Four Factors Associated with Death

According to the burn-unit study, four factors were associated with increased risk of death after the initial injury: age, total burned surface area (TBSA), injury severity score (ISS) and AKIN stage. The first three factors were associated with moderately increased risk (odds ratios of 1.03 to 1.1). AKIN-2 and AKIN-3, however, had extremely high associations with mortality, with odds ratios of 23.7 and 130. Using RIFLE produced similar results, with odds ratios of 46.28 and 126 for the injury and failure stages, respectively.

“One of the interesting results of the study is that using just the four variables of age, severity of injuries, total body area burned and presence of AKI creates a great model with an area under the curve (in the regression analysis) of .98 where perfect predictability would 1.0,” observed Stewart. Such a high correlation “implies that few other factors can explain mortality in this population.

These results raise the possibility that AKI is a major contributor to both morbidity and mortality after combat injury,” wrote Stewart and his colleagues.

Knowing when and why injured personnel develop AKI will make development of targeted interventions more successful, he noted.

Based on creatinine levels, 58% of patients with AKI had the condition on admission, indicating to the researchers that factors related to the immediate post-injury period such as hypotension and use of contrast material were likely responsible. Another 17% developed AKI after the first week, probably as a result of complications during hospitalization including additional exposure to contrast materials, nephrotoxins, and sepsis. The authors attributed development of AKI between admission and Day 8 in one-quarter of the AKI group to a combination of factors.

“The major problem in making a diagnosis of AKI, retrospectively, is that it may be too late. It would be better if we could diagnose it earlier; the best way would be using urinary biomarkers. In the short term, though, we can limit volume expansion and resulting body overload, which prospective studies have shown increase mortality in hospital populations,” said Stewart.

Knowing what other steps can reduce the prevalence of AKI in wounded personnel requires more research, Stewart said, explaining, “Progress in the AKI field has been slow. We know a variety of treatments work in animal models, when we know when the insult occurs. In humans, we don’t. In the long term, we need to design trials to see what therapy is most effective.”

The burn-center study was retrospective and did not prove cause and effect. “Certainly there is a strong association, but it could be because sicker patients are more likely to get KI, or it could be that AKI causes death,” he added. “We are at the hypothesis-generating stage now. It appears that AKI is in the direct cause-effect pathway, but we need additional evidence to prove it.”

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