title: Electrolyte disorders following oral sodium phosphate administration for bowel cleansing in elderly patients.
abstract: BACKGROUND
  Oral sodium phosphate is currently used for colon preparation prior to colonoscopy or barium enema. Sodium phosphate induces hyperphosphatemia, hypocalcemia, and hypokalemia. Elderly patients are at an increased risk for phosphate intoxication due to decreased glomerular filtration rate, medication use, and systemic and gastrointestinal diseases. We investigated these electrolyte disorders and their correlation with creatinine clearance, coexistent diseases, medications, and functional status.
  
  
  METHODS
  Thirty-six hospitalized patients were included in the study. On day 1, patients were administered 2 doses of oral sodium phosphate. Venous blood samples for electrolyte determination were obtained at 7 AM on days 1, 2 (the procedure day), and 3. Urine samples were obtained from 10 patients.
  
  
  RESULTS
  An increase in serum phosphorus level was correlated with a decreased creatinine clearance (R = -0.52; P =.001). Hypocalcemia and hypokalemia were present in 21 (58%) and 20 (56%) patients, respectively. Patients with a serum potassium concentration of 3.5 mEq/L or less on day 2 had a lower serum potassium concentration on day 1 vs those with a serum potassium concentration greater than 3.5 mEq/L on day 2 (P =.03). Five (dependent patients) had a serum potassium concentration of 3 mEq/L or less and 2 had severe diarrhea, necessitating treatment. There were more demented patients with hypokalemia compared with normokalemic patients (P<.05). Urinary fractional excretion of phosphorus tripled on day 2 (P =.01). Potassium and sodium fractional excretion remained unchanged.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Geriatrics Rabin Medical Center, Beilinson and Golda Campuses, Sackler School of Medicine, Tel Aviv University, Petach Tikva, Israel. belo-7@zahav.net.il
authors.forename: Yichayaou
authors.initials: Y
authors.lastname: Beloosesky
authors.forename: Josef
authors.initials: J
authors.lastname: Grinblat
authors.forename: Avraham
authors.initials: A
authors.lastname: Weiss
authors.forename: Boris
authors.initials: B
authors.lastname: Grosman
authors.forename: Uzi
authors.initials: U
authors.lastname: Gafter
authors.forename: Avry
authors.initials: A
authors.lastname: Chagnac
mesh_terms: D000284:Administration, Oral; D000368:Aged; D002400:Cathartics / Q000008:administration & dosage* / Q000009:adverse effects*; D003404:Creatinine / Q000097:blood; D005260:Female; D006801:Humans; D007008:Hypokalemia / Q000139:chemically induced; D008297:Male; D010710:Phosphates / Q000008:administration & dosage* / Q000009:adverse effects*; D012720:Severity of Illness Index; D014883:Water-Electrolyte Imbalance / Q000097:blood / Q000139:chemically induced* / Q000652:urine
chemical_list: D002400:Cathartics; D010710:Phosphates; D003404:Creatinine; C018279:sodium phosphate