Regional scalp block for postcraniotomy analgesia: a systematic review and meta-analysis

Abstract

Background: Up to two-thirds of patients report moderate to severe surgical site pain after craniotomy procedures, and there is understandable reluctance to manage these symptoms with systemic opioids that may impair neurological assessment. Furthermore, there is a lack of consensus and evidence concerning alternative analgesia strategies for cranial neurosurgery. Regional scalp block (RSB) is an established technique that involves infiltration of local anesthetic (LA) at well-defined anatomical sites targeting the major sensory innervation of the scalp. However, the efficacy of RSB in reducing postoperative pain remains unclear. In this study, we sought to systematically identify and review randomized controlled trials (RCTs) of RSB and synthesize an overall estimate of efficacy in a quantitative meta-analysis.

Methods: Medline, EMBASE, and the Cochrane Central Register of Controlled Trials databases were searched for all RCTs evaluating the effect of RSB on postoperative pain after craniotomy. Titles, abstracts, and papers were reviewed independently by 2 authors against predefined inclusion criteria. Two authors independently assessed the quality of included studies and extracted data on patient-reported pain scores, other analgesia requirements, and complications of RSB. Pain scores were scaled to a common 0 to 10 interval with higher scores indicating more severe pain. Meta-analysis of the pooled treatment effect was performed with a random-effects inverse-variance weighted model; heterogeneity was quantified with the I(2) statistic.

Results: The literature search identified 138 unique citations, from which 7 RCTs with a total recruitment of 320 patients met the inclusion criteria. All studies used standard LA drugs (lidocaine, bupivacaine, or ropivacaine); in 3 studies, LA was combined with epinephrine. In 3 studies, RSB was performed preoperatively; in the other 4 studies, it was administered postoperatively after wound closure. No complications attributable to RSB were reported. Meta-analysis found a pooled reduction in pain score at 1 hour postoperatively (N = 5 studies; mean difference, -1.61; 95% confidence interval, -2.06 to -1.15; P < 0.001; I(2) = 0%). Subgroup analysis of preoperative RSB showed significant reduction in pain scores at 2, 4, and 6 to 8 hours after surgery whereas postoperative RSB was associated with significant reduction in pain scores at 2, 4, 6 to 8 and 12 hours assessments. There was also an overall reduction in the opioid requirements over the first 24 hours postoperatively, although with significant heterogeneity among the studies (N = 6 studies; standardized mean difference, -0.79; 95% confidence interval, -1.55 to -0.03; P = 0.04; I(2) = 86%).

Conclusion: Published RCTs of RSB are small and of limited methodological quality but meta-analysis shows a consistent finding of reduced postoperative pain. This evidence supports the use of RSB for patients undergoing craniotomy.