Acute kidney injury is common, parallels organ dysfunction or failure, and carries appreciable mortality in patients with major burns: a prospective exploratory cohort study

Abstract

Introduction: The purpose of this study was to determine the incidence, time course, and outcome of acute kidney injury after major burns and to evaluate the impact of possible predisposing factors (age, gender, and depth and extent of injury) and the relation to other dysfunctioning organs and sepsis.

Method: We performed an explorative cohort study on patients with a TBSA% (percentage burned of total body surface area) of 20% or more who were admitted to a national burn centre. Acute kidney injury was classified according to the international consensus classification of RIFLE (Risk, Injury, Failure, Loss of kidney function, and End-stage kidney disease). Prospectively collected clinical and laboratory data were used for assessing organ dysfunction, systemic inflammatory response, and sepsis.

Results: The incidence of acute kidney injury among major burns was 0.11 per 100,000 people per year. Of 127 patients, 31 (24%) developed acute kidney injury (12% Risk, 8% Injury, and 5% Failure). Mean age was 40.6 years (95% confidence interval [CI] 36.7 to 44.5), TBSA% was 38.6% (95% CI 35.5% to 41.6%), and 25% were women. Mortality was 14% and increased with increasing RIFLE class (7% normal, 13% Risk, 40% Injury, and 83% Failure). Renal dysfunction occurred within 7 days in 55% of the patients and recovered among all survivors. Age, TBSA%, and extent of full thickness burns were higher among the patients who developed acute kidney injury. Pulmonary dysfunction and systemic inflammatory response syndrome were present in all of the patients with acute kidney injury and developed before the acute kidney injury. Sepsis was a possible aggravating factor in acute kidney injury in 48%. Extensive deep burns (25% or more full thickness burn) increased the risk for developing acute kidney injury early (risk ratio 2.25).

Conclusions: Acute kidney injury is common, develops soon after the burn, and parallels other dysfunctioning organs. Although acute kidney injury recovered in all survivors, in higher acute kidney injury groups, together with cardiovascular dysfunction, it correlated with mortality.

Figure 1

Algorithm showing selection of patients. TBSA, percentage burned of total body surface area.

Figure 2

Day of onset of renal dysfunction, respiratory dysfunction, and sepsis. Cumulative percentage of the patients who developed renal dysfunction showing when their plasma creatinine concentration exceeded at least 1.5 × baseline (n = 31, thick line) and who developed severe respiratory dysfunction (sequential organ failure assessment score of 3 to 4 = PaO₂/FiO₂ [arterial partial pressure of oxygen/fraction of inspired oxygen] below 200 mm Hg, n = 28, thin line) and sepsis (n = 27, dotted line). X-axis shows the first 14 days after injury. The remaining times are weeks.

Figure 3

Maximum sequential organ failure assessment (SOFA) score among the patients who developed renal dysfunction (n = 31). SOFA score is calculated on the maximum value for each of five organ dimensions weekly during the first 7 weeks after injury: maximum SOFA respiratory dimension (closed square, open box), cardiovascular dimension (open square, shaded box), coagulation dimension (closed square, diagonal pattern in the box), renal dimension (open square, closed box), and hepatic dimension (open square, open box). Squares indicate the mean, the box indicates standard error, and whiskers indicate 95% confidence interval.