Fluid resuscitation mediates the association between inhalational burn injury and acute kidney injury in the major burn population.

ABSTRACT

BACKGROUND: It is known that acute respiratory distress syndrome and acute lung injury are independent risk factors for developing acute kidney injury (AKI) through complex pathophysiologic mechanisms. Our specific aim is to evaluate the risk factors for AKI postburn injury and whether inhalation thermal injury is an independent risk factor for developing AKI in the major burn population. METHODS: This is an institutional review board-approved, retrospective cohort study of patients admitted to a tertiary burn intensive care unit between 2011 and 2013. We included adults (age 18 years or older) with major burn injury greater than or equal to 20% total burn surface area (TBSA) and patients with confirmed inhalation injury (±major burn). Acute kidney injury was defined using the acute kidney injury network serum creatinine criteria up to 5 days after admission. Patient demographics and clinical data were compared across cohorts using the Wilcoxon rank sum test or Pearson χ2 test, as appropriate. Multiple logistic regression was used to assess the effect of inhalation injury and major burn on the incidence of AKI, adjusting for clinical and demographic confounders. RESULTS: Two hundred fifty-four patient records (90 with inhalation injury and 164 with major burn only) were evaluated. The mean age on admission was 47±19 years and 72% of the cohort were men. There were more men in the major burn group (78% vs 62%; P=.007). No other significant differences were observed in the baseline demographics. The overall incidence of AKI was 28% (95% confidence interval, 22, 33). The unadjusted odds of AKI were nearly double (odds ratio, 1.99; 95% confidence interval, 1.13, 3.49) among those with inhalation injury relative to those with major burn only. However, there was no evidence of an independent inhalational injury effect after adjusting for potential confounders. In particular, TBSA (P=.051), daily 24-hour fluid balance (P<.001), and most recent 24-hour albumin transfusion status (P=.002) were all significantly associated with AKI in the adjusted analysis. Age and packed red blood cell transfusion status were not significant. CONCLUSION: Inhalation thermal injury is not an independent risk factor for AKI after adjusting for TBSA and surrogates for fluid resuscitation. In patients with major burns, intensity of fluid resuscitation may mediate the development of AKI.