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Korean J Anesthesiol > Volume 76(2); 2023 > Article
Hong, Jo, and Oh: Kill two birds with one stone: selective trunk block (SeTB) with single skin penetration
The selective trunk block (SeTB) introduced by Karmakar et al. [1] produces sensorimotor blockade of the entire upper extremity, except for the medial aspect of the upper arm. It can be used for shoulder surgery because SeTB can block the suprascapular nerve before it branches off from the superior trunk. Contrary to its name, SeTB can anesthetize the entire upper extremity ‘non-selectively.' A recently published cadaver anatomic study provides us with valuable information about SeTB as a promising all-purpose brachial plexus block (BPB) technique for upper extremity surgeries [2]. With the advancement of the ultrasound imaging resolution and with several pioneers in this field, we have been able to identify and treat each component of brachial plexus in more detail. We now have more precise BPB techniques, such as the superior trunk [3], the intertruncal [4], and the SeTB [2,5].
The original SeTB requires two injections with separate skin puncture points [5]. The first injection is performed at the interscalene groove and the second at the supraclavicular fossa to block the superior/middle trunks and the inferior trunk, respectively. We suggest a technical modification to the original SeTB. We often get a corner pocket image of the brachial plexus when performing the supraclavicular approach, as we keep the lateral part of the linear probe (HFL50xp: 15–6 MHz, X-Porte, FUJIFILM SonoSite, Inc., USA) away from the clavicle (Fig. 1A). This imaging technique has several advantages including improved cross-sectional visualization of the plexus and avoiding interference of the trapezius muscle during needle manipulation. Furthermore, it provides a clear image of the suprascapular nerve before it branches out from the superior trunk. A corner pocket injection, the second injection of the original SeTB, can be done using this image. In our institution, 10 ml of local anesthetics (1 : 1 mixture of 0.75% ropivacaine and 1% lidocaine) is usually used at the corner pocket injection. Then, without withdrawing the needle completely out of the skin, the medial part of the probe is rotated in the cephalic direction. Using this rotatory movement, the image for the first injection of the original SeTB can be acquired. Subsequently, the needle can be realigned with the probe (Fig. 1B). At this interscalene level, an additional 10 ml to 15 ml of local anesthetics is administered. Thus, the two-stage blockade can be performed with single skin penetration.
Since the blockade is often performed while a patient is awake, a single skin penetration can significantly reduce the patient’s discomfort. The SeTB presented by the original authors is a more advanced BPB technique. Indeed, it is one of the monumental achievements in ultrasound-guided BPB.



This work was supported by research funding from National Research Foundation of Korea (NRF- 2022R1C1C1007982) and Chungnam National University.

Conflicts of Interest

No potential conflict of interest relevant to this article was reported.

Author Contributions

Boohwi Hong (Conceptualization; Funding acquisition; Visualization; Writing – original draft; Writing – review & editing)

Yumin Jo (Conceptualization; Visualization; Writing – original draft; Writing – review & editing)

Chahyun Oh (Conceptualization; Visualization; Writing – original draft; Writing – review & editing)

Fig. 1.
(A) Ultrasound image for the corner pocket injection. The image was acquired when the probe was tilted caudad and rotated so that the lateral part of the probe is away from the clavicle. The needle is targeting below the inferior trunk, the corner pocket of the supraclavicular fossa. (B) Ultrasound image for the injection between the superior and middle trunk of the brachial plexus. The image was acquired when the medial part of the probe was rotated to the cephalad direction while maintaining the lateral part in the same position as the needle penetration. The needle is targeting between the superior and middle trunk. SA: subclavian artery, ST: superior trunk of the brachial plexus, MT: middle trunk of the brachial plexus.


1. Karmakar MK, Areeruk P, Mok LYH, Sivakumar RK. Ultrasound-guided selective trunk block to produce surgical anesthesia of the whole upper extremity: a case report. A A Pract 2020; 14: e01274.
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2. Songthamwat B, Luangjarmekorn P, Kampitak W, Sivakumar RK, Karmakar MK. Ultrasound-guided selective trunk block (SeTB): a cadaver anatomic study to evaluate the spread of dye after a simulated injection. Reg Anesth Pain Med 2022; 47: 414-9.
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3. Kang R, Jeong JS, Chin KJ, Yoo JC, Lee JH, Choi SJ, et al. Superior trunk block provides noninferior analgesia compared with interscalene brachial plexus block in arthroscopic shoulder surgery. Anesthesiology 2019; 131: 1316-26.
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4. Siddiqui U, Perlas A, Chin K, Reina MA, Sala-Blanch X, Niazi A, et al. Intertruncal approach to the supraclavicular brachial plexus, current controversies and technical update: a daring discourse. Reg Anesth Pain Med 2020; 45: 377-80.
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5. Sivakumar RK, Samy W, Pakpirom J, Songthamwat B, Karmakar MK. Ultrasound-guided selective trunk block: Evaluation of ipsilateral sensorimotor block dynamics, hemidiaphragmatic function and efficacy for upper extremity surgery. A single-centre cohort study. Eur J Anaesthesiol 2022; 39: 801-9.
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