A comparative study on the postoperative analgesic efficacy of 20, 30, or 40 mL of 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 volume de anestésico local no bloqueio de plexo braquial pela via posterior propicia analgesia pós-operatória para essas operações de maneira mais eficiente. MÉTODO: Noventa pacientes submetidos a bloqueio do plexo braquial pela via posterior foram divididos aleatoriamente em três grupos de 30. Grupo 1 - volume de 20 mL; Grupo 2 - volume de 30 mL; e Grupo 3 - volume de 40 mL. Em todos os grupos, o anestésico usado foi a ropivacaína a 0,375%. 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 24 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. No grupo de 20 mL houve um maior consumo de analgésicos não-opióides após a 12ª hora de pós-operatório. Nos grupos de 30 e 40 mL a extensão do bloqueio foi muito maior. 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. Os três diferentes volumes estudados promoveram analgesia similar. A maior extensão do bloqueio com volumes maiores não se traduziu em melhor analgesia.

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

SCIENTIFIC ARTICLE

A comparative study on the postoperative analgesic efficacy of 20, 30, or 40 mL of ropivacaine in posterior brachial plexus block^*

Estudio comparativo de la eficacia analgésica postoperatoria de 20, 30 o 40 mL de ropivacaína 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; Gustavo Prosperi Bicalho, 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 e Intensivista do Hospital Lifecenter

^VOrtopedista do Hospital Lifecenter

^{Correspondence to}

SUMMARY

BACKGROUND AND OBJECTIVES: Arthroscopic surgeries of the shoulder are accompanied by severe postoperative pain. Among the analgesic techniques, brachial plexus block offers the best results. The objective of this study was to determine which volume of local anesthetic in the posterior brachial plexus block offers more adequate analgesia for those procedures.

METHODS: Ninety patients undergoing posterior brachial plexus block were randomly divided in three groups of 30 patients: Group 1 – volume of 20 mL; Groups 2 – volume of 30 mL; Group 3 – volume of 40 mL. In all groups 0.375% ropivacaine was the anesthetic used. The blockade was evaluated by testing thermal sensitivity using a cotton ball embedded in alcohol, while postoperative pain was evaluated according to a verbal numeric scale (VNS) in the first 24 hours.

RESULTS: Postoperative analgesia was similar in all three groups according to the parameters evaluated: VNS of moderate pain, length of time until the first complaint of pain, and consumption of opioids. Consumption of non-opioid analgesics was greater in the 20 mL group after the 12^th postoperative hour. In the 30 and 40 mL groups, the extension of the blockade was significantly greater.

CONCLUSIONS: This study demonstrated that posterior brachial block promotes effective analgesia for surgeries of the shoulder. The three different volumes studied promoted similar analgesia. The greater extension of the blockade with larger doses did not translate into better analgesia.

Key Words: ANESTHETIC TECHNIQUES, Regional: brachial plexus blockade; ANESTHETICS, Local: ropivacaine; PAIN, postoperative; SURGERY, Orthopedic.

RESUMEN

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

MÉTODO: Noventa pacientes sometidos al bloqueo del plexo braquial por vía posterior fueron divididos aleatoriamente en tres grupos de 30. Grupo 1 – volumen de 20 mL; Grupo 2 – volumen de 30 mL; Grupo 3 – volumen de 40 mL. En todos los grupos, el anestésico usado fue la ropivacaína a 0,375%. El bloqueo se evaluó a través de la investigación de sensibilidad térmica utilizando algodón con alcohol y el dolor postoperatorio se evaluó secundando una escala numérica verbal (ENV) en las primeras 24 horas.

RESULTADOS: En los tres grupos la analgesia postoperatoria fue similar según los parámetros evaluados; ENV de dolor promedio, tiempo hasta el primer quejido de dolor y consumo de opioides en el postoperatorio. En el grupo de 20 mL hubo un mayor consumo de analgésicos no opioides después de la 12ª hora de postoperatorio. En los grupos de 30 y 40 mL la extensión del bloqueo fue significativamente mayor.

CONCLUSIONES: Este estudio mostró que el bloqueo del plexo braquial por la vía posterior es una técnica que promueve analgesia eficaz para intervenciones quirúrgicas en el hombro. Los tres diferentes volúmenes estudiados promovieron analgesia similar. La mayor extensión del bloqueo con volúmenes mayores no se tradujo en una mejor analgesia.

INTRODUCTION

Pain is one of the main problems after surgeries of the shoulder, and its proper control is fundamental for the fast rehabilitation of these patients ^1,2. Among the postoperative analgesic techniques used in this situation, brachial plexus block has better results ^3-7. Among the techniques of brachial plexus block, the lateral interscalene is used more often ^5-8. Recently, the posterior approach of the interscalene brachial plexus block, also known as paravertebral cervical block ^9-11, has received wide attention. The most adequate volume of local anesthetic that should be used has not been defined. Volumes ranging from 20 to 50 mL have been used ^3-11. The objective of this prospective study, with random distribution of patients among three groups, was to compare the efficacy of postoperative analgesia in arthroscopic surgeries of the shoulder promoted by the posterior brachial plexus block with three different volumes of ropivacaine.

METHODS

After approval by the Ethics Commission and signing an informed consent, 90 patients older than 18 years, physical status ASA I or II, scheduled for arthroscopies of the shoulder, participated in this study. Exclusion criteria included heart disease, respiratory, liver, or renal diseases; allergy to local anesthetics; neuropathies, cognitive deficit; body mass index greater than 45; infection of the skin at the site of the blockade and paralysis of the hemidiaphragm opposite to the blockade. Patients were randomly divided in three groups (group 1 – 20 mL, group 2 – 30 mL, group 3 – 40 mL) using a table of random numbers.

Monitoring consisted of ECG (DII, V5); pulse oximetry and automatic, non-invasive, blood pressure. Patients did not receive pre-anesthetic medication and they were admitted to the hospital on the day of the procedure. Patients were placed on lateral decubitus, with the affected shoulder up, and head on a pillow in anterior flexion. Oxygen (3 L.min^-1) was administered through a nasal catheter. Patients were sedated to remain calm, cooperative, and answering to verbal commands, with 0.1 µg.kg^-1 of intravenous sufentanil. If the effect produced was not satisfactory, sedation would be complemented with up to 3 mg of intravenous midazolam.

With the patient in lateral decubitus, head on a pillow in anterior flexion, the spinous processes of C₆ and C₇ were identified by marking the skin with a dermographic pen. The puncture was 3 cm lateral to the space between the spinous processes. After preparing the skin with alcoholic chlorhexedine, it was infiltrated with 1% lidocaine without adrenaline using a 4.5 ´ 13 mm needle and 1 mL syringe. Afterwards, the path of puncture was infiltrated with a 25 ´ 7 mm syringe and 5 mL of the anesthetic. Using an isolated 22G needle, 100 mm long (Stimuplex A100 BBraun, Germany), connected to the neurostimulator (Stimuplex-DIG, BBraun – Melsungen, Germany) with the initial setting of 1 mA, length of stimulation of 0.1 µs, and frequency of 2 Hz, the needle was introduced perpendicular to the skin. When the transverse process was touched, the needle was removed and reintroduced, angled laterally, to a depth of 2 cm beyond the depth necessary to touch the spinous process, until a motor response was obtained. Motor responses of the levator scapulae, deltoid, or biceps muscles were acceptable. The intensity of the stimulus was progressively reduced until there was no motor response, which would occur, ideally, with a current below 0.5 mA. After verifying the negative aspiration of blood, 2 mL of 2% lidocaine with 1:200,000 adrenaline were injected. When motor response was abolished and heart rate did not increase by more than 20 bpm, the selected volume of local anesthetic was injected, according to the group the patient belonged, in fractionated volumes of 5 mL. When motor response with a stimulus greater than 0.5 mA was abolished, 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 with 20 mL of 0.75% ropivacaine and 20 mL of sterile bidistilled water.

All patients received general balanced anesthesia. Anesthetic induction was accomplished with sufentanil (0.20 to 0.30 µg.kg^-1), propofol (2.0 to 2.5 mg.kg^-1), and cisatracurium (0.15 mg.kg^-1). Sevoflurane was used for maintenance of anesthesia. Clonidine, 1 µg.kg^-1, was used for prophylaxis of nausea and vomiting.

The blockade was evaluated by verifying the thermal sensitivity using cotton embedded in alcohol following the skin representation of nerve roots and nerves in three distinct moments. Thirty minutes after the institution of the blockade, i.e., immediately before induction of general anesthesia; 30 minutes after admission to the recovery room; and twenty-four hours after the blockade, before discharge from the hospital.

Postoperative pain was evaluated using a verbal numeric scale (VNS) ranging from zero (absence of pain) to ten (the worst pain possible). The evaluator did not know the volume of anesthetic injected. In the recovery room, pain evaluation was done 30 minutes after admission and immediately before discharge from the unit. Afterwards, pain was evaluated every 4 hours in the first 24 hours after the blockade. It was considered the greatest severity of the VNS in three different moments, in the recovery room, in the first 12 hours, and between 12 and 24 hours after the blockade. The consumption of analgesics was evaluated by adding the accumulated dose in the recovery room and in the first 24 hours.

Standard supplemental postoperative analgesia was used according to the following parameters:

• VNS of zero – analgesics were not administered;

• VNS from 1 to 3 – intravenous dypirone, 2 g, and ketorolac, 30 mg, except in case of allergy to one of the drugs;

• VNS from 4 to 6 – intravenous dypirone, 2 g, and ketorolac, 30 mg; acetaminophen 500 mg with codeine 30 mg by oral route (except in case of allergy to one of the drugs);

• VNS > 6 – intravenous dypirone, 2 g, ketorolac, 30 mg, and morphine, 4 g (except in cases of allergy to one of the drugs).

It was observed a 6-hour interval before the next dose of dypirone and codeine, 8-hour interval for ketorolac, and 4-hour interval for morphine and codeine/acetaminophen.

Groups were compared regarding VNS scores and consumption of analgesics in three moments (recovery room, in the first 12 hours, and between 12 and 24 hours), the length of time between the blockade and the first complaint of pain, the number of patients with VNS scores below 4, and the territories that were blocked.

Weight, height, pain scale in the recovery room, and the length of time until the first complaint of pain were tested in each group (20, 30, and 40 mL) using the ANOVA. The non-parametric Kruskal-Wallis test was used for age and pain in the first 12 hours, and pain between 12 and 24 hours. In this study, both the interdependency Chi-square test and Fisher Exact test were used to verify the association, or lack of, among the parameters of interest. A level of 5% was considered significant.

RESULTS

All 90 patients completed the study. Analysis of the demographic data showed no statistically significant differences among the three groups (Table I). Table II shows the mean VNS scores in the recovery room, in the first 12 hours, and between 12 and 24 hours. There were no statistically significant differences in VNS in any of the moments. There were also no statistically significant differences in the length of time until the first complaint of pain among the three groups (Figure 1). As for the number of patients whose VNS scores remained below 4, there were also no statistically significant differences among the groups (Figures 2, 3, and ⁴). There were no statistically significant differences among the groups regarding the consumption of morphine (Figures 5 and 6). There were also no statistically significant differences in the consumption of non-opioid analgesics (dypirone and ketorolac) in the recovery room; however, there was a difference (p < 0.05) in the consumption of non-opioid analgesics after discharge from the recovery room. The probability of taking non-opioid analgesics after discharge from the recovery room when the patient received 20 mL of local anesthetic was 5.23 times greater than when he/she received 30 mL. Evaluation of the blockade showed no statistically significant differences (p > 0.05) regarding the effectiveness of the sensitive blockade in the territories of the supraclavicular and axillary nerves. However, in the territories of the radial, musculocutaneous, median, ulnar, cutaneous medial of the forearm, and cutaneous medial of the arm, the sensitive blockade was more frequent (p < 0.05) in patients who received 30 and 40 mL of the local anesthetic than in patients who received 20 mL, 30 minutes after performing the block and 30 minutes after admission to the recovery room (Figure 7).

DISCUSSION

The shoulder is a special joint for many reasons. It receives massive nociceptive stimuli, leading to deep and continuous somatic pain associated with muscle spasm ¹⁵. Besides the rich innervation by C fibers, the shoulder is also innervated by Aa and Ad afferents, which generate pain that does not have a good response to opioids ¹⁶. Among all the articulations in the body, it has the greatest mobility and, for this reason, it is the least stable and more susceptible to lesions ¹⁷. Another particularity of this joint is the participation of the supraclavicular nerve on the innervation of the skin in this area. This nerve is formed by fibers from the C₃ and C₄ roots that not are part of the brachial plexus ¹⁸. Besides, the intercostobrachial nerve, formed by fibers from the T₂ roots, is also a part of the brachial plexus, being responsible for part of the shoulder innervation. It innervates the region of the axilla and medial portion of the arm¹⁸. The axillary and suprascapular nerves, formed by the C₅ and C₆ roots and, therefore, a part of the brachial plexus, are the main nerves responsible for the innervation of this joint ¹.

The technique of brachial plexus block by the interscalene approach was described by Winnie and was, as well still is, used most frequently for surgical interventions of the shoulder ^5-8. In this technique, the brachial plexus is approached at the level of the nerve roots, when they emerge between the anterior and medial scalene muscles. The needle is inserted at the level of the sixth cervical vertebra. One of the reasons for the success of this approach in surgical interventions of the shoulder is that the anesthetic usually disperses to the C₃ and C₄ roots and, therefore, a separate injection to block the supraclavicular nerve is not necessary ¹⁹. On the other hand, the ulnar nerve (C₈, T₁) is often not blocked, even with larger volumes of the anesthetic¹⁹. Since the failure to anesthetize the ulnar nerve is not a problem in shoulder surgeries, this limitation is not important. But the intercostobrachial nerve that is also not blocked is important, therefore the separate blockade of this nerve has been recommended ²⁰.

Several studies proved the safety and efficacy of the posterior approach of the brachial plexus ^9-14. In a prior study it was observed that similarly to the antero-lateral approach of Winnie in the posterior approach the local anesthetic disperses to the roots of the cervical plexus (C₃-C₄) and, therefore, blocks the supraclavicular nerve ²¹. In that study and in ours it was demonstrated that even using small doses of local anesthetic (20 mL), the blockade of the nerves supplying the shoulder (supraclavicular – C₃ and C₄; axillary and suprascapular – C₅ and C₆) was effective ²¹.

The present study confirmed the hypothesis that volumes of 20, 30, and 40 mL of local anesthetic promote equally effective analgesia in the first hours after arthroscopic surgeries of the shoulder. In all three groups pain scores were low, leading to low consumption of opioids. Although the blockade of lower nerve roots of the brachial plexus was more effective in the groups that received 30 and 40 mL of anesthetic, analgesia was not superior to that provided by 20 mL, because the lower roots are not important in the innervation of the shoulder. Therefore, the blockade of those nerves is not necessary. This study also demonstrated that, even with effective blockade of those roots, some of the patients presented moderate to severe pain. This probably was caused by the lack of blockade of the intercostobrachial nerve, which, in this study, was not blocked separately. The group that received 20 mL of anesthetic had a significantly higher consumption of non-opioid analgesics between the 12^th and 24^th hours after the surgery than the groups that received 30 and 40 mL of anesthetic. Since this difference was not present in earlier periods, we concluded that it was due to the smaller mass of local anesthetic used and, therefore, leading to a faster regression of the blockade.

This study demonstrated that the blockade of the brachial plexus by the posterior approach using 20, 30, or 40 mL of local anesthetic was effective in promoting analgesia in the first postoperative hours in surgical procedures of the shoulder. Although the increase in the volume of the anesthetic promoted a more extensive blockade, it did not increase the efficacy of the analgesia.

REFERENCES

Submitted em 10 de julho de 2006

Accepted para publicação em 26 de junho de 2007

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

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Publication Dates

• Publication in this collection
  14 Sept 2007
• Date of issue
  Oct 2007

History

• Accepted
  26 July 2006
• Received
  10 July 2006