Nutritional Support and the Surgical Patient

Yvonne Huckleberry

Disclosures

Am J Health Syst Pharm. 2004;61(7) 

In This Article

Carbohydrates Versus Lipids

The carbohydrate and lipid components of the PN formulation should be individualized for patients whenever possible. Carbohydrates are an important protein-sparing fuel for glucose-dependent tissues, such as bone marrow, erythrocytes, and brain tissue. Providing a minimum of approximately 100-150 g of carbohydrate daily will suppress gluconeogenesis and prevent ketosis.[9,37] In contrast, glucose oxidation can reach a threshold at approximately 5 mg/kg/min.[72,73,74] Infusions in excess of the oxidative capacity can lead to hepatic steatosis, increased rates of carbon dioxide production, and lipogenesis.[73,74] Carbohydrates are typically provided as 70-85% of nonprotein calories.[72]

Intravenous lipids provide an alternative source of nonprotein calories. Including lipids as a component of the PN formulation is suggested to reduce hepatic complications associated with PN, reduce carbon dioxide production, and improve glycemic control.[75] In addition, lipids provide the essential long-chain fatty acids, linoleic acid, and α-linolenic acid. A minimum of 1-2% of calories as linoleic acid is recommended to prevent essential fatty acid deficiency.[76] This minimum can be provided as 500 mL of 20% lipids once weekly.[77] However, excessive amounts of linoleic acid have been associated with the production of immunosuppressive, proinflammatory eicosanoids. For this reason, a maximum infusion rate of 2.5 g/kg/day has been recommended, with the rate further restricted in critically ill patients to 1 g/kg/day.[76] Lipids are typically provided as 15-30% of nonprotein calories.[72]

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