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Early enteral nutrition (EN) is the preferred strategy for feeding the critically ill; however, it is not always possible to achieve sufficient calories and protein with EN alone. The use of supplemental parenteral nutrition (PN) has been advocated as a strategy to avoid complications associated with protein/calorie deficit from inadequate enteral feeding. The purpose of this study was to evaluate the effect of this practice on nutritional and clinical outcomes.
An international, observational study conducted in 2007 and again in 2008 examined nutrition practices in ICUs. Eligible patients were the mechanically ventilated who remained in the ICU for >72 hours and received early EN within 48 hours from admission. Data were collected on patient characteristics and daily nutrition practices for up to 12 days. Patient outcomes were recorded after 60 days. We compared the outcomes of patients who received early EN alone, early EN + early PN, and early EN + late PN (after 48 hours of admission). Regression analyses were conducted to determine the effect of increasing age, APACHE score, days in hospital prior to ICU admission, gastrointestinal dysfunction, nutritional strategy, and other baseline variables and their relationship to being alive and discharged within 60 days.
A total of 2,920 patients from 260 ICUs were eligible for this study; 2,562 (87.7%) in the Early EN group, 188 (6.4%) in the Early PN group, and 170 (5.8%) in the Late PN group. Adequacy of calories and protein was highest in the Early PN group (81.2% and 80.1%, respectively) and lowest in the Early EN group (63.4% and 59.3%) (P < 0.0001). The 60-day mortality rate was 27.8% in the Early EN group, 34.6% in the Early PN group, and 35.3% in the Late PN group (P = 0.02). In a single predictor model, the proportion of patients discharged alive from hospital at 60 days was lower in the group that received Early PN (hazard ratio (HR) 0.75, 95% confidence interval (CI) 0.59 to 0.96) and Late PN (HR = 0.64, 95% CI 0.51 to 0.81) (P = 0.0003) compared with Early EN. These findings persisted after adjusting for known confounders. In subgroup analyses, we could not demonstrate any benefit to supplemental PN in patients with BMI <20.
The supplemental use of PN may improve provision of calories and protein but is not associated with any clinical benefit.