This study looked at parenteral administration of selenium to septic patients and subsequently monitored dynamic changes of selected activities of antioxidant enzymes and the development of clinical status.

Patients will be divided into two groups. Se-group who received selenium supplementation during hospitalization in the form of sodium selenite pentahydrate at 750 mg/day for 6 days immediately after admission to our department (1000 mg of sodium selenite pentahydrate = 333 micrograms of selenium) (Selenase, Vivax; selenium hereinafter).

The placebo group will receive continuous saline NaCl 50 ml/day for 6 days as a continuous infusion (excluding additional infusion therapy). Patients will be further divided into subgroups according to OI on the day of admission to ICU. The oxygenation index (OI) PaO2/FiO2 (partial pressure of oxygen in arterial blood/ fraction of inspired oxygen) ratio in patients will be calculated daily.

The determination of biochemical and hematological parameters of blood samples will be as a part of the routine diagnostic methods. Data collection for the Se-AOX study will be performed at two-day intervals: T1 (1st-2nd day), T2 (3rd-4th day) and T3 (5th-6th day). Kinetic methods for estimating the activities of glutathione peroxidase (GPx, E.C. 1.11.1.9), glutathione reductase (GR, E.C.1.6.4.2) will be performed using a kit (Sigma-Aldrich, Germany) and that of superoxide dismutase (SOD, E.C. 1.15.1.1) by means of the SOD-Assay Kit-WST (Fluka, Japan) following the user manual provided.

Inclusion Criteria:

• sepsis, severe sepsis or septic shock, APACHE II score between 19 and 24 points after admission

Exclusion Criteria:

• mechanical ventilation for less than 24h, neuromuscular disease and terminal illness were also excluding criteria

Critically ill patients with APACHE II score between 19 and 24 points after admission with sepsis, severe sepsis or septic shock during hospitalization as defined by the International Sepsis Definitions Conference