enteral versus parenteral nutrition

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Enteral versus parenteral nutrition J. MacFie Scarborough Hospital, Woodlands Drive, Scarborough YO12 6QL, UK Arti®cial feeding is indicated for patients with pre-existing malnutrition or for those whose oral intake is anticipated to be inadequate for 7 days or more 1 . Not surprisingly, most authorities recommend the the enteral as opposed to the parenteral route. Enteral is considered cheaper and safer, and more physiological in that it preserves gut barrier function. Parenteral, in contrast, may result in mucosal atrophy, bacterial translocation and increased rates of septic morbidity. There is experimental evidence to support these views but what of clinical research? Enteral nutrition is certainly cheaper than parenteral. The average daily cost of a standardized parenteral feed is approximately eight times more than that of an equivalent enteral feed, assuming similar protein and energy intakes. This cost, however, does not take into account delivery systems or associated complications. The increasing propensity of clinicians to employ invasive methods of delivery for enteral nutrition may well offset perceived cost bene®ts. Few studies have speci®cally addressed the additional costs related to nutrition-related morbidity. There is no doubt that enteral nutrition can be provided safely and effectively for prolonged periods. However, it is increasingly recognized that it often fails to achieve targeted calorie requirements, particularly in critically ill patients 2 . This is often a consequence of poor tolerance, manifested by bloating, diarrhoea or continued high-volume nasogas- tric aspirates. None the less, there may be bene®ts attributable to enteral nutrition even when administered at suboptimal rates. These include effects on upper gastrointestinal micro¯ora, splanchnic blood ¯ow and modulation of immune responses, and such factors have led some to advocate early enteral nutrition, especially for patients with trauma or burns. However, the evidence to date in support of this practice is equivocal 3 . Furthermore, these putative bene®ts of enteral nutrition may be offset by complications relating to delivery systems. The increasing popularity of invasive methods of enteral feeding, such as via percutaneous gastrostomies and jejunostomies, has been accompanied by a rise in serious complications 4 . It is frequently stated that total parenteral nutrition TPN) leads to mucosal atrophy and the assumption is made that this predisposes to bacterial translocation which may account for increased septic morbidity. While true in rodents, the evidence is less clear in humans. Bacterial translocation does occur in surgical patients and is associated with an increase in septic morbidity 5 , but TPN has not been shown to be associated with any increase in bacterial translocation 6 . Furthermore, there is no evidence that short-term TPN in humans results in mucosal atrophy 7 . More importantly, both experimental and clinical studies suggest that neither mucosal atrophy nor change in intestinal permeability, the other frequently employed surrogate measure of barrier function, predispose to bacterial translocation 8,9 . These ®ndings suggest that egress between epithelial cells is not the only mechanism responsible for translocation. Whatever the results of investigative studies, the most important endpoint in the enteral versus parenteral debate must be clinical outcome. It is often assumed that parenteral nutrition is associated with a higher incidence of septic complications and a number of studies have reported a higher incidence of sepsis in association with TPN. However, most of these involved patients with abdominal trauma, whose average age and overall prognosis are very different to those of the typical patient who requires parenteral support 2,3,6 . The results of studies comparing enteral with par- enteral nutrition need to be interpreted with caution. First, they need to be considered in the context of overall morbidity. Even if septic morbidity is higher in patients with abdominal trauma receiving TPN, the question arises as to whether or not this might be offset by complications related to delivery systems or a signi®cant incidence of inadequate nutritional support with enteral feeding. Second, it is inappropriate to draw conclusions from studies in which patients who could tolerate an oral intake were randomized to receive TPN; such patients probably do not require TPN in the ®rst place. Third, in many published studies the TPN groups have received different nutritional intakes to enteral groups. This has led many reviewers to suggest that the association of TPN with an increased incidence of sepsis is, in reality, not due to the route of nutritional support but to the increased energy intake received and the associated hyperglycaemia, which is commoner in those receiving TPN 10 . In other words, these studies may simply re¯ect the detrimental effects of overfeeding. Furthermore, the potentially confounding effects of different protein and Leading article ã 2000 Blackwell Science Ltd British Journal of Surgery 2000, 87, 1121±1122 1121

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Page 1: Enteral versus parenteral nutrition

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Page 2: Enteral versus parenteral nutrition

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