Blood transfusions are commonly required after cardiac surgery, but excessive transfusions can lead to complications such as immune reactions, infections, and increased healthcare costs. Salvaging residual blood from the cardiopulmonary bypass (CPB) circuit is one approach to reduce reliance on donor blood. This study compares two methods of blood salvage—centrifugation (CF) and multiple-pass hemoconcentration (MPH)—to determine which provides better patient outcomes in the immediate postoperative period.
This randomized controlled trial involved 61 patients undergoing cardiac surgery with CPB at a Canadian tertiary care hospital. Patients were assigned to either the CF group (n=31) or the MPH group (n=30). The CF method used a cell-washing system to separate and concentrate red blood cells while discarding plasma and clotting factors. The MPH method utilized a hemofilter to remove excess plasma water while retaining proteins and clotting components. Researchers monitored biochemical markers, transfusion rates, fluid balance, and clinical outcomes over the first 12 postoperative hours to evaluate the efficacy of each technique.
Key Findings and Results
After 12 hours, hemoglobin levels were not significantly different between the two groups. However, the MPH group exhibited significantly higher levels of albumin, total protein, fibrinogen, and platelets compared to the CF group. These findings suggest that the MPH method better preserves essential blood components, which could contribute to improved recovery and reduced need for additional transfusions.
Patients in the MPH group also had lower allogeneic transfusion rates, meaning they required fewer donor blood products such as red blood cells, platelets, and fresh frozen plasma. This is a crucial finding, as minimizing transfusions can help reduce the risk of transfusion-related complications.
Another major difference was in fluid balance and weight gain. The CF group had significantly higher fluid retention and weight gain, likely due to the loss of plasma proteins that help regulate fluid distribution. This fluid overload can lead to tissue edema, impaired organ function, and increased postoperative complications. In contrast, the MPH group had better fluid management, with higher urine output and lower cumulative fluid balance.
While both techniques effectively salvaged blood, CF had a faster processing time (5-7 minutes vs. 10-15 minutes for MPH) and consistently cleared heparin from the salvaged blood. However, one notable drawback of MPH was inconsistent heparin clearance, which led to three cases of postoperative bleeding requiring additional intervention. This suggests that close monitoring of heparin levels is necessary when using the MPH technique.
Clinical Implications and Significance
The study suggests that MPH may be the superior method for blood conservation in cardiac surgery. By preserving albumin, clotting factors, and total protein, it enhances colloid osmotic pressure, reducing the risk of fluid overload and edema. Additionally, lower transfusion requirements in the MPH group indicate that it may provide better long-term outcomes by reducing reliance on donor blood.
However, CF remains a viable option due to its quicker processing time and reliable heparin clearance. This could make it a more practical choice in settings where rapid blood salvage is essential. The trade-off is that CF discards more valuable blood components, leading to a greater likelihood of transfusion dependence.
These findings emphasize the importance of tailoring blood conservation strategies based on individual patient needs. For patients at high risk of excessive bleeding, the CF method may be preferable due to its ability to fully remove heparin. Conversely, for patients at risk of fluid overload and transfusion dependence, the MPH method may offer better overall benefits.
Future Research and Considerations
While this study provides valuable insights, it has some limitations. The sample size was relatively small, and larger randomized trials are needed to confirm these findings. Additionally, longer follow-up periods could help determine whether these early biochemical differences translate into meaningful improvements in long-term recovery and survival rates.
Further research could also explore hybrid approaches, combining the rapid heparin clearance of CF with the superior blood component preservation of MPH. Such techniques could provide an optimized strategy for blood conservation, balancing speed, efficiency, and patient safety.
Conclusion
This study provides compelling evidence that MPH offers superior biochemical and clinical outcomes compared to CF. By preserving albumin, fibrinogen, and clotting factors, it helps maintain hemodynamic stability, reduces transfusion needs, and improves fluid balance. However, CF remains an effective alternative, particularly when rapid blood processing and heparin removal are priorities.
Ultimately, the choice between CF and MPH should be guided by patient-specific factors, including bleeding risk, transfusion history, and fluid balance needs. As blood conservation continues to be a major focus in cardiac surgery, further research will be essential to refine these techniques and improve patient outcomes.
Study Ranking = 4.5 (High-Quality Randomized Controlled Trial, but requires larger studies for confirmation).
