CHAPTER 3


of the risk for aluminum toxicity, it is recommended that aluminum intake and exposure be minimized whenever possible (other potential sources of aluminum include heparin, albumin, blood products, and L-cysteine).37 Moreover, because some commercially available PN admixtures have been shown to exceed the widely accepted safe limit for aluminum, regulatory action to reduce aluminum content in PN solutions is needed.38


Additives


Glutamine Glutamine, one of the nonessential AAs, has garnered attention due to its role in immune function. Glutamine is not stable in solution and is typi- cally provided as a glutamine–alanine dipeptide. Research on parenteral glutamine supplementation has been mixed; 1 meta-analysis from 2017 indicated that glutamine-supplemented PN was associated with signifi- cant reductions in hospital mortality, infection rates, and hospital length of stay among adults who were critically ill.39


However, due to concerns


regarding the reliability of current evidence and other trials suggesting potentially increased mortality risk associated with parenteral gluta- mine, the most recent ASPEN critical care guidelines recommend that parenteral glutamine supplementation should not be routinely provided in the critical care setting.5


Carnitine


Carnitine is required for metabolism of fatty acids in the mitochondria. Healthy adults synthesize carnitine from methionine and lysine. Car- nitine is not routinely added to adult PN formulas. Cases of carnitine deficiency, though rare, have been reported in patients with short bowel syndrome.40


Clinical and laboratory symptoms of carnitine deficiency


include muscle weakness, hypotonia, elevated triglycerides, hyperbiliru- binemia, and hypoglycemia. A small 2017 study investigating the clinical utility of carnitine- supplemented PN found that carnitine supplementation was safe and was associated with a significant decrease in postoperative C-reactive protein levels, suggesting a possible benefit in postoperative inflamma- tory recovery.41


Further studies are needed to determine clinical benefits


before routine carnitine supplementation can be recommended in adult PN solutions.


44


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