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On-line version ISSN 1806-907X
Rev. Bras. Anestesiol. vol.56 no.5 Campinas Sept./Oct. 2006
Prevalence of diaphragmatic paralysis after brachial plexus blockade by the posterior approach with 0.2% ropivacaine*
Prevalencia de parálisis diafragmática después del bloqueo del plexo braquial por la vía posterior con ropivacaína a 0,2%
Marcos Guilherme Cunha Cruvinel, TSA, M.D.I; Carlos Henrique Viana de Castro, TSA, M.D.II; Yerkes Pereira Silva, M.D.III; Roberto Cardoso Bessa Júnior, TSA, M.D.IV; Flávio de Oliveira França, M.D.V; Flávio Lago, M.D.V
do Hospital Lifecenter, Especialista em Clínica Médica, Certificado
de Área de Atuação em Dor pela SBA
IIAnestesiologista do Hospital Lifecenter, Especialista em Clínica Médica e Terapia Intensiva
IIIAnestesiologista do Hospital Lifecenter, Especialista, Mestre e Doutorando em Pediatria pela UFMG
IVAnestesiologista do Hospital Lifecenter, Especialista em Terapia Intensiva, Certificado de Área de Atuação em Dor pela SBA
VOrtopedista do Hospital Lifecenter
OBJECTIVES: Brachial plexus blockade by the interscalene approach, described
by Winnie, is one of the most effective techniques in promoting postoperative
analgesia in surgeries of the shoulder. Diaphragmatic paralysis is one of the
consequences of this technique. This paralysis can cause respiratory failure
in patients with prior lung dysfunction. Brachial plexus blockade by the posterior
approach has become increasingly more popular. The objective of this study was
to determine the prevalence of diaphragmatic paralysis after interscalene brachial
plexus blockade by the posterior approach with 0.2% ropivacaine.
METHODS: Twenty-two patients who underwent interscalene brachial plexus blockade by the posterior approach with 0.2% ropivacaine were evaluated in the postoperative period to identify radiological signs of elevation of the hemidiaphragm that could suggest hemidiaphragmatic paralysis. Forty mL of 0.2% ropivacaine were used in 20 patients; inspiratory chest X-rays were done in these patients. Twenty mL of 0.2% ropivacaine were used in two patients, with posterior fluoroscopic evaluation.
RESULTS: There were no complications related to the procedure. The anesthesia was effective in every patient, providing good postoperative analgesia. Every patient in this study presented elevation of the diaphragm compatible with hemidiaphragmatic paralysis.
CONCLUSIONS: We observed that brachial plexus blockade by the posterior approach is associated with a high prevalence of diaphragmatic paralysis, even with low concentrations of local anesthetics.
Key Words: ANESTHETICS, Local: ropivacaine; ANESTHETIC TECHNIQUES, Regional: brachial plexus; COMPLICATIONS: diaphragmatic paralysis; SURGERY, Orthopedic.
Y OBJETIVOS: El bloqueo de plexo braquial por vía interescalénica
descrita por Winnie es una de las técnicas más eficaces para promover
la analgesia postoperatoria de intervenciones quirúrgicas en el hombro.
Una de sus consecuencias es la parálisis diafragmática. En pacientes
con algún grado de disfunción pulmonar previa, esa parálisis
puede conllevar a la insuficiencia respiratoria. El abordaje del plexo braquial
por vía posterior ha conquistado espacio. El objetivo de este estudio
fue el de determinar la prevalencia de parálisis diafragmática,
después del bloqueo de plexo braquial interescalénico por vía
posterior con el uso de ropivacaína a 0,2%.
MÉTODO: Veinte y dos pacientes sometidos al bloqueo del plexo braquial interescalénico por vía posterior con ropivacaína a 0,2% fueron evaluados en el postoperatorio con el objetivo de identificar señales radiológicas de elevación de la cúpula diafragmática sugestivas de parálisis hemidiafragmática. En 20 pacientes se utilizó 40 mL de ropivacaína a 0,2%, en ellos fue realizada la radiografía de tórax en inspiración. En dos fueron utilizados 20 mL de ropivacaína a 0,2%, con la siguiente evaluación fluoroscópica.
RESULTADOS: No hubo complicaciones relacionadas con la realización del bloqueo. En todos los pacientes, el bloqueo fue efectivo y proporcionó una buena analgesia postoperatoria. Se observó una elevación de la cúpula diafragmática compatible con la parálisis hemidiafragmática en todos los casos estudiados.
CONCLUSIONES: En las condiciones de este estudio se pudo observar que el bloqueo del plexo braquial por vía posterior es una técnica que está asociada a la alta prevalencia de parálisis diafragmática, incluso cuando se utilizan bajas concentraciones de anestésico local.
Surgical procedures in the shoulder present severe postoperative pain 1,2. An adequate analgesia allows for a faster recovery. Among the main postoperative analgesia techniques for surgeries in the shoulder, and the one that presents the best results, is the brachial plexus blockade by the interscalene approach 1-19. The brachial plexus can be anesthetized in the interscalene groove using several approaches, such as the anterolateral, described by Winnie, lateral, modified lateral, and posterior. Recently, several authors have shown interest in the posterior approach, which can also be called cervical paravertebral block 20-23.
Phrenic nerve block, with subsequent diaphragmatic paralysis, is one of the main side effects of the brachial plexus blockade above the clavicle. This has been well documented when is secondary to Winnie's technique 24-34. Diaphragmatic paralysis may have severe consequences for the patient with previous respiratory deficiency, being a relative contraindication in this group of patients.
The objective of this study was to determine the prevalence of diaphragmatic paralysis after interscalene brachial plexus blockade by the posterior approach using 0.2% ropivacaine.
After approval by the Ethics Committee and signing of the informed consent, 22 patients, physical status ASA I and II, who underwent arthroscopic surgeries of the shoulder, participated in this study. Twenty of those patients received 40 mL of 0.2% ropivacaine, while two received 20 mL of 0.2% ropivacaine for the brachial plexus blockade by the posterior approach. Every patient received premedication procedure. They were monitored with an EEG, derivations leads DII and V5, pulse oxymeter, and noninvasive blood pressure. They did not receive premedication. Patients were placed in lateral decubitus, lying on the opposite shoulder, their head flexed over the neck and placed on a pillow. Oxygen was administered through a nasal catheter (3 L.min-1). Patients were sedated with IV sufentanil 0.1 µg.kg-1, so they would remain calm, cooperative, and able to answer verbal commands. If the response were not satisfactory, up to 3 mg of midazolam would be administered. After evaluating the effectiveness of the anesthesia (30 min), patients underwent balanced general anesthesia, and also received 100 mg of ketoprophen and 2 g of dipyrone.
With the patient on lateral decubitus, head flexed over the chest and placed on a pillow, the spinal processes of C6 and C7 were marked with a dermographic pen. The point to be punctured was set 3 cm laterally to the space between the spinal processes. After cleaning the skin with alcoholic chlorhexidine, the skin was anesthetized with 1% lidocaine without adrenaline using insulin needle and syringe. Afterwards, the course of the puncture needle was anesthetized using a 25 × 7 mm needle and 5 mL of the local anesthetic. A 100 mm, 22G needle (Stimuplex A100 B. Braun Melsungen, Germany) connected to a neurostimulator (Stimuplex-DIG, B. Braun Melsungen, Germany), with an intensity of 1 mA, stimulation time of 0.1 µs, and frequency of 1 Hz, was introduced perpendicularly. When the transverse process was touched, the needle was withdrawn, angled laterally, and reintroduced 2 cm deeper than the depth necessary to touch the transverse process, until a motor response was obtained. Motor responses of the levator scapulae, deltoid, and biceps muscles were acceptable. The intensity of the stimulus was decreased until there was no motor response, which, ideally, should occur with a current smaller than 0.5 mA. After making sure blood was not aspirated, 2 mL of 2% lidocaine with 1:200,000 adrenaline was injected. When motor response was interrupted, but without a rise greater than 20 bmp in the heart rate, the local anesthetic was injected in fractionated volumes of 5 mL. When the patient did not present any longer a motor response with a stimulus greater than 0.8 mA, the needle was repositioned.
The 20 patients who received 40 mL of the local anesthetic had a chest X-ray, in deep inspiration, done in the postanesthetic recovery unit. The two patients who received 20 mL of the anesthetic had a fluoroscopic exam done in surgical room. The X-rays were analyzed comparing the position of the hemidiaphragms, while in the fluoroscopic exam their movement was observed. A cephalad position of the right hemidiaphragm, greater than three cm above the left one, was considered abnormal. On the other hand, any cephalad positioning of the left hemidiaphragm in relation to the right was considered abnormal. In the absence of any lung condition that would justify an elevation, the abnormal elevation of the blockade ipsilateral diaphragm was considered to be secondary to diaphragmatic paralysis. The anesthesia was evaluated by determining thermal sensitivity using cotton with alcohol 30 minutes after the anesthesia was administered. In the postanesthetic recovery unit, the quality of the analgesia was evaluated by the patients complaints and the amount of morphine used.
Table I shows the demographic data. Table II shows the effectiveness of the anesthesia, while table III presents postoperative pain in the postanesthetic recovery unit. Patients did not present any adverse effects, such as intravascular injection, hematoma caused by the puncture, dyspnea, or hypoxemia. Every patient presented elevation of the hemidiaphragm, compatible with diaphragmatic paralysis (Figures 1 and 2).
Hemidiaphragmatic paresis or paralysis causes important changes in lung function. Urmey and McDonald showed a mean reduction of 27.2% (varying from 21% to 34%) in forced vital capacity (FVC), and 26.4% (varying from 17% to 37%) in the forced expiratory volume in 1 second (FEV1) after interscalene brachial plexus blockade 33. The authors attributed this change to the decrease in inspiratory strength secondary to hemidiaphragmatic paresis or paralysis. The impossibility of taking a complete inspiration, causing a reduction in FVC, is directly responsible for a reduction, at least in equal proportion, in the measurements of expired volume. Besides this reduction, since the diaphragm has some role in expiration, there can be additional reduction of the expiratory volumes 33. Besides decreasing the measurements of lung function, phrenic paresis also changes lung mechanics. There are indications of changes in chest wall mechanics and abdominal wall motion (Figure 3). During hemidiaphragmatic paresis, these changes can lead to atelectasis 34, shown in figure 4.
However, diaphragmatic paresis, or even total paralysis, does not cause respiratory failure in healthy individuals 33. This is confirmed in the series presented here, since not one single patient presented clinical signs of respiratory dysfunction. However, in patients with some degree of prior respiratory dysfunction, diaphragmatic hemiparesis, and especially paralysis, can cause respiratory failure 33. Patients who cannot recruit the accessory and intercostal muscles to compensate for the loss of the diaphragm, such as patients with ankylosing spondylits, patients with contralateral hemidiaphragmatic paralysis or chronic obstructive pulmonary disease are good examples of this situation 27.
Therefore, hemidiaphragmatic paresis or paralysis has direct implications in the choice of anesthetic technique. Patients who, due to an existing disease, cannot tolerate a potential reduction of 25% in lung function are not good candidates for anesthetic techniques that may change diaphragmatic function 33. Patients who underwent cardiac surgery may have chronic hemidiaphragmatic paralysis, more often on the left and, therefore, might not tolerate a contralateral block 35. On the other hand, anesthesia ipsilateral to the paralysis has little or no repercussion.
Surgical procedures of the shoulder are associated with severe postoperative pain, which is hard to control 1,2. Among the analgesic techniques available, brachial plexus blockade is the one that presents the best results 1-19, and the interscalene approach is used more often 1-19. The reason is that the shoulder joint is innervated by the axillary and suprascapular nerves, which arise from the highest roots of the brachial plexus, C5-C6 36. Besides, the skin of the shoulder is innervated by the supraclavicular nerve, originating from the C3-C4 roots (cervical plexus) 36. Consequently, the most effective techniques of brachial plexus blockade for shoulder surgery are those that have a more cranial approach, e.g., interscalene 36. Since the phrenic nerve originates from C3, C4, and C5 roots, it is expected that the most effective techniques to promote analgesia in surgical interventions of the shoulder are also those associated more often with its blockade. Winnie 24 demonstrated that, even with the injection of low volumes of local anesthetics, there is dispersion until the cervical roots. Urmey et al. 27, using Winnie's technique and ultrasound demonstrated that the injection of 34 to 52 mL of mepivacaine had an incidence of diaphragmatic paralysis of 100%. The same authors also demonstrated that 20 mL of local anesthetic causes the same pulmonary changes that 45 mL 25. The study of the dispersion of local anesthetics in the brachial plexus blockade by the interscalene approach using contrast X-ray demonstrated that with volumes varying from 10 to 40 mL the involvement of the lower roots of the brachial plexus (C3-C4) is constant 37. Our study demonstrated that the pattern of diaphragmatic alteration produced by the posterior approach of the brachial plexus was similar to the one produced when Winnie's technique was used.
In general, lower concentrations of the local anesthetic are associated with a smaller degree of motor block, especially ropivacaine, which produces differential sensitive and motor block 38. Even though 0.33% ropivacaine presents the same incidence of hemidiaphragmatic paresis as bupivacaine in equivalent concentrations when Winnie's approach was used, it did not produced as much changes in respiratory volumes 39. This study demonstrated that, even with a concentration of 0.2% there was phrenic block, but the functional consequences of this mechanical block were not evaluated. One would assume that, with these low concentrations, pulmonary changes would be less significant and, consequently, the probability of respiratory failure would be smaller. This hypothesis has to be verified.
This study concluded that brachial plexus blockade by the posterior approach is associated with a high prevalence of diaphragmatic paralysis, even when low concentrations of local anesthetics are used. Therefore, when the patient cannot tolerate a reduction in lung function, this technique should not be used.
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Dr. Marcos Guilherme Cunha Cruvinel
Rua Simão Irffi, 86/301
Coração de Jesus
30380-270 Belo Horizonte, MG
Submitted for publication
05 de janeiro de 2006
Accepted for publication 30 de junho de 2006
* Received from Departamentos de Anestesiologia e Ortopedia do Hospital Lifecenter, Belo Horizonte, MG