More is Not Better: The Role of the Leukocyte Filter in Ex Vivo Lung Perfusion

PURPOSE A leukocyte filter (LF) has been empirically incorporated within ex vivo lung perfusion (EVLP) circuits since the advent of EVLP. However, the utility of the LF has never been fully defined and studies have questioned the beneficial effects of the filter. Additionally, there have been suggestions that such filters may become quickly saturated in use requiring replacement for better effect. Thus, we sought to determine the effects of LFs on EVLP and evaluated whether a conventional arterial filter (AF) would prove to be noninferior. METHODS Porcine donor lungs (n=22) were extracted and placed on the Toronto EVLP platform for 12h. Groups consisted of a LF group (conventional EVLP with a leukocyte filter), an AF group (the conventional leukocyte filter was replaced with an arterial filter), a change of filter group (CF) where the leukocyte filter was clamped and exchanged for a fresh filter after 1h, and a no filter (NF) control group. Due to severely poor performance seen in the CF group, only lungs in the LF, AF, and NF groups were then transplanted into porcine recipients and monitored during a 4h reperfusion period. RESULTS The LF, AF and NF group showed good lung function on EVLP. The CF group demonstrated worse lung function on EVLP. After transplant, LF, AF, and NF groups demonstrated equivalent early lung function performance, but on histological staining, the NF group demonstrated increased lung injury over the other groups. Cytokine levels were not significantly different between groups. CONCLUSIONS The traditional leukocyte filter should be used in the EVLP circuit but can be exchanged for an arterial filter with noninferior performance. Changing the filter after one hour does not add therapeutic benefit, and in fact, makes lung performance worse on EVLP.