Early, Aggressive ICU Nutrition Drawing More Advocates
Practice impacts patient outcomes and hospital budgets alike
By Julie Crawshaw, Critical Care Plus Editor
Most large hospitals today have dedicated icu nutritionists who make nutritional recommendations for every critically ill patient admitted. Though some physicians remain skeptical of studies that support using early, aggressive enteral or parenteral nutritional support to improve patient outcomes, leaders in nutritional research say that those studies which failed to indicate positive effects were improperly conducted.
Gary P. Zaloga, MD, FACN, FACS, FCCM, Medical Director for the Methodist Research Institute at Clarian Health, Indianapolis observes that nutrition has become a highly complex field, one in which most physicians lack background and experience. He says that choosing the right timing, quality and route for nutritional support are essential for its success.
The effectiveness of nutritional agents is disease-specific, Zaloga says, and it’s pretty clear that the major nutritional boosters are glutamine and arginine, both of which are used by immune cells and have regulating properties on different mediators.
Best Products Heavy on Amino Acids
Nutritional research for critical care has focused on finding nutrients that reduce inflammation and bolster immune function. Zaloga says that numerous nutrients in four or five products already on the market have been shown to alter regulation of the immune system and decrease infections.
The best nutritional products contain large amounts of amino acids, Zaloga says, chiefly glutamine and arginine, both of which are used by immune cells and have regulating properties on different mediators. Arginine becomes the essential substrate for conversion to nitric oxide. He adds that many cheap products are available that allow feeding a patient for about $3.50 per day, but these products contain only protein and carbohydrates plus some lipids and vitamins, not the large nutrient dosages demonstrated to be effective. "A problem arises when clinicians who are not very knowledgeable about nutrition dismiss the importance of using pharmaceutical dosages of arginine and glutamine can be as high as 30 grams per day, making up one-third of the entire protein intake," Zaloga says. "When you give such large quantities you inarguably begin to see effects."
Is the Route Question Really Dead?
Zaloga observes that the question of intravenous versus enteral feeding should have been settled years ago because the evidence is overwhelmingly in favor of using enteral feeding, But if you look at practices throughout the United States and the rest of the world, it’s still "absolutely astonishing" how many physicians continue to use intravenous nutrition, which Zaloga describes as very detrimental to patient recovery.
Nutritional guidelines have always directed using enteral nutrition whenever possible, he adds, but to some physicians that means "harness all known means to use enteral mode," while others interpret much less strictly. "If the guidelines simply stated we should not use intravenous feeding it would be simple," Zaloga points out. "But every time I’m on a guideline committee the strong language gets washed out, leaving the clinician with too much leeway in making decisions."
Because guidelines go through many reviewing bodies and changes before they are published, they wind up being worded in such a way that no one knows what they mean. "I’ve had physicians ask me what a specific guideline means," Zaloga says. I knew what it meant because I was present for the discussions, but the finished product wasn’t clear."
Timing is Critical
Both Zaloga and Laura Russo, Registered Dietician at Children’s Memorial Hospital/Chicago firmly believe that the earlier nutritional support begins, the more successful it will be. Starting a nutrition support regimen as soon as possible is particularly important for children, whose have more limited protein reserves than adults, Russo says. She notes that, although elderly patients tend to be frailer than children, their nutritional reserve capacity may be somewhat higher.
Russo says that keeping nitrogen balance positive is essential to avoid muscle breakdown, adding that the balancing act is to estimate correct amounts of calories and protein to be given. Available nutritional guidelines for children are based on predicted values in healthy children and lack correlation for the critically ill child. "There’s a lot of controversy in the literature about how measured and predicted energy expenditures should be compared," she adds. "In the end, using nutrition to help move children out of the ICU almost comes down to having experience with the patient population."
However, Russo points to a study of 2 of 21 critically ill children with SIRS or sepsis in which researchers found that the energy requirements of these children did not increase.1 Twenty-one stable control children, matched for weight, were also studied. Seven patients required inotropic support and 17 received mechanical ventilation. Fifteen patients with SIRS had evidence of bacterial, fungal, or viral infection and were considered septic. The study’s authors speculated that the ill children diverted energy that would normally be used for growth into recovery processes. In contrast, the energy requirement of adult patients with critical illness or those undergoing severe stress is thought to be increased by 30% above normal.
Zaloga and a colleague also studied sepsis effects in older patients2 by viewing various cytokines as part of the inflammatory response. "We found that basically they respond in pretty much the same way as in young people."
Therapies can Boomerang
Therapies can boomerang, however; unforeseen effects of a therapy that appear beneficial at one point in time can come back to bite patient and physician alike at a later date. "Data show that using anti-arrhythmic drugs actually increases sudden death mortality rates, yet we treated patients with them for fifteen years because no one did a survival study," Zaloga says. "And patients who received chemotherapy for Hodgkin’s Disease fifteen years ago are developing second cancers that are probably related to the treatment of the first."
Assessing the risk-benefit is easier in critical care because patients are already near death. "If making changes in nutrition helps provide critically ill patients with another five years of life, it’s worth doing even though we don’t know what the risks are 15 years down the road," Zaloga says. For the non-critically ill, however, he adds that taking pharmaceutical dosages of amino acids long term may increase the risk of auto-immune diseases in later life because the nutrients augment ability of immune cells to react to antigens. And while Omega-3’s are good for reducing inflammation they also diminish wound healing to some degree. "Inhibiting the inflammatory cascade over long periods of time may not be good," Zaloga adds.
Muhammad Shahzad, MD, attending and consulting physician at Kindred Hospital, Northlake, Illinois, is convinced that nutritional support boosts favorable ICU outcomes.
After the first couple of days, Shahzad says, critically ill patients have no protein stores and their body systems, especially skin, begin to break down. Nutritional support, Shahzad says, prevents such breakdowns while providing enough caloric intake as well. "Most of my patients reside in nursing homes," Shahzad says. "If they are nutritionally depleted it can spell disaster." For more information, contact Gary P. Zaloga (317) 962-2000; Laura Russo (773) 880-6930 ext. (2565); Muhammad Shahzad (312) 493-9890.
References
1. Turi RA, et al. Energy metabolism of infants and children with systemic inflammatory response syndrome and sepsis. Ann Surg. 2001;233(4):581-587.
2. Marik PE, Zaloga GP. The effect of aging on circulating levels of proinflammatory cytokines during septic shock. J Am Geriatrics Soc. 2001;49(1):5-9.
3. Zaloga GP. Early enteral nutritional support improves outcome: Hypothesis or fact? Crit Care Med. 1999;27:259-261.
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