title: Warm-blood cardioplegia with low or high magnesium for coronary bypass surgery: a randomised controlled trial.
abstract: OBJECTIVE
  Magnesium (Mg²⁺) is cardioprotective and has been routinely used to supplement cardioplegic solutions during coronary artery bypass graft (CABG) surgery. However, there is no consensus about the Mg²⁺ concentration that should be used. The aim of this study was to compare the effects of intermittent antegrade warm-blood cardioplegia supplemented with either low- or high-concentration Mg²⁺.
  
  
  METHODS
  This study was a randomised controlled trial carried out in two cardiac surgery centres, Bristol, UK and Cuneo, Italy. Patients undergoing isolated CABG with cardiopulmonary bypass were eligible. Patients were randomised to receive warm-blood cardioplegia supplemented with 5 or 16 mmol l⁻¹ Mg². The primary outcome was postoperative atrial fibrillation. Secondary outcomes were serum biochemical markers (troponin I, Mg²⁺, potassium, lactate and creatinine) and time-to-plegia arrest. Intra-operative and postoperative clinical outcomes were also recorded.
  
  
  RESULTS
  Data from two centres for 691 patients (342 low and 349 high Mg²⁺) were analysed. Baseline characteristics were similar for both groups. There was no significant difference in the frequency of postoperative atrial fibrillation in the high (32.8%) and low (32.0%) groups (risk ratio 1.03, 95% confidence interval, CI, 0.82-1.28). However, compared with the low group, troponin I release was 28% less (95% CI 55-94%, p=0.02) in the high-Mg²⁺ group. The 30-day mortality was 0.72% (n = 5); all deaths occurred in the high-Mg²⁺ group but there was no significant difference between the groups (p=0.06). Frequencies of other major complications were similar in the two groups.
  
  
  CONCLUSIONS
  Warm-blood cardioplegia supplemented with 16 mmol l⁻¹ Mg²⁺, compared with 5 mmol l⁻¹ Mg²⁺, does not reduce the frequency of postoperative atrial fibrillation in patients undergoing CABG but may reduce cardiac injury. (This trial was registered as ISRCTN95530505.).
authors.affiliation: Bristol Heart Institute, University of Bristol, Bristol Royal Infirmary, Bristol, BS2 8HW, UK.
authors.forename: Massimo
authors.initials: M
authors.lastname: Caputo
authors.forename: Kirkpatrick C
authors.initials: KC
authors.lastname: Santo
authors.forename: Gianni D
authors.initials: GD
authors.lastname: Angelini
authors.forename: Carlo
authors.initials: C
authors.lastname: Fino
authors.forename: Marco
authors.initials: M
authors.lastname: Agostini
authors.forename: Claudio
authors.initials: C
authors.lastname: Grossi
authors.forename: M-Saadeh
authors.initials: MS
authors.lastname: Suleiman
authors.forename: Barnaby C
authors.initials: BC
authors.lastname: Reeves
mesh_terms: D000368:Aged; D001281:Atrial Fibrillation / Q000209:etiology / Q000517:prevention & control; D015415:Biomarkers / Q000097:blood; D002315:Cardiopulmonary Bypass; D002316:Cardiotonic Agents / Q000008:administration & dosage* / Q000627:therapeutic use; D001026:Coronary Artery Bypass / Q000009:adverse effects / Q000379:methods*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006324:Heart Arrest, Induced / Q000379:methods*; D006801:Humans; D007430:Intraoperative Care / Q000379:methods; D008278:Magnesium Sulfate / Q000008:administration & dosage* / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D016896:Treatment Outcome
chemical_list: D015415:Biomarkers; D002316:Cardiotonic Agents; D008278:Magnesium Sulfate