A randomized trial comparing axillary block versus targeted intracluster injection supraclavicular block for upper limb surgery.

PURPOSE: This randomized trial aimed to validate a new method for brachial plexus blockade, i.e., targeted intracluster injection supraclavicular block (TII SCB), by comparing it with ultrasound-guided axillary block (AXB). We hypothesized that TII SCB would result in a shorter total anesthesia-related time. METHODS: Forty patients undergoing upper limb surgery were randomized to ultrasound-guided TII SCB (n = 20) or AXB (n = 20). In the TII SCB group, we deposited 16 mL of lidocaine 1.5% with epinephrine 5 µg·mL(-1) into the largest neural cluster (i.e., brachial plexus trunks/divisions). Subsequently, an additional 16 mL was divided into equal aliquots and injected inside each satellite cluster. In the AXB group, 5.5 mL were deposited around the musculocutaneous nerve and 23.5 mL were injected at the 6 o'clock position of the axillary artery. The main outcome for comparison between the two groups was the total anesthesia-related time (defined as the sum of block performance and onset times). We also recorded the number of needle passes, procedural pain, and complications (vascular puncture, paresthesia). RESULTS: The TII SCB method provided a quicker mean (SD) onset time compared with the AXB group [9.5 (5.8) min vs 18.9 (6.1) min; mean difference, -9.5 min; 99% CI, -14.7 to -4.2; P < 0.001] and a shorter mean (SD) total anesthesia-related time [20.1 (5.0) min vs 27.2 (6.5) min; mean difference, -7.0 min; 95% CI, -10.9 to -3.1; P = 0.001]. There were no intergroup differences in terms of success rate (95%), procedural pain, vascular puncture and paresthesia. The AXB group displayed a faster performance time [8.2 (1.6) min vs 10.6 (2.6) min; P = 0.001] with fewer median [interquartile range] needle passes (3 [2-6] vs 5 [4-8]; P < 0.001). CONCLUSION: Ultrasound-guided TII SCB provides a quicker onset and a shorter total anesthesia-related time than ultrasound-guided AXB.

Reliability of Waveform Analysis as an Adjunct to Loss of Resistance for Thoracic Epidural Blocks.

BACKGROUND: The epidural space is most commonly identified with loss of resistance (LOR). Although sensitive, LOR lacks specificity, as cysts in interspinous ligaments, gaps in ligamentum flavum, paravertebral muscles, thoracic paravertebral spaces, and intermuscular planes can yield nonepidural LOR. Epidural waveform analysis (EWA) provides a simple confirmatory adjunct for LOR. When the needle is correctly positioned inside the epidural space, measurement of the pressure at its tip results in a pulsatile waveform. In this observational study, we set out to assess the sensitivity, specificity, as well as positive and negative predictive values of EWA for thoracic epidural blocks. METHODS: We enrolled a convenience sample of 160 patients undergoing thoracic epidural blocks for thoracic surgery, abdominal surgery, or rib fractures. The choice of patient position (sitting or lateral decubitus), approach (midline or paramedian), and LOR medium (air or normal saline) was left to the operator (attending anesthesiologist, fellow, or resident). After obtaining a satisfactory LOR, the operator injected 5 mL of normal saline through the epidural needle. A sterile tubing, connected to a pressure transducer, was attached to the needle to measure the pressure at the needle tip. A 4-mL bolus of lidocaine 2% with epinephrine 5 µg/mL was then administered and, after 10 minutes, the patient was assessed for sensory blockade to ice. RESULTS: The failure rate (incorrect identification of the epidural space with LOR) was 23.1%. Of these 37 failed epidural blocks, 27 provided no sensory anesthesia at 10 minutes. In 10 subjects, the operator was unable to thread the catheter through the needle. When compared with the ice test, the sensitivity, specificity, and positive and negative predictive values of EWA were 91.1%, 83.8%, 94.9%, and 73.8%, respectively. CONCLUSIONS: Epidural waveform analysis (with pressure transduction through the needle) provides a simple adjunct to LOR for thoracic epidural blocks. Although its use was devoid of complications, further confirmatory studies are required before its routine implementation in clinical practice.