Enteral Nutrition in Critically Ill Patients

Enteral nutrition delivers essential nutrients to treat or prevent disease-related malnutrition in critically ill patients. This malnutrition, influenced by poor intake and inflammation, can impact the effectiveness of nutrition therapy. Evidence from recent randomised trials in both critically ill and non-critically ill patients has shaped current practices. 

A recent review examines the role of enteral nutrition in managing disease-related malnutrition, presents supporting evidence, and addresses key clinical considerations.

Disease-related malnutrition in hospitalised patients involves poor nutrient intake, impaired nutrient use, and inflammation, leading to reduced body function and composition. It is linked to serious health and economic consequences, including higher mortality, longer hospital stays, and increased costs. Globally, 30–45% of hospitalised adults are malnourished at admission, yet enteral nutrition is underutilised—used in only about 5% of such patients in the U.S. and Europe. This underscores the importance of early identification and appropriate nutritional intervention, including enteral nutrition, particularly in ICU patients and a small proportion of non–critically ill patients.

Medical nutrition therapy (MNT) includes patient counselling and oral nutritional supplements, as well as enteral and parenteral nutrition, while nutrition support refers only to the latter two. The EFFORT trial demonstrated that individualised MNT in malnourished hospitalised patients improved caloric and protein intake and significantly reduced adverse outcomes and mortality compared to standard care. Most patients in the trial met nutritional needs orally, with enteral or parenteral nutrition used only when oral intake remained insufficient after five days.

Recent studies further support the benefits of MNT in hospitalised patients. A 2019 meta-analysis involving 6,803 patients found that MNT significantly reduced mortality up to six months post-discharge, lowered hospital readmissions, improved nutrient intake, and increased body weight, though it did not impact functional outcomes or length of stay. Another large analysis of claims data showed a 21% reduction in in-hospital mortality among 69,000 malnourished patients who received MNT. An updated meta-analysis of 16 randomised trials confirmed that MNT—mainly oral and enteral nutrition—significantly reduced mortality and unplanned readmissions compared to no nutritional therapy.

Nutrition care in hospitalised patients can follow structured, evidence-based pathways. Screening for malnutrition should occur at admission using validated tools like the Malnutrition Screening Tool, MUST, or NRS-2002. Patients at risk should receive a comprehensive assessment using diagnostic criteria such as the GLIM or AAIM criteria. If medical nutrition therapy is needed, efforts should first focus on enhancing oral intake through dietary modifications and supplements. When oral intake is insufficient—providing less than 75% of energy and protein needs—enteral nutrition is recommended unless contraindicated. The timing of initiation depends on nutritional status, clinical condition, and ability to eat. If enteral nutrition is not feasible or tolerated, parenteral nutrition may be considered.

Enteral nutrition is appropriate for patients with conditions that impair oral intake, such as critical illness, neurologic or gastrointestinal disease, cancer, and chronic organ conditions. It is contraindicated in cases like intestinal obstruction, severe shock, or intestinal ischaemia. Most patients needing enteral nutrition have multiple comorbidities and require coordinated, interdisciplinary, patient-centred care. It is widely used in ICUs, where high staffing and multidisciplinary focus may enhance its effectiveness. However, enteral nutrition is less commonly used and studied in non–critical care settings, where evidence remains limited.

Guidelines for enteral nutrition are evolving, supported by high-quality trials over the past 15 years, especially in ICU settings. These studies have clarified aspects such as timing, route, and dosing of nutrition support in critically ill patients. However, earlier guidelines—particularly for non–critically ill medical and surgical patients—were limited by weak evidence, potential commercial bias, and inconsistent methodologies. Ongoing discrepancies between European and U.S. critical care guidelines highlight ongoing uncertainty, especially regarding optimal energy and protein targets during the acute phase of illness.

In the ICU, critically ill patients are often underfed, typically receiving only 50–60% of recommended energy and protein needs during the first week. Multiple randomised trials (e.g., CALORIES, NUTRIREA-2, and NUTRIREA-3) have shown no mortality benefit from early full-dose enteral nutrition compared to parenteral nutrition, and higher doses were linked to increased gastrointestinal complications and harm, especially in patients with organ failure. Similarly, trials assessing higher protein doses (e.g., EFFORT Protein) found no survival benefit and potential harm in certain subgroups, although meta-analyses suggest moderate protein intakes (>1.2 g/kg/day) may be safe. These findings support cautious nutrition strategies during the acute phase, as full-dose feeding may overwhelm the body's impaired metabolic capacity. Despite technological advances like indirect calorimetry, optimal timing and dosing remain uncertain, particularly during the recovery phase (days 9–16), for which no clear guidelines exist.

In non–critically ill medical and surgical patients, evidence supports the benefits of timely and adequate enteral nutrition. Undernutrition—intake below 70% of energy needs—is linked to higher infection risk. In medical patients with multiple conditions, enteral nutrition reduced complications significantly. The OPENS trial in stroke patients showed that hypocaloric feeding led to higher mortality compared to modified full feeding. In surgical patients, early enteral nutrition improves outcomes, including reduced infections and better energy delivery. Early supplemental parenteral nutrition (within 3 days post-op) also led to fewer nosocomial infections than late supplementation. Overall, prompt and sufficient nutrition in these populations improves clinical outcomes and reduces complications.

Source: NEJM

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