Leukocyte filtration improves brain protection after a prolonged period ofhypothermic circulatory arrest: A study in a chronic porcine model

Background: Ischemic cerebral injury follows a well-attested sequence of ev ents, including 3 phases: depolarization, biochemical cascade, and reperfus ion injury. Leukocyte infiltration and cytokine-mediated inflammatory react ion are known to play a pivotal role in the reperfusion phase. These events exacerbate the brain injury by impairing the normal microvascular perfusio n and through the release of cytotoxic enzymes. The aim of the present stud y was to determine whether a leukocyte-depleting filter (LeukoGuard LG6, Pa ll Biomedical, Portsmouth, United Kingdom) could improve the cerebral outco me after hypothermic circulatory arrest. Methods: Twenty pigs (23-30 kg) were randomly assigned to undergo cardiopul monary bypass with or without a leukocyte-depleting filter before and after a 75-minute period of hypothermic circulatory arrest at 20 degreesC. Elect roencephalographic recovery S-100 beta protein levels, and cytokine levels (interleukin 1 beta, interleukin 8, and tumor necrosis factor alpha) were r ecorded up to the first postoperative day. Postoperatively, all animals wer e evaluated daily until death or until electively being put to death on day 7 by using a quantitative behavioral score. A postmortem histologic analys is of the brain was carried out on all animals. Results: The rate of mortality was 2 of 10 in the leukocyte-depletion group and 5 of 10 in control animals. The risk for early death in control animal s was 2.5 (95% confidence interval, 0.63-10.0) times higher than that of th e leukocyte-depleted animals. The median behavioral score at day 7 was high er in the leukocyte-depletion group (8.5 vs 3.5; P =.04). The median of tot al histopathologic score was 8.5 in the leukocyte-depletion group and 15.5 in the control group (P =.005). Conclusion: A leukocyte-depleting filter improves brain protection after a prolonged period of hypothermic circulatory arrest.