The Effect of Scalp Block on Surgical Pleth Index(SPI) During a Mayfield Head-holder Insertion in Neurosurgery : a Randomized Control Trial

Study design is a randomized controlled trial Participants include adult neurosurgical patients scheduled to have a Mayfield head-holder insertion for supratentorial craniotomy Intervention is a scalp block prior to a Mayfield head holder insertion. Comparison is 'no scalp block' Outcome is surgical plethysmographic index (SPI) responses during/after a Mayfield head holder insertion Sample size includes 30 cases (15 cases per arm)

The eligible neurosurgical patients will be randomly allocated, by a concealed randomization process, to receive or not to receive a scalp block after induction and intubation with propofol/fentanyl and cisatracurium. Surgical plethysmographic index, direct arterial blood pressure, heart rate (EEG), End tidal Carbondioxide, Bispectral/entropy (40-60) will be recorded every one minute before/after induction and intubation, before/after the scalp block, and before/after the Mayfield head-holder insertion. The Mayfield head-holder insertion will be performed by a neurosurgeon who will be blinded to the allocated groups.

Data analysis is performed to compare the change of SPI during and after the Mayfield head-holder insertion from the baseline in both groups by using repeated measure ANOVA at the significant level of 0.05.