Effects of obesity on burn resuscitation

The effects of obesity on resuscitation after severe burn are not well understood. Formulas to calculate 24-h resuscitation volumes incorporate body weight, which in obese patients often leads to excessive fluid administration and potential complications such as pulmonary edema, extremity or abdominal compartment syndrome, and longer mechanical ventilation. We evaluated the impact of obesity on 24-h fluid resuscitation after severe burn using a cohort of 145 adults admitted to the burn ICU from January 2014 to March 2017 with >20% total body surface area burns. Patients were divided into four groups based on body mass index: normal weight (index of <25), overweight (25-29.9), obese (30-39.9), and morbidly obese (>40). Median total body surface area burn was 39.4% (interquartile range: 23.5%-49.5%). Patients were 74.5% male and demographics and injury characteristics were similar across groups. Resuscitation volumes exceeded the predicted Parkland formula volume in the normal and overweight groups but were less than predicted in the obese and morbidly obese categories (p<0.001). No difference was found in 24-h urine output between groups (p=0.08). Increasing body mass index was not associated with increased use of renal replacement therapy. Only total body surface area burned, and age were independent predictors of hospital mortality (p<0.001). We conclude that using body weight to calculate resuscitation in obese patients results in a predicted fluid volume that is higher than the volume actually given, which can lead to over-resuscitation if rates are not titrated regularly to address fluid responsiveness.