Comparing retrospective PSU measurements with the LEEP-COVID 2020 study to ascertain similarities in calories per kilogram of body weight for ventilator-dependent COVID-19 patients

ABSTRACT

Background: Critically ill COVID-19 patients are suspected to have high caloric needs.1 Indirect calorimetry (IC) is the gold standard used to measure resting energy expenditure (mREE), but it is expensive and not widely available. Predictive equations are often used to assess metabolic requirements and the Pennsylvania State University (PSU) equation has demonstrated comparable results to IC in identifying caloric requirements for critically ill patients. This article describes a simple, comparative retrospective presentation of PSU calculations to that of the study published in 2020 by Whittle et al. on Longitudinal Energy Expenditure in Critically Ill Patients with COVID-19 (LEEP-COVID).1 PSU measurements were compared to the IC data by the LEEP-COVID study to ascertain similarities in calories per kilogram (kcal/kg) of body weight for ventilator-dependent COVID-19 patients over a duration of 30 days. Methods: A retrospective chart review was performed on critically ill COVID-19 patients between March and June of 2020 to collect their PSU calculations. Patients on extracorporeal membrane oxygenation (ECMO) and volumetric diffusive respirator (VDR), were excluded as these devices could skew the minute ventilation and yield an inaccurate PSU calculation. Patients for whom the PSU data was not clearly labeled were also removed, leaving 38 adult ventilator-dependent COVID-19 patients for review. PSU data was then compared to the LEEP-COVID 2020 study by Whittle et al. Results: Out of the 38 ventilator-dependent COVID-19 patients, the median age was 65 years old, 65.8% were male and 48% had a BMI >30. As illustrated in figure 1, kcal/kg of actual body weight (ABW) for the non-obese group (BMI < 30) from days 0 - 3 21.9 kcal/kg, days 4 - 6 23.5 kcal/kg, days 7 - 9 23.4 kcal/kg, days 10 - 12 24 kcal/kg, days 13 - 15 23.1 kcal/kg, days 16 - 18 22.4 kcal/kg, days 19 - 21 21.3 kcal/kg, days 22 - 24 24.6 kcal/kg, days 25 - 27 19.5 kcal/kg and days 28 - 30 22.9 kcal/kg. Figure 1 also shows the kcal/kg of ABW for the obese group (BMI 30 - 40) from days 0 - 3 19 kcal/kg, days 4 - 6 18.1 kcal/kg, days 7 - 9 18.2 kcal/kg, days 10 - 12 19.6 kcal/kg, days 13 - 15 18.6 kcal/kg, days 16 - 18 20.4 kcal/kg, days 19 - 21 19.2 kcal/kg, days 22 - 24 21.0 kcal/ kg, days 25 - 27 17.8 kcal/kg and days 28 - 30 19.4 kcal/kg. Compared to the LEEP-COVID 2020 study, non-obese ventilated COVID-19 patients from days 0 - 14 had a mREE using IC of 19.2 - 26 kcal/kg ABW and obese patients 17.5 - 21 kcal/kg ABW. Our retrospective study using the PSU equation from days 0 - 15 revealed caloric needs of 21.9 - 24 kcal/kg ABW for non-obese patients and 18 - 19.8 kcal/kg ABW for obese patients. Conclusion: In performing a simple comparative review of the LEEP-COVID study to our retrospective data, we identified that the PSU equation may be useful in estimating the caloric needs for ventilated COVID-19 patients from days 0 - 15.