Ultrasound-based Evaluation of Loss of Lean Mass in Patients with Burns: A Prospective Longitudinal Study

Objectives: To evaluate the loss of lean mass in patients with burns using ultrasonography of the quadriceps muscle of the thigh. Methods: A prospective longitudinal study was conducted using ultrasound of the quadriceps muscle of the thigh to assess the change in thickness in millimeters on days 1, 3 and 7 after study enrollment in 45 patients with burns who were admitted to a burn center (BTC) of a university hospital between April 2020 and September 2021. Patients burns on the thighs, which made it difficult to undertake examinations, were excluded. Depending on where they were admitted, patients were divided into ward and intensive care unit (ICU) patients. ICU patients were considered to have more severe injuries. The general data collected included age, sex, weight, height, area of body surface burn, burn degree and etiology, and airway injury. The data collected for all patients during hospitalization at the BTC were as follows: existence of chronic illness, requirement for mechanical ventilation, Simplified Acute Physiology Score 3 (SAPS 3) and Sequential Organ Failure Assessment (SOFA) on the first day of hospitalization in an intensive care bed in the burn treatment unit (BTU), health-related infection, feeding route, length of hospital stay, and time spent in the BTU. Results: Loss of muscle thickness was observed in all patients between days 1 and 7. The median thickness for all patients on day 1 was 24.50 mm (ITQ 21.22-30.85) and on day 7 it was 18.80 (ITQ 16.07-23.62), with P = 0.0001. The variation in thigh quadricep muscle thickness between day 1 and day 3, a median of - 2.80 mm (ITQ - 3.52-2.02) was obtained for patients on the ward and - 2.50 mm (ITQ - 3.92 to - 1.47) for ICU patients. Between day 3 and day 7, the variation was - 2.55 mm (ITQ - 4.55 to - 1.25) for ward patients and - 2.10 mm (ITQ - 3.12 to - 1.15) for ICU patients. The median thickness variation assessed between day 1 and day 7 was - 4.95 mm (ITQ - 8.25 to - 3.70) for patients on the ward and - 4.40 mm (ITQ - 7, 35 to - 2.90) for ICU patients. A correlation was observed between the variation in muscle thickness in the interval between day 1 to day 3 and age (P = 0.035).Conclusions: Muscle loss occurred early and rapidly within the first seven days of hospitalization, reflecting the impact of burn injury on nutritional risk. An association was