Comparative study for the postoperative analgesic efficacy of 20 mL at 0.5, 0.75, and 1% ropivacaine in posterior brachial plexus block

Abstracts

JUSTIFICATIVA E OBJETIVOS: As intervenções cirúrgicas por via artroscópica no ombro estão relacionadas com a dor pós-operatória de grande intensidade. Dentre as técnicas de analgesia, o bloqueio do plexo braquial é a que oferece os melhores resultados. O objetivo deste estudo foi determinar qual concentração de anestésico local no bloqueio de plexo braquial pela via posterior propicia analgesia pós-operatória mais prolongada para essas operações. MÉTODO: Noventa pacientes submetidos ao bloqueio do plexo braquial pela via posterior foram divididos aleatoriamente em três grupos de 30. Grupo 1: 20 mL de ropivacaína a 0,5%; Grupo 2: 20 mL de ropivacaína a 0,75%; Grupo 3: 20 mL de ropivacaína a 1%. O bloqueio foi avaliado por meio da pesquisa de sensibilidade térmica utilizando-se algodão embebido em álcool e a dor pós-operatória foi avaliada seguindo-se uma escala numérica verbal (ENV) nas primeiras 48 horas. RESULTADOS: Nos três grupos a analgesia pós-operatória foi similar segundo os parâmetros avaliados; ENV de dor média, tempo até a primeira queixa de dor e consumo de opióides no pós-operatório. CONCLUSÕES: Este estudo mostrou que o bloqueio do plexo braquial pela via posterior é uma técnica que promove analgesia eficaz para intervenções cirúrgicas no ombro. Utilizando-se 20mL de ropivacaína, as três diferentes concentrações estudadas promovem analgesia similar.

ANESTÉSICOS, Local; CIRURGIA, Ortopédica; DOR, Pós-operatória; TÉCNICAS ANESTÉSICAS, Regional

SCIENTIFIC ARTICLE

Comparative study for the postoperative analgesic efficacy of 20 mL at 0.5, 0.75, and 1% ropivacaine in posterior brachial plexus block^*

Estudio comparativo de la eficacia analgésica postoperatoria de 20 mL de ropivacaina a 0,5, 0,75 ó 1% en el bloqueo de plexo braquial por la vía posterior

Marcos Guilherme Cunha Cruvinel, TSA^I; Carlos Henrique Viana de Castro, TSA^II; Yerkes Pereira Silva^III; Bruno Salomé de Morais, TSA^IV; Flávio de Oliveira França^V; Flávio Lago^V

^IAnestesiologista do Hospital Lifecenter; Especialista em Clínica Médica; Certificado de Área de Atuação em Dor pela SBA

^IIAnestesiologista do Hospital Lifecenter; Especialista em Clínica Médica; Especialista em Terapia Intensiva pela AMIB

^IIIAnestesiologista do Hospital Lifecenter; Doutor em Pediatria pela UFMG

^IVAnestesiologista do Hospital Lifecenter

^VOrtopedista do Hospital Lifecenter

Correspondence to

SUMMARY

BACKGROUND AND OBJECTIVES: Arthroscopic shoulder surgeries are associated with severe postoperative pain. Among the analgesic techniques available, brachial plexus block has the best results. The objective of this study was to determine which concentration of local analgesic used in the posterior brachial plexus block provides longer postoperative analgesia.

METHODS: Ninety patients undergoing posterior brachial plexus block were randomly divided into three groups of 30 patients each. Group I: 20 mL of 0.5% ropivacaine; Group 2: 20 mL of 0.75% ropivacaine; and Group 3: 20 mL of 1% ropivacaine. The blockade was evaluated by assessing the thermal sensitivity using a cotton pad with alcohol and postoperative pain was evaluated according to a Verbal Numeric Scale (VNS) in the first 48 hours.

RESULTS: Postoperative analgesia was similar in all three groups according to the parameters evaluated: mean VNS, time until the first complaint of pain, and postoperative opioid consumption.

CONCLUSIONS: This study demonstrated that posterior brachial plexus block provides effective analgesia for shoulder surgeries. Twenty milliliters of ropivacaine in the different concentrations used in this study promoted similar analgesia.

Key Words: ANESTHETICS, Local: ropivacaine; ANESTHETIC TECHNIQUE, Regional: brachial plexus; PAIN, Postoperative; SURGERY, Orthopedic.

RESUMEN

JUSTIFICATIVA Y OBJETIVOS: Las intervenciones quirúrgicas por vía artroscópica en el hombro se relacionan con el dolor postoperatorio de gran intensidad. Entre las técnicas de analgesia, el bloqueo del plexo braquial es la que ofrece los mejores resultados. El objetivo de este estudio fue determinar cuál concentración de anestésico local en el bloqueo de plexo braquial por la vía posterior, propicia analgesia postoperatoria más prolongada para esas operaciones.

MÉTODO: Noventa pacientes sometidos al bloqueo del plexo braquial por la vía posterior se dividieron aleatoriamente en tres grupos de 30. Grupo 1: 20 mL de ropivacaina a 0,5%; Grupo 2: 20 mL de ropivacaina a 0,75%; Grupo 3: 20 mL de ropivacaina a 1%. El bloqueo se evaluó a través de la investigación de sensibilidad térmica utilizando algodón con alcohol y el dolor postoperatorio se evaluó según una escala numérico verbal (ENV) en las primeras 48 horas.

RESULTADOS: En los tres grupos la analgesia postoperatoria fue similar según los parámetros evaluados; ENV de dolor medio, tiempo hasta el primer quejido de dolor y consumo de opioides en el postoperatorio.

CONCLUSIONES: Este estudio mostró que el bloqueo del plexo braquial por la vía posterior es una técnica que promueve una analgesia eficaz para intervenciones quirúrgicas en el hombro. Utilizando 20 mL de ropivacaina, las tres diferentes concentraciones estudiadas promueven analgesia similar.

INTRODUCTION

Pain associated with shoulder surgeries is usually severe. Therefore, adequate pain control is fundamental for fast patient rehabilitation ^1,2. Brachial plexus block shows the best results in postoperative analgesia ^3-7. The posterior interscalene brachial plexus block, also known as paravertebral cervical block, is associated with effective pain control in the first postoperative hours ^5-13. The objective of this randomized prospective study was to evaluate whether posterior brachial plexus block with high concentrations of ropivacaine would promote prolonged postoperative analgesia in arthroscopic surgeries. Besides, it also aimed at determining which of the three concentrations provided longer lasting analgesia.

METHODS

After approval by the Ethics Commission and signing of the informed consent, 90 patients, older than 18 years, physical status ASA I or II, scheduled for arthroscopic shoulder surgeries were enrolled in the study. Exclusion criteria were: cardiac, respiratory, liver, and kidney diseases, allergy to local anesthetics, neuropathies, cognitive deficits, body mass index greater than 45, skin infection at the site of the blockade, or paralysis of the contralateral hemidiaphragm. Twenty milliliters of ropivacaine were administered and the patients were randomly divided in three groups (Group 1 - 0.5%, Group 2 - 0.75%, and Group 3 - 1%) using a table with random numbers.

Monitoring consisted of electrocardiogram (D_II, V₅), pulse oximeter, and non-invasive automatic blood pressure. Patients did not receive pre-anesthetic medication and they were all admitted on the day of the surgery. The patients were placed in lateral decubitus with the shoulder to be operated upward, and a pillow was placed under their head, which was flexed in relation to the neck. Oxygen (3 L.min^-1) was administered via a nasal cannula. Sedation was aimed at keeping patients calm, cooperative, and responsive to verbal stimuli. Initially, 0.1 µg.kg^-1 of intravenous sufentanil were administered. If the effect produced was not enough, sedation would be supplemented with up to 3 mg of intravenous midazolam.

With the patients in lateral decubitus, their heads placed on a pillow, and neck flexed in relation to the chest, the spinous processes of C₆ and C₇ were identified and marked with a demographic pen. The puncture site was located 3 cm lateral to the space between the spinous processes. After antisepsis with alcoholic chlorhexedine, the skin was infiltrated with 1% lidocaine without vasoconstrictor using a 4.5 × 13-mm needle and 1-mL syringe. Afterwards, the trajectory of the puncture was infiltrated with 5 mL of anesthetic using a 25 × 7-mm needle. Using a 100-mm 22G needle (Stimuplex A100 BBraun, Melsungen, Germany) connected to a neurostimulator (Stimuplex-DIG, BBraun - Melsungen, Germany), whose initial parameters included intensity of 1 mA, stimulation time 0.1 µs, and frequency of 2 Hz, the needle was introduced perpendicular to the skin. When the needle touched the transverse process, it was removed and reintroduced with a lateral angulation to a depth of 2 cm beyond the transverse process, until a motor response was obtained. Motor responses accepted included those of the deltoid or biceps muscles, besides internal rotation of the shoulder. The intensity of the stimulus was reduced progressively until the absence of motor response, which would, ideally, occur with a current lower than 0.6 mA. After negative aspiration of blood, 2 mL of 2% lidocaine with 1:200,000 adrenaline were administered. When the motor response was interrupted and the heart rate did not show an increase of more than 20 bpm, the local anesthetic was administered, according to the study group, in fractionated 5-mL doses. When a 0.6-mA stimulus did not induce a motor response, the needle was repositioned.

The groups were divided as follows:

• Group 1 - 20 mL of 0.5% ropivacaine

• Group 2 - 20 mL of 0.75% ropivacaine

• Group 3 - 20 mL of 1% ropivacaine.

The solution was prepared as follows:

• Group 1 - 10 mL of 1.0% ropivacaine + 10 mL bidistilled sterile water,

• Group 2 - 20 mL of 0.75% ropivacaine, and

• Group 3 - 20 mL of 1% ropivacaine.

All patients underwent general balanced anesthesia and anesthetic induction with sufentanil (0.40 to 0.50 µg.kg^-1), propofol (2.0 to 2.5 mg.kg^-1), and cisatracurium (0.15 mg.kg^-1). Sevoflurane was used for maintenance. Dexamethasone, 10 mg, and ondansetron, 4 mg, were used for the prophylaxis of nausea and vomiting. Clonidine, 1 µg.kg^-1, was used for controlled hypotension.

The blockade was assessed through thermal sensitivity using a cotton pad with alcohol on the cutaneous representation of the C₃ to C₇ nerve roots thirty minutes after admission to the recovery room. In the first evaluation, thermal sensitivity of the contralateral nerve roots from C₅ to C₆ was also assessed to evaluate a probable epidural block. Postoperative pain was evaluated using a Verbal Numeric Scale (VNS) of pain varying from zero (absence of pain) to ten (the worst possible pain). The evaluator was not aware of the concentration of anesthetic used. In the recovery room, this evaluation was done 30 minutes after the admission of the patient and immediately before his/her discharge. It was then assessed every eight hours during the hospital stay, and through the telephone after the patient was discharged, which was done 24 hours after the surgery. The three higher intensity VNSs in three different moments, in the recovery room, in the first 24 hours, and between 24 and 48 hours were considered. Morphine consumption was evaluated by adding the cumulative dose needed in the recovery room and in the first 24 hours. After this period, the consumption of codeine was evaluated.

All patients received fixed doses of analgesics. During the hospital stay, 2 g of dypirone every 6 hours and 100 mg of ketoprofen every 12 hours, intravenously, were administered. After the hospital discharge, 2 g of dypirone every 8 hours and 200 mg of celecoxib once a day, orally, were prescribed. Supplementary postoperative analgesia was standardized as follows:

During the hospitalization: 4 mg of intravenous morphine every 4 hours for pain greater than 3 on the VNS. After hospital discharge: 30 mg of codeine/500 g of paracetamol, per os, every 4 hours for pain above 3 on the VNS.

All groups were compared regarding VNS scores and analgesic consumption in three moments (recovery room, in the first 24 hours, and between 24 and 48 hours), as well as the time between the blockade and the first complaint of pain.

ANOVA was used to evaluate the weight in all three groups (0.5%, 0.75%, and 1%). The other parameters, namely age, height, pain in the recovery room, pain in the first 24 hours, and pain between 24 and 48 hours, and even the time until the first complaint of pain, were analyzed by the Kruskal-Wallis test. In this study, the Chi-square test for independence and Fisher's exact test were used to verify the association, or the lack of association, among parameters of interest. A level of 5% was considered significant.

RESULTS

All 90 patients completed the study and intercurrences were not observed during the blockade. Analysis of the demographic data did not show statistically significant differences among the three groups (Table I). Thermal sensitivity was blocked on the cutaneous representation of the C₃ to C₇ nerve roots. No cases of contralateral blockade were detected. Table II shows the mean VNS scores in the recovery room, in the first 24 hours, and between 24 and 48 hours. There were no statistically significant differences in the time until the first complaint of pain among the three groups (Table III and Figure 1). Regarding the need of opioids, the groups did not show statistically significant differences in the evaluation periods (Figure 2).

DISCUSSION

Shoulder surgeries are extremely painful and for proper control of pain in those procedures some form of regional technique should be used ³. The interscalene brachial plexus block, described by Winnie (lateral approach) is more commonly used in shoulder surgeries ^5-9. Some alternatives to the Winnie technique have been proposed and, among them, the posterior brachial plexus block has been shown to be safe and effective ^9-16. A prior study observed that the use of 20, 30, or 40 mL of local anesthetic in the posterior approach promoted similar postoperative analgesia ¹³.

In the present study, the hypothesis that high concentrations of ropivacaine in the brachial plexus block associated with non-steroidal anti-inflammatories and dypirone promote prolonged analgesia in arthroscopic surgeries of the shoulder was confirmed. In the three groups in this study, pain scores were low, reflecting on a low consumption of opioids in the first 48 postoperative hours. However, significant differences in the parameters evaluated (VNS scores, time to the first complaint of pain, and opioid consumption) among the different concentrations, namely 0.5, 0.75, and 1%, were not observed.

Single dose regional anesthetic blocks, even using long-lasting local anesthetics, have a limited time of analgesia ¹⁷. This is secondary to removal of the drug from its site of action (peripheral nerve) and subsequent metabolism ad elimination ¹⁸. The duration of single-dose peripheral nerve blocks depends on the dose of the local anesthetic, its liposolubility, the degree of protein binding, and association with adjuvant vasoconstrictors, alpha-2 agonists, or opioids ¹⁸. In the present study, analgesia was effective in the first 48 hours with the association of long-lasting local anesthetic and high concentrations of systemic analgesics (anti-inflammatories, dypirone, and clonidine). However, to obtain analgesia beyond the 48 hours of the study, other alternatives, such as continuous blocks or liposomal preparation of local anesthetics, should be considered ¹⁹. The increase in the concentration from 0.5% to 1% ropivacaine was not effective in prolonging the duration of analgesia. The maximal concentration of ropivacaine for ulnar nerve block has been determined to be between 0.5% and 0.75% ²⁰. Similarly to the results of our study, Klein et al. observed that increasing the concentration from 0.5% to 0.75% of 30 mL of ropivacaine for the interscalene brachial plexus block did not show any benefits in the postoperative analgesia in shoulder surgeries ²¹, which indicates a probable plateau effect in the increase in the concentration of the local anesthetic regarding the prolongation of peripheral nerve blocks. Therefore, this increment in concentration is not related with any clinical benefits and can cause a higher toxicity due to the increase in the mass of anesthetic administered.

This study demonstrated that the posterior brachial plexus block with 20 mL of ropivacaine in the concentrations of 0.5, 0.75, and 1% associated with non-steroidal anti-inflammatories and dypirone promoted adequate and prolonged analgesia in the postoperative period of shoulder surgeries. The higher concentration of the local anesthetic did not increase the efficacy of the analgesia.

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*

Recebido dos Departamentos de Anestesiologia e Ortopedia do Hospital Lifecenter, Belo Horizonte, MG

Publication Dates

• Publication in this collection
  04 Sept 2008
• Date of issue
  Oct 2008

History

• Accepted
  18 June 2008
• Received
  29 Aug 2007