A colleague at the New Zealand Blood Service reports that they are in the process of developing a policy on the provision of blood in cardiac bypass surgery, and that there is some debate about how fresh whole blood should be for priming of the bypass machine. Apparently perfusionists are insisting on whole blood that is less than 48 hours old. The blood bankers are not in a position to provide this at all times and suggest whole blood that is less than 5 days old for both priming and transfusion. The inquiring New Zealander was hoping that colleagues of the e-Network Forum could provide information on their practice in providing blood in cardiac bypass surgery. The New Zealander believes that adopting the BCSH guidelines seems sound but they feel that the need to work more on this and solicit input before coming up with a final policy.

The following comments have been received.

ADDENDA Aug. 16, 2004

1. The Editor comments that a related previous discussion , while not exactly addressing the same target patient population, might be worth reviewing.

ADDENDA Aug. 17, 2004

2. An anesthesiologist at an academic center in Montreal reports that according to published guidelines there is no evidence supporting the use of fresh blood for cardiopulmonary bypass (CPB).  It is his experience that in adults, the use of blood to prime the CPB circuit is infrequent, given the patient’s circulating blood volume is large compared to the priming volume of the circuit. Nonetheless, in smaller anemic patients red cell transfusion may be required during bypass to avoid excessively low hematocrits and to normalize oxygen transport. He adds that while one can make a theoretical argument in favor of fresh blood (improved red cell deformability, increased 2,3 DPG, normal levels of coagulation factors, presence of large platelets), requesting fresh blood for these patients is not evidence-based. His cursory MEDLINE search failed to retrieve relevant citations supporting this practice, despite the considerable number of citations discussing transfusion in the context of CPB. Several trials have attempted to demonstrate the benefits of fresh autologous blood, plasma or platelets re-transfused at the end of CPB but in his opinion, the evidence remains, once again, inconclusive.  He does acknowledge that a possible exception would be for pediatric patients but, even there, the evidence is not compelling, as discussed on the CBBS web site in 2001 (see Editor's comment above). A recent article (J Thorac Cardiovasc Surg. 2004 Apr;127:949-52) showed that the age of blood had a minimal effect on the final constitution of priming solution before and during cardiopulmonary bypass in children undergoing corrective cardiac surgery. Similarly, in infants, the use of FFP in the pump prime remains controversial. The addition of FFP in the pump prime has been associated with decreased transfusion of cryoprecipitates and a trend towards overall decreased patient exposure to blood products (Ann Thorac Surg 2004;77:983-7) whereas the substitution of 5% albumin for FFP significantly reduced perioperative transfusions (Ann Thorac Surg 2003 75:1506-12). On the other hand, the use of a low-prime neonatal CPB circuit (200mL instead of the usual 500mL) was shown to reduce coagulation disturbances in a neonatal piglet model (J Extra Corpor Technol 1999;31:195-201). Such a “mechanical” solution may well be more practical and safer than the use of fresh whole blood which mandates that a number of screening tests be waived (see prior e-Network forum discussion). As for several transfusion practices, requests for fresh blood for CPB are operator dependent, not evidence based and such practices should not be supported by the blood bank (in Québec, Canada, they are not). He concludes saying "On the other hand, well conducted research in this area (clinically relevant hypothesis, adequate sample size, prospective, blinded and randomized design, etc.) is not only welcome, it is essential."

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Ira A. Shulman, MD
CBBS e-Network Forum Editor & Moderator