Radiological evaluation of the spread of different local anesthetic volumes during posterior brachial plexus block

SCIENTIFIC ARTICLE

Radiological evaluation of the spread of different local anesthetic volumes during posterior brachial plexus block ^*

Estudo radiológico da dispersão de diferentes volumes de anestésico local no bloqueio de plexo braquial pela via posterior

Estudio radiológico de la dispersión de diferentes volúmenes de anestésico local en el bloqueo de plexo braquial por vía posterior

Marcos Guilherme Cunha Cruvinel, TSA, M.D.^I; Carlos Henrique Viana de Castro, TSA, M.D.^I; Yerkes Pereira Silva, M.D. ^I; Flávio de Oliveira França, M.D.^II; Flávio Lago, M.D.^II

^IAnestesiologista do Hospital Lifecenter

IIOrtopedista do Hospital Lifecenter

^{Correspondence to}

SUMMARY

BACKGROUND AND OBJECTIVES: Local anesthetic spread during interscalenic block has been thoroughly studied, however there are few studies on posterior block. This study aimed at evaluating the spread of different local anesthetic volumes during posterior brachial plexus block using contrasted X-rays.

METHODS: Participated in this study 16 patients submitted to posterior brachial plexus block, 15 of whom were randomly divided in three groups of five patients: Group 1: 20 mL; Group 2: 30 mL.; Group 3 40 mL. The volume of 10 mL was studied in one patient submitted to continuous posterior brachial plexus block. All patients received 0.375% ropivacaine associated to radio-opaque solution. X-rays of the cervical region were obtained immediately after blockade that were evaluated by thermal sensitivity using cotton soaked in alcohol 30 minutes after being performed and in the PACU.

RESULTS: Radiological and clinical behavior of posterior brachial plexus block is very similar to Winnie’s technique (interscalenic). There is always involvement of cervical plexus and of higher brachial plexus roots (C₅-C₇).

CONCLUSIONS: This study has shown that local anesthetic spread during posterior brachial plexus block is seen primarily in shoulder innervating roots.

Key Words: ANESTHETICS, Local: ropivacaine; ANESTHETIC TECHNIQUES, Regional: brachial plexus; SURGERY, Orthopedic

RESUMO

JUSTIFICATIVA E OBJETIVOS: A dispersão do anestésico local no bloqueio interescalênico foi bem estudada, porém no bloqueio pela via posterior são poucos os estudos. O objetivo deste estudo foi determinar a dispersão de diferentes volumes de anestésico local nesta técnica através de exame radiológico contrastado.

MÉTODO: Dezesseis pacientes submetidos a bloqueio do plexo braquial pela via posterior, 15 foram divididos aleatoriamente em três grupos de cinco: Grupo 1: volume de 20 mL; Grupo 2: volume de 30 mL; Grupo 3: volume de 40 mL. Em um paciente, submetido a bloqueio contínuo do plexo braquial pela via posterior, a administração de um volume de 10 mL foi estudada. Em todos, o anestésico usado foi a ropivacaína a 0,375% associada a solução radiopaca. Foram feitas radiografias da região cervical imediatamente após o bloqueio que foi avaliado através da pesquisa de sensibilidade térmica utilizando-se algodão embebido em álcool, 30 minutos após a sua realização e na sala de recuperação pós-anestésica.

RESULTADOS: O comportamento radiológico e clínico do bloqueio de plexo braquial pela via posterior é muito semelhante aquele descrito com a técnica de Winnie (interescalênico). Invariavelmente há envolvimento do plexo cervical e das raízes mais altas (C₅-C₇) do plexo braquial.

CONCLUSÕES: Este estudo mostra que a dispersão do anestésico local no bloqueio do plexo braquial pela via posterior se dá primariamente nas raízes responsáveis pela inervação do ombro.

Unitermos: ANESTÉSICOS, Local: ropivacaína; CIRURGIA, Ortopédica; TÉCNICAS ANESTÉSICAS, Regional: plexo braquial

RESUMEN

JUSTIFICATIVA Y OBJETIVOS: La dispersión del anestésico local en el bloqueo interescalénico fue bien estudiada; en el bloqueo por la vía posterior son pocos los estudios. El objetivo de este estudio, fue determinar la dispersión de diferentes volúmenes de anestésico local en esta técnica a través de examen radiológico contrastado.

MÉTODO: Dieciséis pacientes sometidos a bloqueo del plexo braquial por vía posterior, 15 fueron divididos aleatoriamente en tres grupos de cinco: Grupo 1: volumen de 20 mL; Grupo 2: volumen de 30 mL; Grupo 3: volumen de 40 mL. En un paciente, sometido al bloqueo continuado del plexo braquial por la vía posterior, la administración de un volumen de 10 mL fue estudiada. En todos, el anestésico usado fue la ropivacaína a 0,375% asociada a solución radiopaca. Fueron hechas radiografías de la región cervical inmediatamente después el bloqueo que fue evaluado a través de la pesquisa de la sensibilidad térmica utilizándose algodón embebido en alcohol, treinta minutos después de su realización y en la sala de recuperación anestésica.

RESULTADOS: El comportamiento radiológico y clínico del bloqueo de plexo braquial por vía posterior es muy semejante de aquél descrito con la técnica de Winnie (interescalénico). Invariablemente hay envolvimiento del plexo cervical y de las raíces más altas (C₅-C₇) del plexo braquial.

CONCLUSIONES: Este estudio muestra que la dispersión del anestésico local en el bloqueo del plexo braquial por la vía posterior se da primariamente en las raíces responsables por la inervación del hombro.

INTRODUCTION

Shoulder arthroscopic surgeries are becoming increasingly common because they are less invasive and provide faster recovery. Acromioplasty, rotating cuff repair and recurrent luxation are among major shoulder arthroscopic surgeries. One problem to be faced in these surgeries is postoperative pain. These procedures are associated to severe and difficult to control postoperative pain ^1-2. Among most common techniques for this aim there are intravenous opioids associated or not to NSAIDs, articular local anesthetics, suprascapular nerve block and brachial and cervical plexus block ^1-17. From these, brachial plexus block is the technique providing the best results ^1,3-5,18-19. Interscalenic block is the most commonly used brachial plexus block technique ^1,3-5,18-19. Great emphasis has been recently given to posterior brachial plexus block, also called cervical paravertebral block ^20-22,24.

The spread of different local anesthetic volumes has been thoroughly studied for interscalenic brachial plexus block, but not so for posterior brachial plexus block ^23,24. Anesthetic spread affects the efficacy and determines the adverse effects of the blockade. This study aimed at evaluating the spread of different local anesthetic volumes during posterior brachial plexus block using contrasted X-rays.

METHODS

After the Ethics Committee approval and their informed consent, participated in this study 16 patients, physical status ASA I, submitted to shoulder procedures. Fifteen were randomly distributed in three groups of five patients: Group 1, 20 mL; Group 2, 30 mL; Group 3, 40 mL. One patient submitted to continuous posterior brachial plexus block has received 10 mL via catheter. All patients were thoroughly explained about the procedures. Monitoring consisted of ECG (D_II, V5), pulse oximetry and non-invasive automatic blood pressure.

No patient was premedicated and all patients were admitted the day of the surgery. Patients were positioned in the lateral position with the shoulder to be operated on upward and the head on a pillow and bent over the neck. Patients received 3 L.min^-1 oxygen via nasal catheter and were sedated with intravenous 0.1 µg.kg^-1 sufentanil to remain relaxed, cooperative and responding to verbal commands. If the effect was not enough, sedation was complemented with up to 3 mg midazolam.

In the lateral position, with the head on a pillow and the neck bent over the chest, spinous processes C₆ and C₇ were marked on the skin with dermographic pen. Puncture site was marked 3 cm laterally to the space between spinous processes. After skin disinfection with anti-germ and alcoholic PVPi, skin was infiltrated with 1% plain lidocaine using needle 27G ½ and syringe 1 mL. Puncture pathway was infiltrated with 25 x 7 mm needle with additional 5 mL of the anesthetic solution. A insulated needle 22G, with 100 mm length (Stimuplex A100 B. Braun, Melsungen, Germany) connected to the nerve stimulator (Stimuplex-DIG, B. Braun – Melsungen, Germany) was perpendicularly introduced in the skin. Initial nerve stimulator intensity was 1 mA, with 0.1 µs stimulation time and frequency of 2 Hz.

When the transverse process was touched, the needle was removed and reintroduced laterally angulated until 2 cm beyond the depth needed to reach the transverse process and until motor response was obtained. Motor responses of scapula elevator, deltoid or biceps muscles were accepted. Then stimulation intensity was progressively decreased until loss of motor response, ideally below 0.5 mA. After negative blood aspiration, 2 mL of 2% lidocaine with 1:200,000 epinephrine were injected. When motor response was interrupted and there was no heart rate increase above 20 bpm, the selected volume of local anesthetic was injected, according to the study group, in incremental volumes of 5 mL. When there was loss of motor response with stimulation above 0.5 mA the needle was repositioned.

Groups were divided as follows:

Group 1 – 20 mL of 0.375% ropivacaine;

Group 2 – 30 mL of 0.375% ropivacaine;

Group 3 – 40 mL of 0.375% ropivacaine.

The solution was prepared as follows: 20 mL of 0.75% ropivacaine, 10 mL sterile bidistilled water and 10 mL non-ionic radio-opaque solution for spinal use, 300 mg.mL^-1 iohexol. Cervical region X-rays were obtained immediately after blockade to study solution spread. One patient received continuous plexus block catheter (Contiplex D100, B. Braun, Melsungen, Germany) through which 10 mL of the solution were injected.

X-rays were evaluated by comparing solution spread with regard to cervical vertebrae and clavicle. Blockade was evaluated by thermal sensitivity with cotton soaked with alcohol thirty minutes after blockade and in the PACU. Postoperative pain was evaluated in the PACU with the verbal numeric scale (VNC) varying from zero (no pain) to 10 (worst imaginable pain). VNC between 1 and 3 was considered mild pain, between 4 and 6 it was considered moderate and above 6 it was considered severe pain.

Demographics data are expressed in mean ± SD and were compared by Student’s t test. Blockade extension was qualitatively described as present or absent and groups were compared by Fisher Exact test considering significant p < 0.05.

RESULTS

Demographics data are shown in table I. Blockade effectiveness is shown in table II. In the PACU, three patients (one in each group) have complained of moderate pain and were medicated with 30 mg ketorolak associated to 2 g dipirone. No patient needed opioids or presented adverse effects, such as intravascular injection, puncture hematoma, dyspnea or hypoxemia.

Solution spread was as follows: Group 1 - in two patients the contrasted area reached C₃ to T₁ and in three C₄ to T₁. No patient had solution spread below the clavicle (Figure 1). Group 2 - one patient (30 mL) presented spread from above C₃ to C₇ (Figure 2) and in three patients the contrasted area went from C₄ to T₁. One patient had solution spread from C₄ to below the clavicle (Figure 3). Group 3 - in three patients the contrasted area went from above C₃ to T₁ (Figure 4) and in one from C₃ to T₁. One patient presented solution spread from below C₃ to below the clavicle. In patient receiving 10 mL the solution was spread from C₄ to T₁ (Figure 5).

DISCUSSION

Posterior brachial plexus block, although not being a new technique, has only recently gained some popularity. Its efficacy for shoulder and proximal humerus procedures has been shown by different authors ^20-22,24. Adequate analgesia after shoulder procedures is not easy since this joint has complex innervation involving cervical plexus nerves, such as the supraclavicular nerve (C₃-C₄), and brachial plexus nerves, such as the axillary nerve (C₅-C₆) ^1-6. So, techniques involving upper brachial plexus are recommended to obtain satisfactory analgesia for these procedures ¹.

Winnie’s is the most commonly used technique ^{1,3-5,14-16,23}. It reaches brachial plexus in the antero-lateral manner and locates it in the interscalenic space between anterior and medium scalene muscles. The posterior approach allows locating the brachial plexus with theoretically less chances of reaching vascular structures, since they would be protected by cervical transverse processes ^20-22. This technique blocks spinal nerves at spinal emergence, lateral to intervertebral foramen ²⁰.

Radiological results have evidenced local anesthetic spread in shoulder innervating roots (C₃-C₆) with the three volumes used. This was clinically translated into effective analgesia for all groups. However, it has been observed that higher volumes had a trend to further spread, both caudally and cranially. Although some authors recommend volumes up to 50 mL, adequate anesthesia for shoulder procedures may be obtained with Winnie’s technique and 20 mL local anesthetic ²⁵.

Our results suggest that the same may be obtained with the posterior approach. When 20 mL local anesthetics were compared to 40 mL using his technique, Winnie has observed a more limited anesthesia with less cranial spread with 20 mL ²⁶. His conclusion was that 20 mL have resulted in low cervical plexus block and lack or incomplete or late blockade of C₈ and T₁ roots, while 40 mL have resulted in total cervical and brachial plexus block. These results have shown that with posterior brachial plexus block, anesthetic spread pattern and blockade behavior with 20 mL to 40 mL volumes are very similar to those found with Winnie’s technique.

Similar to caudal spread, cranial spread is also important since C₃-C₄ roots blockade not only contributes to analgesia but is also involved with diaphragm block (phrenic nerve C₃-C₅). Local anesthetic cranial spread to C₃ through brachial plexus sheath has already been well shown by Winnie’s technique ²³. In our study, cranial spread to C₄ was observed in all patients and above C₄ in seven patients. This result is in line with other studies on this technique, which have evidenced that cervical plexus is often involved in the blockade and have motivated some authors to describe it as cervical-brachial block ^20-22,24-26.

Even with low volumes (10 mL), local anesthetic has spread to cervical plexus with Winnie’s technique ²⁰. Similarly, our study has shown anesthetic spread to low cervical plexus with 10 mL when the posterior approach was used. The anatomic basis for local anesthetic rostral spread, even with low volumes, is a continuous fibrous sheath involving both plexuses ²⁷.

When brachial plexus is approached below the clavicle, local anesthetic spread is not achieved rostrally ²⁷. So, unless the cervical plexus is separately approached, these techniques will not promote effective analgesia for shoulder procedures.

One may infer from this study that local anesthetic spread during posterior brachial plexus block is primarily in shoulder innervating roots. Radiological and clinical behavior of posterior brachial plexus block is very similar to that described by Winnie (interscalenic). There is always cervical plexus involvement and, as the volume increases, there is a trend to more cranial and caudal anesthetic spread.

REFERENCES

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02. Ritchie E, Tong D, Chung F et al - Suprascapular nerve block for postoperative pain relief in arthroscopic shoulder surgery: a new modality? Anesth Analg, 1997;84:1306-1312.

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15. Klein SM, Greengrass RA, Steele SM et al - A comparison of 0.5% bupivacaine, 0.5% ropivacaine, and 0.75% ropivacaine for interscalene brachial plexus block. Anesth Analg, 1998;87: 1316-1319.

16. Eroglu A, Uzunlar H, Sener M et al - A clinical comparison of equal concentration and volume of ropivacaine and bupivacaine for interscalene brachial plexus anesthesia and analgesia in shoulder surgery. Reg Anesth Pain Med, 2004;29: 539-543.

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Submitted for publication April 4, 2005

Accepted for publication June 7, 2005

Correspondence to

Dr. Marcos Guilherme Cunha Cruvinel

Address: Rua Simão Irffi, 86/301 Coração de Jesus

ZIP: 30380-270 City: Belo Horizonte, Brazil

E-mail: [e-mail]

Submitted for publication April 4, 2005

Accepted for publication June 7, 2005

^* Received from Departamentos de Anestesiologia e Ortopedia do Hospital Lifecenter, Belo Horizonte, MG

^*

Received from Departamentos de Anestesiologia e Ortopedia do Hospital Lifecenter, Belo Horizonte, MG

Publication Dates

• Publication in this collection
  13 Feb 2006
• Date of issue
  Oct 2005

History

• Received
  04 Apr 2005
• Accepted
  07 June 2005