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Print version ISSN 0034-7094
Rev. Bras. Anestesiol. vol.51 no.3 Campinas May/June 2001
Axillary brachial plexus block with neurostimulator: evaluation of onset time and efficacy*
Bloqueio do plexo braquial por via axilar com neuroestimulador: verificação da latência e da eficácia
Bloqueo del plexo braquial por vía axilar con neuroestimulador: verificación de la latencia y de la eficacia
Itagyba Martins Miranda Chaves, TSA, M.D.I; Leandro Fellet Miranda Chaves, M.D.II; Clodoaldo Lopes Dias, M.D.II
CET/SBA do HUJF; Professor Adjunto IV da Disciplina de Anestesiologia da FM
IIEx-ME2 do CET/SBA do HUJF (2000)
Background and Objectives: Axillary
brachial plexus block, although widely used due to a low rate of complications,
has some drawbacks which limit its use: failure rate, long onset and restrictions
to forearm and hand surgery. This study aimed at evaluating onset time and efficacy
of axillary brachial plexus block using a nerve stimulator.
Methods: Participated in this prospective and open study, 38 patients physical status ASA I, II and III, aged 13 to 74 years, submitted to upper limb surgery. In the operating room, after monitoring, intravenous line and sedation with 1 to 3 mg midazolam, the patients were submitted to axillary brachial plexus block after the use of a nerve stimulator with decreasing currents starting with 0.9 mA and local anesthetic injection after obtaining fingers and hand motor response with the smallest stimulus. Sensory and motor onset, partial or total sensory and motor efficacy as well as failure and side effects were observed.
Results: Sensory and motor onset were 5.2 + 3.8 and 4.6 + 3.3 minutes, respectively. There were six partial sensory failures, ten partial motor failures and two total motor failures, while in twenty cases there were no failures. Just two cases needed to be reverted to general anesthesia.
Conclusions: We concluded that, in the conditions of our study, the use of nerve stimulator was useful in inducing axillary brachial plexus block, being important to emphasize that in most cases, no more than 0.3 mA was necessary to locate the nerves.
Key Words: ANESTHETICS, Local; bupivacaine; ANESTHETIC TECHNIQUES, Regional: brachial plexus block
JUSTIFICATIVA E OBJETIVOS:
O bloqueio do plexo braquial por via axilar, embora bastante difundido por ter
menor incidência de complicações, apresenta três inconvenientes
que limitam seu uso: índice de falhas, latência longa e restrição
a cirurgias de antebraço e mão. O objetivo deste estudo foi verificar
o tempo de latência e a eficácia do bloqueio do plexo braquial por
via axilar empregando-se um estimulador de nervo.
MÉTODO: Participaram do estudo, aberto, prospectivo, 38 pacientes, estado físico ASA I, II e III, com idades entre 13 e 74 anos, submetidos a cirurgia de membro superior. Na sala de operação, após monitorização, venóclise, sedação com 1 a 3 mg de midazolam por via venosa, os pacientes foram submetidos ao bloqueio do plexo braquial por via axilar, após emprego de estimulador de nervo, com amperagens decrescentes a partir de 0,9 mA e injetando-se o anestésico local, após obtenção de resposta motora dos dedos da mão, com menor amperagem. Foram observadas as latências sensitiva e motora, a eficácia e falhas sensitiva e motora, parciais ou totais, e efeitos colaterais.
RESULTADOS: As latências sensitiva e motora foram, respectivamente, 5,2 + 3,8 e 4,6 + 3,3 minutos. As falhas parciais sensitivas foram em número de seis, as motoras dez e completas duas, enquanto que em vinte casos não ocorreram falhas. Apenas em dois casos foi necessário converter para anestesia geral.
CONCLUSÕES: Concluímos que, nas condições deste estudo, o uso do estimulador de nervo mostrou-se útil para a realização do bloqueio, sendo que, na maioria dos casos, não foi necessário estímulo maior que 0,3 mA.
Unitermos: ANESTÉSICOS, Local: bupivacaína; TÉCNICAS ANESTÉSICAS, Regional: plexo braquial
JUSTIFICATIVA Y OBJETIVOS:
El bloqueo del plexo braquial por vía axilar, aun cuando bastante difundido
por tener menor incidencia de complicaciones, presenta tres inconvenientes que
limitan su uso: índice de fallas, larga latencia y restricción a cirugías
de antebrazo y mano. El objetivo de este estudio fue verificar el tiempo de
latencia y la eficacia del bloqueo del plexo braquial por vía axilar usándose
un estimulador de nervio.
MÉTODO: Participaron del estudio, abierto, prospectivo, 38 pacientes, estado físico ASA I, II y III, con edades entre 13 y 74 años, sometidos a cirugía de miembro superior. En la sala de operación, después de monitorización, venóclisis, sedación con 1 a 3 mg de midazolam por vía venosa, fueron sometidos al bloqueo del plexo braquial por vía axilar, después uso del estimulador de nervio, con amperajes decrecientes a partir de 0,9 mA e inyectándose el anestésico local, después de la obtención de respuesta motora de los dedos de la mano, con menor amperaje. Fueron observadas las latencias sensitiva y motora, la eficacia y fallas sensitiva y motora, parciales o totales, y efectos colaterales.
RESULTADOS: Las latencias, sensitiva y motora fueron, respectivamente, 5,2 + 3,8 y 4,6 + 3,3 minutos. Las fallas parciales sensitivas fueron en número de seis, las motoras diez y completas dos, en cuanto que en veinte casos no ocurrieron fallas. Apenas en dos casos fue necesario convertir para anestesia general.
CONCLUSIONES: Concluimos que, en las condiciones de este estudio, el uso del estimulador de nervio se mostró útil para la realización del bloqueo, siendo que, en la mayoría de los casos, no fue necesario estímulo mayor que 0,3 mA.
Axillary brachial plexus block has proven to be an excellent technique for forearm and hand surgery, however not excluding arm procedures 1. According to Finucane, single axillary injection techniques may take up to 60 minutes to reach all plexus nerves 2. On the other hand, Vieira et al have obtained 97.1% of total supraclavicular blockades using a neurostimulator with a 0.5 mA current for fingers or hand motor responses 3.
Neurostimulators were first used during the 60's 4 and are being increasingly used for their advantages, especially simplicity, safety, good results and relatively low cost.
This study aimed at evaluating onset time and efficacy of axillary brachial plexus block using a neurostimulator.
After the Hospital's Medical Ethics Committee approval and their informed consent, participated in this prospective and open study 38 patients physical status ASA I, II and III, aged 13 to 74 years, submitted to axillary brachial plexus block for upper limb surgery. Exclusion criteria were: patient's refusal, infection on injection site and significant abnormal coagulation.
After monitoring with cardioscopy at DII and non-invasive blood pressure, a venous puncture was performed in the contralateral limb with an 18 or 20 G teflon catheter and hydration was installed with lactated Ringer's. Patients were sedated with 1 to 3 mg intravenous midazolam and were kept conscious and responsive before the blockade and placed in the dorsal horizontal position with the head turned to the opposite side and the upper limb to be blocked in a 90º abduction with supination of forearm and hand. The whole posterior face of the limb was placed on a support. In case of difficulty in palpating the axillary artery, the position described was complemented with a 90º forearm flexion and arm rotation in the cephalad direction. The axillary artery was palpated and its path was identified until the most cephalad point where infiltrative local anesthesia was induced with 1% lidocaine (10 mg) without vasoconstrictor. The technique was performed with an electrically insulated 22G (5.4 cm) needle introduced tangentially to the artery in the cephalad direction, using a nerve stimulator. Stimulation was started with a 0.9 mA current and was progressively decreased until the sole obtention of all fingers flexion or extension, or fist flexion or extension with a 0.1 to 0.5 mA current. After this, 40 ml of 0.375% bupivacaine with epinephrine 1:200,000 were injected, after a test dose with 3 ml, in 5 ml increments with methodic and intermittent aspiration. Needle was kept still during injection and there was visual and oral contact with the patient. If a tourniquet was needed for upper limb ischemia, intercostobrachial nerves and the accessory branch of the internal cutaneous brachial nerve received local anesthesia in the skin of the medial and posterior borders of the proximal third of the arm with 1% lidocaine forming a hemi-bracelet.
Onset time was evaluated by needle pricking test and absence of sensitivity at local clamping sustained for 20 seconds in the regions innervated by radial, median ulnar and musculocutaneous nerves. Motor block was evaluated according to the mnemonic 4 Ps process: PUSH (forearm extension with the triceps to the radial nerve), PULL (forearm extension with biceps to the musculocutaneous nerve), PINCH (clamp between the 5th finger and thumb to the ulnar nerve) and PINCH (clamp between index and thumb to the radial nerve) 6 in addition to the nose index test.
Partial sensory fails were those in which patients referred localized mild pain, and motor fails, absence of motor block of one nerve or more. In those cases, 1 to 2 mg intravenous midazolam with or without 50 to 100 µg fentanyl were administered to allow the surgery to proceed.
Complications such as hypotension (decrease above 25% of baseline), tachycardia or bradycardia (values above or below 25% of baseline), dysrhythmias, signs or symptoms of accidental intravascular injection such as dizziness, hum, perioral numbness, metal taste, irritability, shivering or seizures and also the need to revert to general anesthesia or to exclude patients from the study were recorded.
Mean and standard deviation were used to show demographics, sensory and motor block onset (defined as the beginning of sensory analgesia and beginning of motor block installation).
Age, weight, height, gender and physical status data are shown in table I. Sensory and motor block onset time are shown in table II. In 32 (84.21%) of the 38 patients, less than 0.3 mA current was used and more in the remaining 6 patients as follows: 1 patient (2.63%) with 0.4 mA, 4 patients (10.52%) with 0.5 mA and only 1 (2.63%) with 2.5 mA. Since onset time varies depending on the plexus-composing nerve, the study has not included the onset time evaluation of separate nerves but of the brachial plexus as a whole. Although our objective was a stimulation between 0.1 and 0.5, this single case where response was only obtained with 2.5 mA was not excluded do not to compromise the fidelity of the study.
No patient had side-effects such as hypotension, tachycardia or bradycardia, dysrhythmias, nor other signs or symptoms of accidental intravascular injection such as dizziness, hum, perioral numbness, metal taste, irritability, shivering or seizure, and no patient was excluded.
Efficacy as well as failures are described in table III. There were two total failures with the need to revert to general anesthesia.
Brachial plexus block can be performed by several routes - interscalenic, supraclavicular - Winnie 7 and Winnie modified by Vieira 8 and axillary 1, as well as by different techniques - parestesia 9, nerve stimulator 5, transarterial 6, or combined and, more recently, cold saline-induced parestesia 10. The interscalenic route, although widely used for surgeries above the elbow very often promotes incomplete anesthesia of the ulnar nerve and is not recommended for patients sensitive to 25% reduction in pulmonary function, since phrenic nerve paralysis is present in all cases 11. The supraclavicular route, although being considered the most efffective 13 and reliable technique, poses a risk for phrenic nerve paralysis (up to 50% of cases) and pneumothorax (0.5% to 6%), which may occur up to 12 hours after the blockade. In the modification proposed by Vieira 8, although stating no possibility for pneumothorax, the author does not mention the risk of phrenic nerve paralysis. The axillary route, although eliminating the risk for pneumothorax and phrenic nerve paralysis is traditionally limited to hand and forearm surgeries although recently a study has shown its efficacy for elbow surgeries 12. Moreover, it may in some cases have up to 60 minutes onset time 2.
As to techniques, the intentional search for paresthesias is increasing the incidence of persistent paresthesias, making it undesirable 12. The transarterial route, although a study confirming its efficacy 7, is not free from major complications 13; the use of cold saline does not seem to be widely accepted by the international literature; the neurostimulator results in a higher rate of success as compared to other methods 3-13.
Having said that and taking into consideration Finucane and Vieira's statements 2,3, facing preliminary observations a hypothesis was risen that the axillary brachial plexus approach with the use of neurostimulator and low current would allow for a shorter blockade onset with a better quality and lower incidence of side-effects, especially phrenic nerve blockade and the so feared pneumothorax. The initial proposal was an open study involving patients scheduled for hand and forearm surgeries and, in two cases, surgeries above the elbow using the method described in this study.
Results with the use of neurostimulator and low current, even with a relatively small number of patients, have shown totally acceptable sensory and motor block onset time since when local anesthetics are injected when motor response is obtained with the lower possible current, this indicates that the needle is closer to the target, that is, the nerve stem. Other authors however suggest currents above 0.5 mA 5,6,12. In six cases where onset time was longer, there were localized sensory failures and local anesthetic was injected with currents above 0.3 mA (defined as low) however below 0.5 mA which is the current adopted in this study 3. Only one case needed higher current (2.5 mA), with partial failure that was supplemented with low midazolam-fentanyl doses allowing for the success of the surgery. In the ten motor failure cases, midazolam alone or associated to fentanyl allowed the surgery to be completed. It must be mentioned that most patients evaluated in the post-anesthetic care unit presented total analgesia and motor block. In fact, they should have not been classified as "sensory and motor failure" but as prolonged onset as already mentioned 2. Only two patients (5.3%) had a real total failure with the need to revert to general anesthesia.
We concluded that, in the conditions of this study, the use of a nerve stimulator was useful to perform axillary brachial plexus block and, in most cases, 0.3 mA stimuli were enough for nerve location. We suggest that new prospective, random and blind studies be performed.
We acknowledge Dr. Gabriel Pedrosa Machado (former resident CET/SBA of HUJF) for his precious cooperation in finishing this study.
01. Oliva Filho AL - Bloqueio do plexo braquial via axilar. Rev Bras Anestesiol, 1995;45:(Supl20):116-118.
02. Finucane BT - Practical Aspects of Brachial Plexus Block. Memórias, IV Congresso Panamericano de Anestesia Regional, 1998;77-78.
03. Vieira ZEG, Franco C, Winnie A - Bloqueio do plexo braquial: controvérsias. Anais do 45º Congresso Brasileiro de Anestesiologia, 1998:72.
04. Rodríguez J, Bárcena M, Alvarez J - Axillary brachial plexus anesthesia: electrical versus cold saline stimulation. Anesth Analg, 1996;83:752-754.
05. Raj PP, Montgomery SJ, Nettles D et al - Infraclavicular brachial plexus block: a new approach. Anesth Analg, 1973;52:897-904.
06. Brown DL - Brachial plexus block: an update. Annual Refresher Course Lectures, 1999;241:1-7.
07. Winnie AP - Regional anesthesia of the extremities. ASA Refresher Courses in Anesthesiology, 1991;19:233-251.
08. Vieira JL - Bloqueio do plexo braquial pela via perivascular subclávia modificada. Rev Bras Anestesiol, 1995;45(Sup20): 113-115.
09. Moore DC - Regional Block, 4th Ed, Springfield, Charles C Thomas Publisher, 1979;229.
10. Rodriguez J, Carceller J, Bárcena M et al - Cold saline is more effective in inducing paresthesia than room temperature saline in axillary block. Anesth Analg, 1995;81:329-331.
11. Urmey WF, McDonald M - Hemidiaphragmatic paresis during interscalene brachial plexus block: effects on pulmonary function and chest wall mechanics. Anesth Analg, 1992;74:352-357.
12. Schroeder LE, Horlocker TT, Schroeder DR - The efficacy of axillary block for surgical procedures about the elbow. Anesth Analg, 1996;83;747-751.
13. Stan TC, Krantz MA, Solomon DL et al - The incidence of neurovascular complications following axillary brachial plexus block using a transarterial approach. Reg Anesth, 1995;20:486-492.
Dr. Itagyba Martins Miranda Chaves
Address: Av. Independência, 1585/1403
ZIP: 36016-320 City: Juiz de Fora, Brazil
Submitted for publication June 8, 2000
Accepted for publication October 4, 2000
* Received from CET/SBA do Hospital Universitário de Juiz de Fora (HUJF), MG
01. Oliva Filho AL - Bloqueio do plexo braquial via axilar. Rev Bras Anestesiol, 1995;45:(Supl20):116-118. [ Links ]
02. Finucane BT - Practical Aspects of Brachial Plexus Block. Memórias, IV Congresso Panamericano de Anestesia Regional, 1998;77-78. [ Links ]
03. Vieira ZEG, Franco C, Winnie A - Bloqueio do plexo braquial: controvérsias. Anais do 45º Congresso Brasileiro de Anestesiologia, 1998:72. [ Links ]
04. Rodríguez J, Bárcena M, Alvarez J - Axillary brachial plexus anesthesia: electrical versus cold saline stimulation. Anesth Analg, 1996;83:752-754. [ Links ]
05. Raj PP, Montgomery SJ, Nettles D et al - Infraclavicular brachial plexus block: a new approach. Anesth Analg, 1973;52:897-904. [ Links ]
06. Brown DL - Brachial plexus block: an update. Annual Refresher Course Lectures, 1999;241:1-7. [ Links ]
07. Winnie AP - Regional anesthesia of the extremities. ASA Refresher Courses in Anesthesiology, 1991;19:233-251. [ Links ]
08. Vieira JL - Bloqueio do plexo braquial pela via perivascular subclávia modificada. Rev Bras Anestesiol, 1995;45(Sup20): 113-115. [ Links ]
09. Moore DC - Regional Block, 4th Ed, Springfield, Charles C Thomas Publisher, 1979;229. [ Links ]
10. Rodriguez J, Carceller J, Bárcena M et al - Cold saline is more effective in inducing paresthesia than room temperature saline in axillary block. Anesth Analg, 1995;81:329-331. [ Links ]
11. Urmey WF, McDonald M - Hemidiaphragmatic paresis during interscalene brachial plexus block: effects on pulmonary function and chest wall mechanics. Anesth Analg, 1992;74:352-357. [ Links ]
12. Schroeder LE, Horlocker TT, Schroeder DR - The efficacy of axillary block for surgical procedures about the elbow. Anesth Analg, 1996;83;747-751. [ Links ]
13. Stan TC, Krantz MA, Solomon DL et al - The incidence of neurovascular complications following axillary brachial plexus block using a transarterial approach. Reg Anesth, 1995;20:486-492. [ Links ]