title: Sodium reduction during cardiopulmonary bypass: Plasma-Lyte 148 versus trial fluid as pump primes.
abstract: OBJECTIVE
  We compared effects on plasma sodium concentrations plus calculated plasma tonicity of two "balanced" crystalloid solutions used as 2 L pump primes during cardiopulmonary bypass (CPB): Plasma-Lyte 148 (sodium concentration, 140 mmol/L; potassium concentration, 5 mmol/L) versus a bicarbonate-balanced fluid (sodium concentration, 140 mmol/L; potassium concentration, 0 mmol/L).
  
  
  METHODS
  We analysed pooled data from two prospective interventional studies performed in university-affiliated hospitals, from 50 patients undergoing elective cardiac surgery.
  
  
  METHODS
  Participants were allocated equally to Plasma-Lyte 148 or bicarbonate-balanced fluid, with plasma electrolytes measured by direct ion selective electrodes immediately before bypass (pre-CPB), within 3 minutes of commencement (T2), and before bypass cessation (end-CPB).
  
  
  RESULTS
  Plasma sodium fell at T2 in 46 patients (92%) (P<0.0005). With Plasma-Lyte 148, the mean sodium decreased by 3.0 mmol/L (SD, 1.7 mmol/L), and with bicarbonate-balanced fluid it decreased by 2.2 mmol/L (SD, 1.1 mmol/L) (P=0.002). The mean tonicity fell by >5 mOsm/kg for both groups (P<0.0005). At end-CPB, the mean sodium for both groups remained reduced by >2 mmol/L (P<0.0005). In the group receiving Plasma-Lyte 148, 52% of patients were hyponatraemic (sodium<135 mmol/L) at T2 and end-CPB.
  
  
  CONCLUSIONS
  Sodium reductions were common with both priming solutions, but more severe with Plasma-Lyte 148. Crystalloid priming solutions require sodium concentrations>140mmol/L to ensure normonatraemia throughout CPB.
authors.affiliation: Mater Research, Mater Health Services, University of Queensland, Brisbane, QLD, Australia. john.morgan@mater.org.au.
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Morgan
authors.affiliation: Intensive Care Unit, Royal Brisbane and Women's Hospital, and University of Queensland, Brisbane, QLD, Australia.
authors.forename: Jeffrey J
authors.initials: JJ
authors.lastname: Presneill
authors.affiliation: Department of Anaesthesia, Royal Children's Hospital, Melbourne, VIC, Australia.
authors.forename: Paul G
authors.initials: PG
authors.lastname: Davies
authors.affiliation: Department of Anaesthesia, Princess Alexandra Hospital, and University of Queensland, Brisbane, QLD, Australia.
authors.forename: Gerald
authors.initials: G
authors.lastname: Power
authors.affiliation: Intensive Care Unit, Princess Alexandra and Wesley Hospitals, and University of Queensland, Brisbane, QLD, Australia.
authors.forename: Balasubramanian
authors.initials: B
authors.lastname: Venkatesh
mesh_terms: D000368:Aged; D001639:Bicarbonates / Q000008:administration & dosage* / Q000097:blood*; D002315:Cardiopulmonary Bypass; D000077324:Crystalloid Solutions; D005260:Female; D005942:Gluconates / Q000008:administration & dosage / Q000097:blood; D006801:Humans; D007552:Isotonic Solutions / Q000008:administration & dosage; D015636:Magnesium Chloride / Q000008:administration & dosage / Q000097:blood; D008297:Male; D011189:Potassium Chloride / Q000008:administration & dosage / Q000097:blood; D011446:Prospective Studies; D012964:Sodium / Q000097:blood*; D019346:Sodium Acetate / Q000008:administration & dosage / Q000097:blood; D012965:Sodium Chloride / Q000008:administration & dosage / Q000097:blood
chemical_list: D001639:Bicarbonates; D000077324:Crystalloid Solutions; D005942:Gluconates; D007552:Isotonic Solutions; C012499:Plasma-lyte 148; D015636:Magnesium Chloride; D012965:Sodium Chloride; D019346:Sodium Acetate; D011189:Potassium Chloride; D012964:Sodium