Resting Energy Expenditure, Nutritional Intake, and Postoperative Outcomes in Patients Undergoing Total or Partial Pancreatectomy for Pancreatic Tumors: A Prospective Observational Cohort Study

Background and Rationale Patients undergoing pancreatic resection experience surgical stress, systemic inflammation, and frequent exocrine and endocrine insufficiency that together alter energy metabolism and place them at high risk of nutritional deterioration. Predictive equations and simplified weight-based targets are used routinely to prescribe nutrition when indirect calorimetry is unavailable, but their accuracy in this specific surgical population is poorly characterized, and the degree to which the route and adequacy of postoperative feeding influence recovery has not been examined alongside directly measured energy expenditure in the same patients. This study is designed to address both questions within a single prospective cohort, pairing calorimetry-based measurement of resting energy expenditure with structured documentation of nutritional delivery and clinical outcomes.

Design and Setting The study is a single-center prospective observational cohort study. Consecutive eligible adults undergoing total or partial pancreatectomy for pancreatic tumors are enrolled preoperatively after informed consent. Feeding route is not assigned by the protocol; it is determined case by case by the treating surgical and nutrition support teams according to clinical status and tolerance, and is recorded as an observed exposure. All measurements and data abstraction are performed by trained clinical dietitians and drawn from direct measurement and the medical record.

Indirect Calorimetry Procedure Measured resting energy expenditure (mREE) is determined using a Cosmed Q-NRG+ portable indirect calorimeter. The device is calibrated before each session per the manufacturer's automatic gas-calibration procedure. Measurements are obtained by canopy where feasible, with a face mask used only when a canopy cannot be applied, recording VO₂ and VCO₂. Patients are measured supine, awake, and motionless in the morning after an 8-10 hour fast, at a controlled room temperature of 22-24 °C, following a minimum 20-30 minutes of rest. The first five minutes of each recording are discarded, and steady state is defined as at least five consecutive minutes during which the coefficient of variation in VO₂ and VCO₂ does not exceed 10%. Caffeine and strenuous activity are avoided for at least 12 hours beforehand, and supplemental oxygen is suspended or accounted for where clinically feasible. mREE is derived using the abbreviated Weir equation, mREE = (3.94 × VO₂ + 1.11 × VCO₂) × 1.44, and the respiratory quotient is calculated as VCO₂/VO₂. To reduce the influence of single-timepoint sampling within a dynamic postoperative course, calorimetry is scheduled at more than one time point during the early recovery period where the patient's clinical stability permits, with the exact days recorded.

Estimation of Energy Requirements for Comparison Predicted resting energy expenditure is calculated for each patient using the Harris-Benedict and Schofield equations. Harris-Benedict is applied as: men, 66.47 + 13.75 × weight (kg) + 5.0 × height (cm) - 6.75 × age; women, 665.09 + 9.56 × weight (kg) + 1.84 × height (cm) - 4.67 × age. Schofield is applied by sex and age band. For overweight patients, ideal body weight is used in these equations; for obese patients, corrected weight [ideal body weight + 0.25 × (actual - ideal body weight)] is used. Total energy requirements are additionally estimated from the ESPEN weight-based targets of 25 and 30 kcal/kg of ideal body weight (adjusted using a BMI of 22 kg/m² for overweight and 24.9 kg/m² for obese patients) and compared with mREE adjusted by an activity/stress factor of 1.15. Because the two families of estimates target different quantities - basal/resting expenditure for the equations versus total requirements for the weight-based targets - equation comparisons use raw mREE while weight-based comparisons use mREE × 1.15, and this distinction is retained throughout analysis.

Nutritional Intake and Feeding-Route Documentation For each patient, the route of postoperative nutrition (enteral plus oral, parenteral only, or combined enteral and parenteral) is recorded, together with the formulation used, the daily administered volume, and the delivery rate. Daily energy and protein delivery are quantified and expressed relative to individually calculated requirements to derive an energy deficit and a protein deficit for the early postoperative period. Diet-related symptoms (including diarrhea and abdominal pain) are recorded prospectively. These data support the planned subgroup comparison of outcomes across feeding routes and across strata of energy and protein deficit.