Energy expenditure following biodegradable dermal matrix application in severe burn injury: A pilot study

Biodegradable temporising matrix (BTM) is a dermal substitute developed to reconstruct full thickness burns, yet the subsequent metabolic effects are unknown. This pilot study aimed to 1) measure variation in energy expenditure using indirect calorimetry (IC) in response to BTM application across the continuum of acute burns management and 2) assess accuracy of predictive energy equations commonly used in Australia in adult patients with severe burns.

Energy expenditure was measured (MEE) using IC during distinct time-periods: 'acute surgery'; 'BTM integration'; following 'skin grafting'; and 'acute recovery' and compared to predictive equations (Toronto, Schofield plus injury factor (IF), and the Ratio method from a minimum of 25 kcal/kg/day to a maximum of 40 kcal/kg/day). Agreement was assessed using Lin's concordance correlation coefficient (CCC) and Bland-Altman methods.

Eighteen patients were included (median [Interquartile range] 44 [29-70] years; 39 % [25-56 %] total body surface area burns). MEE reported as estimated marginal means (95 % confidence intervals) for each time-period were: 'acute surgery' 2048 (1847, 2248) kcal; 'BTM integration' 2244 (2071, 2416) kcal; 'skin grafting' 2297 (2123, 2471) kcal; 'acute recovery' 2102 (1918, 2287) kcal, equating to 25 %, 37 %, 41 % and 29 % above predicted basal metabolic rate (Schofield, no injury factor), respectively (all p < 0.001). During 'acute surgery' all equations (Schofield x IF, Minimum and Maximum Ratio method), overestimated energy requirements by 24-42 % (all p < 0.001), except Toronto (-12 %, p = 0.071). Similarly, all equations overestimated energy requirements by 11-27 % throughout 'BTM integration' (all p ≤ 0.01), except Toronto (-5 %, p = 0.12). Following 'skin grafting' Schofield and Maximum Ratio equations overpredicted, while Toronto underpredicted requirements (+16 %, +21 % and -11 %, respectively, p ≤ 0.001). The Maximum Ratio overestimated and Toronto underestimated requirements during 'acute recovery' (+19 %, p = 0.04 and -9 %, p = 0.014, respectively). Average CCC (all time periods) was highest for Toronto at 0.77, with Bland-Altman plots also showing highest accuracy and reliability.

A substantial hypermetabolic response was not observed following BTM application. While the Toronto equation most closely predicted energy requirements, considerable variability was observed, highlighting the value of IC to guide nutrition support in severe burns where nutritional needs change over time. A larger multicentre study is required to substantiate the effect of BTM application on energy expenditure.