Enteral and Parenteral Nutrition

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Which critically ill patients should receive TPN?
Prof R D Griffiths in conjunction with Fresenius-Kabi

Why are these guidelines required?

In the critical care setting, nutritional support influences the outcome for critically ill patients. This guideline seeks to outline the important role of parenteral nutrition in the critically ill patient.

Enteral and parenteral nutrition
The enteral route for nutrition delivery is preferred where it can be safely delivered in the absence of gastrointestinal intolerance. For a small proportion of patients enteral feeding is not possible but in addition for a larger proportion of patients research consistently shows that enteral nutrition does not always cover the total nutritional needs of intensive care unit patients. There has been a reluctance to use parenteral nutrition (PN) or to supplement enteral (EN) or oral nutrition with parenteral nutrition (PN) for the perceived risk that to do so increases the infection and mortality risk. Systematic review evidence acquired from studies in the critically ill shows that while there may be an increased risk of infection there is no added mortality risk [ 1 ]. Parenteral nutrition has changed considerably over the last forty years and many of the complications were a feature of historical PN practice associated with its inappropriate use, unbalanced formulations and liberal overfeeding. Even the risk of infection may be more related to the underlying patient disease and indication for PN rather than modern PN formulations and delivery in ICU.

It has been estimated that around 40% of all patients in hospital are undernourished and this is associated with further complications. Acute critically ill patients lose on average approximately 5-10% of skeletal muscle mass per week during their ICU stay [ 3 ]. Complications such as septicaemia in these patients are to a large extent caused by malnutrition and impaired immunological function [ 2 ].

Complications versus choice of nutrition route
When correctly applied, the complications of PN are less likely to result in death compared with those of EN. Recent studies conclude that PN compared with early EN is risk-neutral overall [ 3 ]. It is reassuring that in critically ill patients, when used with EN in the ICU as a supplement, PN has been confirmed to be risk-neutral or may even offer benefits. However from current data it is not possible to justify the extra cost of supplemental PN when started concurrently with EN at the start of an ICU admission [ 1 ] but more importantly there are no studies where it has been started in the more appropriate situation after EN has been shown to fail in already malnourished ICU patients. It has been demonstrated that nutritional goals were reached in 22% of ICU patients fed via EN compared with 75% with PN [ 2 ]. It must be remembered that under nutrition is a debt that must eventually be repaid and this is also worse if it is compounded! The ACCEPT study showed that survival from intensive care was improved when an evidence based guideline for nutrition was followed and more nutrition delivered more consistently. This was achieved by earlier introduction and more complete enteral nutrition delivery without any decline in the use of PN alone or in supplementation.

Using the guidelines

These guidelines have been developed using a step-by-step approach as follows:

Step 1ASSESSMENTDoes the patient require nutritional support?

Step 2ADMINISTRATIONWhich route(s) should be used?

Step 3ACHIEVEMENT (REVIEW)Are nutrition goals being met? Step 1 Nutritional Risk Screening (adapted from NRS 2002 ESPEN)

Does this patient require nutritional support?

Initial screening of patients is recommended in these guidelines but it is assumed that ALL patients fulfill the criteria for requiring a final screening assessment which follows. The adaptation assumes an affirmative answer to the question “Is the...
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