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Abstract:  

Total parenteral nutrition (TPN) has had a changing role in nutrition support during recent years. Whereas TPN used to be the primary method for feeding hospitalized patients, it is now realized that enteral nutrition is not only a more natural way to feed, but is subject less to complications and has reduced costs associated with it. While nutrition support is viewed as absolutely essential, there exists some controversy over the use of TPN and enteral feeds.

The most significant reason for using enteral nutrition is to minimize complications. However, critical review of the data suggests that enteral nutrition rarely meets feeding objectives (due to less being given, absorbed or tolerated), and TPN is actually not deserving of its somewhat tarnished reputation.

Jeejeebhoy et al. set out to determine if problems associated with TPN (translocation of intestinal bacteria, sepsis, mucosal atrophy) were, in fact, due to overfeeding or other caregiver-induced complications—not the sole result of using TPN. The authors feel that the risks of TPN have been exaggerated, and that while there is a risk for some complications with TPN, it does provide a safe and effective alternative where enteral feeds are not suited, as in gut failure of intolerance of enteral feeding.

Key words:

 Total Parenteral Nutrition (TPN), bacterial translocation, mucosal atrophy, gut failure, sepsis

The role of malnutrition as a risk factor for increased morbidity was first recognized about 40 years ago in hospitalized patients.  Malnutrition has historically been treated with TPN.  With the thought that a little nutrition is was good came the practice a lot of nutrition must be better, hence the term “hyperalimentation”, and its associated overfeeding-related complications.  This review looks at several studies that compared enteral versus parenteral in a variety of disease settings.  In gut failure, critical illness and peri-operative care, the perceived efficacy of enteral nutritional support, combined with the assumed cost benefits have contributed to enteral nutrition’s popularity and TPN’s decreased use.  The author has noted, however, that TPN is still, and should remain, a preferred feeding route due to several misconceptions that exist about its use. 

Results:

Jeejeebhoy examined several studies from past years where TPN either achieved superior results over EN, or where TPN failed and was blamed for the resultant poor outcomes. Both good and bad are detailed below, categorized by disease state. From the studies where TPN failed, Jeejeebhoy identifies several problems with the initial study format, methods, and/or interpretation of results that would have altered the outcome of the study away from the favor of TPN. A brief synopsis of each follows:

  Pancreatitis
With regard to pancreatitis there are several studies that demonstrate the safety and efficacy of TPN. In 1997 McLave et al. randomized 32 patients to receive either TPN of enteral nutrition (EN). No differences were seen between groups with regard to infection or morbidity. In 1998 Windsor et al. confirmed these findings in a study of their own design using 34 patients in which there was no difference seen between TPN or EN with regard to sepsis, length of stay in the hospital (LoS), organ failure or computed tomography score. In 1997 Kalfarentzos evaluated 38 patients on TPN or EN and found that while the TPN group did have a higher incidence of sepsis, they were not hospitalized any longer than the EN group, nor did the need for antibiotics or ventilator support increase.

  Inflammatory Bowel Disease
In Crohn’s disease a randomized, controlled trial compared TPN with EN or TPN given with an oral diet did not show any increased complications due to TPN, and remission rates stayed the same. This Greenberg et al study dates to 1998. In a separate study, Gonzalez-Huix, et al., 1993, patients with acute colitis receiving TPN were shown to have a higher rate of sepsis, however, the rate of colectomy and remission of their disease rates were seen to be the same between the two groups.

  Trauma
In 1989 a study was conducted that randomized 59 patients to either TPN of EN (Moore et al.). The TPN group did show more signs of sepsis, however the TPN group also received significantly more energy, higher levels of insulin and higher levels of plasma glucose. The common feeling is that these patients were classically overfed. However, these patients did not require more antibiotics or more hospitalization.

  Sepsis
In 1988, Cerra et al. randomized 66 patients who were septic and hypermetabolic to EN and TPN and found that there was no difference in the incidence of multi-system organ failure or death between the two groups.

  Procedure-related complications
Catheter-related complications are believed to be more frequent in patients receiving TPN due to cather-related issues. However, in 1988, Lipman found that seven of nine clinical trials randomized trials looking at TPN vs. EN found that the actual incidence of procedure-related complications were higher in the EN groups.

The author found that TPN is the form of nutritional support most suited to patients with gut failure in whom it is life-saving and beneficial when there is malnutrition (1).  It was also found that overfeeding is a common occurrence and can increase the risk of sepsis.  What the author did not find is also noted and interesting.  Namely, that intestinal atrophy and increased bacterial translocation occur with the use of TPN.  TPN is associated with less procedure-related complications than enteral nutrition.  In short, where indicated due to the patient’s inability of receive enteral nutrition, TPN is beneficial in the treatment of malnutrition.

References:

1. Jeejeebhoy K. Enteral and parenteral nutrition:  evidence-based approach.  Proceedings of the Nutritional Society, 60,399-402, 2001.