Kidneys from non-heart-beating donors (NHBD) older than 60 years are associated with a similar risk of graft loss as kidneys from brain-death donors (BDD) in the same age group, according to a new study by British investigators.

In addition, a cold ischemia time of more than 24 hours predicts worse graft survival of BDD kidneys compared with NHBD kidneys.

The government-funded study of 6,490 kidney transplants also confirmed that donor age over 60 years compared to age under 40 years is associated with a significantly increased risk of graft loss for both BDD and NHBD kidneys, a research team led by Dominic Summers, MD, of Addenbrooke’s Hospital in Cambridge, U.K., reported in The Lancet (2013;381:727-734).

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Dr. Summers’ group undertook the study because the U.K. has one of the highest per-capita percentages of NHBD donors in the world. They analyzed data from the National Health Service’s U.K. transplant registry for all adult recipients of deceased-donor kidneys from January 1, 2005 to November 1, 2010. They excluded transplants of kidneys from people who were dead on arrival at the hospital or on whom resuscitation was performed without success in the emergency department as well as kidneys given to people who had received a previous renal transplant or who received donations of other organs at the same time.

The study included 1,827 donors of NHBD kidneys and 4,663 donors of BDD kidneys. The NHBD group had a significantly higher proportion of men than the BDD group (58% vs. 52%).

Significantly more of the NHBDs were smokers (55% vs. 51%), and more died from trauma (16% vs. 12%) and fewer died of stroke (69% vs. 79%).

The NHBD-organ recipients were more likely to be male than the BDD recipients (65% vs. 61%), were older (average of 53 vs. 48 years), were more likely to have an HLA mismatch at level 3 or 4, and were more likely to be non-sensitized at transplantation (81% vs. 79%).

The cold ischemia time also was significantly shorter for NHBD organs, at an average of 14 versus 16.4 hours, whereas the percentage that had machine perfusion was much higher, at 24% versus less than 1%. The latter difference is due to the fact that NHBD kidneys tend to be used in the same hospital at which they are retrieved; therefore, clinicians can use their own cold-perfusion pumps, Dr. Summers explained.

In addition, NHBD kidneys were three times more likely to have delayed graft function than those from BDDs; primary non-function was 1.5 times as likely. However, the rates of kidney rejection within three months and of three-year graft and patient survival were similar in both groups of patients.

A logistic regression analysis showed machine perfusion was associated with a 23% lower risk of delayed graft function.

Kidneys from NHBDs and BDDs over age 60 years produced relatively lower survival rates than did those from donors under age 40. However, longer cold ischemia time—24 hours or more compared with under 12 hours—resulted in significantly lower survival rates among kidneys from NHBDs but not among organs from BDDs.

Graft failure was also 1.53 times more likely for kidneys from NHBDs than BDDs for a cold ischemia time of 12-18 hours versus 12 hours, and 2.36 times more likely for a cold ischemic time of at least 24 hours versus 12 hours.

“We believe that this is likely to be due to additional warm ischemic injury that the NHBD organs suffer in the donation process, accelerating the ischemic damage process,” Dr. Summers told Renal & Urology News. “There can be a benefit in reduced cold ischemic times by shipping out the ‘second’ kidney from a NHBD retrieval, since very few centers can transplant two kidneys simultaneously. This lends support for regional sharing of NHBD organs.”

The team also compared the risk of graft failure of kidneys donated by people of various ages and, after adjusting for a range of variables such as donor age, cold ischemia time, recipient age, and donor hypertension, they found no increased risk of graft failure between kidneys from NHBDs over age 60 and organs from BDDs over age 60. However, as has been shown in previous studies, receiving kidneys from donors older than 60 years—whether NHBDs or BDDs—more than doubled the risk of graft failure within three years of transplant compared with receiving kidneys from donors under age 40.