title: Oxygen delivery during cardiopulmonary bypass (and renal outcome) using two systems of extracorporeal circulation: a retrospective review.
abstract: OBJECTIVE
  To investigate the combined influence of blood flow and haemodilution with either a miniaturized (Mini-CPB) or a conventional cardiopulmonary bypass (C-CPB) circuit on average oxygen delivery during bypass. The influence of this on clinical outcome, particularly renal dysfunction after routine coronary artery bypass surgery (CABG), was measured.
  
  
  METHODS
  Retrospective analysis in two groups of 160 patients based on the surgeon's preference for bypass circuit. We compared consecutive patients undergoing isolated CABG surgery by two surgeons using Mini-CPB with a matched cohort of patients, from the same period, undergoing isolated CABG surgery by four other surgeons using a C-CPB. No trial-related intervention occurred. Data on bypass circuit parameters and clinical outcomes were acquired from routinely collected data sources.
  
  
  RESULTS
  Average cardiopulmonary bypass pump flow was significantly lower with Mini-CPB compared with C-CPB. Mini-CPB resulted in significantly less haemodilution. The resultant calculated average oxygen delivery provided by the two systems was the same. Percentage change in plasma creatinine was significantly and inversely related to the oxygen delivery during CPB. There was no difference in percentage change in plasma creatinine between groups. The risk of having Acute Kidney Injury Network (AKIN) score ≥ 1 increased 1% for every 1 ml min(-1) m(-2) decrease in oxygen delivery (P = 0.0001, OR 0.990, 95% CI 0.984-0.995).
  
  
  CONCLUSIONS
  Despite aiming for the same target pump flow, periodic limitations of venous return to the pump resulted in a significant reduction in average flow delivered to the patient by Mini-CPB. Less haemodilution compensated for this reduction, so that the average oxygen delivery was the same. The association between oxygen delivery and postoperative change in plasma creatinine was evident in both groups. Further work to understand whether there is a particular cohort of patients who benefit (or are put at risk) by one method of CPB vs the other is warranted.
authors: South West Cardiothoracic Centre , Derriford Hospital, Plymouth, UK. mark.bennett4@nhs.net
authors: Mark J
authors: MJ
authors: Bennett
authors: Cha
authors: C
authors: Rajakaruna
authors: Samer
authors: S
authors: Bazerbashi
authors: Gerry
authors: G
authors: Webb
authors: Mayam
authors: M
authors: Gomez-Cano
authors: Clinton
authors: C
authors: Lloyd
mesh_terms: D058186:Acute Kidney Injury / Q000097:blood / Q000209:etiology / Q000503:physiopathology*; D000368:Aged; D015415:Biomarkers / Q000097:blood; D002315:Cardiopulmonary Bypass / Q000009:adverse effects / Q000295:instrumentation*; D001026:Coronary Artery Bypass / Q000009:adverse effects; D003404:Creatinine / Q000097:blood; D004867:Equipment Design; D015199:Extracorporeal Membrane Oxygenation / Q000009:adverse effects / Q000295:instrumentation*; D006438:Hemodilution / Q000009:adverse effects; D006801:Humans; D007668:Kidney / Q000503:physiopathology*; D016015:Logistic Models; D008875:Middle Aged; D008904:Miniaturization; D010100:Oxygen / Q000097:blood*; D012039:Regional Blood Flow; D012189:Retrospective Studies; D012307:Risk Factors; D013997:Time Factors; D016896:Treatment Outcome
chemical_list: D015415:Biomarkers; D003404:Creatinine; D010100:Oxygen
keywords: Cardiac surgery; Extracorporeal circulation; Miniaturized cardiopulmonary bypass; Oxygen delivery