title: Effect of mean arterial pressure, haemoglobin and blood transfusion during cardiopulmonary bypass on post-operative acute kidney injury.
abstract: BACKGROUND
  Acute kidney injury (AKI) after cardiac surgery is a common and serious condition carrying significant costs. During cardiopulmonary bypass (CPB) surgery, modifiable factors may contribute to post-operative AKI. Their avoidance might be a potential target for nephroprotection.
  
  
  METHODS
  The objective of the present study was to identify and determine whether intraoperative hypotension, anaemia, or their combination, red blood cell transfusion or vasopressor use are independent risk factors for post-operative AKI defined by the RIFLE (renal Risk, Injury, Failure, Loss of renal function and End-stage renal disease) classification and other thresholds using a mixed logistic multivariate model.
  
  
  RESULTS
  We analysed 381 468 mean arterial pressure (MAP) measurements from 920 consecutive on-pump cardiac surgery patients. Overall, 19.5% developed AKI which was associated with an 8.2-fold increase in-hospital mortality. Haemoglobin concentration was an independent risk factor for AKI {odds ratio [OR] 1.16 per g/dL decrease [95% confidence interval (CI) 1.05-1.31]; P = 0.018} with systemic arterial oxygen saturation and pressure values not adding further strength to such an association. MAP alone or vasopressor administration was not independently associated with AKI but volume of red blood cell transfusion was, with its effect being apparent at a haemoglobin level of >8 g/dL (>5 mmol/L). In patients with severe anaemia (<25th percentile of lowest haemoglobin), the independent effect of hypotension (>75th percentile of area under the curve MAP <50 mmHg) on AKI was more pronounced [OR 3.36 (95% CI 1.34-8.41); P = 0.010].
  
  
  CONCLUSIONS
  Intraoperative avoidance of the extremes of anaemia, especially during severe hypotension and avoidance of transfusion in patients with haemoglobin levels >8 g/dL (>5 mmol/L) may help decrease AKI in patients undergoing cardiac surgery and represent targets for future controlled interventions.
authors.affiliation: Department of Nephrology and Intensive Care, Charité—University Medicine Berlin, Berlin, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Haase
authors.forename: Rinaldo
authors.initials: R
authors.lastname: Bellomo
authors.forename: David
authors.initials: D
authors.lastname: Story
authors.forename: Angela
authors.initials: A
authors.lastname: Letis
authors.forename: Katja
authors.initials: K
authors.lastname: Klemz
authors.forename: George
authors.initials: G
authors.lastname: Matalanis
authors.forename: Siven
authors.initials: S
authors.lastname: Seevanayagam
authors.forename: Duska
authors.initials: D
authors.lastname: Dragun
authors.forename: Erdmann
authors.initials: E
authors.lastname: Seeliger
authors.forename: Peter R
authors.initials: PR
authors.lastname: Mertens
authors.forename: Anja
authors.initials: A
authors.lastname: Haase-Fielitz
mesh_terms: D058186:Acute Kidney Injury / Q000209:etiology*; D000368:Aged; D001794:Blood Pressure; D001803:Blood Transfusion; D006348:Cardiac Surgical Procedures / Q000009:adverse effects*; D002315:Cardiopulmonary Bypass / Q000009:adverse effects*; D015984:Causality; D003404:Creatinine; D005260:Female; D006454:Hemoglobins / Q000032:analysis*; D017052:Hospital Mortality; D006801:Humans; D007676:Kidney Failure, Chronic; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications; D011184:Postoperative Period; D012189:Retrospective Studies; D012307:Risk Factors; D016896:Treatment Outcome
chemical_list: D006454:Hemoglobins; D003404:Creatinine