Late initiation of parenteral nutrition (day 8) has been associated with better outcomes in critically ill ICU patients.
Critical illness leads to anorexia and the loss of ability to eat normally, predisposing patients to serious nutritional deficits, muscle wasting, weakness, and delayed recovery. Enteral and parenteral feeding are two modes of feeding a critically ill patient who is unable to consume food orally.
AdvertisementEnteral means within or by the gastrointestinal tract. Enteral nutrition is a method which enables one to manage critically ill patients and others who cannot be fed adequately via the normal route. A fluid is given through a tube inserted into the nose, reaching the stomach. The fluid contains essential nutrients that help supplement or replace a normal diet.
Parenteral nutrition is supplied through intravenous route through a large vein in or around the shoulder, neck, or arm. Unlike enteral feeding, the method bypasses the digestive tract and releases nutrients directly into the bloodstream. Parenteral nutrition is generally administered in case of a non-functional gastrointestinal tract or excessive nutritional needs, which cannot be met only with enteral feeding.
Enteral nutrition is associated with fewer complications than parenteral nutrition and is less expensive to administer. However, the use of enteral nutrition alone often does not achieve caloric targets. In addition, it is associated with underfeeding, leading to weakness, infection, an increased duration of mechanical ventilation, and sometimes even death.
Combining parenteral nutrition with enteral nutrition constitutes a strategy to prevent nutritional deficit. But at the same time there may be a risk of overfeeding, which has been associated with liver dysfunction, infection, and prolonged ventilatory support. The increased levels of blood glucose that are associated with parenteral nutrition could contribute to such complications.
Current clinical practice guidelines for nutritional support in critically ill patients are largely based on expert opinion and differ substantially across continents.
• The guidelines of the European Society of Parenteral and Enteral Nutrition (ESPEN) recommend that practitioners consider initiating parenteral nutrition within 2 days after admission to the intensive care unit (ICU) for patients who cannot be adequately fed enterally.
• In contrast, the American and Canadian guidelines recommend early initiation of enteral nutrition but suggest that parenteral nutrition not be initiated immediately. They advice that the parenteral nutrition should be considered after around 7 days.
To study the above effects, Casaer et al. in their recent research compared the effect of late initiation of parenteral nutrition (American and Canadian guidelines) versus early initiation (ESPEN guidelines) on rates of death and complications in adults in the ICU who were nutritionally at risk but not chronically malnourished.
In the study, it was investigated whether preventing a caloric deficit during critical illness by providing parenteral nutrition to supplement enteral nutrition early in the disease course would reduce the rate of complications, or whether withholding parenteral nutrition for 1 week would be clinically superior.
From 1 August 2007 through 8 November 2010, all adults who were admitted to one of the seven participating ICUs were eligible for inclusion in the study if they had a score of 3 or more on nutritional risk screening (NRS) (on a scale of 1 to 7, with a score ≥3 indicating that the patient was nutritionally at risk).
The protocol for administration of enteral and parenteral nutrition was as follows:
Early parenteral nutrition initiation group:
Day 1: 400 kcal per day on ICU day 1 (intravenous 20% glucose solution)
Day 2: 800 kcal per day on ICU day 2 (intravenous 20% glucose solution)
Day 3: On day 3, parenteral nutrition was initiated, with the dose targeted to 100% of the caloric goal through combined enteral and parenteral nutrition.
(The amount of parenteral nutrition was calculated daily as the difference between the total energy intake that was effectively delivered by enteral nutrition and the calculated caloric goal.)
When enteral nutrition covered 80% of the calculated caloric goal or when the patient was judged to be able to resume oral nutrition, parenteral nutrition was reduced and eventually stopped. Parenteral nutrition was restarted whenever enteral or oral intake fell to less than 50% of the calculated caloric needs.
Late parenteral nutrition initiation group:
Patients who were assigned to the late-initiation group received 5% glucose solution in a volume equal to that of the parenteral nutrition administered in the early-initiation group in order to provide adequate hydration, with the delivered volume of enteral nutrition taken into account. If enteral nutrition was insufficient after 7 days in the ICU, parenteral nutrition was initiated on day 8 to reach the caloric goal.
The analysis of the study found that there was no significant difference in mortality rates between late initiation and early initiation of parenteral nutrition among patients in the ICU who were at risk for malnutrition.
However, withholding of parenteral nutrition until day 8 was associated with fewer ICU infections. Late initiation of parenteral nutrition was also associated with a shorter duration of mechanical ventilation and a shorter course of renal-replacement therapy, a shorter ICU stay, a shorter hospital stay without a decrease in functional status, and reduced health care costs.
Withholding of macronutrients in the early stages of a critical illness, regardless of the route of nutrition, may enhance recovery. It is speculated that the increased rates of infection and delayed recovery from organ failure are associated with the early administration of parenteral nutrition. This may be explained by an inadequate clearance of cell damage and microorganisms.
The study results clearly indicate that an early initiation of parenteral nutrition to supplement insufficient enteral nutrition during the first week after ICU admission in severely ill patients at risk for malnutrition appears to be inferior to the strategy of withholding parenteral nutrition until day 8, while providing vitamins, trace elements, and minerals. Late parenteral nutrition was associated with fewer infections, enhanced recovery, and lower health care costs.
Casaer M et al.; Early versus Late Parenteral Nutrition in Critically Ill Adults; 29 June 2011 (10.1056/NEJMoa1102662)