Scholarly article on topic 'Postoperative Analgesic Efficacy of Different Volumes and Masses of Ropivacaine in Posterior Brachial Plexus Block'

Postoperative Analgesic Efficacy of Different Volumes and Masses of Ropivacaine in Posterior Brachial Plexus Block Academic research paper on "Clinical medicine"

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Brazilian Journal of Anesthesiology
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{"Anesthetics / Local / ropivacaine" / "Pain Measurement" / Orthopedics / "Brachial Plexus" / "ANESTÉSICOS / Local / ropivacaína" / "CIRURGIA / Ortopédica" / "DOR / Pós-operatória" / "TÉCNICAS ANESTÉSICAS / Regional / plexo braquial"}

Abstract of research paper on Clinical medicine, author of scientific article — Bruno Salome de Morais, Marcos Guilherme Cunha Cruvinel, Fabiano Soares Carneiro, Flavio Lago, Yerkes Pereira Silva

Abstract Background and objectives The efficacy of posterior brachial plexus block for shoulder surgeries is demonstrated by different authors. However, there is no consensus on the ideal mass and volume of local anesthetic to be employed. The objetive of this study was to compare different volumes and masses of ropivacaine in posterior brachial plexus block in arthroscopic surgeries of the shoulder. Method Sixty patients > 18 years, physical status ASA I and II, scheduled for unilateral arthroscopic surgeries of the shoulder were randomly placed in three groups: A (10mL to 0.5%), B (20mL to 0.5%), C (5mL to 1%). The block was performed with a 22G needle of 100mm connected to neurostimulator, in a point 3cm lateral to the midpoint of C6 and C7 interspace, being injected the solution corresponding to each group. The postoperative pain was evaluated at the recovery room and within the first 24 hours of the postoperative period. The groups were compared on length of time until the first complaint of pain, visual numeric scale (VNS) score and morphine consumption within the first 24 hours. Results There was no statistically significant difference between the three groups related to age, weight and height. There was no difference in length of time until the first complaint of pain, VNS scores over three and morphine consumption in the postoperative period between the groups. Conclusions This study concluded that 5mL of 1% ropivacaine promoted analgesic efficacy similar to 10mL or 20mL of 0.5% ropivacaine in the posterior brachial plexus block using neurostimulator.

Similar topics of scientific paper in Clinical medicine , author of scholarly article — Bruno Salome de Morais, Marcos Guilherme Cunha Cruvinel, Fabiano Soares Carneiro, Flavio Lago, Yerkes Pereira Silva

Academic research paper on topic "Postoperative Analgesic Efficacy of Different Volumes and Masses of Ropivacaine in Posterior Brachial Plexus Block"

Rev Bras Anestesio! 2012; 62: 1: 19-27

SCIENTIFIC ARTICLE

Postoperative Analgesic Efficacy of Different Volumes and Masses of Ropivacaine in Posterior Brachial Plexus Block

Bruno Salome de Morais, TSA 1, Marcos Guilherme Cunha Cruvinel, TSA 2, Fabiano Soares Carneiro, TSA 3, Flavio Lago 4, Yerkes Pereira Silva 5

Abstract: Morais BS, Cruvinel MGC, Carneiro FS, Lago F, Silva YP - Postoperative Analgesic Efficacy of Different Volumes and Masses of Ropivacaine in Posterior Brachial Plexus Block.

Background and objectives: The efficacy of posterior brachial plexus block for shoulder surgeries is demonstrated by different authors. However, there is no consensus on the ideal mass and volume of local anesthetic to be employed. The objetive of this study was to compare different volumes and masses of ropivacaine in posterior brachial plexus block in arthroscopic surgeries of the shoulder.

Method: Sixty patients > 18 years, physical status ASA I and II, scheduled for unilateral arthroscopic surgeries of the shoulder were randomly placed in three groups: A (10 mL to 0.5%), B (20 mL to 0.5%), C (5 mL to 1%). The block was performed with a 22G needle of 100 mm connected to neurostimulator, in a point 3 cm lateral to the midpoint of C6 and C7 interspace, being injected the solution corresponding to each group. The postoperative pain was evaluated at the recovery room and within the first 24 hours of the postoperative period. The groups were compared on length of time until the first complaint of pain, visual numeric scale (VNS) score and morphine consumption within the first 24 hours.

Results: There was no statistically significant difference between the three groups related to age, weight and height. There was no difference in length of time until the first complaint of pain, VNS scores over three and morphine consumption in the postoperative period between the groups.

Conclusions: This study concluded that 5 mL of 1% ropivacaine promoted analgesic efficacy similar to 10 mL or 20 mL of 0.5% ropivacaine in the posterior brachial plexus block using neurostimulator.

Keywords: Anesthetics, Local, ropivacaine; Pain Measurement; Orthopedics; Brachial Plexus.

©2012 Elsevier Editora Ltda. All rights reserved.

INTRODUCTION

Arthroscopic surgeries of the shoulder became a frequent and common reality as they are less invasive, therefore, offering a faster recovery. Those surgeries are associated with highly intense algic stimulus in the postoperative period, and some types of regional anesthesia are recommended to control the pain in those procedures. Several techniques, volumes and concentrations of different local anesthetics have been used,

Received from Lifecenter Hospital, Brazil.

1. MSc; PhD Student in Healthcare Science at Universidade Federal de Minas Gerais (UFMG); Member of the Anesthesia Committee in Organ Transplantation, Anesthsilogist of Lifecenter Hospital and Hospital das Clínicas, UFMG

2. Specialist in General Medicine, Certificate of Work in Pain, Anesthesiologist at Lifecenter Hospital

3. CET Instructor Hospital da Cíónicas UFMG, Anesthesiologist at Lifecenter Hospital and Hospital da Clínicas of UFMG

4. Specialist in Orthopedics; Orthopedian at Lifecenter Hospital

5. Specialist in Anesthesiology and Pediatrician; MSc and PhD in Healthcare Science by UFMG; Professor at the Postgraduation Program in Health Science - Child and Adolescent Health, UFMG, Anesthesiologist at Lifecenter Hospital

Submitted on Fabruary 8, 2011. Approved on May 19, 2011.

Correpondence to:

Dr. Bruno Salome de Morais

Av. do Contorno, 4747, Serra

30110090 - Belo Horizonte, MG, Brasil

E-mail: brunomoraisanest@yahoo.com.br

but there is no clear definition of an ideal combination to be used.

Even though the posterior brachial plexus block or cervical paravertebral block is not a new technique, only recently it had its popularity increased. Its efficacy for both shoulder and proximal humerus surgeries has been evidenced by many authors 1-4.

Regarding the volume used a recent study showed that the interscalene brachial plexus block guided by ultrasonography with 5 mL of 0.5% ropivacaine had the same analgesic efficacy of the group where 20 mL of 0.5% ropivacaine was used, but with lower incidence of diaphragmatic paralysis 5.

So far the analgesic efficacy of posterior brachial plexus block with 5 mL of ropivacaine without the help of ultrasono-graphy has not been evaluated.

Thus, the objetive of this study was to compare different volumes and masses of ropivacaine in posterior brachial plexus block on the quality of postoperative analgesia of arthros-copic surgeries of the shoulder.

METHOD

After approval by the institution's Ethics Committee in Research, and signing an informed consent form, 60 patients > 18 years, physical state ASA I and II, scheduled for uni-

lateral arthroscopic surgeries of the shoulder (acromioplasty, repair of rotator cuff lesion, treatment of recidivating luxation of shoulder or a combination of those procedures) were randomly placed in three groups, receiving different solutions of ropivacaine: A (10 mL to 0.5%), B (20 mL to 0.5%), C (5 mL to 1%). The following patients were excluded from the study: the ones with case history or laboratory exams that indicate change of coagulation, previous neurological deficit, serious chronic obstructive pulmonary disease, mental deficit that hinders the comprehension of the scale of pain, body mass index over 45, allergy to local anesthetic, cutaneous infection on the place of the block or contraindication to use dipyrone, nonsteroidal anti-inflammatory drugs (NSAIDs), dexametha-sone or clonidine.

Monitoring consisted of ECG, pulse oximetry and automatic, non-invasive blood pressure. Patients were placed on lateral decubitus, with the shoulder to be operated up, the head on a pillow and lowered over the neck. Then, patients were sedated to remain calm, cooperative and answering verbal commands. For doing so, it was used 1 ^g.kg-1 of fentanyl and 3 mg of intravenous midazolam. The spinous processes C6 and C7 were marked on the skin with dermographic pen. The puncture point used was 3 cm lateral to the space between the above-mentioned spinous processes. After antisepsis of the skin with degerming and alcoholic Povidone-iodine (PVP-I), an anesthetic button with lidocaine 1% without adrenaline was applied with an insulin needle. A 22G needle, 100 mm long (Stimuplex A100 BBraun, Melsunger, Germany) connected to the neurostimulator (Stimuplex-DIG, BBraun -Melsungen, Germany) with the initial setting of 1 mA, length of stimulation of 0.1 ^s, and frequency of 2 Hz was introduced perpendicular to the skin until a motor response was obtained. Motor responses of the levator scapulae, deltoid, or biceps muscles were acceptable and the loss of this response from 0.6 a 0.3 mA. After verifying the negative aspiration of blood, 2 mL of 2% lidocaine with 1:200,000 adrenaline was injected. Then, the ropivacaine was injected in incremental doses of 5 mL.

Groups were divided as follows, without the knowledge of the surgeon, patient or anesthetist responsible for the evaluation of pain.

• Group A: Posterior brachial plexus block with 10 mL of 0.5% ropivacaine;

• Group B: Posterior brachial plexus block with 20 mL of 0.5% ropivacaine;

• Group C: Posterior brachial plexus block with 5 mL of 1% ropivacaine.

The solution of 0.5% ropivacaine was prepared with 20 mL of 0.75% ropivacaine and 10 mL of sterile bidistilled water for groups A and B whilst on group C it was used the 1% commercialized standard presentation.

After the block, the patients received general balanced anesthesia with fentanyl (2 to 4 ^g.kg-1), propofol (2.0 to 2.5 mg.kg-1), and cisatracurium (0.15 mg.kg-1) and sevoflu-rane (1 to 1.5 CAM). They also received clonidine (1 ^g.kg-1)

and dexamethasone (10 mg) after the anesthetic induction and ondansetron (4 mg), ketoprofen (100 mg) and dipyrone (30 mg.kg-1) immediately after the surgery.

The block was evaluated by verifying the thermal sensitivity using cotton embedded in alcohol following the skin representation of nerve roots from C3 to C7, 30 minutes after admission to the post-anesthetic recovery room. In the first evaluation, the thermal sensitivity of the skin representation of roots from C5 and C6 contralateral to the block was also verified to evaluate the possibility of epidural block. Postoperative pain was evaluated using a visual numeric scale (VNS) ranging from zero (total absence of pain) to 10 (the worst pain possible). The evaluator did not know the concentration of anesthetic injected. In the recovery room, pain evaluation was done 30 minutes after admission and immediately before discharge from the unit. Then, the pain was evaluated by one of the investigators every 8 hours while in the hospital and, on the following day, it was evaluated through telephone contact. To perform the statistical analysis, it was considered the maximum pain and morphine consumption in the recovery room and periods of 12 and 24 hours after being discharged from the unit. All patients received analgesics in a fixed way: intravenous dypirone 2 g at every six hours and ketoprofen 100 mg at every 12 hours. The patients received venous morphine 4 mg at every four hours if they related pain above three in the VNS.

The groups were compared regarding the time to the first complaint of pain, the VNS score and morphine consumption within the first 24 hours. The length of time to the first complaint of pain was considered from the moment of discharge from the recovery room. The patients were categorized in two groups related to the biggest complaint of pain: group one VNS 0 to 3; group two VNS 4 to 10. This categorization was based on the recommendation of the World Health Organization for the association of opioid in the treatment of moderate to intense pain (ENV 4 to 10) 6.

The homogeneity of age, weight and height variables was evaluated by Levene's test whereas gender and physical status (ASA) were analyzed by the Chi-square test. The length of time until the first complaint of pain was evaluated by the non-parametric Kruskal-Wallis test, as this variable did not follow normal distribution. The Chi-square test was used to evaluate the other variables. The number of 19 patients in each group was previously calculated so that it could be noticed a difference of two points in VNS betweeen groups with a sampling capacity of 90% (beta error of 10%) and 95% of trust level (alfa error of 5%), considering the standard deviation of 2.1 obtained in similar previous study 7. All results were considered significant to a significance probability inferior to 5% (p < 0.05).

RESULTS

All 60 patients completed the study and the blocks were performed without any problem. The analysis of the demographic data shows that there was no statistically significant differen-

POSTOPERATIVE ANALGESIC EFFICACY OF DIFFERENT VOLUMES AND MASSES OF ROPIVACAINE IN POSTERIOR BRACHIAL PLEXUS BLOCK

ce between the three groups related to age, weight and height (Table I). There was a prevalence of male patients in group C and ASA I in group A (Table I).

There was a failure of Brachial Plexus Block in a patient of group A, a patient of group B and in two patients of group C (p = 0.717). Three patients of group A, seven patients of group B and two patients of group C presented a motor block of the hand at the end of the surgery, (p = 0.156).

Table II shows the time in hours until the first complaint of pain in the postoperative period and Table III shows the percentage of patients who complained of pain over three in the postoperative period.

There was no difference in time up to the first complaint of pain, VNS group and morphine consumption in the postoperative period between the groups (Figure 1).

Table I - Characteristics of the Patients

Group A (0.5% 10 mL) Group B (0.5% 20 mL) Group C (1% 5 mL) p"

Age (years)* 50.05 ± 11.11 49.00 ± 14.30 47.74 ± 13.81 0.380

Weight (kg)* 76.35 ± 13.79 72.10 ± 13.33 83.74 ± 15.47 0.613

Height (meters)* 1.62 ± 0.21 1.65 ± 0.07 1.72 ± 0.08 0.267

Gender (M/F) 11/9 10/11 16/3 0.045**

ASA (I/II) 17/3 12/9 9/10 0.039**

"Values expressed in average ± SD; **p < 0.05.

Table II - Time (hours) Until the First Complaint of Pain in the Postoperative Period

Group A (0.5% 10 mL) Group B (0.5% 20 mL) Group C (1% 5 mL) p

N 20 21 19 0.373

Average 18.83 19.00 18.00

Average ± SD 17.81 ± 7.23 22.06 ± 11.47 17.29 ± 10.29

SD: standard deviation.

Table III - Evaluation of Pain (VNS)

VNS A BC p

Recovery room 0-3 15/20 (75%) 20/21 (95%) 17/19 (89%) 0.148

4-10 5/20 (25%) 1/21 (5%) 2/19 (11%)

Until 12 hours after discharge from the recovery room 0-3 18/20 (90%) 20/21 (95%) 16/19 (84%) 0.510

4-10 2/20 (10%) 1/21 (5%) 3/19 (16%)

12 to 24 hours after discharge from the recovery room 0-3 11/20 (55%) 13/21 (62%) 9/19 (47%) 0.653

4-10 9/20 (45%) 8/21 (38%) 10/19 (52%)

*Chi-square.

Figure 1 - Percentage of Patients Who Took Morphine. PACU: Post-Anesthesia Care Unit.

DISCUSSION

The arthroscopic surgeries of the shoulder became more frequent as they are less invasive and, therefore, offer a faster recovery. Among the main arthroscopic surgeries of the shoulder are acromioplasty, repair of rotator cuff lesion and treatment of recidivating luxation. Control the pain is one of the main problems in those surgeries, since these procedures are associated with postoperative pain of great intensity and hard to be controlled 89. Among the techniques more commonly employed for this purpose are the use of intravenous opioids associated or not with NSAIDs, the use of articular local anesthetic, suprascapular nerve block and cervical and brachial plexus blocks 8-24. Among such techniques, brachial plexus block offers the best results on the analgesia 1 3-5 20-21. From the techniques of brachial plexus block, the intersca-lene block is more commonly used 8,10-12,25,26. Recently, the posterior brachial plexus block, also known as paravertebral cervical block, has received wide attention 1-372728. Different volumes of anesthetic have already been employed, but there is no definition of the ideal volume.

It was evident that posterior brachial plexus block with 20 mL, 30 mL, and 40 mL of 0.375% ropivacaine offerered the same analgesic efficacy in the postoperative period of ar-throscopic surgeries of the shoulder 27. Similarly, it was observed that the increase in concentration from 0.5% to 0.75% when 30 mL of ropivacaine were employed in the interscalene brachial plexus block did not show benefit in the postoperative analgesia of surgeries of the shoulder 22.

Ipsilateral diaphragmatic paralysis is a common complication expected after brachial plexus block both by the inters-calene and the paravertebral cervical approach, due to the block of phrenic nerve (C3-C5 roots), it may occur in 100% of cases when habitual doses of local anesthetics are used 29 30. However, paresis, and even total hemidiaphragmatic paralysis, does not lead to respiratory failure in healthy people 29. On the other hand, in patients with any degree of previous respiratory disease, diaphragmatic hemiparesis and, especially, paralysis may occur with respiratory failure 29. To avoid diaphragmatic paralysis after brachial plexus block is a benefit to all patients undergoing surgeries of the shoulder, especially obese patients and the ones with pulmonary disease. On the other hand, when brachial plexus block is not performed in those surgeries, the postoperative administration of opioids,

pain or both may significantly increase the risk of pulmonary complications and morbidity 30 31.

A recent study compared interscalene brachial plexus block guided by ultrasonography with 5 mL and 20 mL of 0.5% ropivacaine to perform arthroscopy of the shoulder 5. The authors concluded that the diaphragmatic paralysis was significantly inferior in the 5 mL group compared with the 20 mL group (45% versus 100%), p < 0.05. In addition to that, there was a larger reduction of oxygen saturation in the group that received 20 mL (5.85% versus 1.5%), p = 0.003, in the postoperative period. There was no statistically significant difference in pain, quality of sleep and total morphine consumption scales within 24 hours of the end of surgery.

In addition to the benefits of lower incidence of hemidia-phragmatic paralysis, the reduction of volume of local anesthetic is associated with the smaller risk of morbidity related to intravascular injection.

Even though this study did not evaluate the incidence of diaphragmatic paralysis, it was possible to see that the posterior brachial plexus block, with 5 mL of 1% ropivacaine with the help of neurostimulator, offered postoperative analgesia similar to 10 mL and 20 mL of 0.5% ropivacaine.

The increase of anesthetic mass (20 mL of 0.5% ropiva-caine group) did not mean evident clinical benefit. Since this increase of mass may represent increased risk of toxicity, the use of smaller volume and anesthetic masses seem more interesting. A better strategy to extend the postoperative analgesia would be placing a peripheral catheter with continuous flow, or upon demand of the patient, of low doses of local anesthetic.

A limitation of this study was to use fixed doses of morphine instead of analgesia controlled by the patient to control the escape of pain in the postoperative period and evaluation of analgesic efficacy of different schemes of local anesthetic used. The analgesia controlled by the patient offers a range of advantages compared with the common analgesia, some of them are 32: improved analgesia, early relief of pain, more satisfaction and safety when compared with fixed doses of opioid. Although its benefits are well-defined, this analgesia method is still not available in most national institutes owing to cost.

This study concluded that 5 mL of 1% ropivacaine promoted analgesic efficacy similar to 10 mL or 20 mL of 0.5% ropi-vacaine in the posterior brachial plexus block using neurostimulator and without the help of ultrasonography.

Rev Bras Anestesio! 2012; 62: 1: 19-27

ARTIGO CIENTÍFICO

Eficácia Analgésica Pós-Operatória de Diferentes Volumes e Massas de Ropivacaína no Bloqueio de Plexo Braquial pela Via Posterior

Bruno Salome de Morais, TSA 1, Marcos Guilherme Cunha Cruvinel, TSA 2, Fabiano Soares Carneiro, TSA 3, Flavio Lago 4, Yerkes Pereira Silva 5

Resumo: Morais BS, Cruvinel MGC, Carneiro FS, Lago F, Silva YP - Eficácia Analgésica Pós-Operatória de Diferentes Volumes e Massas de Ropivacaína no Bloqueio de Plexo Braquial pela Via Posterior.

Justificativa e objetivos: O bloqueio do plexo braquial pela via posterior tem sua eficácia para cirurgias de ombro demonstrada por diferentes autores. Entretanto, náo há um consenso sobre a massa e o volume ideal de anestésico local a ser empregado. O objetivo deste estudo é comparar diferentes volumes e massas de ropivacaína no bloqueio do plexo braquial pela via posterior em cirurgias artroscópicas de ombro.

Método: Sessenta pacientes com idade > 18 anos, estado físico ASA I e II, escalados para cirurgias artroscópicas de ombro unilateral foram alocados aleatoriamente em tres grupos: A (10 mL a 0,5%), B (20 mL a 0,5%), C (5 mL a 1%). O bloqueio foi realizado com agulha 22G de 100 mm conectada ao neuroestimulador, em um ponto 3 cm lateral ao ponto médio do interespago de C6 e C7, sendo injetada a solugáo correspondente a cada grupo. A dor pós-operatória foi avaliada na SRPA e nas primeiras 24 horas do pós-operatório. Os grupos foram comparados quanto ao tempo para primeira queixa de dor, a pontuagáo na ENV e ao consumo de morfina nas primeiras 24 horas.

Resultados: Náo houve diferenga estatisticamente significativa entre os tres grupos em relagáo a idade, peso e altura. Náo houve diferenga no tempo até a primeira queixa de dor, ENV superior a tres e consumo de morfina no pós-operatório entre os grupos.

Conclusoes: O presente estudo concluiu que 5 mL de ropivacaína 1% promoveu eficácia analgésica similar a 10 mL ou 20 mL de ropivacaína 0,5% no bloqueio do plexo braquial pela via posterior com o uso do neuroestimulador.

Unitermos: ANESTÉSICOS, Local, ropivacaína; CIRURGIA, Ortopédica; DOR, Pós-operatória; TÉCNICAS ANESTÉSICAS, Regional, plexo braquial.

©2012 Elsevier Editora Ltda. Todos os direitos reservados.

INTRODUÇÂO

As cirurgias artroscópicas do ombro se tornaram uma realidade frequente e rotineira pelo fato de serem menos invasivas e, portanto, proporcionarem uma recuperaçâo mais rápida. Estas cirurgias associam-se ao estímulo álgico de grande in-tensidade no pós-operatório, estando alguma modalidade de anestesia regional recomendada para o controle da dor nes-

Recebido do Hospital Lifecenter, Brasil.

1. Mestre e Doutorando em Ciencias da Saúde pela Universidade Federal de Minas Gerais (UFMG); Membro do Comité de Anestesia em Transplante de Örgäos, Anestesiologista do Hospital Lifecenter e Hospital das Clínicas da UFMG

2. Especialista em Clínica Médica, Certificado de Atuagäo em Dor; Anestesiologista do Hospital Lifecenter

3. Instrutor CET Hospital das Clínicas da UFMG, Anestesiologista do Hospital Lifecenter e Hospital das Clínicas da UFMG

4. Especialista em Ortopedia; Ortopedista do Hospital Lifecenter

5. Especialista em Anestesiología e Pediatra, Mestre e Doutor em Ciencias da Saúde pela UFMG; Orientador Específico do Programa de Pös-Graduagäo em Ciencias da Saúde -Saúde da Crianga e do Adolescente, UFMG, Anestesiologista do Hospital Lifecenter

Submetido em 8 de fevereiro de 2011. Aprovado em 19 de maio de 2011.

Correspondencia para:

Dr. Bruno Salome de Morais

Av. do Contorno, 4747, Serra

30110090 - Belo Horizonte, MG, Brasil

E-mail: brunomoraisanest@yahoo.com.br

ses procedimentos. Diversas técnicas, volumes e concen-tragoes de diferentes anestésicos locais tem sido utilizados náo havendo, entretanto, uma definigáo clara de qual seria a combinagáo ideal.

O bloqueio do plexo braquial (BPB) pela via posterior ou bloqueio paravertebral cervical, embora náo seja uma técnica nova, só recentemente ganhou certa popularidade. Sua eficácia para cirurgias de ombro e úmero proximal tem sido demonstrada por diferentes autores 1-4.

Com relagáo ao volume utilizado, um estudo recente 5 mostrou que o BPB pela via interescalenica guiado por ul-trassonografia com 5 mL de ropivacaína 0,5% apresentou a mesma eficácia analgésica que o grupo onde 20 mL de ropivacaína 0,5% foi utilizado, porém com menor incidencia de paralisia diafragmática.

Até o momento, a eficácia analgésica do BPB pela via posterior com 5 mL de ropivacaína, sem o auxílio da ultrassono-grafia, ainda náo foi avaliada.

Dessa maneira, o objetivo deste estudo é comparar diferentes volumes e massas de ropivacaína no BPB pela via posterior quanto á qualidade da analgesia pós-operatória de cirurgias artroscópicas de ombro.

MÉTODO

Após aprovagao do Comité de Ética em Pesquisa da insti-tuigao e obtengao da assinatura do termo de consentimento pós-informado, 60 pacientes com idade superior a 18 anos, estado físico ASA I e II, escalados para cirurgias artroscó-picas de ombro unilateral (acromioplastia, reparo de lesao de manguito rotador, tratamento de luxagao recidivante do ombro ou uma combinagao destes procedimentos) foram alocados aleatoriamente em trés grupos, recebendo diferentes solugoes de ropivacaína: A (10 mL a 0,5%), B (20 mL a 0,5%), C (5 mL a 1%). Foram excluidos do estudo os pacientes com história clínica ou exames laboratoriais sugestivos de alteragao da coagulagao, déficit neurológico preexistente, doenga pulmonar obstrutiva crónica grave, déficit mental que impossibilitasse a compreensao da escala de dor, índice de massa corpórea maior que 45, alergia a anestésico local (AL), infecgao cutánea no local da realizagao do bloqueio ou con-traindicagao para o uso de dipirona, anti-inflamatório nao es-teroide (AINE), dexametasona ou clonidina.

Os pacientes foram monitorados com ECG, oxímetro de pulso, pressao arterial automática náo invasiva (PANI) e po-sicionados em decúbito lateral com o ombro a ser operado para cima, a cabega apoiada sobre um travesseiro e fletida sobre o pescogo. A seguir foram sedados com objetivo de manté-los calmos, cooperativos e respondendo aos comandos verbais. Para tal, foi utilizado 1 ^g.kg-1 de fentanil e 3 mg de midazolam por via intravenosa. Marcou-se na pele com caneta dermográfica os processos espinhosos de C6 e C7. O ponto de pungao utilizado foi o localizado 3 cm lateral ao espago entre os processos espinhosos citados. Após antis-sepsia da pele com PVPi degermante e alcoólico, realizou-se com agulha de insulina um botao anestésico com lidocaína 1% sem adrenalina. Uma agulha 22G de 100 mm (Stimuplex A100 BBraum, Melsunger, Germany) conectada ao neuro-estimulador (Stimuplex-DIG, Braum - Melsunger, Germany) ligado inicialmente com intensidade de 1 mA, comprimen-to de onda de 0,1 ^s e frequéncia de 2 Hz, foi introduzida perpendicular a pele até que fosse obtida resposta motora. Foram aceitas respostas motoras dos músculos levantador da escápula, deltóide ou bíceps e perda desta resposta entre 0,6 a 0,3 mA. Após aspiragao negativa para sangue, foi realizado dose-teste com 2 mL de lidocaína 2% com adrenalina 1:200.000. A seguir a ropivacaína foi injetada em doses incrementais de 5 mL.

Os grupos foram divididos da seguinte maneira, sem o conhecimento do cirurgiao, paciente ou anestesiologista res-ponsável pela avaliagao da dor.

• Grupo A: BPB pela via posterior com 10 mL de ropivacaína 0,5%;

• Grupo B: BPB pela via posterior com 20 mL de ropiva-caína 0,5%;

• Grupo C: BPB pela via posterior com 5 mL de ropivacaína 1%.

A solugao de ropivacaína 0,5% foi preparada a partir da mistura de 20 mL de ropivacaína 0,75% com 10 mL de água

bidestilada estéril para os grupos A e B enquanto no grupo C foi utilizada a apresentagáo padráo 1% comercializada.

Após a realizagáo do bloqueio, os pacientes foram sub-metidos á anestesia geral balanceada com fentanil (2 a 4 ^g.kg-1), propofol (2,0 a 2,5 mg.kg-1), cisatracúrio (0,15 mg.kg-1) e sevoflurano (1 a 1,5 CAM). Receberam ainda clonidina (1 ^g.kg-1) e dexametasona (10 mg) após a indugáo anestésica e ondansetrona (4 mg), cetoprofeno (100 mg) e dipirona (30 mg.kg-1) ao término imediato do procedimento cirúrgico.

O bloqueio foi avaliado por meio da pesquisa de sensibili-dade térmica utilizando-se algodáo embebido em álcool, se-guindo a representagáo cutánea das raízes nervosas de C3 a C7, 30 minutos após a admissáo na sala de recuperagáo pós-anestésica (SRPA). Na primeira avaliagáo, foi pesquisada também a sensibilidade térmica da representagáo cutánea das raízes de C5 e C6 contralateral ao bloqueio para avaliar a possibilidade de bloqueio peridural. A dor pós-operatória foi avaliada com auxilio da escala numérica visual (ENV) sendo zero (auséncia total de dor) a dez (pior dor imaginável). O avaliador náo teve conhecimento da concentragáo do anestésico injetado. Na SRPA, a avaliagáo foi realizada 30 minutos após a admissáo do paciente e imediatamente anterior á alta. Em seguida, foi avaliada por um dos pesquisadores a cada oito horas durante a internagáo hospitalar e, no dia seguinte, realizada através de contato telefónico. Para realizagáo da análise estatística, foi considerada a dor máxima e consumo de morfina na SRPA e períodos de 12 e 24 horas após a alta da SRPA. Todos os pacientes receberam analgésicos de modo fixo: dipirona 2 g a cada seis horas e cetoprofeno 100 mg a cada 12 horas por via venosa. Os pacientes receberam morfina 4 mg por via venosa a cada quatro horas se relatassem dor acima de trés na ENV.

Os grupos foram comparados quanto ao tempo até a pri-meira queixa de dor, quanto á pontuagáo na ENV e consumo de morfina nas primeiras 24 horas. O tempo para a primeira queixa de dor foi considerado a partir do momento da alta da SRPA. Os pacientes foram categorizados em dois grupos em relagáo a maior queixa de dor: grupo um ENV 0 a 3; grupo dois ENV 4 a 10. Esta categorizagáo foi baseada na recomendagáo da Organizagáo Mundial de Saúde para asso-ciagáo de opioide no tratamento da dor moderada a intensa (ENV 4 a 10) 6.

A homogeneidade das variáveis idade, peso e altura foi avaliada pelo teste de Levene enquanto sexo e estado físico (ASA) pelo teste Qui-quadrado. O tempo até a primeira queixa de dor foi avaliado pelo teste náo paramétrico de Kruskal-Wallis, uma vez que esta variável náo seguiu distri-buigáo normal. Para as demais variáveis, utilizou-se o teste Qui-quadrado. O número de 19 pacientes em cada grupo foi previamente calculado para que se pudesse perceber uma diferenga de dois pontos na ENV entre os grupos com um poder amostral de 90% (erro beta de 10%) e 95% de nível de confianga (erro alfa de 5%), considerando o desvio-padráo de 2,1 obtido em trabalho anterior similar 7. Todos os resultados foram considerados significativos para uma probabilidade de significáncia inferior a 5% (p < 0,05).

EFICACIA ANALGÉSICA POS-OPERATORIA DE DIFERENTES VOLUMES E MASSAS DE ROPIVACAINA NO BLOQUEIO DE PLEXO BRAQUIAL PELA VIA POSTERIOR

RESULTADOS

Todos os 60 pacientes completaram o estudo e os bloqueios foram realizados sem intercorrências. A análise dos dados demográficos mostra que näo houve diferença estatistica-mente significativa entre os três grupos em relaçâo à idade, peso e altura (Tabela I). Houve predomínio de pacientes do sexo masculino no grupo C e ASA I no grupo A (Tabela I).

Houve falha do BPB em um paciente do grupo A, um paciente do grupo B e em dois pacientes do grupo C, (p = 0,717).

Três pacientes do grupo A, sete pacientes do grupo B e dois pacientes do grupo C apresentaram bloqueio motor da mäo ao término da cirurgia, (p = 0,156).

A Tabela II mostra o tempo em horas até a primeira queixa de dor no pós-operatório e a Tabela III o percentual de pacientes que apresentaram queixa de dor superior a três no pós-operatório.

Näo houve diferença quanto ao tempo até a primeira queixa de dor, grupo de ENV e consumo de morfina no pós-ope-ratório entre os três grupos (Figura 1).

Tabela I - Características dos Pacientes

Grupo A (0,5% 10 mL) Grupo B (0,5% 20 mL) Grupo C (1% 5 mL) p"

Idade (anos)* 50,05 ± 11,11 49,00 i 14,30 47,74 i 13,S1 0,3S0

Peso (kg)* 76,35 ± 13,79 72,10 i 13,33 S3,74 i 15,47 0,613

Altura (metros)* 1,62 ± 0,21 1,65 i 0,07 1,72 i 0,0S 0,267

Sexo (M/F) 11/9 10/11 16/3 0,045**

ASA (I/II) 17/3 12/9 9/10 0,039**

*Valores expressos em média ± DP; **p < 0,05.

Tabela II - Tempo (horas) até a Primeira Queixa de Dor no Pós-operatório

Grupo A (0,5% 10 mL) Grupo B (0,5% 20 mL) Grupo C (1% 5 mL) p

N 20 21 19 0,373

Mediana 18,83 19,00 1S,00

Média ± DP 17,81 ± 7,23 22,06 i 11,47 17,29 i 10,29

DP: desvio-padráo.

Tabela III - Avaliagáo da Dor (ENV)

ENV A B C p

SRPA 0-3 15/20 (75%) 20/21 (95%) 17/19 (S9%) 0,14S

4-10 5/20 (25%) 1/21 (5%) 2/19 (11%)

Até 12h após alta da SRPA 0-3 1S/20 (90%) 20/21 (95%) 16/19 (S4%) 0,510

4-10 2/20 (10%) 1/21 (5%) 3/19 (16%)

12 a 24h após alta a SRPA 0-3 11/20 (55%) 13/21 (62%) 9/19 (47%) 0,653

4-10 9/20 (45%) S/21 (3S%) 10/19 (52%)

*Qui-quadrado.

Figura 1 - Percentual de Pacientes que Fizeram Uso de Morfina. SRPA: Sala de Recuperaçäo Pós-Anestésica.

DISCUSSÄO

As cirurgias artroscópicas do ombro estao se tornando mais frequentes pelo fato de serem menos invasivas e, portanto, proporcionarem uma recuperaçao mais rápida. Entre as principais cirurgias do ombro realizadas por via artroscópica es-tao acromioplastia, reparo de lesao do manguito rotador e tratamiento da luxaçao recidivante. Um dos principais problemas enfrentados nestas cirurgias é o controle da dor uma vez que estes procedimentos estao associados à dor pós-operatória de grande intensidade e de difícil controle В9. Entre as técnicas mais comumente empregadas para este objetivo estao o uso de opioides intravenoso associado ou nao aos AINEs, o uso de AL por via articular, o bloqueio do nervo supraescapu-lar e os bloqueios dos plexos braquial e cervical В-24. Dentre estas técnicas, os melhores resultados na analgesia sao ob-tidos com o BPB 1 3-5 20-21. Das técnicas de BPB, a mais comumente usada é o bloqueio por via interescalénica В>10"12>25>26. Recentemente, grande destaque tem sido dado ao BPB por via posterior também chamado bloqueio paravertebral cervical 1-3,7,27,2В. Diferentes volumes de anestésico já foram em-pregados, nao havendo entretanto uma definiçao do volume ideal.

Evidenciou-se que o BPB pela via posterior com 20 mL, 30 mL e 40 mL de ropivacaína a 0,375% ofereceu mesma efi-cácia analgésica no pós-operatório de cirurgias artroscópicas do ombro 27. De modo semelhante, observou-se que o aumento da concentraçao de 0,5% para 0,75% quando 30 mL de ropivacaína foram empregados no bloqueio de plexo braquial por via interescalénica nao mostrou benefício na analgesia pós-operatória de intervenç6es cirúrgicas no ombro 22.

A paralisia diafragmática ipsilateral é uma complicaçao esperada após o BPB tanto pela via interescalénica quanto pela via paravertebral cervical, devido ao bloqueio do nervo frénico (raízes C3-C5), podendo ocorrer em 100% dos casos quando se utiliza doses habituais de anestésicos locais 29 30. Entretanto, a paresia, e até mesmo a paralisia total hemidia-fragmática, nao leva à insuficiéncia respiratória em indivíduos sadios 29. Já nos pacientes com algum grau de disfunçao respiratória prévia, a hemiparesia diafragmática e, principalmente, a paralisia podem manifestar-se com insuficiéncia respiratória 29. Evitar a paralisia diafragmática após a realizaçao do BPB é um beneficio para todos os pacientes submetidos à cirurgia do ombro, sobretudo em obesos e em pacientes com doença pulmonar. Por outro lado, quando o BPB nao é realizado nestas cirurgias, a administraçao pós-operatória de opioides, a dor ou ambos podem aumentar significativamente o risco de complicaç6es pulmonares e a morbidade 30 31.

Um estudo recente 5 comparou o BPB pela via interescalénica guiado por ultrassonografia com 5 mL e 20 mL de ropivacaína 0,5% para realizaçao de artroscopia de ombro. Os autores concluíram que a paralisia diafragmática foi significativamente inferior no grupo 5 mL comparado ao grupo 20 mL (45% versus 100%), p < 0,05. Além disto, houve maior queda da saturaçao de oxigénio no grupo que recebeu 20 mL (5,В5% versus 1,5%), p = 0,003, no pós-operatório. Nao hou-

ve diferença estatisticamente significativa nas escalas de dor, qualidade do sono e consumo total de morfina em 24h do término da cirurgia.

Além dos beneficios de diminuiçao da incidência de paralisia hemidiafragmática, a reduçao do volume de anestésico local está associada ao menor risco de morbidade relacionada à injeçao intravascular.

Apesar do presente estudo nao ter avaliado a incidência de paralisia diafragmática, foi possivel verificar que o BPB pela via posterior, com 5 mL de ropivacaína 1% com o auxilio do neuroestimulador, ofereceu analgesia pós-operatória similar a 10 mL e 20 mL de ropivacaína 0,5%.

O aumento da massa anestésica (grupo ropivacaína 20 mL a 0,5%) nao se traduziu em beneficio clínico evidente. Como esse aumento da massa pode representar aumento de risco de toxicidade, o uso de volume e massas anestésicas menores parece ser mais interessante. Melhor estratégia para prolongamiento da analgesia pós-operatória seria a instalaçao um cateter periférico com infusao contínua, ou sob demanda do paciente, de baixas doses de AL.

Uma limitaçao desse estudo foi a utilizaçao de doses fixas de morfina em vez da analgesia controlada pelo paciente (ACP) para o controle do escape de dor no pós-operatório e avaliaçao da eficácia analgésica dos diferentes esquemas de AL utilizados. A ACP oferece uma série de vantagens em relaçao à analgesia convencional, dentre elas 32: melhor analgesia, alívio precoce da dor, maior satisfaçao e segurança quando comparada a doses fixas de opioide. Apesar de seus benefícios bem definidos, devido ao custo, este método de analgesia ainda nao se encontra disponível na maioria das instituiçôes nacionais.

O presente estudo concluiu que 5 mL de ropivacaína 1% promoveu eficácia analgésica similar a 10 mL ou 20 mL de ropivacaína 0,5% no BPB pela via posterior com o uso do neuroestimulador e sem auxílio da ultrassonografia.

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