Postoperative assessment of daily energy expenditure. Comparison of two methods

The reference method for determining resting energy expenditure (REE) in clinical nutrition practice is measurement by indirect calorimetry; however, indirect calorimetry has some limitations, is expensive and not widely available. Therefore, the most used methods to estimate the caloric requirements in intensive care patients are predictive equations. The Harris-Benedict equations (HBE) are the most common formulae in the clinical setting. The SenseWearA (R) armlet (SWA) is a noninvasive device that monitors skin temperature, heat flux, galvanic skin response and movement. These data as well as anthropometric characteristics are used to calculate REE. The aim of this study was to evaluate the levels of agreement and interchangeability of REE estimated by HBE (EEHBE) and measured by SWA (EESWA) in normometabolic patients after elective bowel resection with laparotomy. Furthermore, postsurgical pain therapy by continuous thoracic epidural anaesthesia (t-PDA) was compared with continuous intravenous pain therapy regarding EESWA in these patients. After obtaining approval by the ethics committee and written informed consent 57 patients participated in the study procedures. A total of 50 patients (23 male, 27 female) were finally included in the data analysis because 7 patients did not meet the criterion of > 80% on-body time of the SWA. Additional (a priori) exclusion criteria were metabolic or cardiopulmonary decompensation or postoperative mechanical ventilation. Before induction of general anesthesia 26 patients received a thoracic epidural catheter. Immediately after surgery the SWA was placed on the right upper arm of each patient for 24 h. A continuous pain therapy was started either an epidural application of ropivacain 0.2% and sufentanil or in the other 24 patients an intravenous infusion of metamizol and tramadol. The data showed good agreement between EESWA and EEHBE. The mean on-body time was found to be 22.94 +/- 4.77 h. There were no significant differences between EESWA and EEHBE (p > 0.05) corresponding to a high Pearson's coefficient of correlation of 0.985. The mean bias (EESWA-EEHBE) was -0.569 +/- 0.378 kcal/kgBW/24 h reflecting a minimal systematic underestimation of REE by SWA of -2.9% compared to EEHBE. The Bland-Altman plot shows interchangeability of EESWA and EEHBE. It was noted that 94% of the data points (47 out of 50 patients) were within +/- 2 SD and the remaining 3 data points were lying close to the 95% interval. The same results (no significant differences between EESWA and EEHBE) were obtained after differentiation of EEHBE into low (< 18 kcal/kgBW/24 h, n = 9), medium (18-21 kcal/kgBW/24 h, n = 30) and high (> 21 kcal/kgBW/24 h, n = 11) energy ranges. There were no significant differences in EESWA regarding postsurgical pain therapy regimens. The SWA showed reliable concordance with daily REE estimated by HBE in normometabolic postsurgery patients. This noninvasive, convenient and easy to handle device may be helpful in determining energy requirements as part of metabolic monitoring. Further research is needed to validate the method in patients with severe metabolic disturbances. The energetic requirements of patients with postoperative t-PDA were not different from those with intravenous pain therapy.