If parenteral nutrition is determined to be beneficial, the two venous access sites are central and peripheral. Cancer patients usually have central IV catheters to accommodate multiple IV therapies. If this is not the case, a peripheral catheter can be placed, although care must be taken to avoid overuse of the peripheral accesses with nutritional support and anticancer therapies. Numerous peripheral infusions and venesections can result in vessel sclerosis. The following discussion highlights both types of access:[27,29]
Central venous catheters
- May utilize single-, double-, or triple-lumen catheters for delivery of medication, blood and blood products, and parenteral nutrition without interruption.
- Placement of lines should be done by an experienced surgical team to minimize risk of pneumothorax, hemothorax, hematuria, aneurysms, venous or nerve damage, and microbial contamination. Evaluation of catheter tip location and site care is critically important.
- Short-term support can be provided via Cordis or Swan Ganz catheters; long-term support can be provided via Hickman or Broviac catheters.
Peripheral venous catheters
- A short canula is placed in the arm (either the percutaneous subclavian vein in adults or the arteriovenous fistulas are used as access sites).
- Catheters must be located in peripheral vessels with high blood flow to facilitate rapid dilution of the formula; access may be alternated to avoid thrombophlebitis.
- Peripherally inserted central catheters (PICC lines) are used for long-term support; the tip of the catheter must be placed in a central vein such as the superior or inferior vena cava to decrease risk of infection and thrombosis.
Parenteral nutrition formulas are tailored to individual clinical status and nutritional needs. The formulas contain a combination of amino acids, dextrose, lipids, vitamins, minerals and trace elements, fluids, electrolytes, and, possibly, additives such as insulin, heparin, and antacids.
Solutions running through peripherally placed lines must be altered by reducing the percentage of calories from carbohydrates (hypertonic) and increasing the percentage from lipids (isotonic). Peripheral solutions with a final dextrose concentration lower than 10% and an osmolarity lower than 900 mOsm/kg are generally well tolerated. The mandatory alteration in macronutrients can present problems with delivery of recommended calories/nutrients.
Central infusions are not limited by osmolarity because they use a large vein; this feature makes central venous access a good choice for severely stressed, hypermetabolic individuals and/or individuals requiring a fluids restriction.
Many drugs and compounds are not compatible with parenteral solutions and should not be added to the solutions or even run through parenteral solution-designated lines to avoid the chance of interaction or precipitation. Pharmacists should be consulted in the preparation of parenteral nutrition solutions and before any additional medications or compounds are added.
Incompatibility with drugs is just one of a number of possible complications associated with parenteral nutrition administration. Complications can be categorized as mechanical (vein thrombosis, pneumothorax, and catheter tip misplacement) or metabolic (hyperglycemia/hypoglycemia, hypokalemia, and elevated liver function tests). Because of the precision that is required to order, administer, and maintain this type of support, trained and experienced medical personnel should be involved. Many facilities have dedicated nutritional support multidisciplinary teams.