Single-Entry Selective Trunk Block (S-SeTB): An Innovative Approach to Complete Upper Extremity Anesthesia in Weapon-Wounded Patients in Low-Resource Settings

Abstract

Background: Regional anesthesia for upper extremity surgery in weapon-wounded patients is challenging, particularly in low-resource settings. Existing techniques often require multiple needle entries and ultrasound probe repositioning, increasing complexity and risk. There is a need for a simpler, effective technique providing complete anesthesia from the shoulder to the hand.

Methods: We developed a novel ultrasound-guided regional anesthesia technique-the Single-entry Selective Trunk Block (S-SeTB)-which targets the superior trunk (ST), middle trunk (MT), and C8 ventral ramus (C8VR) with local anesthetic diffusion to the inferior trunk (IT). The procedure uses one skin entry point to deliver three injections and is combined with a superficial cervical plexus (SCP) block using the same entry and ultrasound plane. Over 600 procedures were performed in field hospitals operated by the International Committee of the Red Cross, with observations documented.

Results: The S-SeTB consistently achieved full anesthesia of the upper extremity, including the shoulder and clavicle, without the need for conversion to general anesthesia. The technique was well tolerated and effective in complex trauma cases. No major complications were reported. Compared to conventional selective trunk blocks or hybrid brachial plexus approaches, the S-SeTB required lower anesthetic volumes (20-25 mL) and demonstrated reduced procedural complexity and risks (eg, pneumothorax, vascular puncture).

Conclusion: The S-SeTB, combined with SCP and intercostobrachial nerve blocks, offers a reliable, resource-efficient, and safer alternative to traditional brachial plexus block techniques. It is particularly well-suited for austere environments where anesthesia resources and safety margins are limited. Further prospective studies are ongoing to evaluate block dynamics and confirm efficacy.

Keywords: SeTB; brachial plexus anesthesia; conflict-zone anesthesia; low-resource anesthesia; selective trunk block; ultrasound-guided regional anesthesia.

Figure 1

Sonographic anatomy of the superior trunk, middle trunk, and C8 ventral ramus at the midpoint between the scalene groove and the supraclavicular fossa. (A) Patient position and ultrasound probe placement; (B) sonoanatomy of the trunks and C8 ventral ramus for the single-entry selective block; (C) the anatomy illustration demonstrates the ultrasound beam’s position (plane) and the neural structures visible at a level between the supraclavicular fossa and interscalene groove.

Figure 2

Anatomical variation with middle trunk located within the middle scalene muscle and muscular bridge separating the middle trunk to C8 ventral ramus.

Figure 3

Sequential ultrasound technique for single-entry selective trunk block. (A) Patient positioning and ultrasound screening technique using three key scanning points: the supraclavicular fossa (1), the scalene groove (2), and a midpoint between these two locations (3). (B) Sonographic view at supraclavicular fossa, illustrating the brachial plexus. (C) Sonographic view at the midpoint between the supraclavicular fossa and the scalene groove, illustrating C8Vr, MT, and ST. (D) Sonographic view of the scalene groove, illustrating the C5, C6, and C7 nerve roots.

Figure 4

Single-entry selective trunk block (S-SeTB) combined with superficial cervical plexus (SCP) block. The illustration shows the needle trajectories (dashed lines) for performing the S-SeTB alongside the SCP block using a single skin entry point. Dashed line 1: Needle path targeting the C8VR blockade. Dashed line 2: Needle path between the ST and MT. Dashed line 3: Needle path for the SCP block.

Figure 5

Sonographic views before and after local anesthetic injection. Injection was performed at the scalene groove between the superior trunk and middle trunk, and between the first rib-T1 transverse process complex. Note the spread of local anesthetic in the supraclavicular fossa, particularly at the “corner pocket” region and the scalene groove.

Figure 6

Diaphragmatic assessment before (A) and 30 min after (B) single entry-selective trunk block. Note the reduction in diaphragm excursion after the S-SeTB.

Figure 7

Course of the transverse cervical artery and its relationship to the brachial plexus at the truncal level. The transverse cervical artery is positioned between the middle trunk and the C8 ventral ramus, as demonstrated in the Doppler image (B).

Figure 8

Sonograms of dorsal scapular nerve, long thoracic nerve, and Needle pathway during S-SeTB. (A) Sonogram depicting the dorsal scapular nerve emerging from the C5 nerve root. (B) Sonogram illustrating the superior (ST) and middle (MT) trunks of the brachial plexus, along with the C8 ventral ramus (C8VR). The dorsal scapular nerve (DSN) and long thoracic nerve (LTN) are identified within the middle scalene muscle (highlighted by a large white arrow), with the ultrasound probe positioned midway between the interscalene groove and the supraclavicular fossa. (C) Simulated needle trajectory (dashed arrow) during the S-SeTB, targeting the C8 ventral ramus as well as the middle and superior trunks. The yellow dashed circle highlights the proximity of the needle pathway to the DSN and LTN, emphasizing the potential risk of nerve injury.

Figure 9

Variations in the course of the dorsal scapular artery relative to the brachial plexus trunks at supraclavicular fossa. (A) The dorsal scapular artery passing between the middle trunk and the inferior trunk. (B) The dorsal scapular artery passing between the middle trunk and the superior trunk.