Route of PN Administration Peripheral versus Central Vein Infusion

PN can be administered via a smaller peripheral vein (e.g., cephalic or basilic vein) or via a larger central vein (e.g., superior vena cava) (see Fig. 100-1). PPN is infused via a peripheral vein and generally is reserved for short-term administration (up to 7 days) when central venous access is not available. PN formulations are hyperosmolar, and PN infusion via a peripheral vein can cause thrombophlebitis. Factors that increase the risk of phlebitis include high solution osmolality, extreme pH, rapid

infusion rate, vein properties, catheter material, and infusion time via the same vein. The osmolarity of PPN admixtures should be limited to 900 mOsm/L or less to minimize the risk of phlebitis. The approximate osmolarity of a PN admixture can be calculated from the osmolarity of the individual components:

• Amino acids approximately 10 mOsm/g (or 100 mOsm/1% final concentration in PN)

• Dextrose approximately 5 mOsm/g (or 50 mOsm/1% final concentration in PN)

FIGURE 100-1. Selected vascular anatomy. (Reprinted from Krzywda EA, Andris DA, Edmiston CE, Wallace JR. Parenteral Access Devices. In:Gottschlich MM, ed. The A.S.P.E.N. Nutrition Support Core Curriculum: A Case-Based Approach—The Adult Patient. Silver Spring, MD: American Society for Parenteral and Enteral Nutrition:2007:300-322 with permission from the American Society for Parenteral and Enteral Nutrition (A.S.P.E.N.). A.S.P.E.N. does not endorse the use of this material in any form other than its entirety.)

FIGURE 100-1. Selected vascular anatomy. (Reprinted from Krzywda EA, Andris DA, Edmiston CE, Wallace JR. Parenteral Access Devices. In:Gottschlich MM, ed. The A.S.P.E.N. Nutrition Support Core Curriculum: A Case-Based Approach—The Adult Patient. Silver Spring, MD: American Society for Parenteral and Enteral Nutrition:2007:300-322 with permission from the American Society for Parenteral and Enteral Nutrition (A.S.P.E.N.). A.S.P.E.N. does not endorse the use of this material in any form other than its entirety.)

• Sodium (chloride, acetate, and phosphate) = 2 mOsm/mEq

• Potassium (chloride, acetate, and phosphate) = 2 mOsm/mEq

• Magnesium sulfate = 1 mOsm/mEq

PPN admixtures should be coinfused with IV lipid emulsion when using the 2-in-1 PN because this may decrease the risk of phlebitis due to the iso-osmolarity and close to neutral pH of IV lipid emulsions (Table 100-2). Infectious and mechanical complications may be lower with PPN compared with central venous PN administration.

However, because of the risk of phlebitis and osmolality limit, PPN admixtures have low macronutrient concentrations and therefore usually require large fluid volumes to meet a patient's nutritional requirements. Given these limitations, every effort should be made to obtain central venous access and initiate central PN when it is unlikely a patient will tolerate enteral or oral nutrition within approximately 7 days.

Central PN refers to the administration of PN via a large central vein, and the catheter tip must be positioned in the vena cava (see Fig. 100-2). Central PN allows the infusion of a highly concentrated, hyperosmolar nutrient admixture. The typical os-molarity of a central PN admixture is about 1,500 to 2,000 mOsm/L. Central veins have much higher blood flow, and the PN admixture is diluted rapidly on infusion, so phlebitis is usually not a concern. Patients who require PN therapy for longer periods of time (greater than 7 days) should receive central PN. One limitation of central PN is the need for placing a central venous catheter and an x-ray to confirm placement of the catheter tip. A commonly used central catheter for PN infusion is a peripherally inserted central venous catheter (PICC) which is inserted into a peripheral vein but the catheter tip is placed in the superior vena cava (see Fig. 100-3). Central venous catheter placement may be associated with complications, including pneumothorax, arterial injury, air embolus, venous thrombosis, infection, chylothorax, and brachial plexus injury.1,21

FIGURE 100-2. Percutaneous nontunneled catheter. (Reprinted from Krzywda EA, Andris DA, Ed-miston CE, Wallace JR. Parenteral Access Devices. In:Gottschlich MM, ed. The A.S.P.E.N. Nutrition Support Core Curriculum: A Case-Based Approach—The Adult Patient. Silver Spring, MD: American Society for Parenteral and Enteral Nutrition:2007:300-322 with permission from the American Society for Parenteral and Enteral Nutrition (A.S.P.E.N.). A.S.P.E.N. does not endorse the use of this material in any form other than its entirety.)

FIGURE 100-2. Percutaneous nontunneled catheter. (Reprinted from Krzywda EA, Andris DA, Ed-miston CE, Wallace JR. Parenteral Access Devices. In:Gottschlich MM, ed. The A.S.P.E.N. Nutrition Support Core Curriculum: A Case-Based Approach—The Adult Patient. Silver Spring, MD: American Society for Parenteral and Enteral Nutrition:2007:300-322 with permission from the American Society for Parenteral and Enteral Nutrition (A.S.P.E.N.). A.S.P.E.N. does not endorse the use of this material in any form other than its entirety.)

FIGURE 100-3. Peripherally inserted central venous catheter. (Reprinted from Krzywda EA, Andris DA, Edmiston CE, Wallace JR. Parenteral Access Devices. In: Gottschlich MM, ed. The A.S.P.E.N. Nutrition Support Core Curriculum: A Case-Based Approach—The Adult Patient. Silver Spring, MD: American Society for Parenteral and Enteral Nutrition:2007:300-322 with permission from the American Society for Parenteral and Enteral Nutrition (A.S.P.E.N.). A.S.P.E.N. does not endorse the use of this material in any form other than its entirety.)

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