title: The relationship between ionized and total serum magnesium concentrations during abdominal surgery.
abstract: OBJECTIVE
  To determine the necessity for ionized magnesium (iMg) assay by evaluating the effect of abdominal surgery without massive transfusion on total magnesium (Mg) and iMg concentrations.
  
  
  METHODS
  Prospective, observational study.
  
  
  METHODS
  Operating rooms at a university teaching hospital.
  
  
  METHODS
  31 patients without electrolyte abnormalities who were scheduled for abdominal surgery.
  
  
  METHODS
  None.
  
  
  METHODS
  Serum electrolytes, iMg, ionized calcium, proteins before and after surgery, and urine Mg were recorded.
  
  
  RESULTS
  Total Mg and iMg decreased: Mg 23%, iMg 15%; p < 0.0001. Total and iMg were highly correlated (r = 0.728, p < 0.0001). Urine Mg output remained within normal limits (mean 0.24 mmol/hr).
  
  
  CONCLUSIONS
  During abdominal surgery without massive transfusion, both total and ionized hypomagnesemia occur. Changes in iMg and total serum Mg concentrations are closely correlated. Total serum Mg assay, while overestimating the prevalence of ionized hypomagnesemia, is sufficient to screen for hypomagnesemia.
authors.affiliation: Department of Anesthesiology, Duke University Medical Center, Durham, NC 27710, USA. lanzi001@mc.duke.edu
authors.forename: Marcella J
authors.initials: MJ
authors.lastname: Lanzinger
authors.forename: Eugene W
authors.initials: EW
authors.lastname: Moretti
authors.forename: Robert F
authors.initials: RF
authors.lastname: Wilderman
authors.forename: Habib E
authors.initials: HE
authors.lastname: El-Moalem
authors.forename: John G
authors.initials: JG
authors.lastname: Toffaletti
authors.forename: Richard E
authors.initials: RE
authors.lastname: Moon
mesh_terms: D000005:Abdomen / Q000601:surgery*; D000328:Adult; D000418:Albumins / Q000032:analysis; D000768:Anesthesia, General; D001798:Blood Proteins / Q000032:analysis; D002118:Calcium / Q000097:blood; D004573:Electrolytes / Q000097:blood; D005260:Female; D006801:Humans; D007477:Ions; D008274:Magnesium / Q000097:blood* / Q000652:urine; D008297:Male; D011446:Prospective Studies; D013514:Surgical Procedures, Operative
chemical_list: D000418:Albumins; D001798:Blood Proteins; D004573:Electrolytes; D007477:Ions; D008274:Magnesium; D002118:Calcium