Invited comment: lipids and the development of immune dysfunction and infection

Nutrition of the critically ill — a 21st-century perspective

Health care-induced diseases constitute a fast-increasing problem. Just one type of these health care-associated infections (HCAI) constitutes the fourth leading cause of death in Western countries. About 25 million individuals worldwide are estimated each year to undergo major surgery, of which approximately 3 million will never return home from the hospital. Furthermore, the quality of life is reported to be significantly impaired for the rest of the lives of those who, during their hospital stay, suffered life-threatening infections/sepsis. Severe infections are strongly associated with a high degree of systemic inflammation in the body, and intimately associated with significantly reduced and malfunctioning GI microbiota, a condition called dysbiosis. Deranged composition and function of the gastrointestinal microbiota, occurring from the mouth to the anus, has been found to cause impaired ability to maintain intact mucosal membrane functions and prevent leakage of toxins - bacterial endotoxins, as well as whole bacteria or debris of bacteria, the DNA of which are commonly found in most cells of the body, often in adipocytes of obese individuals or in arteriosclerotic plaques. Foods rich in proteotoxins such as gluten, casein and zein, and proteins, have been observed to have endotoxin-like effects that can contribute to dysbiosis. About 75% of the food in the Western diet is of limited or no benefit to the microbiota in the lower gut. Most of it, comprised specifically of refined carbohydrates, is already absorbed in the upper part of the GI tract, and what eventually reaches the large intestine is of limited value, as it contains only small amounts of the minerals, vitamins and other nutrients necessary for maintenance of the microbiota. The consequence is that the microbiota of modern humans is greatly reduced, both in terms of numbers and diversity when compared to the diets of our paleolithic forebears and the individuals living a rural lifestyle today. It is the artificial treatment provided in modern medical care - unfortunately often the only alternative provided - which constitute the main contributors to a poor outcome. These treatments include artificial ventilation, artificial nutrition, hygienic measures, use of skin-penetrating devices, tubes and catheters, frequent use of pharmaceuticals; they are all known to severely impair the microbiomes in various locations of the body, which, to a large extent, are ultimately responsible for a poor outcome. Attempts to reconstitute a normal microbiome by supply of probiotics have often failed as they are almost always undertaken as a complement to - and not as an alternative to - existing treatment schemes, especially those based on antibiotics, but also other pharmaceuticals.

Nutrition of the critically ill - emphasis on liver and pancreas

About 25 million individuals undergo high risk surgery each year. Of these about 3 million will never return home from hospital, and the quality of life for many of those who return is often significantly impaired. Furthermore, many of those who manage to leave hospital have undergone severe life-threatening complications, mostly infections/sepsis. The development is strongly associated with the level of systemic inflammation in the body, which again is entirely a result of malfunctioning GI microbiota, a condition called dysbiosis, with deranged composition and function of the gastrointestinal microbiota from the mouth to the anus and impaired ability to maintain intact mucosal membrane functions and prevent leakage of toxins-bacterial endotoxins and whole or debris of bacteria, but also foods containing proteotoxins gluten, casein and zein and heat-induced molecules such as advanced glycation end products (AGEs) and advanced lipoxidation end products (ALEs). Markedly lower total anaerobic bacterial counts, particularly of the beneficial Bifidobacterium and Lactobacillus and higher counts of total facultative anaerobes such as Staphylococcus and Pseudomonas are often observed when analyzing the colonic microbiota. In addition Gram-negative facultative anaerobes are commonly identified microbial organisms in mesenteric lymph nodes and at serosal "scrapings" at laparotomy in patients suffering what is called "Systemic inflammation response system" (SIRS). Clearly the outcome is influenced by preexisting conditions in those undergoing surgery, but not to the extent as one could expect. Several studies have for example been unable to find significant influence of pre-existing obesity. The outcome seems much more to be related to the life-style of the individual and her/his "maintenance" of the microbiota e.g., size and diversity of microbiota, normal microbiota, eubiosis, being highly preventive. About 75% of the food Westerners consume does not benefit microbiota in the lower gut. Most of it, refined carbohydrates, is already absorbed in the upper part of the GI tract, and of what reaches the large intestine is of limited value containing less minerals, less vitamins and other nutrients important for maintenance of the microbiota. The consequence is that the microbiota of modern man has a much reduced size and diversity in comparison to what our Palelithic forefathers had, and individuals living a rural life have today. It is the artificial treatment provided by modern care, unfortunately often the only alternative, which belongs to the main contributor to poor outcome, among them; artificial ventilation, artificial nutrition, hygienic measures, use of skin penetrating devices, tubes and catheters, frequent use of pharmaceuticals, all known to significantly impair the total microbiome of the body and dramatically contribute to poor outcome. Attempts to reconstitute a normal microbiome have often failed as they have always been undertaken as a complement to and not an alternative to existing treatment schemes, especially treatments with antibiotics. Modern nutrition formulas are clearly too artificial as they are based on mixture of a variety of chemicals, which alone or together induce inflammation. Alternative formulas, based on regular food ingredients, especially rich in raw fresh greens, vegetables and fruits and with them healthy bacteria are suggested to be developed and tried.

A 3-month double-blind randomised study comparing an olive oil- with a soyabean oil-based intravenous lipid emulsion in home parenteral nutrition patients

Intravenous lipid emulsions (ILE) have demonstrated advantages including prevention of essential fatty acid (EFA) deficiency; however, too much EFA can down regulate fatty acid elongation leading to an imbalance of nutritional compounds in plasma and cell membranes. An olive oil-based ILE containing long-chain triacylglycerols (LCT) with a low content (20 %) of PUFA was administered for home parenteral nutrition (HPN) and compared with a conventional soyabean oil-based ILE (PUFA content, 60 %). Thirteen patients (26–92 years) with stable intestinal failure were randomised after a 1-month run-in period with a medium-chain triacylglycerols–LCT-based ILE, to receive 3 months of HPN with either olive oil- (n6) or soyabean oil-based (n7) ILE. The nutritional impact and safety of HPN, oral intakes and absorption rates, phospholipid fatty acids in plasma and lymphocyte cell membrane were assessed. The only clinical event reported was one case of pneumonia (soya group). In both groups, 20 : 3n-9:20:4n-6 ratios remained within normal ranges (0·03–0·07). There was a significant increase of γ-linolenic acid (γ-LA) in plasma and lymphocyte cell membrane (P=0·02) and of oleic acid in plasma (P<0·01) in the olive compared with the soya group. A significant correlation was found between γ-LA (day 90 – day 0) in plasma and PUFA parenteral intakes (P=0·02), but neither with fat intakes nor with fat absorption rates. In conclusion, plasma and lymphocyte EFA pattern remained in normal ranges without EFA deficiency with both lipid emulsions, despite a lower content ofn-3 andn-6 series with the olive oil-based ILE.

Nutrition and Immune Function

The complexity of the immune system allows for a multitude of potential avenues for nutrient modulation, but this also increase the challenge of producing a predictable in vivo response. Because the immune response is a cascade of biologic events, development of nutritional support paradigms cannot and should not be made in a vacuum or with the expectation of a singular response. It is absolutely imperative that the clinician/nutritionist understand the differences in metabolIc and physiologic responses to disease states (ie, shock, trauma, organ-specific dysfunction) so as to maximize immunocompetence through specialized feeding practices. This level of understanding is invaluable, especially when considering the possible benefit of nutrient combinations for immunomodualtion.

Bioecologic Control of Inflammation and Infection in Critical Illness

Surgical and medical emergencies and treatments are still affected by an unacceptably high rate of morbidity and mortality. Sepsis is the most common medical and surgical complication and the tenth most common cause of death. Antibiotics and antagonists and inhibitors of proinflammatory cytokines have not met expectations. Selective bowel decontamination is no longer a treatment option. After more than 30 randomized clinical trials and 30 years of dedicated efforts to combat sepsis by the use of various combinations of antibiotics, we seem ready to conclude that the vigorous use of antibiotics does not significantly reduce mortality in critically ill patients. Side effects and price constitute important obstacles, especially when it comes to use of cytokine antagonists and inhibitors.

Improved immune functions with administration of a low-fat diet in a burn animal model

The purpose of this study was to characterize the impact of a low-fat (LF; 1% fat) diet, a high-fat (HF; 25% fat) diet, and a standard (SD; 5% fat) diet on immune and oxidative parameters in a 20% body surface area burn animal model fed ad libitum for 10 days postinjury. Although the mechanisms are poorly understood, the amount of dietary lipid in nutritional support has been shown to have immunomodulatory effects after burn injury. Burned mice fed the LF diet showed a normal response in activated splenocyte proliferation compared to burned animals that received the SD or HF diet. Animals fed the SD and HF diets presented increased production of nitric oxide and prostaglandin E2 response after burn injury, which is associated with inhibited splenocyte proliferation. The total thiol concentration in spleen cells from burned animals kept on the HF diet was significantly higher than that in unburned animals, while no increase in these oxidative parameters was observed in LF-fed burned animals. Moreover, the LF diet significantly reduced hepatic lipid peroxidation, as measured by malonaldehyde concentration, compared to the other two diets. These results suggest that the administration of a LF diet in mice after a burn injury prevents inhibition of in vitro splenocyte proliferation and reduces the intensity of oxidative stress.

Formulation of enteral diets

The number of enteral diets has increased from a handful in the 1970s to over 100 at present. These can be classified as polymeric, chemically defined, disease-specific, and specialized diets, as well as oral dietary supplements. The properties, indications, pros and cons for the use of these diets are outlined in an effort to assist clinicians in their selection.

The effect of highly purified eicosapentaenoic and docosahexaenoic acids on monocyte phagocytosis in man

The n-3 fatty acids (FA) from marine sources are known to exert antiinflammatory effects on monocyte function. There is still controversy whether n-3 FA may increase the susceptibility to infections. The present study was designed to assess the effect of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) on monocyte phagocytosis and respiratory burst activity. Fifty-eight healthy men were randomized to take a daily supplement of 3.8 g highly purified EPA (n = 20), 3.6 g DHA (n = 19), or corn oil (n = 19) for 7 wk. Mononuclear leukocytes were collected, isolated, and cryopreserved prior to and after dietary supplementation. Paired samples were analyzed in the presence of autologous serum in a crossover design. Monocyte phagocytosis and respiratory burst activity were measured by flow cytometry after ingestion of Escherichia coli. Monocytes retained their phagocytic ability and respiratory burst activity after supplementation. No reduction in internalization of bacteria was registered. Dietary n-3 FA and particularly EPA improved bacterial adherence to the monocyte surface. In the crossover experiments, there was an adverse effect of serum enriched with n-3 FA on bacterial adherence. We conclude that monocytes retain their phagocytic potential after supplementation with purified EPA and DHA.

Home parenteral lipids in AIDS: a three-month study

Parenteral nutrition is a part of the nutritional support regimen of patients with AIDS-associated wasting syndrome and gastrointestinal dysfunction. The cholesterol (CHOL) level in human immunodeficiency virus (HIV) membrane is very high, and recent lipid formulations with high phospholipid (PL) content have demonstrated the ability to trap CHOL from endogenous sources, modifying the composition of cell membranes. We administered lipid-based home parenteral nutrition for 3 mo to malnourished AIDS patients. The patients were randomly divided into two groups: 23 received the regular 20% fat emulsion formulation, and 27 received a 2% formulation enriched 10-fold with PLs but containing the same amount of triglycerides. All patients gained weight and improved their activity level. Those receiving the high-PL composition showed increased serum CHOL concentrations (from 147 to 241 mg/dL; P < 0.01), but no increase was seen in the number of CD4 cells or improvement in immune function. HIV infectivity was not modified. Patients receiving regular PLs had significantly decreased (P < 0.02) IgA concentrations (from 776 to 300 mg/dL) and improved mitogen response to phytohemagglutinin and to concanavalin A. This formula, too, had no effect on HIV infectivity. We conclude that standard parenteral nutritional influences the nutritional and immune status of malnourished AIDS patients. A PL-enriched parenteral formulation can trap CHOL, but it does not affect the immune profile or HIV infectivity in patients with advanced disease.

Enteral nutrition and the critically ill

Critically ill patients invariably require nutritional intervention. Traditionally, enteral nutrition has not been widely employed in this patient population. This is due in part to the success of present-day parenteral nutrition, and to difficulties encountered with enteral feeding. Recent evidence has demonstrated that enteral is preferable to parenteral nutrition in terms of cost, complications, gut mucosal maintenance, and metabolic and immune function. Enterally administered nutritional support can and should be utilised as the preferred route of nourishment for the critically ill. The appropriate choice of access and formula, as well as a rational strategy for implementation, should improve the likelihood of success. This article describes the unique features of critical illness as they pertain to nutritional support, the benefits of enteral nutrition, and the obstacles to success, and offers suggestions which may improve the ability to provide nutrients adequately via the intestinal tract.

The use of modular nutrients in pediatrics

BACKGROUND

Nutrient modules are commonly used by pediatricians and dietitians. There is no readily available current literature to which those using nutrient modules can refer. Therefore, we review nutrient module composition, module use in pediatrics, and complications associated with the use of nutrient modules.

METHODS

Using an online database, Meduline, we searched the literature from 1996 through 1995.

RESULTS

Nutrient modules are single or multiple nutrients that can be combined with a diet to add nutrients or to change the composition of the diet. These nutrients exist as a food or as medically compounded elements of a diet but alone are not complete foods.

DISCUSSION

The addition of modules to a diet can alter the composition of a diet so that a single nutrient may become deficient and the diet cannot support normal growth and development. With use of nutrient modules, diets can be prepared to meet the specific needs of children with common or rare nutritional problems.

CONCLUSION

Health care providers who use nutrient modules must understand the importance of diet composition and the careful monitoring of pediatric patients.

Early enteral administration of a formula (Impact) supplemented with arginine, nucleotides, and fish oil in intensive care unit patients: results of a multicenter, prospective, randomized, clinical trial

OBJECTIVE

To determine if early enteral feeding, in an intensive care unit (ICU) patient population, using a formula supplemented with arginine, dietary nucleotides, and fish oil (Impact), results in a shorter hospital stay and a reduced frequency of infectious complications, when compared with feeding a common use enteral formula (Osmolite.HN).

DESIGN

A prospective, randomized, double-blind, multicenter trial.

SETTING

ICUs in eight different hospitals.

PATIENTS

Of 326 patients enrolled in the study, 296 patients were eligible for analysis. They were admitted to the ICU after an event such as trauma, surgery, or sepsis, and met a risk assessment screen (Acute Physiology and Chronic Health Evaluation II [APACHE II] score of > or = 10, or a Therapeutic Intervention Scoring System score of > or = 20) and study eligibility requirements. Patients were stratified by age (< 60 or > or = 60 yrs of age) and disease (septic or systemic inflammatory response syndrome).

INTERVENTIONS

Patients were enrolled and full-strength tube feedings were initiated within 48 hrs of the study entry event. Enteral feedings were advanced to a target volume of 60 mL/hr by 96 hrs of the event. One hundred sixty-eight patients were randomized to receive the experimental formula, and 158 patients were randomized to receive the common use control formula.

MEASUREMENTS AND MAIN RESULTS

Both groups tolerated early enteral feeding well, and the frequency of tube feeding-related complications was low. There were no significant differences in nitrogen balance between groups on study days 4 and 7. Patients receiving the experimental formula had a significant (p = .0001) increase in plasma arginine and ornithine concentrations by study day 7. Plasma fatty acid profiles demonstrated higher concentrations of linoleic acid (p < .01) in the patients receiving the common use formula and higher concentrations of eicosapentaenoic and docosahexaenoic acid (p < .01) in the patients receiving the experimental formula. The mortality rate was not different between the groups and was significantly (p < .001) lower than predicted by the admission severity scores in both feeding groups. In patients who received at least 821 mL/day of the experimental formula, the hospital median length of stay was reduced by 8 days (p < .05). In patients stratified as septic, the median length of hospital stay was reduced by 10 days (p < .05), along with a major reduction in the frequency of acquired infections (p < .01) in the patients who received the experimental formula. In the septic subgroup fed at least 821 mL/day, the median length of stay was reduced by 11.5 days, along with a major reduction in acquired infections (both p < .05) in the patients who received the experimental formula.

CONCLUSIONS

Early enteral feeding of the experimental formula was safe and well tolerated in ICU patients. In patients who received the experimental formula, particularly if they were septic on admission to the study, a substantial reduction in hospital length of stay was observed, along with a significant reduction in the frequency of acquired infections.

Metabolic changes in lymphoid organs as induced by fatty acids-rich diets during ageing

Previous reports of our laboratory have shown that w-6 PUFA-rich diets (UC) given to rats during 6 weeks causes important changes of the metabolism of the lymphoid organs. In this study, the effect of saturated fatty acids-rich diet (SC) and also the persistence of the changes caused by (UC) were investigated during ageing (14 months). The major changes previously reported for UC fed rats, during 6 weeks, fully persisted when this feeding condition was maintained for 14 months. Moreover, the SC group also showed modifications of the activities of key enzymes of glucose and glutamine metabolism of the lymphoid organs with ageing. Both groups fed fatty acids-rich diets markedly reduced the rate of lipogenesis in the liver, spleen, and thymus in contrast to slight changes reported for 6 weeks. These results suggest that fatty acids-rich diets, by causing important metabolic alterations, may pronounce the impairment of the immune function observed during ageing.

Effect of fatty acid-rich diets on thymocyte proliferation and thymus involution during growing

The effect of poly-unsaturated and saturated fatty acid-rich diet on the proliferation response of T and B lymphocytes in vitro was investigated. Also, a mitotic index of thymocytes and of thymus epithelial reticular-like cells and thymic involution coefficient were examined in vivo. w-6 PUFA-rich diet enhanced the rate of T (eightfold) and B (fourfold) lymphocyte proliferation, whereas saturated fatty acids did not show an important effect. However, both fat-rich diets increased the mitotic index of thymocytes and thymus involution index in vivo. These findings suggest that fat-rich diets may accelerate thymus involution during growing, possibly aggravating the impairment of the immune function which usually occurs under this condition.

Nutritional management of cats with infectious disease

The effect of malnutrition in patients with a variety of ailments is known to be deleterious to their overall quality of life, response and tolerance to therapy, and ultimate survival. These effects may be amplified in feline patients with infectious disease owing to the blunting of immunologic responsiveness that results from malnutrition. This vicious cycle of infection, ensuing malnutrition, and subsequent immunocompromise may not allow the patient to mount an attack on the invading pathogen adequately. The most logical means to reverse this cycle is to ensure an adequate nutritional state in the patient. Initial attempts at maintaining or increasing voluntary oral intake should be initiated in the short term. However, enteral or parenteral support should be instituted as quickly as possible if these should fail. Much is yet to be discerned about specific optimal supplementation techniques and dietary formulations for feline patients; however, the application of relatively simple and general principles of nutritional support offer our feline patients with infectious disease the best opportunity to overcome their disease.

Short-term dietary lipid manipulation does not affect survival in two models of murine sepsis

Dietary lipid manipulation has been shown to have various effects on the immune system, depending on the amount of fat, degree of saturation, and type of fat used. In this study we investigated the role of different sources of fat at different levels on the survival of mice in two models of peritonitis, one with Pseudomonas aeruginosa and the other with Salmonella typhimurium. CF1 mice were pair-fed diets with 5% or 40% of total calories as fat. The source of fat used was coconut oil, oleic acid, safflower oil, or fish oil. Three other diets were tested as well, one with no fat, one with only 0.5% of total calories linoleic acid as the only source of fat, and a control diet that had 12% of total calories as corn oil. At the end of 2 weeks of feeding the experimental diets, mice were challenged with Ps aeruginosa intraperitoneally and mortality was recorded over 1 week. After 3 weeks of feeding the experimental diets, mice were challenged with S typhimurium and mortality was recorded over 2 weeks. No significant differences were seen on survival among groups fed different levels of fat, as well as different sources of fat. We conclude that, overall, 2- and 3-week manipulation of dietary fat does not affect outcome from infection in these models.

Intravenous nutritional support and the surgeon: where next?

Over the past twenty five years the development of total parenteral nutrition has in many ways revolutionised the practice of surgery. It has enhanced survival in otherwise high mortality operations such as oesophageal surgery, especially with anastomotic complications. It has changed significantly the management of fistulae, either post operative or associated with diseases such as Crohn's enteritis. Here a basic general principle is applied--that a fistula will close if there is no distal obstruction and the throughput can be diminished. This can be achieved by withholding oral feeding and using the parenteral route. It has allowed survival in the short gut syndrome from whatever cause and it is interesting to see the degree of "intestinal adaptation" that occurs once the first critical year is survived with the help of intravenous nutrition. The assessment of nutritional status is difficult and while the level of serum albumin may be taken as a clinical standard, it is obvious that many patients survive extensive surgery with low albumin levels and also that there appears to be a lag period to the restoration of albumin levels, even with otherwise successful nutritional support and with other parameters being satisfactory. Even complex formulae using a combination of laboratory and antropometric parameters is not fully satisfactory as an absolute assessment of nutritional status. It is now interesting to see that nutrition can affect both immune competence and even carcinogenesis. The lipid element in intravenous nutrition may cause dysfunction of immunity and vitamin status, gastric and platelet function with impaired oxygen diffusion leading to increased wedge pressures.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of anaesthesia and surgery on the immune response

Alterations have been found to occur in every component of immune response during anaesthesia and surgery. These alterations represent the body's general physiological responses and are mainly dependent on the extent of surgery, as well as other factors such as the patient's age and health status, medication and blood transfusion. Anaesthetic and operative complications have profound effects on these responses. Basically, the immune response to anaesthesia and surgery is a beneficial reaction, needed in local host defences and wound healing and in preventing the body from making autoantibodies against its own tissues. The responses may, however, contribute to the development of postoperative infections and spread of malignant disease. During uncomplicated conventional surgery, the immune response usually passes clinically unnoticed without any harmful effects. Absent responses and excessively high responses, on the other hand, harm the patient. Our understanding of immunological phenomena and our possibilities of controlling mediator activation are now lagging behind the technical advances made in operative treatment. If we want to decrease operative morbidity and mortality to below their present levels, more attention should be directed to immune responses to major surgery, injuries and operative complications with massive mediator release which place the surgical patient at risk. Experimental evidence suggests that results of treatment in injured and operated patients can in the future be improved by controlling immune responses and their mediator systems. Our current level of knowledge of immune responses is already helping us to avoid many immune-mediated complications. However, routine interference with these responses is not indicated.

The metabolic effects of thermal injury

Major thermal injury is associated with extreme hypermetabolism and catabolism as the principal metabolic manifestations encountered following successful resuscitation from the shock phase of the burn injury. Substrate and hormonal measurements, indirect calorimetry, and nitrogen balance are biochemical metabolic parameters which are useful and more readily available biochemical parameters worthy of serial assessment for the metabolic management of burn patients. However, the application of stable isotopes with gas chromatography/mass spectroscopy and more recently, new immunoassays for growth factors and cytokines has increased our understanding of the metabolic manifestations of severe trauma. The metabolic response to injury in burn patients is biphasic wherein the initial ebb phase is followed by a hypermetabolic and catabolic flow phase of injury. The increased oxygen consumption/metabolic rate is in part fuelled by evaporative heat loss from wounds of trauma victims, but likely also by a direct central effect of inflammation upon the hypothalamus. Although carbohydrates in the form of glucose appear to be an important fuel source following injury, a maximum of 5-6 mg/kg/min only is beneficial. Burn patients have accelerated gluconeogenesis, glucose oxidation, and plasma clearance of glucose. Additionally, considerable futile cycling of carbohydrate intermediates occurs which includes anaerobic lactate metabolism and Cori cycle activity arising from wound metabolism of glucose and other substrates. Similarly, accelerated lipolysis and futile fatty acid cycling occurs following burn injury. However, recent evidence suggests that lipids in the diet of burned and other injured patients serve not only as an energy source, but also as an important immunomodulator of prostaglandin metabolism and other immune responses. Amino acid metabolism in burn patients is characterized by increased oxidation, urea synthesis, and protein breakdown which is prolonged and difficult to reduce with current nutritional therapy. However, the current goal of nutritional support is to optimize protein synthesis. Specific unique requirements may exist for supplemental glutamine and arginine following burn injury but further research is needed before enhanced branched chain amino acids supplements can be recommended for burn patients. Recent research investigations have revealed the importance of enteral feeding to enhance mucosal defense against gut bacteria and endotoxin. Similarly, research has demonstrated that many of the metabolic perturbations of burns and sepsis may be due, at least in part, to inflammatory cytokines. Investigation of their pathogenesis and mechanism of action both at a tissue and a cellular level offer important prospects for improved understanding and therapeutic control of the metabolic disorders of burn patients.

Long-term feeding with structured lipid composed of medium-chain and N-3 fatty acids ameliorates endotoxic shock in guinea pigs

The metabolic and physiologic responses to 7-hour endotoxin infusion (5.0 mg/kg h) were evaluated in guinea pigs following 6 weeks of dietary enrichment with diets containing either chemically structured lipid (SL) composed of medium-chain triglycerides (MCT) and long-chain triglycerides (LCT) in the form of N-3 polyunsaturated fatty acids (PUFAs), or safflower oil (SO), which is high in N-6 fatty acids. Plasma phospholipid fatty acid profiles, arterial blood pH, PCO2, PO2, HCO3, lactate, blood pressure, oxygen consumption, and energy expenditure were examined. Plasma phospholipid fatty acids profiles reflected dietary intake with SL-fed animals demonstrating a significantly higher N-3 to N-6 fatty acid ratio compared with SO-fed animals. SL-fed animals responded to endotoxemia with a mild metabolic acidosis with respiratory compensation, which was associated with moderate lactatemia (3 mmol/L). SO-fed animals developed a severe metabolic acidosis with acidemia and respiratory compensation, which was associated with hyperlactatemia (8 mmol/L, P less than .05 v SL). No differences were observed in blood pressure, oxygen consumption, energy expenditure, or respiratory quotient during endotoxemia between dietary groups compared with controls. We conclude that diets enriched with structured lipid composed of medium-chain and N-3 fatty acids can attenuate the sequelae of endotoxemia.

Nutritional consequences of major gastrointestinal surgery. Patient outcome and starvation

Advances in major gastrointestinal surgery and the existence of a significant number of high-risk patients necessitate a detailed knowledge of the metabolic response to surgery and the need for adjunctive nutritional therapy. Such surgery has the potential to cause significant nutritional consequences affecting patient outcome. Often, patients present malnourished preoperatively because of their chronic gastrointestinal disease, advanced age, or comorbidity. Still others are at great risk for developing malnutrition postoperatively secondary to the hypercatabolism of prolonged illness or postoperative complications. In addition, the surgical alterations of the gastrointestinal tract might disrupt normal function sufficiently to result in chronic nutritional deficiencies. Because starvation is no longer an acceptable condition, these concerns need to be recognized prior to surgery, and if indicated, nutritional support must be initiated preoperatively. Placement of feeding jejunostomy catheters for early enteral support should be considered for all high-risk patients. Equally important, surgeons should maintain a watch for future nutritional innovations that will improve their ability to meet patients' nutritional requirements.

Practicalities of lipids: ICU patient, autoimmune disease, and vascular disease

Although the use of lipids should be individualized, certain generalizations are appropriate. 1. Lipid infusion should be limited in the fulminately septic patient to 10% of total calories in an effort to reduce immunosuppression. 2. The stressed, nonseptic patient with difficulties in ventilator weaning or TPN-induced hepatic dysfunction may reap benefit from a reduction in dextrose calories and the provision of daily lipids. 3. Patients with severe autoimmune disease have had mild amelioration of symptoms with PUFA supplementation. The relative benefits of omega-6 vs omega-3 continue to be examined. 4. Dietary immunomodulation in transplant and burns remains an area of active investigation. 5. Patients with fat-free TPN show transient declines in serum lipids. The development of a "fat-solubilizer" remains in the experimental realm. 6. The provision of fish oil, high in W-3 EPA, has shown promise in atherosclerosis and immunomodulation. The changes in the relative amounts of each prostaglandin class depend on precursor prevalence.

Use of parenteral medium-chain triglyceride emulsion for maintaining seizure control in a 5-year-old girl with intractable diarrhea

Medium-chain triglycerides (MCT) are an important component of an enteral ketogenic diet for seizure control. Previously, it was difficult to maintain ketosis when parenteral (iv) nutrition therapy was necessary. The use of iv MCT in a 5-year-old girl with Lennox-Gastaut syndrome who had diarrhea and dehydration is reported. Conventional 20% iv fat emulsion (long-chain triglycerides, LCT) and dextrose free hyperalimentation (HAL) in a 4:1 ketogenic ratio did not maintain adequate ketosis during bowel rest. Compassionate use of iv MCT (Clintec Nutrition) infused as a 70:30 MCT/LCT ratio plus HAL maintained moderate ketosis. Seizures were well controlled during the iv MCT regimen, which allowed normal daily functioning. Complications included abnormal liver function tests and severe iron deficiency anemia of unknown etiology. Serum triglyceride and cholesterol levels increased to 1717 mg/dl and 614 mg/dl, respectively, but decreased with a reduction of lipid infusion and use of an antihyperlipemic drug. Nutritional status was maintained. In this case, iv MCT proved to be a relatively safe and effective short-term method of continuing parenteral nutrition while maintaining ketosis for seizure control.