H.G.D. Leuvenink

The Prognostic Value of Renal Resistance During Hypothermic Machine Perfusion of Deceased Donor Kidneys

Vascular renal resistance (RR) during hypothermic machine perfusion (HMP) is frequently used in kidney graft quality assessment. However, the association between RR and outcome has never been prospectively validated. Prospectively collected RR values of 302 machine‐perfused deceased donor kidneys of all types (standard and extended criteria donor kidneys and kidneys donated after cardiac death), transplanted without prior knowledge of these RR values, were studied. In this cohort, we determined the association between RR and delayed graft function (DGF) and 1‐year graft survival. The RR (mmHg/mL/min) at the end of HMP was an independent risk factor for DGF (odds ratio 21.12 [1.03–435.0]; p = 0.048) but the predictive value of RR was low, reflected by a c‐statistic of the receiver operator characteristic curve of 0.58. The RR was also found to be an independent risk factor for 1‐year graft failure (hazard ratio 12.33 [1.11–136.85]; p = 0.004). Determinants of transplant outcome are multifactorial in nature and this study identifies RR as an additional parameter to take into account when evaluating graft quality and estimating the likelihood of successful outcome. However, RR as a stand‐alone quality assessment tool cannot be used to predict outcome with sufficient precision.

Hypothermic machine preservation in liver transplantation revisited: concepts and criteria in the new millennium.

To overcome the present shortage of liver donors by expansion of the existing donor pool and possibly lengthening of the storage time, hypothermic machine perfusion of the liver as a dynamic preservation method is revisited. The three most important aspects are defined to be the type of preservation solution, the characteristics of perfusion dynamics, and the oxygen supply. Reviewing hypothermic liver machine perfusion experiments, the University of Wisconsin machine preservation solution is the solution most used. It is also found that nothing conclusive can be said about the optimal perfusion characteristics, since either perfusion pressure or perfusion flow is reported. The best estimation is perfusion of the liver in a physiological manner, i.e. pulsatile arterial perfusion and continuous portal venous perfusion. The applied pressures could be chosen to be somewhat lower than physiological pressures to prevent possible endothelial cell damage. Oxygen supply is necessary to achieve optimal preservation of the liver. The minimal amount of partial oxygen pressure required is inversely related to the normalized flow. Incorporating these features in a system based on existing standard surgical and organ sharing procedures and which is able to work stand-alone for 24 h, weighing less than 23 kg, could successfully implement this technique into every day clinical practise.

Complement mediated renal inflammation induced by donor brain death : role of renal C5a-C5aR interaction

Kidneys retrieved from brain‐dead donors have impaired allograft function after transplantation compared to kidneys from living donors. Donor brain death (BD) triggers inflammatory responses, including both systemic and local complement activation. The mechanism by which systemic activated complement contributes to allograft injury remains to be elucidated. The aim of this study was to investigate systemic C5a release after BD in human donors and direct effects of C5a on human renal tissue. C5a levels were measured in plasma from living and brain‐dead donors. Renal C5aR gene and protein expression in living and brain‐dead donors was investigated in renal pretransplantation biopsies. The direct effect of C5a on human renal tissue was investigated by stimulating human kidney slices with C5a using a newly developed precision‐cut method. Elevated C5a levels were found in plasma from brain‐dead donors in concert with induced C5aR expression in donor kidney biopsies. Exposure of precision‐cut human kidney slices to C5a induced gene expression of pro‐inflammatory cytokines IL‐1 beta, IL‐6 and IL‐8. In conclusion, these findings suggest that systemic generation of C5a mediates renal inflammation in brain‐dead donor grafts via tubular C5a‐C5aR interaction. This study also introduces a novel in vitro technique to analyze renal cells in their biological environment.

Hypothermic Machine Perfusion Of The Liver And The Crucial Balance Between Perfusion Pressures And Endothelial Injury

Hypothermic machine perfusion (HMP) provides better protection against cold ischemic injury than cold storage in marginal donor kidneys. Also, in liver transplantation a switch from static cold storage to HMP could be beneficial as it would allow longer preservation times and the use of marginal donors. A critical question concerning application of HMP in liver preservation is the crucial balance between perfusion pressure and occurrence of endothelial injury. Rat livers were cold-perfused for 24 hours to study perfusion pressures for both hepatic artery and portal vein. Cold storage served as control and was compared to HMP-preserved livers using a mean arterial perfusion pressure of 25 mm Hg and a portal perfusion pressure of 4 mm Hg (25% of normothermic liver circulation) and to HMP at 50 mm Hg and 8 mm Hg perfusion, respectively (50% of normothermic liver circulation). UW solution was enriched with 14.9 micromol/L propidium iodide (PI) to stain for dead cells and with an additional 13.5 micromol/L acridine orange to stain for viable hepatocytes. A low PI-positive cell count was found using HMP at 25% of normal circulation compared to cold storage. The PI count was high for the HMP group perfused at just 50% of normal circulation compared to HMP at 25% and compared to cold storage. In summary, for liver HMP, perfusion at 25% showed complete perfusion with minimal cellular injury. HMP using perfusion pressures of 25 mm Hg for the hepatic artery and 4 mm Hg for the portal vein is feasible without induction of endothelial injury.

Complement Mediated Renal Inflammation Induced by Donor Brain Death: Role of Renal C5a-C5aR Interaction: Renal C5a-C5aR Interaction in Brain Death

Kidneys retrieved from brain‐dead donors have impaired allograft function after transplantation compared to kidneys from living donors. Donor brain death (BD) triggers inflammatory responses, including both systemic and local complement activation. The mechanism by which systemic activated complement contributes to allograft injury remains to be elucidated. The aim of this study was to investigate systemic C5a release after BD in human donors and direct effects of C5a on human renal tissue. C5a levels were measured in plasma from living and brain‐dead donors. Renal C5aR gene and protein expression in living and brain‐dead donors was investigated in renal pretransplantation biopsies. The direct effect of C5a on human renal tissue was investigated by stimulating human kidney slices with C5a using a newly developed precision‐cut method. Elevated C5a levels were found in plasma from brain‐dead donors in concert with induced C5aR expression in donor kidney biopsies. Exposure of precision‐cut human kidney slices to C5a induced gene expression of pro‐inflammatory cytokines IL‐1 beta, IL‐6 and IL‐8. In conclusion, these findings suggest that systemic generation of C5a mediates renal inflammation in brain‐dead donor grafts via tubular C5a‐C5aR interaction. This study also introduces a novel in vitro technique to analyze renal cells in their biological environment.