Is the blade a separate subtool? I wasnt really sure by the answer you gave cryrid.
If not, it would be worth while spliting the mesh into polygroups and then into subtools as you can subd each subtool to the maximum polycount that your machine can handle.
Another option would be to retopo the blade and re-project.
Also using HD sculpting would work. You can sculpt with 000's of millions with that turned on