STS blood conservation guidelines: the role of leukocyte filtration

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.