If a patient is entirely PN dependent, certain micro-nutrients need to be provided. Some PN solutions require the addition of carnitine and selenium (if not provided in multi-trace element solutions) and iron dextran (if the patient is not receiving transfusions). All serum levels should be monitored on a monthly basis or every 6-12 months if in the long-term phase of support. There may be other micro-nutrients not yet identified that may be deficient in the purified PN solution, which is another reason to begin enteral feedings as soon as feasible. Monitoring for excess losses is also important. For example, with increased stool/ostomy losses, the patient may require increased zinc in the PN solution (Table 4).
Excess micronutrients can be caused by contamination, such as the case with aluminum, or clearance. Copper and manganese can accumulate and become directly hepatotoxic since both elements depend on the biliary pathway for excretion. Therefore, in the presence of cholestasis, there will be increased intrahepatic accumulation. Manganese has also been reported to deposit in brain tissue, so copper and manganese levels should be monitored routinely.
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