Manganese Provision in Parenteral Nutrition: An Update

Manganese (Mn) is an essential micronutrient required for the activity of metalloenzymes. It is an essential component of parenteral nutrition (PN), but requirements are low. Mn status is difficult to assess, with the commonest method being measurement of its concentration in whole blood. This method has limitations, including artifactually high concentrations resulting from contamination of specimen tubes. Mn toxicity is a well-recognized complication of PN, the risk of which increases if there is cholestasis or if the patient has received high doses. It usually presents with parkinsonian-like symptoms but may be detected presymptomatically as hypermanganesemia or as increased signal intensity of the basal ganglia upon T1-weighted magnetic resonance imaging. Caution is necessary when providing Mn for patients on long-term PN (>1 month). It is advisable to withhold supplementation if hypermanganesemia or cholestasis develops. Deficiency of Mn is rare in patients treated with PN. PN regimens are contaminated with Mn in amounts likely to meet requirements. Consequently, it is debated whether PN should be routinely supplemented with Mn. The currently recommended dose of Mn in adults treated with PN is 55 g/d, but the doses provided by most currently available multi-trace element products exceed this. In response to calls for new products to be developed, 2 new multi-trace element products are currently available in Europe that provide Mn doses of 55 g/d. Once these products are in general use, it is likely that the incidence of Mn toxicity will decrease.