WordNet (r) 3.0 (2006):

operate on
    v 1: perform surgery on; "The doctors operated on the patient
         but failed to save his life" [syn: operate on, operate]

Moby Thesaurus II by Grady Ward, 1.0:

28 Moby Thesaurus words for "operate on":
   act on, act upon, affect, bandage, bathe, care for, concentrate on,
   cure, diagnose, doctor, flux, focus on, give care to, heal,
   influence, massage, minister to, nurse, physic, plaster, poultice,
   purge, remedy, rub, splint, strap, treat, work on