Risk factors for acute respiratory distress syndrome in severe burns: prospective cohort study

Age and inhalation injury are important risk factors for acute respiratory distress syndrome (ARDS) in the burned patient; however, the impact of interventions such as mechanical ventilation, fluid balance (FB), and packed red blood cell transfusion remains unclear. The purpose of this study was to determine the incidence of moderate and severe ARDS and its risk factors among burn-related demographic variables and clinical interventions in mechanically ventilated burn patients. Risk factors for death within 28 days were also evaluated.

A prospective longitudinal study was carried out over a period of 30 months between July 2015 and December 2017. Patients older than 18 years, with a burn injury and under mechanical ventilation were included. The outcomes of interest were diagnosis of ARDS up to seven days after admission and death within 28 days. The proportional Cox regression risk model was used to obtain the hazard ratio for each independent variable.

The cases of 61 patients were analyzed. Thirty-seven (60.66%) of the patients developed ARDS. The groups of patients with or without ARDS did not present differences regarding age, sex, burned body surface, or prognostic scores. Factors independently related to the occurrence of ARDS were age (hazard ratio [HR] = 1.04; 95% confidence interval [CI] 1.02-1.06; P < 0.001), inhalation injury (HR = 2.50; 95% CI 1.25-5.02; P = 0.01), and static compliance (HR = 0.97; 95% CI 0.94-0.99; P = 0.03). Tidal volume, driving pressure, acute renal injury, and FB between days 1 and 7 were similar in both groups. Accumulated FBs of 48, 72, 96, and 168 hours were also similar. Mortality at 28 days was 40.98% (25 patients). ARDS (HR = 3.63, 95% CI 1.36 to 9.68; P = 0.01) and burned body surface area (HR = 1.03, 95% CI 1.02 to 1.05; P < 0.001) were associated with death in 28 days.

ARDS was a frequent complication and a risk factor for death in patients under mechanical ventilation, with large burned areas. Age and inhalation injury were independent factors for ARDS. Current tidal volume, driving pressure, red blood cell transfusion, acute renal injury, and FB were not predictors of ARDS.