Comparison between a high-perfomance liquid chromatographic method and a gas chromatographic method for the quantification of serum thiopental for the diagnosis of brain death in critically ill patients

Thiopental, as many other centrally acting drugs, can depress the electroencephalogram, so serum levels of these drugs must be well below their therapeutic range for a reliable diagnosis of brain death. While for many of these drugs fast and simple immunossays are available, for thiopental only chromatographic tests are available. We compared a high-performance liquid chromatographic method with an ultraviolet detector (HPLCUV) and a gas chromatographic method with a flame ionization detector (GC-FID) for the quantification of serum thiopental. From January to July 2011, serum samples collected from 25 critically ill patients were processed either by both HPLC-UV and GC-FID for the quantification of serum thiopental. A satisfactory correlation was found between the methods. Although both methods were reliable, easy to perform and fast enough, the GC-FID method seemed to fit to our needs better than the HPLC-UV method. This was due to the extreme sensitivity of GC in quantifying serum thiopental well below the therapeutic level, and also because GC is easier and faster to perform in a setting which usually needs a rapid turn-around time.