Background
Enteral nutrition involves giving liquid nutrition by a tube directly into the stomach or small intestine. Current clinical practice guidelines recommend nutrition support within 48 hours of injury or admission to an intensive care unit (ICU). It is seen as an essential part of the management of critically ill patients and may help to support the function of the gut. If full enteral nutrition is not possible, nutrients can also be given through a catheter into a vein, called supplemental parenteral nutrition (SPN). Evidence from randomized controlled trials (RCTs) is needed to support these guideline recommendations.
Review question
Do adults admitted in an ICU, who receive early enteral nutrition within 48 hours, have better clinical outcomes than those for whom enteral nutrition is delayed (after 48 hours of initial injury or ICU admission), and does additional SPN have added benefits?
Study characteristics
We searched the literature until April 2019 for RCTs that compared early enteral nutrition with delayed enteral nutrition, with or without SPN, in adults in an ICU. RCTs, if designed and conducted properly, represent the highest methodological standard in clinical research. We included seven RCTs with 345 participants. Participants were admitted to the ICU for more than 72 hours with medical, surgical, or trauma diagnoses. Six trials with 318 participants compared early enteral nutrition with delayed enteral nutrition. One trial with 27 participants compared early enteral nutrition with SPN versus delayed enteral nutrition with SPN.
Key results
Overall, results showed no clear differences in the number of deaths within 30 days (one study, 38 participants), intolerance to feeding (one study, 59 participants), or development of pneumonia (four studies, 192 participants), between those who received early enteral nutrition or delayed enteral nutrition. We assessed the evidence as very low-quality, meaning the findings could potentially change with additional studies.
In the one small trial that also gave SPN, the number of deaths, people with infectious complications, and the duration of mechanical ventilation were not clearly different between those who received early enteral nutrition or delayed enteral nutrition (very low-quality evidence).
Future trials should continue to look into the impact of early enteral nutrition, with or without SPN, on important clinical outcomes in adults hospitalized in ICUs.
Quality of the evidence
We assessed the quality of the evidence as very low, meaning we were uncertain about the findings, as included studies were small, and provided an unclear description of the methods that they used. Participants in the studies had different causes for their critical illness. The outcomes were not always measured in the same way or at the same time in the different trials; some trials did not report on them.
Due to very low-quality evidence, we are uncertain whether early enteral nutrition, compared with delayed enteral nutrition, affects the risk of mortality within 30 days, feed intolerance or gastrointestinal complications, or pneumonia.
Due to very low-quality evidence, we are uncertain if early enteral nutrition with supplemental parenteral nutrition compared with delayed enteral nutrition with supplemental parenteral nutrition reduces mortality, infectious complications, or duration of mechanical ventilation.
There is currently insufficient evidence; there is a need for large, multicentred studies with rigorous methodology, which measure important clinical outcomes.
Early enteral nutrition support (within 48 hours of admission or injury) is frequently recommended for the management of patients in intensive care units (ICU). Early enteral nutrition is recommended in many clinical practice guidelines, although there appears to be a lack of evidence for its use and benefit.
To evaluate the efficacy and safety of early enteral nutrition (initiated within 48 hours of initial injury or ICU admission) versus delayed enteral nutrition (initiated later than 48 hours after initial injury or ICU admission), with or without supplemental parenteral nutrition, in critically ill adults.
We searched CENTRAL (2019, Issue 4), MEDLINE Ovid (1946 to April 2019), Embase Ovid SP (1974 to April 2019), CINAHL EBSCO (1982 to April 2019), and ISI Web of Science (1945 to April 2019). We also searched Turning Research Into Practice (TRIP), trial registers (ClinicalTrials.gov, ISRCTN registry), and scientific conference reports, including the American Society for Parenteral and Enteral Nutrition and the European Society for Clinical Nutrition and Metabolism. We applied no restrictions by language or publication status.
We included all randomized controlled trials (RCTs) that compared early versus delayed enteral nutrition, with or without supplemental parenteral nutrition, in adults who were in the ICU for longer than 72 hours. This included individuals admitted for medical, surgical, and trauma diagnoses, and who required any type of enteral nutrition.
Two review authors extracted study data and assessed the risk of bias in the included studies. We expressed results as risk ratios (RR) for dichotomous data, and as mean differences (MD) for continuous data, both with 95% confidence intervals (CI). We assessed the certainty of the evidence using GRADE.
We included seven RCTs with a total of 345 participants. Outcome data were limited, and we judged many trials to have an unclear risk of bias in several domains.
Early versus delayed enteral nutrition
Six trials (318 participants) assessed early versus delayed enteral nutrition in general, medical, and trauma ICUs in the USA, Australia, Greece, India, and Russia.
Primary outcomes
Five studies (259 participants) measured mortality. It is uncertain whether early enteral nutrition affects the risk of mortality within 30 days (RR 1.00, 95% CI 0.16 to 6.38; 1 study, 38 participants; very low-quality evidence). Four studies (221 participants) reported mortality without describing the timeframe; we did not pool these results. None of the studies reported a clear difference in mortality between groups.
Three studies (156 participants) reported infectious complications. We were unable to pool the results due to unreported data and substantial clinical heterogeneity. The results were inconsistent across studies.
One trial measured feed intolerance or gastrointestinal complications; it is uncertain whether early enteral nutrition affects this outcome (RR 0.84, 95% CI 0.35 to 2.01; 59 participants; very low-quality evidence).
Secondary outcomes
One trial assessed hospital length of stay and reported a longer stay in the early enteral group (median 15 days (interquartile range (IQR) 9.5 to 20) versus 12 days (IQR 7.5 to15); P = 0.05; 59 participants; very low-quality evidence).
Three studies (125 participants) reported the duration of mechanical ventilation. We did not pool the results due to clinical and statistical heterogeneity. The results were inconsistent across studies.
It is uncertain whether early enteral nutrition affects the risk of pneumonia (RR 0.77, 95% CI 0.55 to 1.06; 4 studies, 192 participants; very low-quality evidence).
Early enteral nutrition with supplemental parenteral nutrition versus delayed enteral nutrition with supplemental parenteral nutrition
We identified one trial in a burn ICU in the USA (27 participants).
Primary outcomes
It is uncertain whether early enteral nutrition with supplemental parenteral nutrition affects the risk of mortality (RR 0.74, 95% CI 0.25 to 2.18; very low-quality evidence), or infectious complications (MD 0.00, 95% CI -1.94 to 1.94; very low-quality evidence). There were no data available for feed intolerance or gastrointestinal complications.
Secondary outcomes
It is uncertain whether early enteral nutrition with supplemental parenteral nutrition reduces the duration of mechanical ventilation (MD 9.00, 95% CI -10.99 to 28.99; very low-quality evidence). There were no data available for hospital length of stay or pneumonia.