60 patients, the major risks are electrolyte and glucose disturbances, sometimes also related to complications <strong>of</strong> the underlying disease. In longterm parenterally-fed patients, the risk <strong>of</strong> developing micro- and macronutrient deficiencies must be taken into account, because <strong>of</strong> the difficulty in providing an adequate and complete PNadmixture. In bone marrow transplanted patients, the major deficiency risk is related to the limited administration <strong>of</strong> lipids, <strong>of</strong>ten not given because <strong>of</strong> sespis, and pharmacologic incompatibility with other therapies. In children EFA-deficiency can be detected after 1 week without a EFA intake that is at least 1% <strong>of</strong> the total daily calorie intake; linoleic and linolenic acids are not synthesized by humans and are both considered essential; they are the precursors <strong>of</strong> arachidonic acid (from linoleic) and <strong>of</strong> docosahexaenoic and eicosapentaenoic acids (from linoleic acid), which are involved in central nervous system development. These essential fatty acids are necessary for growth, skin and hair integrity, regulation <strong>of</strong> cholesterol metabolism, decreased platelet aggregation, and lipotropic activity. The parenteral lipid emulsions are represented by long chain fatty acids (LCT), by a mixture <strong>of</strong> long and medium chain triglycerides (LCT-MCT), and by the more recent olive oil derivates. Their use is <strong>of</strong>ten limited because <strong>of</strong> concern about the effects on immune and reticulo-endothelial systems, by the mediation <strong>of</strong> several systems, including increasing E2 production, decreasing T helper / T suppressor ratio, inhibiting neutrophil migration, chemotaxis, endotoxin clearance, and complement synthesis and depressed natural killer and lymphokine activated killer activity by blockage <strong>of</strong> interleukin-2 binding to its receptor. 2,4 PN solution means a complete admixture <strong>of</strong> at least glucose, nitrogen, salts, minerals; the provision <strong>of</strong> glucose and salts is not parenteral nutrition, but hydration support. Lipids need not be given daily, but they must be given one/two days a week in order to cover basal needs; zinc and copper supplementation will be required if PN lasts for more than 2 week, while complete provision <strong>of</strong> all known trace elements is strongly indicated for PN <strong>of</strong> longer duration, in order to avoid a deficiency syndrome. The complexity <strong>of</strong> a PN solution grows with the duration <strong>of</strong> the artificial support, particularly if nutrition is exclusively being given by the pare-nteral route, i.e. in patients who cannot eat even small amounts <strong>of</strong> food. The definition <strong>of</strong> parenteral intakes is based on the metabolic status <strong>of</strong> the patient (presence <strong>of</strong> hypercatabolism and/or malnutrition) and on theoretical calorie and nitrogen needs; the intakes must be closely monitored to avoid the most frequent complications. In critically ill patients, a constant infusion rate generally allows better metabolic tolerance, especially for lipids, which must be delivered over at least 8-12 hours in order to reduce the risk <strong>of</strong> hypertriglyceridemia which can occur if the infusion rate exceeds clearance capacity (the infusion rate should be a maximum <strong>of</strong> 0.17 g/kg/h). 2 The use <strong>of</strong> glutamine, a conditionally-essential aminoacid, has been claimed to be important in decreasing mortality and morbidity in patients undergoing bone marrow transplantations, as well as in other clinical conditions. Its role in muscle function, in nitrogen transport to the cells, as a primary fuel for enterocytes, and in preserving the integrity <strong>of</strong> mucosal structure and function <strong>of</strong> the intestine, appear to be crucial and many clinical trials have been performed in order to demonstrate its effect, given either parenterally or orally. There is, however, no clear evidence so far that glutamine is useful in improving outcome in these patients and its use needs further investigation. 3 Liver disease is a main metabolic complication <strong>of</strong> PN, but can occur in any cancer patient due to therapy or to graft-versus-host disease. Its best prevention is avoidance <strong>of</strong> prolonged enteral fasting, infections, and surgery. As far as concerns the PN admixture, the lower the calorie content, the lower the probability <strong>of</strong> developing liver disease: as a rule, calorie intake should not exceed the (theoretical) needs, so as to reduce the risk <strong>of</strong> hepatic fat deposition. The evolution toward severe liver damage is more frequent in low-birth weight neonates and in children on long-term parenteral nutrition (months, years). This having been said, in any given situation it is more likely that liver involvement is related to the underlying disease than to well-conducted parenteral nutrition. 1,2,6 In conclusion, even in the absence <strong>of</strong> RCT clearly demonstrating its efficacy on disease outcome, artificial nutritional support seems to be useful in bone marrow transplanted patients in order to avoid or correct malnutrition, which is a frequent and multifactorial complication <strong>of</strong> the procedure. An experienced team (nurses, surgeon, pediatrician, pharmacist) is the best preventive measure against technical and metabolic complications. References 1. A.S.P.E.N. Board <strong>of</strong> Directors. Guidelines for the use <strong>of</strong> parenteral and enteral nutrition in adult and pediatric patients. JPEN 1993; 17:1SA- 38SA. 2. Candusso M. Nutrizione del bambino ospedalizzato: principi e pratica. M&B 2000; 19:289-94. 3. Demirer S, Aydintug S, Ustun C, et al. Comparison <strong>of</strong> the efficacy <strong>of</strong> medium chain triglycerides with long haematologica vol. 85(supplement to n. 11):November 2000
61 chain triglycerides in total parenteral nutrition in patients with hematologic malignancies undergoing peripheral blood steam cell transplantation. Clin Nutr 2000; 19:253-8. 4. Klein S, Kinney J, Jeejeebhoy K et al. Nutrition support in clinical practice: review <strong>of</strong> published data and recommendations for future research directions. JPEN 1997; 21:133-56. 5. Lipman T. Grains or veins: is enteral nutrition really better than parenteral nutrition? A look at the evidence. JPEN 1998: 22:167-82. 6. Mauer AM, Burgess JB, Donaldson S, et al. Special nutritional needs <strong>of</strong> children with malignancies: a review. JPEN 1990; 14:315-24. 7. Schloerb PR, Skikne B. Oral and parenteral glutamine in bone marrow transplantation: a randomized, double-blind study. JPEN 1999; 23:117-22. haematologica vol. 85(supplement to n. 11):November 2000
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