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Rev. Bras. Anestesiol. vol.52 no.3 Campinas May/June 2002
Anatomical basis for infraclavicular brachial plexus block *
Bases anatómicas para el bloqueo anestésico del plexo braquial por vía infraclavicular
Luiz Carlos Buarque de Gusmão, M.D.I; Jacqueline Silva Brito Lima, M.D.II; José Carlos Prates, M.D.III
IProfessor Adjunto IV do Departamento
de Morfologia da Universidade Federal de Alagoas. Mestre e Doutor em Anatomia.
Membro Titular do Colégio Brasileiro de Cirurgiões
IIProfessora Auxiliar de Ensino da Universidade Federal de Alagoas
IIIProfessor Titular da Disciplina de Anatomia Descritiva e Topográfica da Escola Paulista de Medicina. Mestre e Doutor em Anatomia
BACKGROUND AND OBJECTIVES: This study
shows the constant infraclavicular fossa presence, aiming at using it as a pathway
for infraclavicular brachial plexus block. Determining the point where brachial
plexus fascicles may be located within the fossa, the authors have proposed
measurements from the anterior surface of the clavicle and the angle formed
by the deltoid muscle and the clavicle (deltoclavicular angle). The first measurement
allows the in-depth location of the site crossed by the brachial plexus. The
second determines fascicles projection within the fossa, corresponding to the
needle insertion point on the skin.
METHODS: Measurements were made between the anterior surface of the clavicle and brachial plexus fascicles, and from the deltoclavicular angle to superficial fascicles projection. Based on the anatomic findings a technique of infraclavicular brachial plexus approach was proposed.
RESULTS: A hundred infraclavicular regions in cadavers were analyzed. Infraclavicular fossa was detected in 96 cases where brachial plexus fascicles were totally or partially (97.9%) located. The distance between the anterior surface of the clavicle and brachial plexus fascicles was in average of 2.49 cm and from the deltoclavicular angle to superficial fascicles projection was 2.21 cm.
CONCLUSIONS: Values obtained allow for the precise location of the needle insertion point which, when perpendicular to the skin, reaches brachial plexus without danger of causing pneumothorax or vascular injury, providing more safety to anesthesiologists and allowing the return to the practice of brachial plexus block below the clavicle.
Key words: ANATOMY: brachial plexus; ANESTHETIC TECHNIQUES, Regional: brachial plexus blockade
JUSTIFICATIVA Y OBJETIVOS: Buscamos demostrar
en este estudio la presencia constante de la fosa infraclavicular, con la finalidad
de su utilización como vía de acceso para el bloqueo anestésico
del plexo braquial por via infraclavicular. Con la idea de solucionar el punto
donde los fascículos del plexo braquial pueden ser localizados en el interior
de la fosa, propusimos medidas a partir de la face anterior de la clavícula
y del ángulo formado por el encuentro del músculo deltóide con
la clavícula (ángulo deltoclavicular). La primera medida permite localizar
en profundidad el local donde pasa el plexo braquial. Ya la segunda, determina
la proyección de los fascículos dentro de la fosa, lo que corresponde
al punto de entrada de la aguja en la superficie cutánea.
MÉTODO: Fueron efectuadas medidas entre la face anterior de la clavícula y los fascículos del plexo braquial, y del ángulo deltoclavicular hasta la proyección superficial de los fascículos. Con base en los encuentros anatómicos fue propuesta una técnica de abordaje del plexo braquial por via infraclavicular.
RESULTADOS: Fueron analizadas 100 regiones infraclaviculares de cadáveres fijados. La fosa infraclavicular fue detectada en 96 casos. En ésas, los fascículos del plexo braquial se localizan totalmente o parcialmente en 97,9%. La medida comparada entre la face anterior de la clavícula y los fascículos del plexo, fue de 2,49 cm y del ángulo deltoclavicular hasta la proyección superficial de los fascículos estaba en 2,21 cm.
CONCLUSIONES: Los datos obtenidos permiten la determinación exacta del punto de introducción de la aguja, la cual, dirigida perpendicular a la piel, alcanza el plexo braquial sin peligro de provocar pneumotórax o lesión vascular, posibilitando una mayor seguridad a los anestesiologistas, y permitiendo la vuelta de la práctica del bloqueo del plexo abajo de la clavícula.
Brachial plexus block has several complications and may induce an incomplete blockade when axillary 1,2, supraclavicular 3,4 and interscalenic 4-6 routes are adopted. As an alternative, some anesthesiologists 7-9 have returned to the infraclavicular route with a relative success in addition to a lower complication rate. However, there were still reports on vascular and chest wall punctures with consequent pneumothorax. Reviewing several infraclavicular techniques, we observed the following:
Hirschel 10 (1913) was the first to use the infraclavicular approach but actually he used the axillary approach and deposited the drug above the first rib.
Bazy 11 (1917) located the crycoid process and the anterior tubercle of the 6th cervical vertebra and drawn an anesthetic line between both points. A 9 cm needle was introduced below the clavicle and directed to the vertebral tubercle. The drug was deposited after the needle surpassed clavicles posterior margin.
Babitsky 12 (1918) introduced a needle between the angle formed by the 2nd rib and the clavicle and the anesthetic drug was deposited there.
Labat 13 (1932) used the same Bazys anesthetic line, but the drug was injected with an 8 cm needle in two stages. In the first stage, the drug was injected in the same point preconized by Bazy. Then, the arm was bent toward the chest and another injection of the same drug was performed without moving the needle.
Balog 14 (1924) has modified Bazys technique using the same point, however the needle was introduced toward the costal grid until reaching the second rib. Then the needle was brought slightly backwards and the drug was deposited.
Raj et al. 7 (1973) have determined that the needle should be introduced in a middle point of the clavicle. The long needle was laterally directed avoiding chest wall puncture.
Sims 8 (1977) has modified Raj et al. technique classified by him as a difficult to master technique due to not very clear reference points and pectoral muscles thickness. His technique uses a standard 3.8 cm needle which, directed downward, outward and backward, reaches the brachial plexus 2 to 3 cm after crossing the skin.
Whiffler 10 (1981) has proposed the location of subclavian and axillary arteries. Both points would be connected by a line. From the crycoid process a line is drawn perpendicular to the first and puncture is performed where both lines meet. Arterial puncture is reported in 50% of cases.
Imbelloni et al. 15 (1991) have determined that a site should be marked 1.5 cm below the point where the lateral third and two medial thirds of the clavicle meet, and this point should be 1.5 to 2 cm medial to the crycoid process. Using a neurostimulator, 50 ml lidocaine with 1.6% epinephrine are injected.
Observing that the plexus is almost always located within the infraclavicular fossa, we decided to prove that the fossa is a space found in most individuals, and to evaluate the topographic relationship of fascicles with axillary vessels at this level. Finally, and based on those data, we proposed a new infraclavicular approach for anesthetic block based on well defined anatomic principles and repair points easily identified so that this route could once more be safely used with a minimum of failures and complications.
In compliance with Federal Law 8501 from November 30, 1992 and after institutional approval, 100 infraclavicular regions of fixed cadavers of both genders and belonging to the Morphology Departments of Escola Paulista de Medicina and Universidade Federal de Alagoas were analyzed.
After infraclavicular fossa identification (96% of cases) brachial plexus fascicles were dissected and identified. The distance from the anterior face of the clavicle to the brachial plexus fascicles and the angle determined by the deltoid muscle and the clavicle until reaching fascicles projection on the skin, were measured. Axillary vessels position in relationship to fossas floor was checked.
Based on anatomical findings, an infraclavicular brachial plexus approach was proposed, which may become an alternative anesthetic technique.
The infraclavicular fossa could be identified in 96 out of 100 regions analyzed (Figure 1). The remaining 4 cases without fossa belonged to individuals with hypertrophied muscles and just one deltopectoral sulcus extending superiorly to the clavicle.
Brachial Plexus Position in the Infraclavicular Fossa
The presence of brachial plexus fascicles within the infraclavicular fossa was confirmed in 96 cases, which were included in the study because our proposal was based on anesthetic block via infraclavicular fossa.
In 41 cases (42.7%) brachial plexus fascicles were totally in the infraclavicular fossa floor.
In 53 cases (55.2%), fascicles were partially located in the infraclavicular fossa and partially covered by the clavicular portion of the greater pectoral muscle.
In 2 cases (2.1%) all fascicles were hidden by the greater pectoral muscle.
Axillary Artery Position
Since the axillary artery is the most lateral vessel, its position was irrelevant for this study. In 79 cases (82.3%) the axillary artery was totally covered by greater pectoral muscle clavicular bundle. In 13 cases (13.5%) the artery was partially located in the infraclavicular fossa. In 4 cases (4.2%) the artery was totally within the fossa.
Anesthetic Route via Infraclavicular Fossa
We tried to thoroughly locate the brachial plexus access site where the insertion point would be the infraclavicular fossa. At this access, reference points are easy to locate (anterior face of clavicle and deltoclavicular angle) allowing for an accurate location of the points where brachial plexus fascicles cross the infraclavicular fossa and at what depth they are located. Mean measurements performed in the 96 fossae as from the deltoclavicular angle toward the center of the fossa until reaching superficial plexus projection was 2.21 cm. On the other hand, mean measurements in the anterior-posterior direction as from the anterior face of clavicle to the meeting of brachial plexus fascicles was 2.49 cm.
The angle formed by the junction of deltoid muscle anterior margin and the clavicle must be initially determined. Then, an angles bisectrix to the center of the fossa and measuring approximately 2.21 cm should be plotted. This point corresponds to brachial plexus superficial projection and where the needle should be inserted perpendicular to the skin (Figure 2). To avoid brachial plexus traction, the upper limb should remain pending along the body or in slight abduction. The head does not need to be rotated to the opposite side because it does not interfere with plexus fascicles position. On the other hand, the depth of the needle to be introduced perpendicularly to the skin until reaching plexus fascicles is determined as from the anterior face of the clavicle until the needle reaching a depth of 2.5 cm (approximate value) (Figure 3). Since this depth was obtained when the needle reached the first fascicle, it is desirable that the needle be introduced 3 to 3.5 cm to avoid the risk of the injection not reaching the axillary sheath or reaching only the lateral fascicle, which is more anterior in this site.
Techniques described in the literature use several points below the clavicle, which sometimes are over the greater pectoral muscle and sometimes beside the coracoids, or even over the infraclavicular fossa, which is more seldom mentioned. Only Imbelloni et al. mention the importance of the infraclavicular fossa for brachial plexus anesthetic block. However, the junction of the lateral third with the two medial thirds of the clavicle mentioned in their technique not always corresponds to the infraclavicular fossa and, when corresponding, the technique does not specify the fossa site where plexus fascicles travel. On the other hand, the technique makes use of the electrical neurostimulator, which is not always available in our anesthetic centers.
We were only concerned with the access route to be used and with data to locate brachial plexus fascicles. Anesthetic maneuvers, drug type, quantity and concentration are not issues to be dealt with in this study.
It has been shown that in the upper axilla, brachial plexus fascicles are, most of times, within the infraclavicular fossa and laterally to axillary vessels, which are in general located posteriorly to the greater pectoral muscle, thus outside the infraclavicular fossa.
To be safe in inducing the blockade, it is necessary that the anesthesiologist be informed about brachial plexus depth and its location within the infraclavicular fossa. Deltoclavicular angle is easy to identify and its 2.21 cm bisectrix plotted to the center of the fossa represents, almost errorless, the exact brachial plexus superficial projection site. Depth is better determined as from a fixed and stable structure, in this case the clavicle. This way, we have information about puncture site and the depth in which the drug should be deposited. The needle, perpendicular at this point and directed from anterior to posterior allows for brachial plexus fascicles to be reached and also prevents axillary artery and chest wall puncture.
We believe that further studies should be performed using the knowledge obtained from our observations to compare this access to existing ones, thus contributing for the evolution and improvement of brachial plexus anesthetic block.
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Submitted for publication July 10, 2001
Accepted for publication November 23, 2001
* Received from Disciplina de Anatomia Descritiva e Topográfica do Departamento de Morfologia da Escola Paulista de Medicina (UNIFESP)