Trace elements – Commentary

This is a timely review, documenting the important subject of trace element measurement and replacement in the critically ill population. As stated in this review, they are rarely considered in the day-to-day management of the critically ill patient.

Trace elements are essential nutrients with a large range of functions. Deficiencies do occur, not only because of pre-morbid chronically low levels but also due to increased losses through the gut, urine and skin during critical illness. Trace element deficiencies appear to be most severe in those patients who suffer major burn injuries where losses of trace elements through burn wound exudate are significant. These may delay wound healing, which together with graft failure is a major issue after a burn injury. In this particular group of patients it may not only just be necessary to meet normal trace element requirements, but it is also possible that in large burns, pharmacological manipulation (i.e. to above recommended daily requirements) may have some morbidity and mortality benefit.

It is important however, to remember that trace elements may be toxic and prolonged replacement of high doses may be deleterious. This review clearly documents these issues. Some trace elements such as aluminium are elevated after severe burn injuries and attempts to minimise aluminium loading are necessary to hasten the patient's skeletal recovery.

One of the problems in the measurement of trace elements is that they are bound to protein carriers, so static measurements may not be representative and can be misleading. Moreover, replacement in those patients with hypoproteinaemia may be futile, as the trace element may not be delivered to the tissues.

In summary, there is little evidence for giving pharmacological doses of trace elements to burns patients despite this being common practice in many units. There is insufficient evidence to make any recommendations in a general critically ill patient group. Common sense suggests that treatment should be directed at correcting deficiencies, which interestingly may often be possible with standard nutritional therapy.

Further work needs to be carried out to establish optimal doses and duration of treatment especially in burns patients.