Retrograde Autologous Priming and Mannitol for Reducing Hemodilution in Cardiac Surgery

Retrograde Autologous Priming for Preserving Hemoglobin Peri-operatively With or Without Mannitol: A Pilot Study

Hemodilution reduces concentrations of blood constituents: concentration of hemoglobin, red blood cells (hematocrit), physiological ions and coagulation factors that can contribute to impaired hemostasis and increasing the risk of perioperative blood transfusions. This pilot study will assess the feasibility of a large RCT to evaluate 2 techniques for reducing hemodilution during cardiac surgery: 1) retrograde autologous priming and 2) intraoperative mannitol. The aim of this pilot trial is to demonstrate feasibility of a larger trial to evaluate whether retrograde autologous priming and/or mannitol are superior to conventional priming alone.

The use of large volumes of artificial priming fluids is still very high in cardiac surgery for routine CABG surgery with cardiopulmonary bypass. The resulting hemodilution is deleterious for patients and often requires counter measures to maintain fluid balance during and after surgery. Retrograde autologous priming and mannitol are simple low-cost solutions to the problem of hemodilution but their effectiveness, either alone or in combination, is unclear due to a lack of high-quality evidence. RAPPER-MAN is a single-centre 2x2 factorial cluster randomized trial. Participants will be randomly assigned (1:1:1:1 ratio) to the intervention groups: 1) Retrograde autologous priming (≥600 mL) + mannitol (0.3 g/kg bolus), 2) Retrograde autologous priming (≥600 mL) alone, 3) Conventional priming + mannitol (0.3 g/kg bolus), and 4) Conventional priming alone. The primary outcome is the change in hemoglobin concentration during cardiopulmonary bypass. Retrograde autologous priming will be performed within 10 minutes before, and mannitol will be added to the venous reservoir of the CPB machine within 5 minutes before, the start of cardiopulmonary bypass. The results of the larger trial are expected to have broad implications for fluid management in cardiac surgery in Canada.

Inclusion Criteria:

1. ≥18 years of age.
2. Undergoing a first-time cardiac surgical procedure (i.e. isolated CABG, isolated single cardiac valve surgery or a combination of both or isolated ascending aorta replacement) with the use of cardiopulmonary bypass (CPB) and median sternotomy.

Exclusion Criteria:

1. Left ventricle ejection fraction <25%
2. Emergency surgery
3. History of bleeding disorder
4. Inherited thromboembolic or infective endocarditis (active)
5. Previous cardiac surgery
6. Severe renal impairment (serum creatinine >250 μmol/L)
7. Hemoglobin <80 g/L
8. Thrombocytopenia (<50,000 platelets per μL)
9. Expected circulatory arrest
10. Body weight ≤50 kg
11. Allergy to mannitol
12. Pregnancy or breast feeding