Evaluating the Addition of Hemodiafiltration to EVLP - Impact on the Regeneration of Marginal Donor Lungs

Hemodiafiltration (HDF) is a variation of conventional HD. By the addition of a substitution solution, convection forces are significantly increased. This substitution solution is added to the blood and is completely removed again in the dialyzer. This increases the negative pressure on the dialysate side and the removal of toxins through convection. The substitution solution can be added in a pre-dilution (before the dialyzer) or post-dilution (after the dialyzer) manner. Pre-dilution is associated with longer run times, less filter clotting, but is also less effective in removing toxins. Post-dilution offers a better toxin clearance capacity, but is associated with an increased risk of filter clotting. Several studies have shown that HDF provides higher clearance rates for both small and middle molecule solutes. Moreover, effective cytokine removal has been shown in HDF both in acute and chronic renal disease patients.

Lung transplantation has become a standard treatment for patients suffering from end-stage lung diseases. One of the major obstacles in the modern transplant era is the fact that the need for organs by far exceeds availability. This leads to growing waiting lists with mortality rates ranging between 10-30%. On the other hand, up to 80% of offered lungs from brain dead donors are rejected because they do not meet predefined donor selection criteria.

Recently, ex vivo lung perfusion (EVLP) has become available as a tool to expand the donor pool. Based on experimental work by Stig Steen, the Toronto lung transplant group developed an EVLP system with the purpose to evaluate lungs with uncertain quality. Consequently, Aigner et al. have expanded the indications for EVLP by showing that primarily unacceptable donor lungs can be reconditioned and then become suitable for transplantation. This concept of organ repair by EVLP has recently been highlighted by a number of publications.