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Print version ISSN 0034-7094
Rev. Bras. Anestesiol. vol.55 no.4 Campinas July/Aug. 2005
Posterior brachial plexus block with nerve stimulator and 0.5% ropivacaine*
Bloqueo del plexo braquial por la vía posterior con el uso de neuroestimulador y ropivacaína a 0,5%
Lúcia Beato, TSA, M.D.I; Gustavo Camocardi, TSA, M.D.II; Luiz Eduardo Imbelloni, TSA, M.D.III
IAnestesiologista da Casa de Saúde
Santa Maria e Clínica São Bernardo
IIAnestesiologista do Hospital Municipal Barata Ribeiro
IIIDiretor do Instituto de Anestesia Regional
BACKGROUND AND OBJECTIVES: There
are several approaches to the brachial plexus depending on the experience of
the anesthesiologist and the site of the surgery. Posterior brachial plexus
block may be an alternative for shoulder, clavicle and proximal humerus surgery.
This study aims at presenting the results of patients submitted to posterior
brachial plexus block with 0.5% ropivacaine and the aid of nerve stimulator.
METHODS: Participated in this study 22 patients aged 17 to 76 years, physical status ASA I and II, scheduled for shoulder, clavicle and proximal humerus surgery, who were submitted to posterior brachial plexus block with the aid of a nerve stimulator starting at 1 mA. When adequate muscle contraction was obtained, the current was decreased to 0.5 mA. If the response persisted, 40 mL of 0.5% ropivacaine was injected. The following parameters were evaluated: block onset, analgesia and motor block duration, complications and side effects.
RESULTS: Blockade was effective in 20 out of 22 patients, mean onset time was 15.52 min, mean surgical duration was 1.61 h. Mean analgesia duration was 15.85 h and mean motor block duration was 11.16 h. There were no clinical signs or symptoms of toxic effects of local anesthetics and no patient presented side effects.
CONCLUSIONS: Posterior brachial plexus block with the aid of nerve stimulator provides effective anesthesia, is very comfortable for patients and easy to perform.
Key Words: ANESTHETICS, Local: ropivacaine; ANESTHETIC TECHNIQUES, Regional; brachial plexus; SURGERY, Orthopedic
JUSTIFICATIVA Y OBJETIVOS: Existen varios
modos de abordar el plexo braquial dependiendo de la experiencia del anestesiologista
y de la región que será operada. El bloqueo del plexo braquial por
la vía posterior puede representar una alternativa para cirugías de
hombro, clavícula y húmero proximal. El objetivo de este estudio fue
mostrar los resultados observados en pacientes sometidos a bloqueo del plexo
braquial por la vía posterior con el uso del neuroestimulador y ropivacaína
MÉTODO: Veintidós pacientes con edad entre 17 y 76 años, estado físico ASA I y II, sometidos a cirugías ortopédicas envolviendo el hombro, clavícula y húmero proximal fueron anestesiados con bloqueo de plexo braquial por la vía posterior utilizando neuroestimulador desde 1 mA. Lograda la contracción deseada, la corriente fue disminuida para 0,5 MA y, permaneciendo la respuesta contráctil, fueron inyectados 40 mL de ropivacaína a 0,5%. Fueron evaluados los siguientes parámetros: latencia, analgesia, duración de la cirugía, duración de la analgesia y del bloqueo motor, complicaciones y efectos colaterales.
RESULTADOS: El bloqueo fue efectivo en 20 de los 22 pacientes; la latencia media fue de 15,52 min; la duración media de la cirugía fue de 1,61 hora. La media de duración de la analgesia fue de 15,85 horas y del bloqueo motor 11,16 horas. No fueron observados señales y síntomas clínicos de toxicidad del anestésico local y ningún paciente presentó efectos adversos del bloqueo.
CONCLUSIONES: En las condiciones de este estudio el bloqueo del plexo braquial por la vía posterior con el uso del neuroestimulador y ropivacaína a 0,5% demostró que es una técnica efectiva, confortable para el paciente y de fácil realización.
There are several approaches to the brachial plexus, including paresthesia, transarterial puncture, loss of resistance and neurostimulation. Blockade techniques vary according to surgical site and anesthesiologist's experience, and may be performed by interscalenic, intersternocleidomastoid, supraclavicular, infraclavicular or axillary approach 1.
Interscalenic is one of the most popular approaches for orthopedic surgeries involving the shoulder 2, with advantages for patients, surgeons and anesthesiologists 3.
Posterior brachial plexus access, also known as cervical paravertebral block, is an alternative. It has been firstly described by Kappis 4 in 1912 and remained forgotten for almost 80 years before Pippa 5 in 1990, rediscovered the technique and applied loss of resistance to locate the plexus.
The administration of 30 to 40 mL of 0.5% ropivacaine promotes brachial plexus block similar to that promoted by 0.5% subclavian perivascular, axillary or interscalenic bupivacaine 6.
This study aimed at describing posterior brachial plexus block approach with the aid of nerve stimulator, as well as presenting the results obtained with 0.5% ropivacaine.
After the approval of the Publication and Disclosure Board, Clínica São Bernardo, RJ, participated in this prospective study 22 patients aged 17 to 76 years, physical status ASA I and II, submitted to orthopedic shoulder, clavicle and proximal humerus surgeries. Exclusion criteria were patients with infections at blockade site. All patients were thoroughly informed about the technique and gave their consent to participate in the study. Patients were not premedicated. After venous access with 18G or 20G catheter in the contralateral limb, intravenous lactated Ringer's was started. Monitoring consisted of cardioscopy at DII lead, noninvasive blood pressure and pulse oximetry. Patients were sedated with intravenous fentanyl (1.5 µg.kg-1) before blockade, and after blockade installation, sedation was complemented with intermittent (1 mg) midazolam boluses.
Patients were placed in the lateral position with the head comfortably supported by a pillow. The arm to be anesthetized was turned upward and cervical spine was bent. An imaginary line of the posterior cricoid cartilage was drawn on the neck, towards the apophysis of the 6th cervical vertebra. Puncture site corresponded to a point 3 cm laterally to midline of C6 and C7 intervertebral space (Figure 1).
After subcutaneous infiltration with 2% lidocaine (80 mg), an 100 mm insulated needle connected to a nerve stimulator (Stimuplex®, B. Braun Melsungen AG, 21G 0.8 x 100 mm needle) adjusted to release a square pulsatile current of 1 mA, at 1 Hz, was slightly laterally inserted 4 to 7 cm, attempting to stimulate axillary nerve with deltoid or suprascapular muscle contraction with shoulder elevation. When desired contraction was obtained, current was decreased to 0.5 mA and if response persisted, 40 mL of 0.5% ropivacaine were administered after negative aspiration of blood.
Anesthesia was evaluated by painful stimulation with surgical clamp to determine the extension of sensory block on the shoulder and the arm at 20 minutes and at the end of surgery. Motor block was evaluated by modified Bromage's scale: 0 = no block, total arm and forearm flexion; 1 = partial block, total forearm and partial arm flexion; 2 = almost complete block, inability to flex the arm and decreased ability to flex the forearm; 3 = total block, inability to flex both arm and forearm at 20 minutes and at surgery completion.
The following parameters were also evaluated: 1) anesthesia onset: time between anesthetic injection and loss of sensitivity in the studied area (axillary nerve); 2) surgery duration: time between anesthetic injection and surgery completion; 3) sensory block duration: time between anesthetic injection and total sensitivity recovery evaluated by painful stimulation with surgical clamp on shoulder and arm; 4) motor block duration: time between motor block installation and total recovery of movements; 5) analgesia duration: time between onset and the first analgesic request by patient; 6) complications and side effects.
Failure was defined as absence of anesthesia in areas supplied by supraclavicular, suprascapular and axillary nerves 20 minutes after local anesthetic injection, when general anesthesia was induced. To correct rotator cuff injuries with incision on the anterior axillary line innervated by T1-T2 thoracic branches, subcutaneous infiltration was performed with 10 mL of 0.5% ropivacaine.
One patient was given 1 mL iohexol contrast (300 mg.mL-1) to confirm needle location. Five patients were given 20 mL contrast associated to anesthetic agent to evaluate the spread of the local anesthetic solution.
At the end of the surgery, patients were transferred to the ward, after recovery in the operating room and, in case of pain, intravenous meperidine (30 mg) and dipirone (2 g) were administered. Patients were followed for 48 hours to evaluate complications at blockade site and satisfaction with the technique.
Results were evaluated by descriptive analysis of studied variables and, when adequate, by mean and standard deviation.
Blockade nerves at 20 minutes and at surgery completion are shown in table III and only the axillary nerve was blocked in all patients. Analgesia was adequate in 20 out of 22 patients, partial in 1 out of 22 patients and there has been total failure in 1 out of 22 patients. Motor block at 20 minutes was absent (level 0) in 1 out of 22 patients, level 1 in 4 out of 22 patients, level 2 in 8 out of 22 patients and level 3 in 9 out of 22 patients. At surgery completion, there was no motor block (level 0) in 1 out of 22 patients, level 2 in 8 out of 22 patients and level 3 in 13 out of 22 patients (Table III). There has been anesthesia on the anterior-lateral aspect of the neck and the ear (C2 and C3) in one patient.
No patient presented side effects such as hypotension, arrhythmias or other signs and symptoms of accidental intravascular injection, such as dizziness, tinnitus, perioral tingling, metal taste, irritability, shivering or seizure.
No patient presented dyspnea and cyanosis, which could represent unilateral diaphragm paralysis secondary to phrenic nerve block, and no patient has developed Horner's Syndrome or laryngeal-recurrent nerve paralysis. One patient developed hematoma at the operative site, which may have contributed for severe postoperative pain complaint.
With the development of new surgical techniques involving the scapulohumeral region, regional anesthesia has become increasingly important for providing further intra and postoperative comfort, promoting adequate analgesia and early hospital discharge. In our study, posterior brachial plexus block had a success rate of 91% (20 out of 22 patients) with only one total failure.
Pain induced by this procedure has a dynamic component and may go from moderate at rest to severe on mobilization. Approximately 70% of patients refer severe pain after surgeries involving major joints (shoulder and knee), being more severe when compared to post hysterectomy, gastrectomy or thoracotomy pain (60%) 7. This is due to massive nociceptive discharge originated by highly innervated joint tissues, which produces severe somatic pain and periods of reflex spasm of muscles innervated by the same spinal segments 7. In addition, periarticular structures have not only afferent C fibers, but also Aa and Ab fibers 8, being the latter poorly blocked by opioids 9.
Posterior brachial plexus block has promoted effective anesthesia for shoulder, clavicle and proximal humerus procedures. Patients were comfortably operated in the seating position and sedated with low fentanyl and midazolam doses. General anesthesia was needed in three patients only. Among these, one had total blockade failure and the other two needed general anesthesia complementation due to surgical procedure characteristics (shoulder arthroplasty and arthroscopy). There was one partial failure complemented with 100 µg intravenous fentanyl associated to intermittent 1 mg intravenous midazolam doses.
For rotator cuff correction with incision on the anterior axillary line innervated by T1-T2 thoracic branches, subcutaneous tissue was infiltrated with local anesthetics because no brachial plexus block technique consistently blocks this region 10.
The administration of 40 mL ropivacaine has promoted mean 16-hour analgesia, varying from 9 to 24 hours, with no need for opioids, being considered adequate and long-lasting, allowing for early hospital discharge in less than 24 hours for some patients.
To completely anesthetize the shoulder, it is mandatory to block supraclavicular, suprascapular and axillary nerves. The supraclavicular nerve (C3-C4) promotes sensorial innervation of the capsule extending to the second rib and involving the shoulder. The suprascapular nerve (C5-C6) contains sensory fibers from the posterior capsule of the shoulder, the acromion-clavicular junction and from the skin of the proximal third of the humerus and the axilla, being responsible for 70% of joint innervation. These nerves may need isolated blockade to promote analgesia during shoulder procedures 11. Our study has shown supraclavicular nerve block in 20 out of 22 patients, suprascapular nerve block in 20 out of 22 patients, and axillary nerve block in all patients at surgery completion, thus being an alternative for shoulder blockade.
In the posterior block technique, anesthetic solution is injected close to the origin of spinal nerves originating from the intervertebral foramen, site in which anesthetic spread is less affected by septum. As in other paravertebral blocks, gravity may be the most important factor directing the spread of anesthetic solutions 12-14, which can explain the blockade of more caudal roots observed in most patients at surgery completion. Although the number of studied patients was low, no systemic or local complications were observed, which has also been described in another study 4 where the author has compared the posterior approach to Winnie's technique and has only found complications with the latter.
Whenever brachial plexus block is performed, there is concern about the volume of local anesthetic to be injected. The potential ratio between injected volume and extension of analgesia has been firstly described in 1961 15. Volumes between 40 and 55 mL are associated to higher brachial plexus block success rates, regardless of the approach 16. Diluted solutions and higher volumes favor blockade expansion both cranially and caudally 17.
Ropivacaine is a well-tolerated local anesthetic with efficacy similar to bupivacaine. However, it may represent a better option for its lower neurological and cardiovascular toxicity 6. In this posterior brachial plexus block series, 40 mL of 0.5% ropivacaine were responsible for the success in 20 out 22 patients.
The use of nerve stimulator for brachial plexus location has the advantage of promoting muscle contraction when getting close to the nerve (electric stimulation response), with no need for painful mechanical stimulation (paresthesia), which may potentially cause nerve injury, although infrequently. Positive results with nerve stimulators reach 97% 18.
In the conditions of our study, posterior brachial plexus block with nerve stimulator has shown to be a comfortable technique for patients (lateral position), easy to perform (easily identifiable spinous processes), in addition to being safe and effective.
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Dra. Lúcia Beato
Address: Rua Gal Dionísio, 44/201- Humaitá
ZIP: 22271-050 City: Rio de Janeiro, Brazil
Submitted for publication March 3, 2004
Accepted for publication March 14, 2005
* Received from Clínica São Bernardo, Casa de Saúde Santa Maria e Hospital Municipal Barata Ribeiro, Rio de Janeiro, RJ