Does intraoperative analgesia modify the immune response in surgical patients?

The effect of epidural analgesia combined with inhalational anesthesia on the perioperative immune response was measured by using two-color analysis for the classification of functional lymphocyte subpopulations. Twenty-eight patients undergoing upper abdominal surgery were divided into four groups: group 1, isoflurane and with N₂O group 2, sevoflurane with N₂O; group 3, epidural analgesia plus isoflurane with N₂O; and group 4, epidural analgesia and sevoflurane with N₂O. Peripheral lymphocyte subpopulations were measured before, during, and after the operation by using anti-CD4 and anti-CD8 monoclonal antibodies. Moreover, two-color analysis was performed using two kinds of monoclonal antibodies: anti-CD4 and anti-CD29W, and anti-CD4 and anti-CD45R. A decrease in CD4⁺ cells and CD4⁺ CD29W⁺ cells (helper-inducer T lymphocytes) was observed after the operation in groups 1, 2, and 4. Additionally, stress hormones such as epinephrine (EP), norepinephrine (NE), and cortisol (CO) were measured. EP was increased during and after the operation in groups 1 and 2, and after the operation in group 4, but the level was maintained throughout the study in group 3. In conclusion, prevention of noxious stimuli originating from operative fields by epidural block could prevent the increase in EP and the reduction of helper-inducer T cells in patients undergoing upper abdominal surgery.