Contralateral cerebral hemoglobin oxygen saturation changes in patients undergoing thoracotomy with general...

Perioperative analgesia during thoracotomy is often achieved by combining paravertebral block (PVB) with general anesthesia (GA). Functional near-infrared spectroscopy (NIRS) can detect changes in cerebral oxygenation resulting from nociceptive stimuli in the awake state or under sedation. We used NIRS to measure changes in cerebral blood flow provoked by thoracotomy incision made under GA and determine how these changes were influenced by supplementation of GA with PVB.

Thirty-four patients undergoing elective thoracotomy were enrolled. Patients were randomly assigned to a group receiving only GA, or GA combined with PVB (GA + PVB). Changes in cerebral oxygenated hemoglobin (ΔO₂Hb), deoxygenated-Hb (ΔHHb), and total-Hb (ΔtotalHb) were evaluated by NIRS as surgery began.

In the GA group, ΔO₂Hb was significantly higher in the hemisphere contralateral to the side of surgery when the incision was made and 2 min after incision compared with the ipsilateral side (start of surgery, P < 0.01; 2 min, P < 0.05). In contrast, there were no significant changes in the ΔO₂Hb at any of the time points in the GA + PVB group. Comparable with ΔO₂Hb, the concentration of ΔtotalHb was significantly higher in the contralateral hemisphere in the GA group at the start of surgery (P < 0.05).

Changes in the cerebral O₂Hb concentration were detected by NIRS immediately after surgical incision under GA, but not in the presence of a PNB. NIRS could be used to monitor surgical pain. PVB inhibited changes in oxygenation induced by incision-provoked pain.