Hemodynamic and bispectral index changes following skull pin attachment with and without local anesthetic infiltration of the scalp

We studied the hemodynamic and bispectral index (BIS) changes in 44 patients undergoing cervical diskectomy with attachment of a Gardner-Wells tong (with two sharp conical pins) to the skull to facilitate intraoperative bone graft insertion. Patients were induced with fentanyl, thiopentone, and rocuronium and maintained with 66% nitrous oxide and 0.5% isoflurane, Before insertion of the pins, patients were randomly allocated to have either saline or lidocaine infiltration of the scalp at the proposed pin sites. Two minutes later, the pins were driven into the scalp. The BIS, mean arterial pressure (MAP), and heart rate (HR) were recorded before (baseline) and at 30, 60, 90, and 120s after pin insertion. Data were compared with the baseline values and between the groups. A significant increase in MAP and HR occurred throughout the study period in the saline group. Skull pinning increased BIS throughout the study period in the saline group only, with maximal increases observed at 90 and 120s (66.1 +/- 6.3 at 90s and 65.7 +/- 6.4 at 120s versus a baseline value of 62 8, P < 0.001). The increase in BIS was significant in the saline group compared with the lidocaine group at each time point. In conclusion, increases in MAP, HR, and BIS produced by skull pinning were prevented by prior local anesthetic infiltration.