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.
Enteral means within or by the
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.
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.
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.
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
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
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%
Day 3: On day 3, parenteral nutrition was initiated, with
the dose targeted to 100% of the caloric goal through combined enteral and
(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
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.
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.
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
M et al.; Early versus Late Parenteral Nutrition in Critically Ill Adults; 29
June 2011 (10.1056/NEJMoa1102662)