title: Blood ionized magnesium concentrations during cardiopulmonary bypass and their correlation with other circulating cations.
abstract: OBJECTIVE
  The recent introduction of new measurement technology (using ion specific electrodes) makes intraoperative evaluation of blood ionized magnesium (Mg2+, or iMg)--the bioactive fraction of circulation magnesium--possible. The goals of this study were: (1) to examine the longitudinal pattern(s) of change in blood iMg during cardiopulmonary bypass (CPB); and (2) to determine the relationship of iMg to Ca2+ (iCa), K, pH, Na, and hematocrit (Hct) during CPB.
  
  
  METHODS
  Blood was collected serially before, during, and after CPB on 30 patients undergoing elective coronary artery bypass graft procedures and the iMg was measured with an AVL Scientific Corp., model 988-4 instrument.
  
  
  RESULTS
  Overall, 73% of iMg results were abnormally low, 50% during CPB. Some cases had both hypo- and hyperionized magnesemic episodes. There were low iCa during CPB in 97% of cases. Using Spearman's rank order correlations and p < 0.05, iMg and K were directly correlated before, during, and after bypass, suggesting their parallel movement between tissue and blood. iMg and iCa were directly correlated before, and inversely correlated after, CPB, but unassociated during bypass. iMg and Na were inversely correlated after bypass in all cases. iMg was inversely correlated to pH and positively correlated to Hct during CPB only, and only in patients with concurrent association of iMg and iCa.
  
  
  CONCLUSIONS
  Blood iMg depletion occurs frequently in CPB patients. iMg changes are not readily predictable. The association of intraoperative iMg depletion with postsurgical atrial fibrillation--reported to have a hypomagnesemic connection- should be investigated.
authors.affiliation: Department of Surgery, School of Medicine, University of Washington, Seattle 98195-7110, USA.
authors.forename: S
authors.initials: S
authors.lastname: Aziz
authors.forename: W G
authors.initials: WG
authors.lastname: Haigh
authors.forename: G A
authors.initials: GA
authors.lastname: Van Norman
authors.forename: R J
authors.initials: RJ
authors.lastname: Kenny
authors.forename: M A
authors.initials: MA
authors.lastname: Kenny
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001145:Arrhythmias, Cardiac / Q000517:prevention & control; D002118:Calcium / Q000097:blood; D002315:Cardiopulmonary Bypass; D002412:Cations / Q000097:blood*; D005260:Female; D006801:Humans; D008274:Magnesium / Q000097:blood*; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative; D011183:Postoperative Complications / Q000517:prevention & control; D018709:Statistics, Nonparametric
chemical_list: D002412:Cations; D008274:Magnesium; D002118:Calcium