Ultrasound guided supraclavicular perivascular block. Anatomical, technical medial approach description and changes in regional perfusion

Abstract

IntroductionSupraclavicular block is usually performed using a lateral to medial approach, although a medial to lateral approach is also feasible. Block onset may be evaluated through the sympathetic effect associated with the sensitive and motor blockade. ObjectiveTo describe the ultrasound-guided supraclavicular block using a medial approach, evaluating the sensitive, motor, and sympathetic block onset. Materials and methodsAn ultrasound-guided supraclavicular block was performed in a fresh cadaver with 20ml volume (2ml of iodine and 1ml of methylene blue). A CT scan was performed and sagittal sections were obtained. The clinical phase included 10 patients undergoing a medial approach block; the onset of the block was evaluated based on a motor, sensory and sympathetic assessment (measuring flow changes in the humeral artery, the palmar temperature, and the perfusion index). ResultsAdequate distribution of the contrast medium was observed in the cadaver, with complete spread through the brachial plexus, both in terms of the CT-reconstruction as in the anatomical cross sections. A significant change in all the sympathetic block parameters was observed 5min after the bock: temperature (32.5±1.8°C to 33.4±1.7°C; p=0.047), humeral arterial flow (105±70ml/min to 192±97ml/min; p=0.007), and thumb perfusion index (5±3 to 10±3%; p=0.002). The block was effective and uneventful in all patients. ConclusionsThis supraclavicular approach achieves a homogeneous distribution throughout the brachial plexus, with high anesthetic efficacy. Regional changes secondary to the sympathetic block occur early after the block.