Enteral versus parenteral feeding. Effects on septic morbidity after blunt and penetrating abdominal trauma

A prospective randomized trial of total parenteral nutrition after major pancreatic resection for malignancy

OBJECTIVES

The authors examined the impact of adjuvant total parenteral nutrition after major pancreatic resection for malignancy.

SUMMARY BACKGROUND DATA

Previous studies have suggested a benefit to perioperative nutritional support for patients undergoing major gastrointestinal surgery.

METHODS

A prospective, randomized study was conducted using patients who had undergone a major pancreatic resection with randomization on postoperative day one to either receive or not receive adjuvant total parenteral nutrition.

RESULTS

No benefit could be demonstrated by the use of adjuvant parenteral nutrition in this setting. Complications were significantly greater in the group receiving total parenteral nutrition. These complications tended to be those associated with infection.

CONCLUSIONS

Routine applications of postoperative parenteral nutrition to patients undergoing major pancreatic resection for malignancy cannot be recommended. Further studies are required to determine the reason that infectious complications in these patients are increased.

Enteral access

The enteral route is the preferred method of nutrition support in patients with functional gastrointestinal tracts. Many techniques for obtaining enteral access are available, and the decision regarding which one to use depends on several issues, including anticipated duration of support, aspiration risk, and local expertise. Using laparotomy, laparoscopy, fluoroscopy, or endoscopy, tubes can be placed into the stomach, the duodenum, and the jejunum. Nasogastric and nasoenteric tubes are useful for short-term supplementation; however, patients needing support for more than 6 weeks may be better served with a more permanent tube. In this review, specific methods for obtaining enteral access are discussed along with their advantages and disadvantages.

Pentobarbital coma in neurosurgical patients: nutrition considerations

Neurosurgical patients in pentobarbital coma are a complex nutrition support population. Physiologic changes associated with the primary injury to the brain, combined with the pharmacodynamic influences of barbiturate therapy, contribute to the difficulties of initiating aggressive nutrition support. Early nutritional repletion is important to the overall outcome of traumatically injured patients. Consequently, factors that influence nutrition support decisions must be understood to assure appropriate intervention. The metabolic changes associated with traumatic head injury, pentobarbital therapy, and nutrition support strategies are reviewed.

Nutrition support in critical illness

Sepsis, shock, multiple trauma, and burns are often associated with altered metabolism characterized by severe catabolism, wasting of the lean body mass, immune dysfunction, and compromised wound healing. Nutrition support is one of the mainstays in the management of these critically ill patients and is aimed at minimizing these complications. The purpose of this article is to compare stress hypermetabolism and starvation metabolism, to review current recommendations for the provision of energy and substrate to the critically ill patient, and to review pertinent literature regarding enteral vs parenteral nutrition. Finally, this article will provide a brief overview of new and future therapies with emphasis on specific substrates and growth factors and the potential for their use in the critically ill patient.

Fiber-containing formula and needle catheter jejunostomies: a clinical evaluation

Despite the high frequency of diarrhea, chemically defined diets have traditionally been used with needle catheter jejunostomies, a common form of postpyloric enteral access, to avoid tube occlusion. We reviewed our experience with 57 patients fed a fiber-containing diet to determine the incidence of catheter occlusion and diarrhea. Eight catheters temporarily occluded but were reopened and remained patent for an additional 6.3 +/- 3.1 days for an overall success rate of 91% (52 of 57). The five remaining occluded catheters were removed after 6.2 +/- 1.8 days. Four of the five patients with occluded catheters tolerated gastric feedings, but one required a permanent jejunostomy. Diarrhea occurred in six (10.5%) of the 57 patients given the fiber-containing formula. We concluded that a fiber-containing formula can be administered through needle catheter jejunostomies if the catheter is irrigated daily and if no medications are given via the catheter. A fiber-containing formula may reduce the incidence of diarrhea in jejunostomy-fed patients compared with patients fed chemically defined diets.

Failure of topical vegetable oils to prevent essential fatty acid deficiency in a critically ill patient receiving long-term parenteral nutrition

This case report describes the failure of topical vegetable oils containing esters of linoleic acid to prevent essential fatty acid deficiency in a critically ill patient with trauma. A 40-year-old black man injured in a motor vehicle accident developed essential fatty acid deficiency after being maintained on long-term, fat-free parenteral nutrition plus topical vegetable oil application because of the presence of severe hypertriglyceridemia. Biochemical evidence of this deficiency included a decrease in serum linoleic, a-linolenic, and arachidonic acid levels with a corresponding increase in oleic and palmitoleic acid levels. Cutaneous manifestations consistent with this syndrome were also present. After 3 weeks of daily topical treatments with vegetable oils rich in linoleic acid, biochemical abnormalities of deficiency were still evident. Over the following 2 1/2 months, 4% to 22% of the total caloric intake was delivered as intravenous fat in addition to continued topical administration of vegetable oil. Only after supplementation with intravenous fat did the patient demonstrate clinical and biochemical signs of improvement. The results show that cutaneous administration of vegetable oils as the sole source of linoleic acid may be unable to prevent or treat essential fatty acid deficiency in a critically ill surgical patient.

Impairment of pulmonary macrophage function with total parenteral nutrition

OBJECTIVE

The effects of total parenteral nutrition (TPN) administration on pulmonary macrophage function and host response to gram-negative pulmonary infection were evaluated.

SUMMARY BACKGROUND DATA

Administration of TPN resulted in increased infectious complications in traumatized and perioperative patients, but underlying mechanisms are unclear.

METHODS

Twenty-six male Wistar rats underwent central vein cannulation and were randomized to isocaloric feeding of a regular chow diet (RD) plus saline infusion or TPN without chow diet for 7 days. Pulmonary alveolar macrophage (PAM phi) superoxide production, Candida albicans phagocytosis and killing, and tumor necrosis factor (TNF) production in response to endotoxin (LPS) were assessed. Mesenteric lymph nodes (MLN) were cultured. A second group of rats (n = 6/group) were inoculated intratracheally with a sublethal dose of 9 x 10(9) live Escherichia coli per animal, and the lungs were cultured quantitatively 72 hours later to assess bacterial clearance. Finally, 11 RD-fed rats and 13 TPN-fed rats received intratracheal inoculation of 1.4 x 10(10) live E. coli and were included in follow-up.

RESULTS

Administration of TPN was associated with a significant increase in bacteria positive MLN compared with those in the RD group (p < 0.01). Pulmonary alveolar macrophage superoxide production, Candida albicans phagocytosis and killing, TNF production, and pulmonary clearance of bacteria were decreased significantly in TPN-fed rats compared with those fed a regular chow diet (p < 0.05). These pulmonary macrophage function changes were associated with a significantly higher mortality in TPN-fed rats compared with RD-fed rats after higher dose pulmonary E. coli inoculation.

CONCLUSIONS

Defective host pulmonary antimicrobial immune responses during TPN are associated with intestinal bacterial translocation, and may explain increased infectious complications.

The modulatory role of gut hormones in elemental diet and intravenous total parenteral nutrition-induced bacterial translocation in rats

We have previously shown that parenteral and certain elemental diets promote bacterial translocation and that this diet-induced bacterial translocation can be prevented by the provision of bulk-forming dietary fiber. The goal of the current study was to test the hypothesis that fiber's protective effect on diet-induced bacterial translocation was mediated by trophic gut hormones. This hypothesis was tested by using bombesin (which stimulates gut hormone release) or the somatostatin analog Sandostatin (which inhibits gut hormone release) to modulate gut hormone release in rats receiving rat food, intravenous total parenteral nutrition, or an elemental diet. Both bombesin and fiber were effective in preventing elemental diet-induced bacterial translocation, whereas octreotide acetate abrogated the protective effect of fiber. Bombesin was also effective in limiting bacterial translocation in parenterally fed rats. Although both enteral (elemental diet) and parenteral diet-induced bacterial translocation were associated with cecal bacterial overgrowth, loss of small-bowel weight, and loss of mucosal protein content, none of these factors seemed to be primarily responsible for bacterial translocation. Because bombesin decreased the incidence of villous injury in the elemental diet-fed rats and decreased the incidence of villous injury and prevented loss of intestinal barrier function to horseradish peroxidase in the parenterally fed rats, it is possible that bombesin exerted its protective effect by limiting mucosal injury and preserving barrier function.

Bacterial translocation in mesenteric ischemia-reperfusion injury: is dysfunctional motility the link?

The authors previously reported that mesenteric ischemia and reperfusion (I/R) in a chronic newborn piglet model creates dysfunctional intestinal motility. Whether this leads to inadequate bacterial clearance and translocation (BT) through the gastrointestinal tract remains unclear. To test this hypothesis the authors used their chronic piglet model (weight, 3.5 +/- 0.3 kg; age, 18 +/- 4 days; on formula feeding); nonocclusive mesenteric ischemia was induced via reversible pericardial tamponade. Mesenteric flow (SMA Doppler measurement via the retroperitoneal approach) was decreased to 25% +/- 5% of baseline for 300 minutes in the ischemia group (n = 7) and followed by 14 hours of reperfusion in the I/R group (n = 6). Control subjects had a sham operation (n = 7). Mesenteric lymph nodes (MLN), liver (L), spleen (S), ileum, peritoneum, and blood were harvested for blind quantitative microbial analysis. Subjects in the control group had no cultures positive for growth. Eighty-five percent of animals in the ischemia group had positive MLN cultures only (P < .05 v control). All piglets in the I/R group had positive MLN cultures (P < .05 v control), and one third of them manifested bacteremia. Histological examination did not show mucosal disruption in any group. The validity of this model is confirmed by the negative cultures in the control group and by the presence of normal ileal flora in all animals. In the ischemia and I/R groups, MLN cultures were consistently positive with gram-negative bacilli (Escherichia coli and/or Klebsiella pneumoniae). When subjects of the I/R group had more than 1,000 colonies in the MLN, bacteremia with the translocating organisms was also identified.(ABSTRACT TRUNCATED AT 250 WORDS)

Strategies for attenuating protein-catabolic responses in the critically ill

Specialized enteral and parenteral nutrition are now a standard components of care in critically ill patients. This adjunctive therapy corrects and prevents nutrient deficiencies, attenuates the loss of body protein, and improves clinical outcomes in malnourished patients. Several novel strategies designed to improve the metabolic and clinical effects of specialized nutrition are under vigorous clinical investigation. These new approaches include increased emphasis on enteral feeding to maintain intestinal absorptive, immune, and barrier function; administration of conditionally essential amino acids (glutamine, arginine); use of specialized lipid products and antioxidants; and administration of growth factors such as human growth hormone. Randomized, controlled clinical trials will define the clinical and metabolic efficacy and cost-effectiveness of these therapies in specialized nutrition support.

Clinical significance of translocation

The gastrointestinal tract, besides being the organ responsible for nutrient absorption, is also a metabolic and immunological system, functioning as an effective barrier against endotoxin and bacteria in the intestinal lumen. The passage of viable bacteria from the gastrointestinal tract through the epithelial mucosa is called bacterial translocation. Equally important may be the passage of bacterial endotoxin through the mucosal barrier. This article reviews the evidence that translocation of both endotoxin and bacteria is of clinical significance. It summarises recent published works indicating that translocation of endotoxin in minute amounts is a physiological important phenomenon to boost the reticuloendothelial system (RES), especially the Kupffer cells, in the liver. Breakdown of both the mucosal barrier and the RES capacity results in systemic endotoxaemia. Systemic endotoxaemia results in organ dysfunction, impairs the mucosal barrier, the clotting system, the immune system, and depresses Kupffer cell function. If natural defence mechanisms such as lipopolysaccharide binding protein, high density lipoprotein, in combination with the RES, do not respond properly, dysfunction of the gut barrier results in bacterial translocation. Extensive work on bacterial translocation has been performed in animal models and occurs notably in haemorrhagic shock, thermal injury, protein malnutrition, endotoxaemia, trauma, and intestinal obstruction. It is difficult to extrapolate these results to humans and its clinical significance is not clear. The available data show that the resultant infection remains important in the development of sepsis, especially in the critically ill patient. Uncontrolled infection is, however, neither necessary nor sufficient to account for the development of multiple organ failure. A more plausible sequelae is that bacterial translocation is a later phenomenon of multiple organ failure, and not its initiator. It is hypothesized that multiple organ failure is more probably triggered by the combination of tissue damage and systemic endotoxaemia. Endotoxaemia, as seen in trauma patients especially during the first 24 hours, in combination with tissue elicits a systemic inflammation, called Schwartzmann reaction. Interferon gamma, a T cell produced cytokine, is thought to play a pivotal part in the pathogenesis of this reaction. This reaction might occur only if the endotoxin induced cytokines like tumour necrosis factor and interleukin 1, act on target cells prepared by interferon gamma. After exposure to interferon gamma target cells become more sensitive to stimuli like endotoxin, thus boosting the inflammatory cycle. Clearly, following this line of reasoning, minor tissue damage or retroperitoneal haematoma combined with systemic endotoxaemia could elicit this reaction. The clinically observed failure of multiple organ systems might thus be explained by the interaction of tissue necrosis and high concentrations of endotoxin because of translocation. Future therapeutic strategies could therefore focus more on binding endotoxin in the gut before the triggering event, for example before major surgery. Such a strategy could be combined with the start of early enteral feeding, which has been shown in animal studies to have a beneficial effect on intestinal mucosal barrier function and in traumatized patients to reduce the incidence of septic complications.

[Antibiotic prophylaxis in multiple trauma patients]

Infection prophylaxis in multiple trauma patients includes prophylaxis of infections due to surgery, which is the true one as well as the prophylaxis of secondary acquired infections which are more frequent, especially in case of co-existing shock. The association an aminopenicillin with a beta-lactamase inhibitor is recommended for prophylaxis of surgical infections. These antibiotics need to be administered early and in high doses, as the pharmacokinetic parameters are modified in trauma patients, with an increased volume of distribution and a shortened half-life of elimination. Prevention of secondary infection relies on a medico-surgical treatment of haemorrhagic shock. Other preventive measures, such as early enteral nutrition, selective decontamination of the digestive tract and immunotherapy, still need to prove their efficacy.

Total parenteral nutrition, bacterial translocation, and host immune function

Total parenteral nutrition (TPN) is associated with increased infectious complications in trauma and perioperative patients compared with enteral nutrition support. This study evaluated the effects of TPN on splenocyte and peritoneal macrophage (PM phi) function and intestinal bacterial translocation. Male Wistar rats underwent central vein cannulation and were randomized to isocaloric feeding of a regular chow diet (RD) plus saline infusion or TPN for 7 days. Splenocytes and PM phi were harvested to assess concanavalin A mitogenesis, superoxide production, and Candida albicans phagocytosis. Bacteria-positive mesenteric lymph nodes (MLNs) were found in 77% (10 of 13) of TPN-fed rats compared with 17% (2 of 12) of RD-fed rats (p < 0.05). Splenocyte mitogenesis, PM phi superoxide production, and C. albicans phagocytosis were significantly decreased in the TPN group compared with results in the RD group. In a second study, rats received RD, TPN, and parenteral nutrition (PN) with 10% or 20% of calories given as oral chow (PN and 10% chow and PN and 20% chow) for 7 days. PN and 10% chow reversed the TPN-induced suppression of C. albicans phagocytosis. PN + 20% chow significantly increased splenocyte mitogenesis, PM phi superoxide production, and C. albicans phagocytosis and killing to normal levels and was associated with a decreased incidence of bacteria-positive MLN. Thus, administration of TPN is associated with impaired PM phi microbicidal and splenocyte proliferative function. These defective cellular functions were reversed with a small amount of oral feeding.

Gut mucosal nutritional support--enteral nutrition as primary therapy after multiple system trauma

Over the past 10 years, several clinical and experimental studies report the potential benefit of enteral nutrition as primary therapy after multiple system trauma. In this study, 98 patients sustaining blunt and penetrating trauma were randomised to receive either enteral or parenteral feeding for 15 days. There were significantly fewer infectious complications in patients randomised to receive enteral feeding with particular benefit shown in the most severely injured patients. Serum protein concentrations correlated with the clinical outcome with an increase in constitutive protein and decrease in acute phase protein concentrations occurring in the enteral group through a decrease in septic complications and possible direct hepatic 'reprioritisation'. Enteral feeding serves as a primary therapy affecting the outcome of critically ill patients.

Risk of abdominal septic complications after feeding jejunostomy placement in patients undergoing splenectomy for trauma

Compared with total parenteral nutrition, enteral feeding via jejunostomy reduces septic complications in patients with severe trauma. However, violation of the bowel with insertion of a jejunostomy tube may increase the risk of intra-abdominal abscess (IAA), particularly if no simultaneous gastrointestinal tract injury exists. The records of 123 patients requiring splenectomy for trauma at a level I trauma center during a 6-year period (1986 to 1992) were reviewed to examine the incidence of IAA in patients with and without simultaneous jejunostomy placement in the presence and absence of gastrointestinal tract injuries. Thirty patients had jejunostomies placed (J), and 93 did not (NoJ). There were no significant differences between the groups in age, Abdominal Trauma Index, Injury Severity Score, or transfusion requirements. The incidence of IAA was not significantly different between the J and NoJ groups in the presence or absence of gastrointestinal tract injuries. Thus, jejunostomy placement does not increase the incidence of IAA after splenectomy regardless of the presence of a gastrointestinal tract injury.

Enteral nutrition in the critically ill patient: a critical review of the evidence

OBJECTIVE

To examine the relationship between enteral nutrition (EN) and infection in the critically ill.

SETTING

Computerized search of published research and review of relevant reference lists.

STUDY SELECTION

151 citations were reviewed and 39 articles met selection criteria. Primary studies were included if they evaluated EN in critically ill humans and its effect on infectious morbidity and mortality.

MEASUREMENTS AND RESULTS

Relevant data were abstracted on the timing and impact of EN on morbidity, the optimal route of administration, composition and pH of EN, and bacterial contamination of EN. The evidence from human studies that EN, particularly early EN, results in reduced septic morbidity as compared to parenteral nutrition is limited to small, unblinded studies with non-rigorous definitions of pneumonia. There is no evidence to support a preference of feeding into the stomach versus the small bowel. The addition of fish oil, arginine, glutamine and fiber to enteral feeds has a variable impact on survival in animal models; there are no trials in critically ill patients that demonstrate a reduction in infectious morbidity and mortality. Acidification of enteral nutrition results in decreased bacterial colonization of the stomach in critically ill patients. Bacterial contamination of enteral nutrition is an important source of infection.

CONCLUSIONS

Evidence from experimental data in critically ill patients suggests that enteral nutrition may have a favourable impact on gastrointestinal immunological function and infectious morbidity.

Elemental diet-induced bacterial translocation can be hormonally modulated

BACKGROUND

The authors have previously documented that feeding mice an elemental diet resulted in bacterial translocation (BT) that could be prevented by the provision of dietary fiber. To test whether the protective effect of fiber was related to the stimulation of trophic gut hormones, the effects of sandostatin and bombesin were tested.

METHODS

Mice fed either chow or the elemental diet were stratified into several groups and the ability of bombesin (10 micrograms/kg, tid) or sandostatin (100 micrograms/kg bid) to modulate BT was examined. After 14 days, mice were sacrificed and BT, cecal bacterial population levels, mucosal protein, and small bowel weight was measured. Segments of the ileum and jejunum were examined histologically.

RESULTS

Incidence of elemental diet-induced BT (75%) was reduced by fiber (9%) or the administration of bombesin (13%) (p < 0.01). Although sandostatin did not promote BT in chow-fed mice, it reversed the protective effect of fiber on BT (75%) (p < 0.01).

CONCLUSION

Elemental diet-induced bacterial translocation can be modulated hormonally and the beneficial effects of fiber on diet-induced BT appears to be hormonally mediated.