Introduction:

Supraclavicular 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.

Objective:

To describe the ultrasound-guided supraclavicular block using a medial approach, evaluating the sensitive, motor, and sympathetic block onset.

Materials and methods:

An ultrasound-guided supraclavicular block was performed in a fresh cadaver with 20 ml volume (2 ml of iodine and 1 ml 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).

Results:

Adequate 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 5 min after the bock: temperature (32.5 ± 1.8 °C to 33.4 ± 1.7 °C; p = 0.047), humeral arterial flow (105 ± 70ml/min to192 ± 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.

Conclusions:

This 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.

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