Pulmonary injury mediated by activated leukocytes is a recognized complication of cardiopulmonary bypass. The aim of this paper is to systematically analyze the effects of systemic leukofiltration within the cardiopulmonary bypass circuit on pulmonary injury and related clinical outcomes. We performed a systematic search to identify randomized controlled trials reporting on the effects of systemic leukofiltration on respiratory parameters. Random effect meta-analytical techniques were applied to identify differences in outcomes between the two groups. Sensitivity and subgroup analyses were undertaken to evaluate study heterogeneity. Incorporating 995 patients, 21 studies satisfied the inclusion criteria. Systemic leukofiltration significantly increased the PaO2/FiO2 ratio within 12 hours of bypass cessation, (weighted mean difference (WMD), 25.97; 95% confidence interval (CI), 3.41-48.53; p = 0.02) but this effect was lost by 24 hours (WMD, 12.98; 95% CI, -7.93-33.89; p = 0.22). Leukofiltration significantly reduced the duration of ventilatory support postoperatively (WMD, -2.11 hours; 95% CI, -0.65 to -3.58; p = 0.005), but had no impact on postoperative chest infection, intensive care length of stay or hospital length of stay. The heterogeneity of the included studies was high, due to poor quality study design and failure to include patients at high risk of pulmonary complications. Systemic leukofiltration may attenuate bypass-related lung injury in the early postoperative period, but this does not seem to translate to clinically significant differences in outcomes.

Cardiopulmonary bypass causes a systemic inflammatory reaction. Activation of leukocytes is an important part of this process, and is known to directly contribute to the development of postoperative coagulopathy, and thus hemorrhage. The removal of leukocytes from the cardiopulmonary bypass circulation, using specialized filters, has been proposed as one method for attenuating this inflammatory response. However, there is no consensus on its effectiveness. We used meta-analytical techniques to systematically assess the literature reporting on the potential effect of systemic leukofiltration on perioperative hemorrhage. Random effects modeling was used to calculate overall estimate, and heterogeneity was assessed. Systemic leukofiltration made no significant impact on chest tube drainage in the first 24 hours (weighted mean difference [WMD], x23.9 ml; 95% confidence interval [CI], x95.48-47.61; p = 0.51) or on the total packed red cell transfusion requirements of each patient (WMD, 7.84 ml; 95% CI, x80.13-95.81; p = 0.86). The studies performed in this area thus far are highly heterogeneous, due in part to relatively poor-quality design and inadequate matching of their study groups. Although further high-quality trials on systemic leukofiltration may be appropriate, other strategies to reduce the coagulopathy associated with cardiopulmonary bypass should be sought and evaluated.

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