عوارض تغذیه بیش از حد در بیماران بخش ویژه:
ساعت ٩:٥٤ ‎ق.ظ روز ۱۳٩٠/۱۱/۱۱   کلمات کلیدی:

گاهی فکر می کنیم تغذیه بیش از حد و پر کالری به درمان بیماری های جسمی و تنفسی کمک می کند در حالیکه داستان به این سادگی ها نیست:

Be Alert for Overfeeding
Jason Sperry MD
Heidi L. Frankel MD
Providing inadequate caloric supplementation during times of critical illness is associated with negative effects. Equally as detrimental is the administration of excessive calories, or overfeeding. Overfeeding is associated with significant metabolic disorders including hyperglycemia, elevated serum triglycerides, and subsequent hepatic steatosis. In addition, overfeeding may cause a significant increase in CO2 production that can be deleterious to those with respiratory insufficiency and may make ventilator weaning challenging (or impossible).
What to Do
To avoid overfeeding, accurate estimates of energy and caloric requirements of critically ill patients are required. Critically ill patients typically undergo a period of catabolism, which can be associated with significant body protein loss, depending on the severity of critical illness and the length of the catabolic process. Calculation of nitrogen balance can quantify the extent of catabolism and evaluate the efficacy of supplemental nutrition in these patients. Nitrogen balance is calculated by subtracting total nitrogen losses (urine, stool, insensible losses) from nitrogen intake (1 g nitrogen per 6.25 g of protein). The primary mode of nitrogen excretion is urinary, and 24-hour urine collection for urinary urea nitrogen (UUN) is the most common means of measurement. Fecal and insensible losses are typically small but estimated. UUN can be a poor estimate of overall nitrogen losses in burn patients, when urine output is low (<1L/d), in patients with acute or chronic renal failure and in patients with enteric fistulas where exceedingly high losses occur in the fistulae output.
Alternatively, nutritional assessment can be accomplished via indirect calorimetry, where O2 consumption and CO2 production are measured and a respiratory quotient (RQ) is calculated at the patient's bedside. An RQ of 0.7 is typical of fat oxidation and an RQ of <0.7 suggests ketosis, lipolysis, and underfeeding. An RQ ≥1.0 exemplifies primary carbohydrate metabolism and possible overfeeding. Because of the accuracy of measurements required for indirect calorimetry, it is generally limited to those who are on ventilatory support. Since changes in minute ventilation, cardiac output, fraction of inspired
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oxygen, and acid-base status can affect CO2 production and O2 uptake, indirect calorimetry must also be performed, with the patient at a relative steady state for maximal accuracy.
Suggested Readings
Brandi LS, Bertolini R, Santini L, et al. Effects of ventilator resetting on indirect calorimetry measurement in the critically ill surgical patient. Crit Care Med. 1999;27(3):531–539.
Dickerson RN, Tidwell AC, Minard G, et al. Predicting total urinary nitrogen excretion from urinary urea nitrogen excretion in multiple-trauma patients receiving specialized nutritional support. Nutrition. 2005;21(3):332–338.
Hunter DC, Jaksic T, Lewis D, et al. Resting energy expenditure in the critically ill: estimations versus measurement. Br J Surg. 1988;75(9):875–878.
Long CL, Schaffel N, Geiger JW, et al. Metabolic response to injury and illness: estimation of energy and protein needs from indirect calorimetry and nitrogen balance. J Parenter Enteral Nutr. 1979;3(6):452–456.
Mann S, Westenskow DR, Houtchens BA. Measured and predicted caloric expenditure in the acutely ill. Crit Care Med. 1985;13(3):173–177.