title: Nadir hematocrit during cardiopulmonary bypass: end-organ dysfunction and mortality.
abstract: OBJECTIVE
  To discover the effects of the lowest hematocrit during cardiopulmonary bypass on end-organ function and mortality in patients who did not receive red blood cell transfusion and to identify predictors of nadir hematocrit.
  
  
  METHODS
  From November 1, 2004, to October 1, 2009, 7957 patients underwent cardiac surgery supported by cardiopulmonary bypass and were not transfused. The relationship between nadir hematocrit and morbidity, markers of end-organ function, and survival was studied using generalized propensity score analysis. Factors associated with nadir hematocrit were identified by linear regression.
  
  
  RESULTS
  Median nadir hematocrit was 30% (25th to 75th percentile, 27%-33%). Lower nadir hematocrit was associated with higher maximum intraoperative lactic acid (intrasubject correlation, -0.44). After risk adjustment, nadir hematocrit was associated with worse renal function (lower estimated glomerular filtration rate; P = .012), more myocardial injury (higher troponin level; P = .004), longer postoperative ventilator support (P < .001), longer hospital stay (P < .001), and higher mortality (P = .042). Female gender, older age, lower body mass index, higher New York Heart Association class, and combined valve procedure and coronary artery bypass were associated with lower nadir hematocrit; however, the strongest correlate was preoperative hematocrit (correlation coefficient, 0.74).
  
  
  CONCLUSIONS
  Although red blood cell transfusion has associated morbidity risk, there must be a tradeoff between adverse effects of low hematocrit during cardiac surgery and those of transfusion. The strong association of nadir hematocrit with preoperative hematocrit suggests the need for investigation and optimization before elective cardiac surgery.
authors.affiliation: Department of Thoracic and Cardiovascular Surgery, Cleveland Clinic, Cleveland, Ohio, USA.
authors.forename: Gabriel
authors.initials: G
authors.lastname: Loor
authors.forename: Liang
authors.initials: L
authors.lastname: Li
authors.forename: Joseph F
authors.initials: JF
authors.lastname: Sabik
authors.forename: Jeevanantham
authors.initials: J
authors.lastname: Rajeswaran
authors.forename: Eugene H
authors.initials: EH
authors.lastname: Blackstone
authors.forename: Colleen G
authors.initials: CG
authors.lastname: Koch
mesh_terms: D000368:Aged; D000740:Anemia / Q000097:blood / Q000209:etiology* / Q000401:mortality / Q000628:therapy; D015415:Biomarkers / Q000097:blood; D002315:Cardiopulmonary Bypass / Q000009:adverse effects* / Q000401:mortality; D005260:Female; D005919:Glomerular Filtration Rate; D006331:Heart Diseases / Q000097:blood / Q000209:etiology* / Q000401:mortality; D006400:Hematocrit; D017052:Hospital Mortality; D006801:Humans; D007674:Kidney Diseases / Q000097:blood / Q000209:etiology* / Q000401:mortality / Q000503:physiopathology; D019344:Lactic Acid / Q000097:blood; D007902:Length of Stay; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods*; D009820:Ohio; D011237:Predictive Value of Tests; D057216:Propensity Score; D011446:Prospective Studies; D012042:Registries; D012121:Respiration, Artificial; D018570:Risk Assessment; D012307:Risk Factors; D016019:Survival Analysis; D013997:Time Factors; D014336:Troponin / Q000097:blood
chemical_list: D015415:Biomarkers; D014336:Troponin; D019344:Lactic Acid