Acute Normovolemic Hemodilution on Urine Neutrophil Gelatinase-associated Lipocalin Levels

The study population will consist of 50 adult patients less than 70 years old undergoing elective coronary artery bypass graft (CABG) surgery with anticipated CPB duration less than 2 hours at the University of Maryland Medical Center (UMMC). Patients less than 70kg in weight and patients with renal insufficiency and/or hemoglobin levels less than 12g/dL will be excluded. We shall also exclude patients with heart failure (EF \<40%) and any significant hepatic or pulmonary comorbidities, including pulmonary hypertension. Patients undergoing emergency and redo cardiac surgery and those with inherited or acquired bleeding disorders will also be excluded. This study will be a non-blinded randomized prospective observational study. Due to the nature of the intervention being evaluated, blinding will not be achievable. We shall randomly divide patients into 2 groups, where one group will be managed with ANH and the other without (control group). Patients managed with ANH will have 12cc/kg of blood salvaged and stored at room temperature prior to CPB. The stored blood will then be administered to the patient after CPB. Intravascular volume will be replenished in a 1:1 ratio with balanced crystalloid solution during blood salvage. The other group of patients will receive an empiric 7cc/kg bolus of intravenous balanced crystalloid solution prior to CPB. On average, crystalloid infusions are limited to about 500cc prior to CPB to minimize hemodilution of blood. Patients will otherwise be managed according to normal protocols and pathways used in the perioperative management of CS patients at UMMC.