title: The impact of haemodilution and bypass pump flow on cerebral oxygen desaturation during cardiopulmonary bypass--A comparison of two systems of cardiopulmonary bypass.
abstract: OBJECTIVE
  To determine the influence of haemodilution, bypass flow rates and calculated oxygen delivery during cardiopulmonary bypass (CPB) with either a conventional CPB (C-CPB) circuit or a miniaturised (Mini-CPB) circuit on cerebral oxygen desaturation. The effect of minimal haemodilution with a Mini-CPB was investigated.
  
  
  METHODS
  Eighty patients scheduled for elective cardiac surgery.
  
  
  METHODS
  Oxygenated haemoglobin (O2Hb) and tissue oxygenation index (TOI) were measured with near-infrared spectroscopy (NIRS).
  
  
  RESULTS
  The average indexed bypass pump flow was significantly lower with Mini-CPB. When combined with haemoglobin concentration, the average oxygen delivery was the same between groups. Patients in the C-CPB group had a greater duration and severity of cerebral desaturation to a level <20% below baseline values, but none reached the depth and duration of the cerebral desaturation associated with poor outcome. Cerebral oxygen desaturation with C-CPB was significantly associated with low flows during bypass, whereas desaturation with Mini-CPB was associated with low perioperative haemoglobin concentration.
authors.affiliation: Department of Cardiothoracic Anaesthesia, South West Cardiothoracic Centre, Plymouth, UK mark.bennett4@nhs.net.
authors.forename: M J
authors.initials: MJ
authors.lastname: Bennett
authors.affiliation: Department of Clinical Perfusion, South West Cardiothoracic Centre, Plymouth, UK.
authors.forename: M
authors.initials: M
authors.lastname: Weatherall
authors.affiliation: Department of Clinical Perfusion, South West Cardiothoracic Centre, Plymouth, UK.
authors.forename: G
authors.initials: G
authors.lastname: Webb
authors.affiliation: Department of Cardiothoracic Anaesthesia, South West Cardiothoracic Centre, Plymouth, UK.
authors.forename: S F
authors.initials: SF
authors.lastname: Dudnikov
authors.affiliation: Department of Cardiac Surgery, South West Cardiothoracic Centre, Plymouth, UK.
authors.forename: C T
authors.initials: CT
authors.lastname: Lloyd
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001783:Blood Flow Velocity; D002315:Cardiopulmonary Bypass / Q000379:methods*; D005260:Female; D006438:Hemodilution / Q000379:methods*; D006454:Hemoglobins / Q000378:metabolism*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010092:Oximetry / Q000379:methods*; D010100:Oxygen / Q000097:blood*
chemical_list: D006454:Hemoglobins; D010100:Oxygen
keywords: cardiopulmonary bypass; cerebral oximetry; haemodilution; miniaturised extracorporeal circulation; tissue oxygenation index