Fonte: James W Bonz, MD, Medicina d’urgenza, Yale School of Medicine, New Haven, Connecticut, USA
L’accesso venoso centrale è necessario in una moltitudine di situazioni cliniche, tra cui l’accesso vascolare, il vasopressore e la somministrazione caustica di farmaci, il monitoraggio della pressione venosa centrale, la rianimazione del volume, la nutrizione totale dei genitori, l’emodialisi e la flebotomia frequente. Ci sono tre vene nel corpo a cui si accede per la cannulazione venosa centrale: la giugulare interna, la succlavia e il femore. Ognuno di questi vasi ha vantaggi e svantaggi distinti con considerazioni anatomiche uniche.
La cannolazione della vena femorale può essere facilmente eseguita sia sotto guida ad ultrasuoni che utilizzando i punti di riferimento della superficie; pertanto, l’accesso femorale viene spesso utilizzato quando è necessario il posizionamento emergente di un catetere venoso centrale (CVC) (come nel caso di codici medici e rianimazioni di traumi). Inoltre, la cannolazione dell’arteria femorale consente di eseguire contemporaneamente altre procedure necessarie per la stabilizzazione, come la rianimazione cardiopolmonare (CPR) e l’intubazione.
Il posizionamento di successo di un CVC femorale richiede una comprensione pratica dell’anatomia del bersaglio, l’accesso con ultrasuoni procedurali e la fluidità nella tecnica Seldinger.
La tecnica Seldinger è l’introduzione di un dispositivo nel corpo su un filo guida, che viene posizionato attraverso un ago a parete sottile. Nel caso dell’inserimento di CVC, il dispositivo è un catetere intravascolare e il vaso bersaglio è una vena centrale. In primo luogo, la nave bersaglio viene cannulata con un ago a parete sottile calibro 18. Un filo guida viene quindi fatto passare attraverso l’ago fino a quando non viene posizionato in modo appropriato all’interno del recipiente. L’ago viene rimosso e un dilatatore viene fatto passare sopra il filo per dilatare la pelle e i tessuti molli al livello del vaso. Il dilatatore viene quindi rimosso e il catetere viene fatto passare sopra il filo fino a quando non viene posizionato in modo appropriato all’interno del vaso. Infine, il filo guida viene rimosso.
Il principale svantaggio di un CVC femorale è l’alta incidenza di infezione dovuta alla vicinanza all’inguine (e spesso a causa della natura quasi sterile sotto la quale sono collocate le CVC emergenti). Le linee femorali devono essere sostituite all’inizio del decorso ospedaliero del paziente se è necessario un accesso centrale prolungato. Una linea posizionata con sterilità minima deve essere sostituita non appena il paziente è stabile.
Femoral vein access for CVC insertion is most frequently used in the crashing or coding patient. The femoral lines can be placed quickly, with or without ultrasound guidance, and would not interfere with performing other emergent procedures, such as airway management and CPR.
The immediate complication risks are lower than for IJ and subclavian CVCs. There is no risk of pneumothorax as there is in both IJ and subclavian lines; nor is there any difficulty in controlling accidental arterial hemorrhage from arterial puncture. In the case of an accidental arterial puncture, the femoral artery can be easily compressed at this site. In addition to the risks of systemic and local infection, arterial puncture and bleeding, and thrombosis associated with any CVC insertion sites, femoral CVCs have a risk of bladder perforation and even peritoneal perforation. Femoral CVCs must be replaced once the patient is stable, with a different CVC placed in an alternative location because of the high infection rate of femoral CVCs.
To enhance procedural fluidity and avoid errors during the CVC placement, it is important to make two important preparations to the kit prior to starting. Be certain to remove the cap to the central lumen, which is the distal port (of a triple-lumen catheter) so that the wire will be able to pass freely as you slide the catheter over the wire. It is also critical to prepare the wire by retracting it slightly within the sheath so that the J curve is straight and can easily feed into the needle.
The most important and difficult aspect of the Seldinger technique in any CVC placement is in cannulating the target vessel and successfully advancing the guide wire. Practitioners often enter the vessel with the needle successfully, only to find that they have difficulty passing the wire once they remove the syringe, which often is due to the needle losing its position and exiting the vessel. To reduce needle migration, it is recommended to brace the hand that holds the needle against the body of the patient. Use of ultrasound allows the practitioner to verify needle location within the vessel.
Central venous access is necessary in a multitude of clinical situations and the femoral vein is one of the common sites used to establish this access.
This anatomical location is often used when emergent placement of a central venous catheter-or CVC-is needed, such as in the case of medical codes and trauma resuscitations. Because, it allows for the simultaneous performance other procedures needed for stabilization, such as cardio-pulmonary resuscitation and intubation.
Here, we’ll illustrate how the femoral vein can be easily cannulated either under ultrasound guidance or with the use of surface landmarks only. Both procedures require knowledge of the Seldinger technique – discussed in the IJ CVC video of this collection.
Begin by gathering the necessary supplies. These include: a CVC kit, sterile gloves and a sterile bundle that contains mask, bonnet, gown, full body drape, sterile ultrasound probe cover, sterile syringes with sterile saline, and dressings. The commercially available CVC kits are usually comprised of: 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 usually provided in a sterile tray wrapped with a sterile cover.
After all the supplies have been collected, place the patient in the supine position and abduct and externally rotate the leg to be utilized in order to maximize access to the target area. Understanding the anatomy of this region helps in locating the femoral vein. The inguinal ligament runs diagonally from the anterior iliac spine to the pubic tubercle. The structures passing through the inguinal region from lateral to medial can be remembered by the mnemonic “NAVEL”: Nerve, Artery, Vein, Empty space, and Lymphatics. In order to localize the femoral vein, first palpate the pubic tubercle. Then move your fingers laterally until you feel the femoral pulse. The vein is located just medial to the pulsating artery.
Next, at the bedside, apply acoustic gel to the ultrasound probe and place the transducer just lateral to the pubic tubercle. Orient it in a transverse plane by aligning the indicator on the transducer to the left – that is the patient’s right, to obtain a cross-sectional view of the structures in this area. Applying slight pressure with the transducer will help distinguish the compressible femoral vein from the pulsatile femoral artery.
After localizing the vessel, clean the skin with chlorhexidine – scrub vigorously for 30 seconds, and then allow it to dry for 60 seconds. Next, open the CVC kit by grasping the non-sterile outside surfaces and unfolding the wrap outward. This allows the inner surface of the wrap to remain sterile along with the contents of the kit. Now open the sterile bundle, put on the bonnet and mask and open the portion containing the gown, drape, ultrasound probe cover and 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. At this point, put on the sterile gown and gloves and drape the patient’s groin area.
If using ultrasound for the procedure, have an assistant place additional acoustic gel on the probe. Hold the sterile cover open and ask the assistant to drop the probe inside, maintaining the sterility of the outside of the cover. Now while grasping the probe firmly within the cover have the assistant unfurl the sheath over approximately four feet of the cord. Next, separate the contents of the kit to make them more accessible, and retract the guidewire slightly within the sheath to straighten out the J curve so that it feeds easily into the introducer needle. Draw lidocaine into a syringe to be injected for local anesthesia, and lastly, flush the lumens of the catheter with saline leaving the distal lumen unlocked, as this is where the wire will pass through.
With the ultrasound probe wrapped inside the sterile sleeve, once more identify the target vessel, verifying its location. Note the depth of the femoral vein. If the vein is 2 cm deep, then the needle will need to be introduced 2 cm inferior to the transducer so that the tip reaches the plane of the ultrasound beam at the depth of the target.
Start by injecting lidocaine at the insertion site creating a wheal and then anesthetizing the surrounding soft tissues. Remember to pull the plunger before injecting to ensure that you are not within a vessel. Next, attach an empty syringe to the introducer needle and insert the needle into the insertion site at a 45° angle, aiming cephalad. Fan the ultrasound probe in order to follow the tip of the needle as it advances, and simultaneously pull back on the plunger. Observe the needle tip as it enters the vessel and confirm the location in the femoral vein by drawing blood easily into the syringe. With the introducer needle in the vessel, gently remove the syringe without changing the depth at which the needle is positioned. Blood return should be dark and non-pulsatile.
Now lower the angle of the needle to 30° and feed the guidewire through the introducer needle into the vessel to a depth of 20 cm, which is marked by 2 black lines on the guidewire. If resistance is met, confirm that the angle of the needle is not too steep and re-try. If it still does not pass easily, remove the wire and reattach the syringe to confirm that blood can still be easily aspirated. If not, then the needle is no longer in the vessel. If blood draws freely into the syringe, but there is still difficulty advancing the guide wire, then verify its location within the vessel lumen by using the ultrasound in the longitudinal view. You may be able to overcome difficulty in passing the wire by retracting the wire a few centimeters and rotating it 90°. This reorients the J tip and may allow for free passage. Never force the guidewire.
When the wire has advanced to the desired location, 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 to 3 centimeters, gently rotating it to dilate the skin and soft tissues. Subsequently, remove the dilator and feed the catheter over the guidewire until it is completely inserted – 20 cm. Once the catheter is inserted, remove the guidewire. Next, attach a syringe containing sterile saline to the distal port of the CVC, aspirate to verify blood return, and then flush the lumen. Repeat this step for each lumen on double or triple lumen catheters and cap the ports of each lumen.
Subsequently, with the help of a two-part clamp, hold the catheter in place. Then anesthetize the skin, and suture the clamp in place through the eyelets. To complete the procedure, apply a sterile dressing in accordance with the practices of the medical facility and dispose of all sharps.
If using the landmark-guided technique, palpate the femoral artery as described previously, and insert the introducer needle just medial to the pulse. If this attempt is unsuccessful, move the insertion sight slightly more medial until you are able to draw blood freely. The rest of the procedure is exactly same as the insertion technique using ultrasound guidance.
“CVC insertion in the femoral vein is most commonly performed in emergency situations because it can be placed quickly, with or without ultrasound guidance, and the procedure does not interfere with other procedures such as CPR or airway management.”
“The immediate complication rate is lower than both IJ and subclavian vein procedures because there is no risk of pneumothorax and accidental arterial puncture can be easily addressed with direct pressure.”
“The major disadvantage of femoral CVC’s is the high incidence of infection due to the proximity to the groin and because they are often placed under quasi-sterile conditions in emergency situations. For this reason, femoral CVC’s should be replaced with a catheter in another location if sustained central venous access is required. In addition, femoral catheterization also carries the risk of bladder and peritoneal perforation.”
You have just watched a JoVE video on central venous catheter insertion into the femoral vein with and without ultrasound guidance. After watching this, you should have a better sense of the critical steps of this procedure and how ultrasound guidance can help enhances the success of CVC placement in femoral vein. As always, thanks for watching!
