DOI: 10.1097/CCM.0B013E318162B8DE

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PMID: 18216642

Issn Print: 0090-3493

Publication Date: 2008/02/01


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The need for precise dose information of sodium selenite in the SIC study and rectification of GPx-3 plasma concentration

Xavier Forceville

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The SIC study is very interesting and nicely reported (1). However, there is a lack of precision regarding dosages, and this must be clarified since the study is of great clinical interest. Precision of dose is also required to make accurate comparisons with other studies and meta-analyses. In the abstract and the Methods sections, it is reported that “the patient received 1000 μg sodium selenite as a 30-min bolus injection followed by 14 daily continuous infusion of 1000 μg intravenously or placebo.” Therefore, taking into account the respective molecular weight of sodium selenite (Na2SeO3, 172.9 g/mol) and selenium (Se, 78.9 g/mol), this should have corresponded to a total of selenium administration of 6.9 mg. However, in the Methods section the authors state that “the total amount of selenium was 15 mg within 14 days.” This amount corresponds to approximately twice the dose of sodium selenite that they mentioned in the previous sentence. The authors should specify precisely whether the administered dose was a) 1000 μg of sodium selenite as a bolus followed by a 14-day continuous infusion of 1000 μg intravenously, corresponding to 7 mg of selenium within 14 days; or b) 1000 μg of selenium, as sodium selenite, as a bolus followed by a 14-day continuous infusion of 1000 μg intravenously, corresponding to 15 mg of selenium within 14 days. This is a very important point.
In addition, the authors need to clarify a point made in the introduction (1) referring to the supposed correlation between GPx-3 activity and severity of the diseases: “The GPx-3 activity in serum, which is the main activity in serum, is negatively correlated with the severity of the diseases.” The cited study, published in Critical Care Medicine in 1998, of which I am the first author, does not support a negative correlation of GPx-3 activity with the severity of diseases (2). On the contrary, in the 1998 study we only measured plasma selenium concentration and not GPx (see Methods section and also Discussion): “Nevertheless, we did not measure plasma or tissue SeGPx concentrations in our patients” (Discussion, p. 1541, third column, third paragraph, line 11). In the Discussion, however, we did mention that the observed decrease of plasma selenium concentration might be related to selenium tissue uptake for synthesis of selenoenzymes like glutathione peroxidase (in tissues).
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