SAN ANTONIO, TX--Kidney injuries have dramatically increased death rates in military personnel evacuated to burn units in Iraq and Afghanistan.

Up to 30% of those wounded troops suffer acute kidney injury (AKI) and, with the severe form of the injury, nearly two-thirds of those die, compared with a rate of 2 in 1,000 of patients without the condition, according to a new study published in the Clinical Journal of the American Society of Nephrology. Even those with minimal AKI have significantly increased death rates of between 4% and 8.3%, depending on what measurement system is used.

Members of the 455th Contingency Aeromedical Staging Facility load litter patients onto a bus for transport to the Craig Joint Theater Hospital at Bagram Air Field, Afghanistan, after an aeromedical flight in June. Photo by Senior Airman Krista Rose.

As dire as the situation may sound, that information also creates opportunities for saving lives, according to Capt. Ian Stewart, MD, USAF, of the San Antonio Military Medical Center at Fort Sam Houston, TX.

While age, injury severity and burn area cannot be altered, “AKI represents a critical variable, and it’s the only one you can change. If we intervene, we may be able to alter the outcome,” said Stewart, who was one of the study authors.

Researchers used the two mostly widely-accepted classification systems for AKI, Acute Kidney Injury Network (AKIN) and Risk-Injury-Failure-Loss-End Stage (RIFLE) to categorize 692 patients admitted to the U.S. Army Institute of Surgical Research Burn Center between January 2003 and November 2008, based on a retrospective review of their recorded serum creatinine levels. AKI prevalence rates were 23.8% by RIFLE criteria and 29.9% using the AKIN criteria.

Even patients with relatively minimal AKI had a substantially increased death rate: 8.3% according to RIFLE and 4.0% for those categorized under AKIN. Death rates for patients with moderate and severe AKI rose quite sharply: 21.4% (Injury level in RIFLE) to 33.3% (AKIN-2) and 62.5% (Failure by RIFLE) to 65.1% (AKIN-3). Patients without AKI had a mortality rate of 0.2%. In the total population, 41 patients died. Only one was in the non-AKI group.

While AKI has been associated with increased mortality in other patient groups, “Our research extended those findings to wounded warriors with respect to burn injury and showed poor outcomes in the short-term,” Stewart told U.S. Medicine.

Kidney Disease Challenge for VA

“In the long term, the VA may be challenged to care for the patients with kidney injury who survive, as they have long-term consequences, including higher risk for renal function decline and mortality,” he added.

Indeed, those patients who survive the initial injury and AKI do not always have a favorable prognosis, partly because of less-than-optimal treatment for the kidney issues, according to another study in the same journal.

Researchers from Vanderbilt University Medical Center and the Tennessee Valley VA Healthcare System used a VA database to identify 3,929 survivors of AKI who were hospitalized between January 2003 and December 2008 and who continued to have poor kidney function a month after their injury.

Of those, 22% died over a one-year surveillance period. Part of the problem was that, despite the severity of their kidney disease, only 8.5% of patients were referred to a kidney specialist before dying, starting dialysis or experiencing an improvement in kidney function.

“This study shows that only a minority of patients who do not recover their kidney function after an AKI event are seen by a kidney specialist, highlighting an important opportunity for a more integrated approach in maintaining the kidney health of these patients,” researcher Michael Matheny, MD, said in a press release from the American Society of Nephrology. “The findings also underscore the need for more research to help identify those patients who are at highest risk for persistent kidney problems and who might benefit from the input of a kidney specialist."