Similarly, a direct correlation has been noted between the presence and magnitude of biomarker elevations postoperatively and both intermediate- and long- term risk of death.1028 5.2.4.1. Transfusion: Recommendation Class I 1. Aggressive attempts at blood conservation are indi- cated to limit hemodilutional anemia and the need for intraoperative and perioperative allogeneic red blood cell transfusion in CABG patients.1029 1032 (Level of Evidence: B) Numerous large observational studies have identified peri- operative allogeneic red blood cell transfusion(s) as an independent risk factor for adverse outcomes, including death.1029 1032 A prospective observational study of 8004 patients demonstrated that the transfusion of allogeneic red blood cells in CABG patients was associated with an in- creased risk of low-output heart failure irrespective of the extent of hemodilutional anemia.1030 An adverse outcome may be caused by immunomodulation (known to occur with red blood cell transfusion), initiation of a systemic inflamma- tory response and its associated direct negative myocardial effects, reduced red blood cell capacity for adequate oxygen delivery1031,1032 (diphosphoglycerate function in banked blood may cause tissue hypoxia), and changes in red blood cell morphology of transfused blood. Regardless of etiology, myocardial depression is observed consistently after alloge- neic red blood cell transfusion, and this effect appears to be dose dependent. Even risk-adjusted survival rates after CABG in patients transfused with allogeneic red blood cells 5.2.5. Perioperative Dysrhythmias: Recommendations Class I 1. Beta blockers should be administered for at least 24 hours before CABG to all patients without contra- indications to reduce the incidence or clinical se- quelae of postoperative AF.604 608,608a 608c (Level of Evidence: B) 2. Beta blockers should be reinstituted as soon as possible after CABG in all patients without contra- indications to reduce the incidence or clinical se- quelae of AF.604 608,608a 608c (Level of Evidence: B) Class IIa 1. 