UV-radiation reduces bacterial contamination when using an autotransfusion unit

Objective: To investigate the effects of UV-radiation of autologous blood on bacteria and red blood cells when using intraoperative sampling of autologous blood using a cell separator - an established method for reducing the need for donor blood during surgery - which is reported to have a bacterial contamination rate of 5-75%, due mainly to coagulase-negative staphylococci (CNS). Methods: Cell-separator blood was diluted to a haematocrit level permitting transmission of 1% of the UV-radiation used in this study ( lambda 254 nm, coat thickness 1 mm). CNS samples were irradiated for 2, 4, 10, 20 and 30 seconds. Free haemoglobin and methaemoglobin levels were measured, and erythrocytes examined microscopically at the end of the procedure. Results: Blood samples had to be diluted to a haematocrit of 1% to permit transmission of 1% of the UV light. The optimal irradiation duration was 4 seconds, when bacteria were completely eliminated. Longer irradiation durations were associated with increasing levels of free haemoglobin and methaemoglobin, the levels of which at 4 seconds exposure were 12.5 mg/L and 15.5%, respectively. Conclusions: It is possible to prevent CNS contamination of cell-separator blood by irradiation with UV light. Prior to clinical application, however, the method will need to be modified to minimize side effects and increase its decontamination efficacy.