The association between nutritional adequacy and 28-day mortality in the critically ill is not modified by their baseline nutritional status and disease severity

The association between nutritional adequacy and 28-day mortality in the critically ill is not modified by their baseline nutritional status and disease severity

by Charles Chin Han Lew, Gabriel Jun Yung Wong, Ka Po Cheung, Robert J. L. Fraser, Ai Ping Chua, Mary Foong Fong Chong and Michelle Miller

Background

During the initial phase of critical illness, the association between the dose of nutrition support and mortality risk may vary among patients in the intensive care unit (ICU) because the prevalence of malnutrition varies widely (28 to 78%), and not all ICU patients are severely ill. Therefore, we hypothesized that a prognostic model that integrates nutritional status and disease severity could accurately predict mortality risk and classify critically ill patients into low- and high-risk groups. Additionally, in critically ill patients placed on exclusive nutritional support (ENS), we hypothesized that their risk categories could modify the association between dose of nutrition support and mortality risk.

Methods

A prognostic model that predicts 28-day mortality was built from a prospective cohort study of 440 patients. The association between dose of nutrition support and mortality risk was evaluated in a subgroup of 252 mechanically ventilated patients via logistic regressions, stratified by low- and high-risk groups, and days of exclusive nutritional support (ENS) [short-term (≤ 6 days) vs. longer-term (≥ 7 days)]. Only the first 6 days of ENS was evaluated for a fair comparison.

Results

The prognostic model demonstrated good discrimination [AUC 0.78 (95% CI 0.73–0.82), and a bias-corrected calibration curve suggested fair accuracy. In high-risk patients with short-term ENS (≤ 6 days), each 10% increase in goal energy and protein intake was associated with an increased adjusted odds (95% CI) of 28-day mortality [1.60 (1.19–2.15) and 1.47 (1.12–1.86), respectively]. In contrast, each 10% increase in goal protein intake during the first 6 days of ENS in high-risk patients with longer-term ENS (≥ 7 days) was associated with a lower adjusted odds of 28-day mortality [0.75 (0.57–0.99)]. Despite the opposing associations, the mean predicted mortality risks and prevalence of malnutrition between short- and longer-term ENS patients were similar.

Conclusions

Combining baseline nutritional status and disease severity in a prognostic model could accurately predict 28-day mortality. However, the association between the dose of nutrition support during the first 6 days of ENS and 28-day mortality was independent of baseline disease severity and nutritional status.

Nutritional Status and Mortality in the Critically Ill

Nutritional Status and Mortality in the Critically Ill
Mogensen, K et al
December 2015 - Volume 43 - Issue 12


Objectives: The association between nutritional status and mortality in critically ill patients is unclear based on the current literature. To clarify this relation, we analyzed the association between nutrition and mortality in a large population of critically ill patients and hypothesized that mortality would be impacted by nutritional status. Design: Retrospective observational study.
Setting: Single academic medical center. Patients: Six thousand five hundred eighteen adults treated in medical and surgical ICUs between 2004 and 2011. Interventions: None. Measurements and Main Results: All cohort patients received a formal, in-person, standardized evaluation by a registered dietitian. The exposure of interest, malnutrition, was categorized as nonspecific malnutrition, protein-energy malnutrition, or well nourished and determined by data related to anthropometric measurements, biochemical indicators, clinical signs of malnutrition, malnutrition risk factors, and metabolic stress. The primary outcome was all-cause 30-day mortality determined by the Social Security Death Master File. Associations between nutrition groups and mortality were estimated by bivariable and multivariable logistic regression models. Adjusted odds ratios were estimated with inclusion of covariate terms thought to plausibly interact with both nutrition status and mortality. We used propensity score matching on baseline characteristics to reduce residual confounding of the nutrition status category assignment. In the cohort, nonspecific malnutrition was present in 56%, protein-energy malnutrition was present in 12%, and 32% were well nourished. The 30-day and 90-day mortality rates for the cohort were 19.1% and 26.6%, respectively. Nutritional status is a significant predictor of 30-day mortality following adjustment for age, gender, race, medical versus surgical patient type, Deyo-Charlson index, acute organ failure, vasopressor use, and sepsis: nonspecific malnutrition 30-day mortality odds ratio, 1.17 (95% CI, 1.01–1.37); protein-energy malnutrition 30-day mortality odds ratio, 2.10 (95% CI, 1.70–2.59), all relative to patients without malnutrition. In the matched cohort, the adjusted odds of 30-day mortality in the group of propensity score-matched patients with protein-energy malnutrition was two-fold greater than that of patients without malnutrition. Conclusion: In a large population of critically ill adults, an association exists between nutrition status and mortality.