Published in Nutrition in Clinical Practice, September 2021
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Patients critically ill with COVID-19 are often hypermetabolic, which in turn is often associated with an increased protein catabolism. While the majority of these patients receive a calculated protein intake via enteral nutrition (EN), there is a paucity of data on which to determine actual protein requirements. Buckley et al (USA) evaluated the protein requirements by investigating the nitrogen accretion response to varying protein intakes for the critically ill ventilator-dependant patients with COVID-19.
This was a retrospective observational study in which adults admitted to the ICU (Oct 20-Jan 21) with COVID-19, requiring mechanical ventilation within 7 days of admission were eligible. Patients received continuous EN (estimated energy and protein requirements were based on actual or ideal body weight if obese) and a 24-hr urine collection was completed to determine nitrogen balance and creatinine clearance.
Twenty-two patients (mean age 66 years, 64% male, mean BMI 30 kg/m2) were enrolled in the study and all patients contributed at least 1 nitrogen balance test. A high rate of hospital mortality was observed (about 2/3 of the studies population) with prolonged ICU and hospital length of stays. The average target energy intake was ~1350-1800kcal/day (~1450-1650kcal/day for the obese) and target protein intakes were 105-175g/day (130-165g/day for the obese). The nitrogen balance was highly variable with most patients experiencing a substantial negative balance, with the nitrogen balance among all protein intakes averaged -12.2g/day. Nitrogen equilibrium or a positive nitrogen balance was only achieved in 5 out of 29 observations, and were in those who received higher protein intakes (~1.2g/kg/day). Most patients did not meet their intended caloric or protein goals due to the challenges of EN feeding including gastric feeding intolerance and ileus.
The authors acknowledge that this is based on a small sample, however highlights the variability of nitrogen accretion and the challenge of achieving nitrogen balance. Their linear regression analysis suggests 1.5g/kg/day to achieve nitrogen equilibrium, however due to such high variability an individualised approach is still required for this critically unwell set of patients.