyte abnormalities in the elderly".
"The frequency and severity of hypokalemia is due to intestinal potassium loss associated with inadequate renal potassium conservation and is apparently more prevalent in frail patients".
"Assessment of serum electrolytes, phosphorus, and calcium prior to sodium phosphate preparation is advised, and in selected patients, postprocedural assessment and correction may be required".