Risk factors for insufficient ultrasound-guided supraclavicular brachial plexus block

PURPOSE: Ultrasound-guided supraclavicular brachial plexus block (SCBPB) is performed by surgeons for upper limb anesthesia; however, certain patients need additional local anesthesia. This study aimed to identify risk factors for additional local anesthetic injection requirements. METHODS: In total, 269 patients receiving ultrasound-guided SCBPB were enrolled. Patient age, sex, body mass index, anesthetic drug dose, surgeon expertise (hand surgeon or resident), tourniquet time, comorbidities (diabetes mellitus and mental disorders), and preoperative blood pressure representing anxiety were compared between the additional local anesthesia and no additional local anesthesia groups matched for background using propensity scores. Receiver operating characteristic analysis was performed to determine risk factor cut-off values with the highest predictive potential. RESULTS: Of 269 patients, 41 (15.2%) required additional intraoperative local anesthesia. Among surgical sites, elbow surgery showed the highest prevalence of the need for additional local anesthesia (17/41, 41%). A high body mass index and high systolic blood pressure before surgery were identified as risk factors for additional intraoperative local anesthesia requirement. Furthermore, systolic blood pressure > 170 mmHg (area under the curve, 0.66) predicted the need for intraoperative local anesthesia with 36% sensitivity, 89% specificity, 37.5% positive predictive value, and 88.6% negative predictive value. The median systolic blood pressure was significantly greater in patients requiring additional local anesthesia than in those not requiring it [151 (139–171) mmHg vs. 145 (127–155) mmHg; P = 0.026]. CONCLUSION: Elbow surgery, obesity, and high systolic blood pressure (> 170 mmHg) before surgery are predictive of additional intraoperative local anesthesia requirement. LEVEL OF EVIDENCE: Prognostic Level III