Abstract
Background: Indirect calorimetry (IC) accurately measures a patient’s metabolic rate and energy needs, guiding nutrition support for critically ill patients. The American Society of Enteral and Parenteral Nutrition (ASPEN) recommends IC for accurate calorie prescriptions. While estimations based on weight or equations exist, they are unreliable due to patient variations and can lead to over- or underfeeding, both harmful. Our study (Jan 2020 - Dec 2022) found low use of IC for critical patients (only 11 cases). The barriers were faulty equipment, doubts about IC’s value, outdated procedures, and training gaps. An interdisciplinary team was formed in January 2023 to address these issues and optimize nutrition support using IC.
Methods: UCSF’s IC task force addressed low utilization. Staff evaluated new metabolic carts (Q-NRG and the CCM express) for user experience, accuracy, and cost. A purchase request is awaiting delivery. Policies were updated for accurate IC implementation, including patient selection and data interpretation. A screening method and IC study process were developed. Educational sessions empowered multidisciplinary teams on IC benefits and its use. While a new cart is awaited, updated procedures and trained staff ensure optimal use when available.
Results: IC use increased for critically ill patients. RD estimates vs. IC measurements showed poor agreement. In 81% of patients, IC resulted in adjustments to nutrition prescriptions. Based on measured REE, there were underfeeding (50%) and overfeeding (31%) cases. Summary of the findings about kcal/day needs: Estimated vs. measured kcal/day agreed within 10% for only 19% of patients. The mean difference between estimated and measured kcal/day was 497 kcal. A wide range of kcal/kg needs were observed: 19-49 kcal/kg for BMI < 30 (n = 28), 27-35 kcal/kg for BMI > 30 (n = 4).
Conclusions: Despite challenges, IC use has increased at UCSF in 2023 and 2024. It has led to nutrition prescription adjustments for 81% of measured patients, highlighting the importance of IC in providing accurate and individualized care. Continued multidisciplinary collaboration and access to a reliable metabolic cart are essential to maintaining this trend and establishing IC as a standard of care when providing nutrition support interventions for critically ill, mechanically ventilated adult patients.
Footnotes
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