Acute Normovolemic Hemodilution in Complex Cardiac Surgery

Postoperative bleeding in cardiac surgery is a frequent complication, and cardiac surgery utilizes 15-20% of the national blood supply. Packed red blood cells (pRBCs) are associated with worse short and long term outcomes. For each unit transfused, there is an additive risk of mortality (death) and cardiac adverse events. Despite current guidelines and numerous approaches to bleeding reduction, \>50% of the patients undergoing cardiac surgery receive transfusions. Acute normovolemic hemodilution (ANH), a blood conservation technique that removes whole blood from a patient immediately prior to surgery, could be a valuable method to reduce transfusion in complex cardiac surgery. At the University of California, Los Angeles (UCLA), ANH is routinely utilized in patients who refuse allogenic blood transfusions such as Jehovah's Witnesses. ANH has been shown to be safe with minimal risk to patients. ANH has been studied in simple cardiac surgery, such as coronary artery bypass grafting, however it has not been studied in complex cardiac surgery, such as aortic surgery and adult congenital heart disease. ANH has been demonstrated to reduce pRBC transfusion in lower risk cardiac surgery without any significant complications. Complex heart surgery utilizes more blood products. This study could identify the benefits of ANH in a higher risk surgical group.

Adult patients undergoing complex heart surgery will be randomized to 1 of 2 groups using block randomization: the intervention arm receiving acute normovolemic hemodilution (ANH) or the control arm receiving standard of care.

As day of surgery hemoglobin (Hgb)/hematocrit (Hct) is critical to the final determination for study participation, patients will be randomized to control or intervention arms after the first intraoperative arterial blood gas (ABG) is obtained. The Hb/Hct obtained from this ABG is used to determine the postdilutional hematocrit using specific pre-ANH and post-ANH equations. Patients with pre-ANH or post-ANH postdilutional Hct lower than 22-24 will not be eligible for inclusion in the ANH arm of the study.

For the Study Group: Using sterile techniques, ANH is performed by removing 8-10cc/kg of whole blood with a maximum of 700cc, from the patient in the OR prior to incision. Whole blood will be collected and stored at room temperature. Hemodynamics are assessed during whole blood removal to ensure adequate stability. ANH will be discontinued if the patient becomes hemodynamically unstable (i.e. significant hypotension greater than 20% reduction from pre-ANH, unstable arrhythmia, evidence of myocardial ischemia or evidence of worsening myocardial function). After whole blood removal, the patient is hydrated to maintain isovolemia with an equivalent volume of crystalloid and/or colloid given, and the blood is stored in the OR at room temperature. After cardiopulmonary bypass (CPB) is complete, the whole blood is returned to the patient. Whole blood stored at room temperature will be transfused within 8 hours of initial collection. After 8 hours, ANH whole blood will be considered expired and will be transfused back to the patient prior to expiration and not discarded. Laboratory coagulation and ROTEM studies (assess blood clotting) will be resent after the ANH blood is returned to the patient. Transfusion requirement will be continuously reassessed based upon laboratory values and surgical assessment of clinical bleeding.

For the Control Group: Blood conservation will not be performed in the OR. Coagulation labs (i.e. platelet count, fibrinogen level and ROTEM studies) are sent while the patient in on bypass. After separation from bypass, coagulation laboratory studies and clinical bleeding are assessed in collaboration with the surgeon. Based on laboratory values and surgical assessment, allogenic transfusions (donor/recipient not the same person) occur in a targeted fashion (i.e. clinical bleeding with platelet count less than 150 x10E3/uL and a ROTEM results indicative of inadequate clot strength will result in platelet transfusion). Transfusion requirements are continuously reassessed based upon updated laboratory values and surgical assessment of clinical bleeding.

Data will also be collected and recorded from the medical record for both groups.

Eligibility Criteria:
Inclusion Criteria:

* Adult patients presenting for elective cardiac surgery
* Surgical procedures to include:

  * Redo surgery
  * Adult congenital heart disease surgery (ACHD)
  * Aortic surgery including aortic surgery requiring deep hypothermic circulatory arrest

Exclusion Criteria:

* low risk cardiac surgery
* cardiac surgery not requiring cardiopulmonary bypass
* baseline anemia (Hgb \< 13 for men and 12 for women)
* post-dilution Hct \< 21-24 (basis for this is increased risk of AKI on CPB with Hct 21-22)
* preop treatment for anemia
* high-risk ischemia lesions (critical left main, multi-vessel disease, active/recent chest pain, unstable angina, presence of a balloon pump, recent history of myocardial infarction (MI) either non-ST elevation MI (NSTEMI) / ST-elevation MI (STEMI), regional wall motion abnormalities on echo)
* low left ventricular systolic function (LVEF \< 35-40%) - decompensated heart failure
* Hypertrophic obstructive cardiomyopathy (HOCM) patients with significant left ventricular outflow tract (LVOT) gradients
* history of recent blood transfusion
* history of recent gastrointestinal (GI) bleed
* patient refusal to participate in the study
* severe aortic stenosis (AS) with reduced LVEF
* pulmonary hypertension
* underlying significant liver disease impairing synthetic function (elevated PT/INR or PTT) at baseline
* clotting disorders, inherited or acquired or iatrogenic coagulopathy (i.e. thrombocytopenia, pancytopenia)
* baseline chronic kidney disease (CKD) stage 3/above or End-stage renal disease (ESRD) +/- hemodialysis
* hemodynamically unstable patients including sepsis/recently treated sepsis
* preoperative extracorporeal membrane oxygenation (ECMO) or high suspicion for postoperative ECMO
* emergent cases