Ann Thorac Surg 2008;86:1174. doi:10.1016/j.athoracsur.2008.07.110
© 2008 The Society of Thoracic Surgeons
Original Articles: Adult Cardiac
Invited Commentary
Song Wan, MD, FRCS
Division of Cardiothoracic Surgery, The Chinese University of Hong Kong, Prince of Wales Hospital, Hong Kong, China
(Email: swan{at}cuhk.edu.hk).
Aiming to limit blood loss, the recycling of cardiotomy blood shed during open-heart operations with the use of cardiopulmonary bypass (CPB) has been a routine, worldwide practice for the past 5 decades. Nonetheless, the majority of cardiac surgeons recognize that the pericardial blood shed not only contains a mixture of debris, but is also a rich source of activated tissue factors, markers of clotting and fibrinolysis, and pro-inflammatory mediators. Therefore, it has generally been the belief that the intraoperative application of a cell saver could be beneficial in reducing neurologic impairment after CPB (ie, limiting cerebral microemboli) and improving blood conservation through autologous red cell salvage. Surprisingly, the findings from a carefully conducted randomized clinical trial turned out to contradict this belief. In their recent report, the Cardiotomy Trial investigators [1] stated that "contrary to expectations, the processing of cardiotomy blood before re-infusion results in greater blood product use with greater postoperative bleeding in patients undergoing cardiac surgery." In addition, "there is no clinical evidence of any neurologic benefit with this approach in terms of postoperative cognitive function." These fundamental observations seem to indicate that the use of cell savers is no longer justified.
Fortunately, the story does not end here. The same group of investigators [2] dug further into their data and found that the processing of cardiotomy blood did produce some beneficial effects in a subgroup (n = 154) of the Cardiotomy trial patients (total, n = 266). The treated patients experienced reduced pulmonary and systemic vascular resistance, but an increased postoperative cardiac index. Although it may seem unclear to readers why these measurements were not analyzed in the remaining 112 patients in the Cardiotomy Trial [1], the available evidence suggests that the intraoperative use of a cell saver may have a positive impact on restraining the inflammatory response to CPB.
Taking the two Cardiotomy Trial reports [1, 2] together, the question for practicing cardiac surgeons of whether to use a cell saver during CPB becomes even more interesting but remains largely open. Is it possible that the cell saver has a positive influence but also some negative effects? If not for blood conservation or neuroprotection, should we use it just for the purpose of reducing inflammatory reactions? We must focus on better exploring the underlying mechanisms before making up our mind. As the authors [1, 2] of the Cardiotomy Trial reports proposed, the processing of shed pericardial blood involves centrifugation, washing, and filtration, which may, for instance, lead to the loss of many clotting factors and platelets, thus explaining the increased bleeding after CPB. However, the reduced inflammatory response could simply result from the effective removal of activated leukocytes [3]. If that is the case, then rather than using a costly cell saver device, an improved leukocyte depletion filter might be sufficient to achieve a similar goal.
In this regard, the Cardiotomy Trial investigators [1, 2] are to be commended not only for a job well done, but also for stimulating others to delve deeper into the problem.
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References
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- Rubens FD, Boodhwani M, Mesana T, Wozny D, Wells G, Nathan HJ. The Cardiotomy Trial: a randomized, double-blind study to assess the effect of processing of shed blood during cardiopulmonary bypass on transfusion and neurocognitive function Circulation 2007;116:I89-I97.[Medline]
- Boodhwani M, Nathan HJ, Mesana TG, Rubens FD, Cardiotomy Investigators Effects of shed mediastinal blood on cardiovascular and pulmonary function: a randomized, double-blind study Ann Thorac Surg 2008;86:1167-1174.[Abstract/Free Full Text]
- Wan S, LeClerc JL, Vincent JL. Inflammatory response to cardiopulmonary bypass: mechanisms involved and possible therapeutic strategies Chest 1997;112:676-692.[Medline]
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