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a Bioengineering Unit, Wolfson Building, University of Strathclyde, 106 Rottenrow, Glasgow, G4 ONW Scotland
b University of North Texas Health Sciences Centre, 2400 Camp Bowie Blvd, Fort Worth, Texas 76107
c University of Kirikkale, Angora Evleri G-8, Bl. No:1, Beysukent Ankara, 06800 Turkey
(Email: terrance.gourlay{at}strath.ac.uk; ao-yurvati{at}hsc.unt.edu; sgunaydin{at}isnet.net.tr).
We write in reference to the recent joint clinical practice guidelines and recommendations of The Society of Thoracic Surgeons (STS) and Society of Cardiovascular Anesthesiologists for perioperative blood transfusion and blood conservation in cardiac surgery [1].
Although we applaud the efforts to provide clear guidance and recommendations for blood conservation, we disagree with the committees’ position on leukocyte filtration, and we are particularly concerned by the notion that there is a lack of clinical evidence to support the use of leukocyte filtration. The effect of leukocyte filtration on blood product usage has not been extensively studied, but there is evidence from at least one focused clinical study that demonstrates just such a benefit [2], and there is anecdotal evidence from many investigators suggesting that this may be a real clinical effect. However, most importantly, we believe that there are a wide variety of very positive and real outcome benefits associated with the use of leukocyte filtration that justify and support their use in routine clinical practice.
The inference that neutrophils trapped by leukocyte filters may exacerbate inflammatory mechanisms is not new, and this has been widely discussed in the clinical world. This suggestion stems from the work of Scholz and colleagues [3] who observed that leukocyte filtration failed to limit neutrophil stimulation and augmented polymorphonuclear leukocyte elastase levels. Although some have tried to argue that increasing the circulating elastase may break down the structural protein elastin that holds endothelial cells together, and in this way may worsen clinical outcome, critically, the authors in this particular study noted that "we did not find clinical disadvantages related to any filtration strategy tested." This conclusion supports our belief that the assay used to measure elastase can not distinguish between active and inactive elastase. Therefore, the functional significance of having elevated elastase levels, as measured by the available technology, is not really known.
Although the committee may have taken a somewhat narrow position of leukocyte filtration, we believe that if one reviews all the available literature, it is clear that there is an overwhelming body of evidence that supports its use in clinical practice. To state that leukocyte filtration technology is capable of removing significant numbers of activated and therefore potentially injurious neutrophils has long been well-established [4–6], and the clinical significance of this has been confirmed in many clinical studies including those of Patel and colleagues [7], Olivencia-Yurvati and colleagues [8], and Tang and colleagues [9]. These studies have all confirmed that leukocyte filtration has a significant and positive impact on outcomes.
The body of evidence supporting the application of leukocyte depletion during cardiopulmonary bypass is substantial and continues to grow. However, we recognize that more work is required to investigate the most appropriate leukocyte depletion strategy for both routine and high-risk patients. This important clinical work is ongoing, and recent studies have suggested that there is a synergistic effect from combining the range of available anti-inflammatory technologies, including leukocyte depleting filters, during cardiopulmonary bypass [10–13].
In conclusion, we strongly believe that leukocyte depletion technology has a significant role to play in moderating the inflammatory injury commonly associated with open heart surgery. Despite a substantial body of supportive evidence, we accept that further work is required to determine the most suitable strategic method of use, and the cohort of patients that will benefit most significantly from its application. However, our clinical and laboratory experience strongly supports a role for leukocyte depletion during open heart surgery, and we believe that the potential for positive clinical impact of this relatively simple and uncomplicated technology is much underestimated, and has been, to some extent, misrepresented in the committee’s report.
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  V. A. Ferraris Reply Ann. Thorac. Surg., March 1, 2008; 85(3): 1139 - 1139. [Full Text] [PDF]
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