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Allan, Kirstie, Grimble, George, Whelan, Kevin and Illingworth, Sarah (2025) Metabolic response, energy expenditure and nutritional status of patients undergoing coronary artery bypass surgery. Clinical Nutrition ESPEN, 68. p. 869. ISSN 2405-4577
Background: Heart failure affects 26 million people worldwide, with approximately 7000 people undergoing coronary artery bypass graft (CABG) surgery in the UK annually. The metabolic response to surgery leads to variations in energy expenditure which may not correspond to estimates based on predicted equations. As a result, there is a risk of over or under feeding to the detriment of the patient (1,2).
Aims: This study measured the effect of CABG surgery on measured total energy expenditure (mTEE), nutritional status and body composition during the pre-operative, post-operative and rehabilitation periods.
Methods: In this prospective observational study of adult male patients undergoing CABG surgery, mTEE was measured through Basal Metabolic Rate (BMR) from Indirect Calorimetry (IC) with added Physical Activity Level (PAL) factor. Nutritional status was assessed from weight, mid-upper-arm circumference (MUAC) and Subjective Global Assessment (SGA) scores. Measurements were taken during: pre-operative (12 to 72 hours before surgery); post-operative (1 - 4 hours after surgery); and rehabilitation (6 to 10 days after surgery). Differences between groups of measurements were assessed using ANOVA, paired-sample t-tests or the Wilcoxon signed rank test.
Results: Eleven patients were recruited. There was a significant decrease in energy expenditure (mTEE) after surgery (p = 0.002), mean body temperature was 35.45 ± 0.80 °C. Thereafter, energy expenditure increased during rehabilitation (p=0.003). Skeletal muscle mass decreased as evidence by a reduction in MUAC (p = 0.012), whilst nutritional status worsened during rehabilitation (p = 0.046).
Conclusions:
Despite the surgical insult, these patients did not become hypercatabolic and showed reduced energy expenditure during the post-operative period. Nutritional status worsened overall and skeletal muscle mass reduced. This study highlights the difficulty of estimating energy expenditure. Sedation, cooling and immobilisation will be expected to reduce energy expenditure, whereas injury will increase it. The net effect may therefore be a reduction in energy expenditure. Accurate estimations can only be made after measuring energy expenditure or by use of prediction equations validated for use in similar patient groups.
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