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Parenteral nutritional support solutions can be designed to deliver adequate nutrients to most patients. The basic parenteral solution is composed of dextrose, amino acids, and water. Electrolytes, minerals, trace elements, vitamins, and medications can also be added. Most commercial solutions contain the monohydrate form of dextrose that provides 3.4 kcal/g. Crystalline amino acids are available in a variety of concentrations, so that a broad range of solutions can be made up that will contain specific amounts of dextrose and amino acids as required.
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Typical solutions for central vein nutritional support contain 25–35% dextrose and 2.75–6% amino acids depending upon the patient's estimated nutrient and water requirements. These solutions typically have osmolalities in excess of 1800 mOsm/L and require infusion into a central vein. A typical formula for patients without organ failure is shown in Table 29–4.
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Solutions with lower osmolalities can also be designed for infusion into peripheral veins. Typical solutions for peripheral infusion contain 5–10% dextrose and 2.75–4.25% amino acids. These solutions have osmolalities between 800 and 1200 mOsm/L and result in a high incidence of thrombophlebitis and line infiltration. These solutions will provide adequate protein for most patients but inadequate energy. Additional energy must be provided in the form of emulsified soybean or safflower oil. Such intravenous fat solutions are currently available in 10% and 25% solutions providing 1.1 and 2.2 kcal/mL, respectively. Intravenous fat solutions are isosmotic and well tolerated by peripheral veins.
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Typical patients are given 200–500 mL of a 20% solution each day. As much as 60% of total calories can be administered in this manner.
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Intravenous fat can also be provided to patients receiving central vein nutritional support. In this instance, dextrose concentrations should be decreased to provide a fixed concentration of energy. Intravenous fat is associated with less glucose intolerance, less production of carbon dioxide, and less fatty infiltration of the liver and has been increasingly utilized in patients with hyperglycemia, respiratory failure, and liver disease. Intravenous fat has also been increasingly used in patients with large estimated energy requirements. The maximum glucose utilization rate is approximately 5–7 mg/min/kg. Patients who require additional calories can be given them as fat to prevent excess administration of ...