Effect of pre-incisional anterior scalp block on intraoperative opioid consumption in adult patients undergoing elective craniotomy to remove tumor: study protocol for a randomized double-blind trial

Background: Scalp block is a selective nerve block technique to inhibit the afferent input from nerves that innervate the scalp, including supratrochlear, supraorbital, zygomaticofacial, and zygomaticotemporal nerves for the anterior scalp. The greater and lesser occipital nerves innervate the posterior scalp. Methods/Design: This study is a prospective, randomized, double-blind, placebo-controlled trial, which will be performed to examine the benefits of a pre-incisional anterior scalp block with 0.5% bupivacaine in adult patients who are scheduled for supratentorial craniotomy to remove tumor. Primary outcome will be the difference of intraoperative fentanyl consumption between patients who receive anterior scalp block with 0.5% bupivacaine and those who receive normal saline solution administration. Secondary outcomes will be the hemodynamic changes from preoperative baseline at a skull pin insertion and the time from the end of surgery to successful extubation. Discussion: Skull pin insertion is known as the strongest stimulus prior to craniotomy. The results from previous studies are inconclusive regarding the advantage of scalp block as a pre-emptive analgesic technique. This study will fill this knowledge gap, and examine whether this technique is worth performing as a standard technique. Trial registration: ClinicalTrials.gov identifier: NCT02057367; registered in February 2014. Ethics: This study protocol was approved by the Ethics Committee of Maharaj Nakorn Chiang Mai Hospital, Chiang Mai University, Thailand (approval number: ANE-2556-01510) and will be performed in accordance with the Declaration of Helsinki. Informed consent: Written informed consent will be obtained from participants prior to inclusion in this study