A COMPREHENSIVE SYSTEMATIC REVIEW OF THE EFFECTIVENESS OF REGIONAL SCALP BLOCK IN CRANIOTOMY ON POSTOPERATIVE PAIN AND INTRAOPERATIVE HAEMODYNAMIC RESPONSE

Abstract

Introduction: Craniotomy is followed by moderate-to-severe surgical-site pain in a majority of patients, yet analgesia in this population is constrained by the need to preserve neurological assessment and to avoid opioid-induced hypercapnia and intracranial hypertension. Skull-pin (Mayfield) fixation, scalp incision, and craniotomy each generate an abrupt sympathetic discharge that raises arterial pressure and heart rate, with potential consequences for cerebral perfusion pressure, aneurysm transmural tension, and haemorrhage risk. Regional scalp block offers a physiologically rational solution that addresses both problems with a single intervention. Methods: The study strictly adhered to the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) 2020 guidelines Randomised controlled trials and primary comparative studies evaluating regional scalp block against placebo, no block, local infiltration, or systemic analgesia in patients undergoing craniotomy were eligible. Two reviewers independently performed screening, data extraction, and risk-of-bias appraisal using RoB 2 and ROBINS-I, with certainty of evidence rated by GRADE. Random-effects meta-analysis using the DerSimonian-Laird estimator generated mean differences, standardised mean differences, and risk ratios with 95% confidence intervals across sixteen prespecified outcome domains. Results: Forty-one studies comprising 2,984 participants (1,587 block, 1,397 comparator) were included; 38 were randomised controlled trials. Regional scalp block produced a large and statistically robust reduction in early postoperative pain at 1-2 hours (mean difference −1.74 points; 95% CI −2.07 to −1.42; I²=42%; P<0.0001) that persisted at 6-8 hours (−1.35; 95% CI −1.72 to −0.99; P<0.0001), 24 hours (−0.81; 95% CI −1.04 to −0.57; P<0.0001), and 48 hours (−0.48; 95% CI −0.76 to −0.20; P<0.001). Haemodynamic protection was pronounced at the most noxious stimulus: mean arterial pressure at skull-pin insertion fell by 14.24 mmHg (95% CI −17.24 to −11.25; P<0.0001) and heart rate by 11.19 beats·min⁻¹ (95% CI −13.87 to −8.50; P<0.0001), with attenuated but still significant effects at skin incision (−9.46 mmHg and −8.89 beats·min⁻¹, both P<0.0001). Intraoperative opioid consumption was substantially reduced (SMD −1.03; 95% CI −1.25 to −0.80; P<0.0001), as was 24-hour consumption (−16.66 mg; 95% CI −21.89 to −11.42; P<0.0001), while time to first rescue analgesia was prolonged by 2.91 hours (95% CI 2.03 to 3.79; P<0.0001). Block reduced postoperative nausea and vomiting (RR 0.65; 95% CI 0.51 to 0.83; P<0.001), intraoperative hypertensive responses (RR 0.36; 95% CI 0.27 to 0.49; P<0.0001), and persistent incisional pain at 2-3 months (RR 0.56; 95% CI 0.34 to 0.93; P=0.025). Serum cortisol (SMD −0.80; 95% CI −1.10 to −0.51) and time to tracheal extubation (−4.08 minutes; 95% CI −5.74 to −2.42) both favoured block. All sixteen outcome domains reached statistical significance in favour of regional scalp block. Meta-regression identified local anaesthetic concentration as the dominant modifier of analgesic magnitude (β=−2.18 points per 1% w/v; P<0.0001; 84% of τ² explained), and an Emax model estimated a half-maximal effective concentration of 0.163% ropivacaine-equivalent. Exploratory summary ROC analysis yielded an AUC of 0.753 for freedom from moderate-to-severe pain at 24 hours and 0.726 for absence of a hypertensive pinning response. No case of local anaesthetic systemic toxicity, seizure, or permanent neurological injury attributable to the block was reported in 1,587 exposed patients. Funnel plots were symmetrical (Egger P=0.53) and GRADE certainty was high for haemodynamic outcomes and moderate for most analgesic outcomes. Conclusion: Regional scalp block delivers clinically meaningful, statistically robust, and internally consistent benefit across analgesic, haemodynamic, opioid-sparing, neuroendocrine, recovery, and safety domains in patients undergoing craniotomy. Pre-incisional blockade with a long-acting amide local anaesthetic at a concentration of at least 0.5% ropivacaine-equivalent, optionally supplemented with dexmedetomidine or a corticosteroid, should be considered a default component of enhanced recovery pathways for cranial neurosurgery.