The Acute Respiratory Distress Syndrome: Role of Nutritional Modulation of Inflammation Through Dietary Lipids

An Anthology of Advances in Enteral Tube Feeding Formulations

This article summarizes several major advances in tube feeding formulas marketed in the United States. It traces the progress in tube feeding formulas, starting with blenderized formulas to commercially available intact-nutrient formulas and culminating in the introduction of the concept of immunonutrition. The impact of packaging is also described.

The Use of Specialized Enteral Formulas in Pulmonary Disease

The relationship between pulmonary disease and nutrition is significant. Malnutrition and its associated adverse pulmonary effects can directly affect outcomes in the individual with pulmonary disease. The use of nutrition support is common for these patients as a supportive or therapeutic measure. Historical reports of adverse respiratory function associated with high parenteral carbohydrate intakes have led to the controversial use of high-fat enteral products in patients with chronic pulmonary dysfunction. The rationale for using this type of formula is that by providing less carbohydrates, carbon dioxide production will be reduced, respiratory quotient will therefore decrease, and a favorable respiratory outcome will result. In the patient with acute respiratory distress syndrome, an inflammatory state exists in which proinflammatory mediators are produced and affect the course of the disease. An enteral formula with modified lipids designed to modulate eicosanoid production and therefore influence the inflammatory cascade is available. This article reviews the rationale for use of modified enteral formulas in both chronic and acute pulmonary disease, reviews the available studies evaluating the efficacy of these formulas, and provides overall recommendations for the use of specialized enteral formulas in individuals with pulmonary disease.

Perioperative nutritional support: immunonutrition, probiotics, and anabolic steroids

Nutritional support in surgical patients has evolved from simple provision of adequate calories to retard loss of lean body mass to the provision of specific nutrients in an attempt to manipulate metabolic and immune responses. Although still limited, the current understanding of this complex subject indicates that the type, route, amount, and composition of nutritional support provided to patients can affect their outcome. Further studies are, however, needed to better characterize the exact nutritional support that is most beneficial for a specific disease state and a specific patient.

Nutrition therapy for ALI and ARDS

The importance of nutrition support in critically ill patients with acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) cannot be overstated. ALI and ARDS are characterized by a proinflammatory response associated with hypercatabolism that could lead to significant nutrition deficits. Nutrition support is necessary to prevent cumulative caloric deficits, malnutrition, loss of lean body mass, and deterioration of respiratory muscle strength. Furthermore, early delivery of enteral nutrition has been associated with the modulation of stress and the systemic immune response as well as the attenuation of disease severity.

Providing optimal nutritional support on the intensive care unit: key challenges and practical solutions

Many patients in the intensive care unit are malnourished or unable to eat. Feeding them correctly has the potential to reduce morbidity and even mortality but is a very complex procedure. The inflammatory response induced by surgery, trauma or sepsis will alter metabolism, change the ability to utilise nutrients and can lead to rapid loss of lean mass. Both overfeeding and underfeeding macronutrients can be harmful but generally it would seem optimal to give less during metabolic stress and immobility and increase in recovery. Physical intolerance of feeding such as diarrhoea or delayed gastric emptying is common in the intensive care unit. Diarrhoea can be treated with fibre or peptide feeds and anti-diarrhoeal drugs; however, the use of probiotics is controversial. Gastric dysfunction problems can often be overcome with prokinetic drugs or small bowel feeding tubes. New feeds with nutrients such as n-3 fatty acids that have the potential to attenuate excessive inflammatory responses show great promise in favourably improving metabolism and substrate utilisation. The importance of changing nutrient provision according to metabolic and physical tolerance cannot be understated and although expert groups have produced many guidelines on nutritional support of the critically ill, correct interpretation and implementation can be difficult without a dedicated nutrition health care professional such as a dietitian or a multidisciplinary nutritional support team.

Immunonutrition and critical illness: an update

Dietary supplementation with nutrients that have physiologic effects on immune function has been shown to be beneficial in subsets of patients with surgical and medical critical illness. However, several meta-analyses have suggested potential harm when immune nutrients are used inappropriately. This has led to concern among clinicians that in turn has curtailed the more widespread use of immunonutrition as a therapeutic modality. This article discusses the mechanisms by which immune nutrients can be used to modulate alterations in innate and acquired immunity associated with critical illness. In addition, recent evidence-based clinical practice guidelines for use of immunonutrition in adults is reviewed as a means to clarify some of the more controversial issues and provide a "roadmap" for the practitioner.

An evaluation of the safety and efficacy of an anti-inflammatory, pulmonary enteral formula in the treatment of pediatric burn patients with respiratory failure

Respiratory failure is associated with a high mortality rate in burned children. Recently, a specialized pulmonary enteral formula (SPEF) was commercially introduced as an adjunct intervention in acute lung injury management. SPEF contains condition-specific nutrients to modulate the inflammatory response. The study examined SPEF impact in critically ill, pediatric burn patients with respiratory failure. Medical records of acute burn patients admitted December 1997 to October 2006 were reviewed for SPEF treatment. Respiratory and renal indices were compared on the first and final days of SPEF use. Nineteen patients with respiratory failure received SPEF for a mean of 10.8 +/- 0.9 days during their acute burn course. Mean age was 5.3 +/- 1.5 years. Mean total body surface area burn was 44.3 +/- 5.4% with 32.5 +/- 6.4% full thickness. Patients were admitted 2.3 +/- 0.9 days postburn. Significant improvements in peak pressure, PEEP, FiO2, P:F ratio, Pco2, Po2, and ETco2 were noted. Seventeen of the 19 patients survived despite the fact that 9 of the 19 patients developed severe barotrauma requiring multiple tube thoracotomies, and all 19 had extremely poor prognoses at SPEF initiation. Adult SPEF formula for critically ill, pediatric burn patients with respiratory failure is safe and well tolerated. SPEF seems to facilitate recovery from acute lung injury as evidenced by improvements in oxygenation and pulmonary compliance.

Immune-modulating enteral formulations: optimum components, appropriate patients, and controversial use of arginine in sepsis

Nutrients have traditionally been viewed as a means to provide basic calories to sustain homeostasis. However, critically ill, surgical, and trauma patients are in a constant dynamic state between systemic inflammatory response (SIRS) and compensatory anti-inflammatory response (CARS). Results from ongoing research strongly support the use of specific nutrients to modulate the immune and/or metabolic response. These agents can now be considered therapeutic tools in the management of complex hypermetabolic diseases. The principle of using nutrients as a therapeutic strategy rather than just as "nutritional support" requires a shift in the current dogma. The most common nutrients found in currently available enteral immune-modulating formulas are omega-3 fatty acids (eicosapentaenoic acid and docosahexaenoic acid), antioxidants, nucleotides, glutamine, and arginine. Multiple individual reports and at least five meta-analyses using combinations of immune-modulating nutrients have reported almost uniform beneficial results. However, certain conflicting hypotheses continue to revolve around the use of arginine in septic patients.