Prevalence and Risk Factors of Enteral Nutrition Intolerance in Intensive Care Unit Patients: A Retrospective Study
Introduction
Critically ill patients admitted to the intensive care unit (ICU) face a heightened risk of malnutrition, particularly during prolonged stays. Early enteral nutrition (EN) is widely advocated to maintain gut integrity, reduce complications, and improve clinical outcomes. However, feeding intolerance (FI), characterized by gastrointestinal (GI) dysfunction, often disrupts EN delivery. FI manifests through symptoms such as vomiting, high gastric residual volume (GRV), or abdominal distension, leading to inadequate caloric intake and adverse outcomes, including prolonged mechanical ventilation (MV) and increased mortality. Despite its clinical significance, FI lacks a standardized definition, complicating its identification and management. This study aimed to investigate the prevalence of FI among ICU patients receiving early continuous EN and identify associated risk factors to guide clinical practice.
Methods
Study Design and Population
This retrospective cohort study analyzed data from 1,057 ICU patients who received early continuous EN via nasogastric tubes between January 2014 and August 2019. Patients with jejunal feeding tubes, those who did not receive EN within the first two ICU days, or those with incomplete medical records were excluded. Data on demographics, clinical scores (APACHE II, SOFA), diagnoses, treatments, and EN parameters were collected.
Feeding Protocol
EN was initiated within 48 hours of ICU admission, administered continuously via a nasogastric tube at a target energy intake of 25 kcal/kg/day. GRV was measured every 4 hours using a 20-mL syringe; EN was paused if GRV exceeded 200 mL. Prokinetics or jejunal feeding was considered for persistent intolerance.
Definitions and Outcomes
FI was defined as GRV ≥200 mL and/or vomiting. Sensitivity analyses used a stricter threshold (GRV ≥500 mL and/or vomiting) to assess risk factors. Primary outcomes included FI prevalence during the first seven ICU days and associated risk factors identified through multivariate logistic regression.
Statistical Analysis
Continuous variables were reported as means (standard deviation) or medians (range), and categorical variables as frequencies. Univariate and multivariate analyses identified FI predictors. Variables with P <0.05 in univariate analysis or clinical relevance were included in the multivariate model. Analyses were conducted using SPSS 25.0.
Results
Patient Characteristics
The cohort comprised 587 males (55.5%) and 470 females (44.5%), with a mean age of 56.1 years. Median ICU stay was 10 days, and 138 patients (13.1%) died during hospitalization. Common diagnoses included pulmonary infection (30%), sepsis/septic shock (18.1%), and kidney failure (16.8%).
Prevalence of Feeding Intolerance
FI occurred in 10.95% of patients during the first seven ICU days. Daily FI rates peaked on day 2 (15.04%, 159/1,057), with 148 patients showing GRV ≥200 mL and 11 experiencing vomiting. By day 3, FI prevalence dropped to 11.67% (114/977), and on day 7, it was 12.03% (86/715).
Risk Factors for Feeding Intolerance
Multivariate Analysis Using GRV ≥200 mL
Mechanical ventilation (MV) and continuous renal replacement therapy (CRRT) emerged as independent risk factors. MV increased FI risk nearly twofold (OR: 1.928, 95% CI: 1.064–3.493, P = 0.03), while CRRT doubled the odds (OR: 2.064, 95% CI: 1.233–3.456, P = 0.006).
Sensitivity Analysis Using GRV ≥500 mL
CRRT and acute renal failure (ARF) were significant predictors. CRRT increased FI risk sixfold (OR: 6.199, 95% CI: 2.108–18.228, P = 0.001), and ARF tripled the risk (OR: 3.445, 95% CI: 1.115–10.707, P = 0.032).
Discussion
High Prevalence of FI in Early ICU Stay
The study highlights that FI occurs most frequently during the initial days of ICU admission, aligning with prior observations. The peak incidence on day 2 may reflect acute physiological stress or delayed EN initiation. Notably, vomiting was rare (<2%), suggesting GRV monitoring drives FI diagnosis in clinical practice.
Mechanical Ventilation as a Key Risk Factor
MV independently predicted FI, likely due to altered GI motility from sedation, supine positioning, or hemodynamic instability. Positive-pressure ventilation may reduce splanchnic blood flow, exacerbating GI dysfunction.
Impact of CRRT and Renal Failure
CRRT emerged as a robust predictor of FI, likely due to fluid shifts, metabolic disturbances, or inflammatory responses in critically ill patients. ARF’s association with FI under stricter GRV thresholds underscores the interplay between renal dysfunction and GI motility.
Clinical Implications
The findings underscore the need for vigilant monitoring in high-risk patients, particularly those on MV or CRRT. Prokinetic agents or post-pyloric feeding may mitigate FI in these populations. However, routine GRV measurement remains contentious due to variability in techniques and thresholds.
Limitations and Future Directions
This single-center retrospective study has limitations, including potential selection bias and inconsistent GRV measurement practices. The lack of standardized FI definitions complicates comparisons across studies. Future prospective trials should validate these risk factors and explore mechanistic links between CRRT, MV, and GI dysfunction.
Conclusion
FI affects over 10% of ICU patients during early EN, with MV and CRRT identified as independent risk factors. These findings emphasize tailored monitoring and intervention strategies for vulnerable populations. Standardizing FI definitions and advancing research into its pathophysiology remain critical to optimizing EN delivery and outcomes in critical care.
doi.org/10.1097/CM9.0000000000001974
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