Ultrasound- Guided Retro Superior Costotransverse Ligament (SCTL) Compartment Block

Study Overview
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Brief Summary
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Thoracic paravertebral block (TPVB) is a regional anaesthetic technique that produces ipsilateral, segmental, somatic and sympathetic nerve blockade of multiple contiguous thoracic dermatomes. Although it is a safe technique, the needle tip comes close to the pleura during the injection, therefore, increasing the potential for pleural puncture and pneumothorax, especially when performed by inexperienced physicians. With the recently described retro superior costotransverse ligament (SCTL) compartment (using MRI) which has been shown to be in direct continuity with the intervertebral foramen, the investigators propose that the block needle need not pierce the SCTL and lie close to the pleura but can be positioned safely behind the ligament to deposit the local anaesthetic (LA). Therefore, this study aims to describe the sonoanatomy of the retro SCTL compartment and evaluate the block injection technique and sensory dynamics in patients scheduled for video-assisted thoracoscopic surgery (VATS).

Detailed Description
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During a TPVB the LA is injected into the paravertebral space adjacent to the thoracic vertebra and close to the intervertebral foramen. Traditionally, either landmark or ultrasound-guided, TPVB is performed by depositing the LA anterior to the superior costotransverse ligament (SCTL), i.e. the block needle typically pierces the SCTL to reach the wedge-shaped TPVB space. Although it is a safe technique, the needle tip comes close to the pleura during the injection, therefore, increasing the potential for pleural puncture and pneumothorax, especially when performed by inexperienced physicians. Recently, with the help of 3D micro computer tomography (CT), Cho T and colleagues have demonstrated in cadavers that the medial part of the SCTL does not end at the base of the transverse process but extends anteriorly to the vertebral body dividing the wedge-shaped paravertebral space into a retro SCTL compartment (posterior to SCTL) and a true paravertebral space (anterior to SCTL). Also, they demonstrated that the SCTL, as it extends to the vertebral body, forms a medial slit near the intervertebral foramen through which the ventral rami enters the true paravertebral space. Furthermore, they highlighted that the retro SCTL space or compartment is in direct communication with the intervertebral foramen and epidural space medially and to the true paravertebral space (through the medial and lateral slits). It is evident from their study that the retro SCTL compartment contains both the divisions of the spinal nerve, i.e., the ventral and dorsal rami, the latter exits the compartment to enter the erector spinae plane. Hence, with this new concept, it appears that the block needle tip needs not to pierce the SCTL as required in a conventional TPVB and LA deposited at the retro SCTL compartment, theoretically can spread to the paravertebral space, intervertebral foramen and the epidural space, to block the spinal nerves and its divisions, and the sympathetic trunks. The investigators believe that the LA injection in the retro SCTL compartment, owing to its close relationship with the intervertebral foramen, thoracic spinal nerve, and the sympathetic trunks, will also produce rapid onset of ipsilateral and or bilateral segmental somatic and sympathetic blockade of the thoracic dermatomes, akin to TPVB. In addition, as the needle tip lies farther away from the pleura (posterior to SCTL) the investigators believe that this technique may also be safer in terms of the potential risk of pleural puncture or pneumothorax than a conventional TPVB.

Official Title
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Ultrasound-Guided Retro Superior Costotransverse Ligament (SCTL) Compartment Block: Description of Sonoanatomy, Technique and Block Dynamics

Conditions
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Thoracic Surgery, Video-Assisted

Intervention / Treatment
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* Procedure: Retro SCTL compartment block


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Phase 1: Healthy volunteers of age 18-60 years Phase 2: Patients age 18-80 years scheduled for video assisted thoracoscopic surgery (VATS) Exclusion Criteria: Phase 2: 1. Patient refusal 2. Local skin site infection 3. Coagulopathy 4. History of allergy to local anesthetics

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 80 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Sonoanatomy and retro SCTL compartment block<br>During phase 1, ten healthy human volunteers will be involved. A bilateral ultrasound scan will be performed in the paravertebral region to describe the sonoanatomy of the retro SCTL compartment. During phase 2, participants who are scheduled for video-assisted thoracoscopic surgery (VATS) will receive an ultrasound-guided multi-level (T3-4, T5-6 and T7-8) retro SCTL compartment block. | Procedure: Retro SCTL compartment block<br>* For phase 1, healthy human volunteers will be positioned in the lateral position with the side to be scanned in the non-dependent position. An ultrasound scan sequence to describe the retro SCTL space will be performed on both sides. During phase 2, participants who are scheduled for video-assisted thoracoscopic surgery (VATS) will receive an ultrasound-guided multi-level (T3-4, T5-6 and T7-8) retro SCTL compartment block. After positioning the participants, cleaning and draping the injection site, under sterile aseptic precautions and local anaesthetic infiltration, the block needle is inserted at the corresponding vertebral level (T7-T8) under ultrasound guidance in-plane to the ultrasound beam. Once the needle tip reaches the lateral aspect of the inferior articular process and behind the SCTL ligament, the desired volume (6ml/each level) of LA will be injected. This process will be continued at the remaining two vertebral levels (T5-T6 and T3-T4).<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Ultrasound visualization of the retro SCTL compartment in volunteers | The following structures will be assessed: The SCTL, The medial extension of SCTL in front of the intervertebral foramen, The retro SCTL compartment behind the medial extension of the SCTL, and The true paravertebral space. The quality of ultrasound visibility (ultrasound visibility score, UVS) of each structure will be assessed using a 4-point Likert scale (0= not visible, 1= hardly visible, 2= well visible, 3= very well visible). | Within 30 minutes after entering the procedure room | 
| Readiness for surgery | An overall sensory score of =<30 on the ipsilateral hemithorax (loss of sensation to cold stimulus (ice cube), NRS: 0-100, 0= no sensation, 100= normal sensation) Sensation block assessment: T2-L5 spinal nerves | Within 30 minutes after the block at 5 minutes interval | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Complete sensory block | An overall sensory score 0 on the ipsilateral hemithorax (loss of sensation to cold stimulus (ice cube), NRS: 0-100, 0= no sensation, 100= normal sensation) Sensation block assessment: T2-L5 spinal nerves | Within 30 minutes after the block at 5 minutes interval | 
| Block performance time | The time taken from the start of the local anaesthetic (LA) skin infiltration to the end of the LA injection for the block. | Within 30 minutes after entering the procedure room | 
| Total amount of vasopressor used | The total amount of vasopressor requirements after the completion of the block and through the surgical period will be recorded. | After completion of the block and through the surgical period, an average of 6 hours | 
| Total amount of morphine used | The total amount of morphine requirements through the surgical period and post anaesthesia care unit (PACU) period, until the discharge of participants from the PACU, will be recorded. | During surgical period and postanesthesia care unit (PACU) period, an average of 6 hours | 
| Postoperative pain score | Postoperative pain score in the form of a numerical rating scale (NRS) will be recorded in the post anaesthesia care unit (PACU) at rest and movement (cough), at arrival and discharge from PACU. (NRS: 0-100, 0= no pain, 100= worst imaginable pain) | At arrival and discharge from postanesthesia care unit (PACU) | 
| Postoperative sensory score before discharge | Sensory score on bilateral hemithorax (loss of sensation to a cold stimulus (ice cube), NRS: 0-100, 0= no sensation, 100= normal sensation), when discharge from postanesthesia care unit (PACU). Sensation block assessment: T2-L5 spinal nerves | At discharge from postanesthesia care unit (PACU) | 
| Complications | Any complication directly related to the retro SCTL compartment block (vascular puncture, pleural puncture, or local anaesthetic toxicity) will be recorded. | Within 45 minutes after the block, within 24 hours post surgery and at 1 week after the surgery | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Superior costotransverse ligament, Video assisted thoracoscopic surgery, Thoracic paravertebral block, Retro superior costotransverse ligament compartment