Fig. 2. Production of interleukin (IL)-1β (A ), IL-6 (B ), and tumor necrosis factor (TNF) α (C ) by peripheral blood mononuclear cells in the two study groups. Levels of the proinflammatory cytokines were more elevated in the patient-controlled epidural analgesia (PCEA) group. Values are mean (±SEM). PA = preemptive analgesia.