Energy expenditure measured using indirect calorimetry after elective cardiac surgery in ventilated postoperative patients: A prospective observational study

Background & aims: Resting energy expenditure (REE) following cardiac surgery is not determined. We conducted this prospective observational study to clarify this, comparing REE to basal energy expenditure (BEE) estimated using the Harris-Benedict equation (HBE). Methods: Consecutive patients who underwent cardiac surgery (coronary artery bypass graft sursgery, valve surgery, and total arch replacement) in our hospital from September 2013 to March 2015 were included. Patients who were <18 years of age, undergoing hemodialysis, or had undergone emergency surgery were excluded. REE was measured using indirect calorimetry during intubation, or at 9 a.m. on postoperative day 1 in the intensive care unit. BEE was estimated using the HBE and compared with REE. Patients were divided into 2 groups: patients who received cardiac surgery with cardiopulmonary bypass (CPB) (on-pump group; n = 34) and without CPB (off-pump group; n = 13). Results: We enrolled 47 patients. Mean age, body weight, and height were 73 ± 10 years (mean ± standard deviation), 55 ± 10 kg, and 155 ± 10 cm, respectively. BEE was 1147 ± 148 kcal/day. The average REE during ventilation was 1314 ± 148 kcal/day (23.9 ± 6.8 kcal/kg/day), significantly higher than estimated BEE (114 ± 35% BEE, p < 0.0001). The average REE was not significantly different between the 2 groups (24 ± 7 vs. 24 ± 6 kcal/kg/day, p = 0.87). Conclusions: REE was 1314 ± 148 kcal/day (23.9 ± 6.8 kcal/kg/day), or 1.14 times higher than the estimated BEE, in postoperative cardiac surgery patients. The average REE was not significantly different between the on-pump and off-pump groups.