Fonte: James W Bonz, MD, Emergency Medicine, Yale School of Medicine, New Haven, Connecticut, EUA
O acesso venoso central é necessário em uma infinidade de situações clínicas para monitoramento hemodinâmico, entrega de medicamentos e amostragem de sangue. Há três veias no corpo que são acessadas para cannulação venosa central: a jugular interna, a subclávia e a veia femoral.
O acesso venoso central através da veia subclávia tem várias vantagens sobre outros possíveis locais. A colocação do cateter venoso central subclávio (CVC) está associada a menor taxa de infecção e trombose do que a jugular interna e a CVC femoral. A linha subclávia pode ser colocada rapidamente usando marcos anatômicos e muitas vezes são realizadas em configurações de trauma quando coleiras cervicais obliteram o acesso à veia jugular interna (IJ). A desvantagem mais significativa do acesso subclávio é o risco de pneumotórax devido à proximidade anatômica com a cúpula do pulmão, que fica apenas superficial à veia subclávia. Além disso, no caso de uma punção arterial inadvertida, o acesso à artéria subclávia é impedido pela clavícula, o que dificulta efetivamente a compressão do vaso.
A colocação bem sucedida do CVC subclávio requer uma boa compreensão do trabalho da anatomia do vaso alvo, bem como fluidez na realização do procedimento Seldinger (introdução do cateter em um vaso sobre o fio guia, que é inserido através de uma agulha de parede fina). Primeiro, a veia subclávia é cânulada com uma agulha de parede fina de calibre 18. Em seguida, passa-se um fio-guia que pensa a agulha até que esteja adequadamente posicionada dentro do vaso. Em seguida, a agulha é removida, um dilatador é passado sobre o fio para dilatar a pele e tecido mole, e o cateter é passado sobre o fio até que ele seja devidamente posicionado dentro do vaso. Por fim, o fio guia é removido e o cateter é suturado no lugar.
Existem vários tipos de kits CVC comumente disponíveis comercializados por diferentes fabricantes. CvCs podem ter um único lúmen, um lúmen duplo, ou um lúmen triplo. Para efeitos desta discussão, colocaremos uma CVC de três lúmens, pois isso é comumente necessário quando vários medicamentos diferentes precisam ser entregues simultaneamente. O procedimento para colocar qualquer tipo de CVC é o mesmo.
Subclavian vein placement for CVCs is preferred by many practitioners for the rapidity of the procedure, predictable anatomy of the target vessel, and reduced infection rate. Many neurosurgeons and neurocritical care specialists prefer the subclavian vein over the IJ vein due to the lower risk of CVC-associated thrombosis, which carries an additional and unnecessary risk in a patient with increased intracranial pressure (ICP).
As the other CVC placement procedures, subclavian CVCs carry the risk of systemic and local infections, thrombosis, arterial puncture, and bleeding. Since the external pressure cannot be applied to the subclavian artery in the event of accidental puncture, this location is less appealing to many practitioners. Additionally, subclavian vein access is associated with the highest rate of pneumothorax. However, these risks can be reduced with full-barrier sterile precautions, experience, excellent knowledge of the anatomy, and procedural fluidity in the Seldinger technique.
Central venous access via the subclavian vein has several advantages over other possible locations. First, the central venous catheter, or CVC, can be placed quickly using anatomic landmarks. Second, it can be performed in trauma setting when cervical collars obliterate the access to the internal jugular vein. And third, the rate of thrombosis and infection is lower than both internal jugular and femoral CVC.
This video will demonstrate the insertion of a subclavian CVC using the Seldinger technique.
First, gather the supplies necessary for the procedure, including: a CVC kit, sterile gloves and a sterile bundle that contains a mask, bonnet, gown, full body drape, sterile syringes, sterile saline, and dressings. A typical commercially available CVC kit contains: a catheter, a j-tip guide wire, a dilator, a #11 scalpel, an introducer needle, 1% Lidocaine, several syringes and smaller needles, a suture needle with suture, a CVC clamp, surgical dressing, gauze, and chlorhexidine. The contents are in a sterile tray, which is wrapped with a sterile cover.
Once the supplies have been collected, place the patient supine with their feet elevated – the Trendelenberg position. This position engorges the target vessel and helps decrease the risk of an air embolus. It may be helpful to place a rolled towel under the medial scapula to accentuate the physical landmarks. However, too much shoulder retraction may decrease the space between the clavicle and first rib, compressing the subclavian vein. Because of the presence of the thoracic duct and higher pleural dome on the left side, the right subclavian vein is generally preferred for venous access. The insertion site is just underneath the clavicle, at the point where the vein passes between the clavicle and the first rib. In this location, the first rib acts as a barrier to the lung underneath, helping prevent a pneumothorax.
The next step is to clean the area with chlorhexidine, scrubbing vigorously for 30 seconds, then allowing it to dry for 60 seconds. After this, open the CVC kit by grasping the non-sterile outer surface and unfolding the wrap outward, thereby keeping both the inner surface of the wrap and the contents of the kit sterile. Next, open the sterile bundle and put on the bonnet and mask. Then open the portion containing the gown, drape and sterile saline, and lay out the sterile gloves. If your institution does not use the sterile bundle, these items may need to be gathered separately and dropped onto your sterile field. When all of the supplies are open, put on the sterile gown and gloves and place sterile drapes around the patient’s clavicle.
Now, prepare the contents of the kit, separating them to make them more accessible, and draw lidocaine into a syringe. Also, retract the guidewire slightly within the sheath to straighten out the J curve. Finally, flush the lumens of the catheter with saline and leave the distal lumen uncapped.
To identify the insertion site using surface landmarks, place your non-dominant index finger in the sternal notch. Then, with the thumb, identify the middle third of the clavicle, medial to where it bends cephalad. The insertion site of the introducer needle is one fingerbreadth below the medial portion of the middle third of the clavicle and the needle will be aimed towards the index finger, just above the sternal notch.
Inject lidocaine into the skin, creating a wheal at the insertion site, and anesthetize the surrounding soft tissues, down to the periosteum of the clavicle, along the anticipated trajectory. Next, attach an empty syringe to the introducer needle and insert the needle into the insertion site at a 10° angle to the skin, aiming towards the sternal notch. Advance the needle while pulling back on the plunger of the syringe. The needle should graze the underside of the clavicle and pass into the subclavian vein where it is sandwiched between the clavicle and the first rib. Insertion of the needle into the vein will be confirmed by aspiration of dark blood into the syringe. Once the needle is in the vein, remove the syringe, taking care not to change the depth and position of the needle. Blood return should be dark and non-pulsatile. Then feed the guidewire into the needle to a depth of 15 cm, as determined by marks on the wire.
With the wire in position, nick the skin at the insertion site with the scalpel, remove the introducer needle, and pass the dilator over the guidewire to a depth of 2 – 3 cm, gently rotating it to dilate the skin and soft tissues. Next, remove the dilator and pass the catheter over the guidewire to a depth of approximately 15cm in adult men. Then remove the guidewire. After that, attach a sterile syringe to the distal port of the catheter and aspirate to confirm blood return. Then flush the lumen with sterile saline. Repeat this step for each lumen on a double or triple lumen catheter.
To secure the catheter in the desired location, place a 2-part clamp around the catheter, anesthetize the skin, and suture the clamp to the skin through the eyelets. Finally, place a sterile dressing over the insertion site and dispose of all sharps according to the practices of the medical facility. Then obtain a chest x-ray to verify proper line position and to rule out a pneumothorax.
“Insertion of a central venous catheter in the subclavian vein is preferred by many practitioners because of the predictable anatomy of the target vessel rapidity of the procedure and low infection rate”
“The most significant disadvantage of the subclavian access is the risk of pneumothorax due to the anatomic proximity to the dome of the lung, which lies just deep to the subclavian vein. In addition, in the event of an inadvertent arterial puncture, the access to the subclavian artery is impeded by the clavicle, which makes it difficult to effectively compress the vessel.”
“However, all of these risks can be minimized with the use of sterile precautions, knowledge of the anatomy, and fluidity with the Seldinger technique.”
You have just watched a JoVE video on the placement of a subclavian central venous catheter. You should now have a better understanding of both the anatomical and technical considerations of this procedure. As always, thanks for watching!
