NEW YORK (Reuters Health) - Kidneys procured for transplant after cardiac death (as opposed to after brain death) do better when preserved with a perfusion pump rather than cold fluid, a new review shows. "Although the use of pulsatile perfusion does come at a cost, it can be beneficial and cost-saving if used in the correct population of donor kidneys," Dr. Alp Sener from Western University, London, Ontario, Canada told Reuters Health. But, Dr. Sener added, "There still remains a vast list of unknown contributors to final renal allograft function, including identifying the optimal length of time that kidney should be left on pump so as to maximize outcomes, as well as determining optimal perfusion pump settings and temperature." Dr. Sener and colleagues compared "donation after cardiac death" (DCD) kidneys that were put on pulsatile perfusion with those placed in cold storage in terms of delayed graft failure and one-year graft survival, in a systematic review. Altogether they looked at nine studies: four randomized controlled trials, one prospective but nonrandomized trial, three retrospective studies, and one cohort study. The rate of delayed graft function was 36% lower in perfusion-pumped kidneys from DCD donors than in kidneys stored in static cold fluid (p=0.03). This finding held true in subgroup analyses of only randomized trials and only nonrandomized trials. As reported December 5th online in The Journal of Urology, graft survival at one year tended to favor perfusion pump kidneys, but the overall effect failed to achieve statistical significance, except in the subgroup analysis that included only nonrandomized studies. "We believe all DCD kidneys should be 'pumped,'" coauthor Dr. Vivian McAlister, currently deployed in Afghanistan, told Reuters Health by email. "Further research is looking at extending conditions under which we can successfully transplant DCD kidneys." "Obviously it is too costly to just 'pump' every kidney that we transplant (especially in Canada where we have quite tight surgical transplant budgets) so we try to be selective in which kidneys we pump; hence the reason we prefer to pump DCD and ECD (extended-criteria donor) kidneys," coauthor Dr. Thomas McGregor told Reuters Health by email. Coauthor Dr. Patrick Luke predicts - also by email - that "static cold storage will become an entity of the past." Dr. Sener explains, "We currently have novel and exciting data from ongoing porcine and discarded human kidney experiments that the supplementation of standard preservation solutions with endogenously produced small molecules, including hydrogen sulfide and carbon monoxide, during the time of pulsatile perfusion has a significant impact on improving early graft function as well as in minimizing the cellular and tissue damage that is associated with transplantation." "These therapies have the potential to make a significant impact on clinical practice in the near future and may shape the way we view standard organ preservation solutions." Dr. Michael J. Goldstein from the Mount Sinai Medical Center, New York, medical director of the New York Organ Donor Network (New York City's local Organ Procurement Organization, or OPO) agrees with the authors. "We should always favor machine perfusion (MP) over cold static storage," Dr. Goldstein told Reuters Health by email. "In NY, we pump more kidneys per year than any other location in the world, close to 750 annually. We have learned that MP reduces delayed graft failure and prolongs allograft survival over organs that are not pumped or pumped for little amount of the cold ischemic time." "Improvements in organ preservation allow transplant surgeons to challenge the limits that have been imposed by past experience," Dr. Goldstein added. "In order to provide better access to transplantation and utilize more organs, surgeons must broaden their acceptance standards and use new approaches to improve organ quality and function." But despite what seems like uniform endorsement of pulsatile perfusion, there is room for disagreement. In email to Reuters Health, Dr. Dorry Segev from Johns Hopkins Medical Institution, Baltimore, Maryland, said, "The reduction of delayed graft function associated with pulsatile perfusion has not correlated, in most studies, with better allograft function or survival, leaving us to wonder what kind of physiologic changes actually occur with pulsatile perfusion and what the real purpose is for this preservation modality." Dr. Segev added, "Some centers use pulsatile perfusion to expand acceptance patterns for marginal organs, although some centers accept the same organs without pulsatile perfusion parameters." "Given the current evidence in the field, the choice of storage should remain based on institutional practice and technical experience with the available modalities," Dr. Segev concluded.