Supplemental parenteral nutrition improves immunity with unchanged carbohydrate and protein metabolism in critically ill patients: The SPN2 randomized tracer study

Abstract

Background & aims: Individualized supplemental parenteral nutrition (SPN) providing measured energy expenditure from day 4 reduced infectious complications in a previous study including 305 intensive care (ICU) patients. The study aimed at investigating the metabolic, and immune responses underlying the clinical response of the previous trial.

Methods: Randomized controlled trial enrolling 23 critically ill patients on day 3 (D3) of admission to the ICU who were fed less than 60% of their energy target by the enteral nutrition (EN) alone: allocation to either continued EN or to SPN to a target validated by indirect calorimetry. Protein and glucose metabolism (primary endpoint) were investigated with tracer isotopes on D4 and D9. Secondary endpoints: 1) immune response, investigated in serum and in stimulated peripheral blood mononuclear cells (PMBC), by dosing a panel of cytokines (infectious complications were recorded), and 2) Muscle mass was assessed by ultrasound of the thigh.

Results: Comparable at baseline, the SPN group (n = 11) received more energy (median 24.3 versus 17.8 kcal/kg/day: p < 0.001) and proteins (1.11 versus 0.69 g/kg/day: p < 0.001) than the control group during the five days' intervention, resulting in a less negative energy balance by D9 (p = 0.0027). Net protein breakdown and Glucose kinetics on D9 did not differ, within or between groups. In agreement with a decrease in infection rate, immune response in the SPN group showed decreased serum IL-6 (p = 0.024), IL-1β, IL-10 levels and TNF-α secretion by PBMC (p = 0.018) at D9. Muscle mass loss from D4 to D15 tended to be less in the SPN group (-16% versus -23%: p = 0.06). Clinical course by D28 did not differ.

Conclusions: Feeding patients to cover an individualised measured energy target with SPN from D4 to cover needs, was associated with improved immunity, less systemic inflammation and a trend to less muscle mass loss.

Clinical trial registry: NCT02022813 at https://clinicaltrials.gov/.

Keywords: Critical illness; Glucose kinetics; Immune response; Infection; Muscle mass; Protein turnover.