VSITE Review: Vascular Access

April 29th, 2020

 

Audible Bleeding VSITE review—Vascular Access

 

Script by Sammy Siada, MD

 

Sammy Siada is a second year vascular fellow at the University of Colorado.  He completed medical school at University of North Texas and did general surgery at the University of California san Francisco in Fresno. 

 

Dr. Rafael Malgor is an associate professor of vascular surgery and the program director for the vascular surgery fellowship at University of Colorado school of medicine.  He attended general surgery residency and a vascular surgery fellowship in brazil. He then completed a research fellowship at the Mayo Clinic in Rochester followed by a second Vascular surgery integrated residency at Stonybrook University in New York.  He’s also done an advanced aortic fellowship in Nuremberg Germany

 

Endovascular procedures are the cornerstone of any modern vascular surgery practice. Because most endovascular procedures are performed percutaneously using arterial or venous access, it is critical that vascular surgeons are facile with various techniques and devices used for endovascular access. Today we’ll be discussing the various access sites, techniques for access, closure devices, and complications.

 

What factors play a role when choosing a site for access?

·      The factors to think about when thinking about which vessel to access are:

o   The appropriateness of the access site the procedure performed

o   Ability to obtain hemostasis at the conclusion of the procedure

o   Ability to convert to open if necessary

o   Effects of access on the tissues supplied by the accessed vessel and distal limb perfusion

 

What makes a vessel appropriate for access?

·      One of the most important factors when planning your access is the size of the vessel. The vessel needs to be able to accommodate the catheters and devices that will be used to perform the procedure. For instance, a brachial artery with less than 4mm diameter should not be accessed by a large bore sheaths, such as a 12Fr sheath.

·      The vessel also needs to be a in a location that can allow access to the target vessel of interest. Additionally, the vessel needs to have an area that is relatively healthy to access the vessel safely and minimize complications. Heavily calcified vessels especially those with anterior wall calcification might not be appropriate for access.

 

What about the ability obtaining hemostasis at the end of the procedure?

·      The ability to obtain hemostasis is critical to be able to perform endovascular procedures safely which is one reason why the common femoral artery is the most commonly accessed vessel.

·      Hemostasis is most commonly achieved through manual compression by compressing the artery against the femoral head. The brachial artery can also be compressed against the humerus, but because it’s a more mobile vessel, compression is less effective and can lead to hematoma or pseudoaneurysm formation which may necessitate an operation to prevent compression of the median nerve

·      Patients who will need to be uninterruptedly anticoagulated peri and postoperatively pose a challenge to hemostasis. The use of closure devices is very important in these situations to prevent access bleeding.

·      A variety of closure devices can also be used to assist in hemostasis, each with their own inherent advantages and disadvantages. In general, closure devices are contraindicated in small diameter and heavily calcified vessels.

 

In any minimally invasive procedure, there is always a chance that you may need to convert to open. How does converting to open play a role in vascular access?

·      Conversion to open is uncommon with vessel access accounting for <5% of the cases. Sometimes a large sheath is accidentally pulled out and a cutdown becomes necessary to repair the artery. Closure devices aren’t 100% effective in hemostasis and may also require a cutdown for definitive control if they fail, especially when obtaining large bore access.

·      This makes choosing the right vessel critical. For example, if a large sheath is accidentally pulled out of the CFA during an EVAR, the repair can be done through a straightforward groin cutdown. In contrast, the subclavian artery is rarely accessed percutaneously because converting to open would require a more challenging peri-clavicular incision or even a thoracotomy for repair.

 

Large diameter sheaths are often used, particularly in aortic procedures. These sheaths can be occlusive which can result in downstream tissue ischemia. What considerations should be taken when thinking about downstream tissue ischemia?

·      When performing diagnostic procedures using small diameter sheaths and catheters, anticoagulation may or may not be necessary depending on how diseased the access vessel is.

·      However, when using large devices (e.g. in EVARs), the sheaths can be partially or completely occlusive which mandates full anticoagulation to prevent thrombosis. The other thing to consider is the length of time that the sheath remains in the vessel as the leg can only tolerate ischemia for 4-6 hours. This is usually pertinent when performing complex endovascular aortic procedures.

·      To minimize downstream tissue ischemia, a large bore sheath should be pulled back to decrease the length of vessel obstruction by its shaft in order to unblock proximal vessel collateral branch vessels. For instance, when performing an aortic procedure through a femoral access attempt to pull the sheath back into the external iliac artery to increase distal limb perfusion through the internal to femoral artery collateral branch vessels.  

·      The long story short is to be liberal with anticoagulation when there is reduced flow in the vessel such as the iliofemoral system during EVAR or tibial access

 

Do the principles that we’ve described also apply to veins?

·      The same principles apply but there are some notable differences between arterial and venous access.

·      Veins are a low-pressure system, so hemostasis is easier to achieve and hemorrhagic complications are much less common. However, this poses a challenge during access as there is less radial force keeping the vein open making the vein more susceptible to compression by the ultrasound probe and the needle.

·      If a large bore sheath is necessary to perform a venous procedure, a suture-mediated closure device can be utilized to achieve hemostasis especially in patients that will be kept fully anticoagulated

·      Additionally, a syringe may be needed to confirm access and can also prevent air embolism

 

Let’s talk about accessing the common femoral artery. Why is the CFA the most common vessel used for access?

·      It is large caliber and can accommodate large sheaths up to 26-28 Fr. It also allows for a wide set of procedures and is ergonomically easy to work with given its location. It is relatively easy to hold manual pressure and if a conversion to open is needed, a femoral cutdown is relatively straightforward.

 

 Where in the common femoral artery is the best spot to access?

·      The ideal puncture site is in the CFA in the medial third of the femoral head in between the inguinal ligament and the femoral bifurcation in the middle of the femoral head.

·      Accessing the vessel above the inguinal ligament makes compressing the artery very difficult which can lead to life-threatening retroperitoneal bleed.

·      A puncture that is too distal and into the SFA increase the risk of thrombosis or dissection causing acute limb ischemia as well as AV fistula formation between the superficial femoral and profunda femoris artery.

 

What are the different ways to obtain CFA access?

·      There are three different ways to access the CFA: manual palpation, fluoroscopic guided, and ultrasound guided.

·      With manual palpation, a finger is placed above and below the desired access point directly on the pulse and the needle is inserted in between the two fingers.

·      Fluoroscopic guidance uses bony landmarks relative to the position of the needle.

·      The standard of care in the modern era for obtaining CFA access is to use ultrasound guidance. Ultrasound allows visualization of the vessel and surrounding structures. PAD within the vessel can readily be identified with ultrasound, allowing safe access in a relatively disease-free part of the artery. Ultrasound also clearly shows the femoral bifurcation. Using ultrasound allows for subtle corrections in the angle of the needle and how it interacts with the surrounding tissues. It is rapid, real-time, inexpensive, and safe.

 

What anatomic considerations should be taken when accessing the CFA?

·      The CFA is the continuation of the external iliac artery as it courses under the inguinal ligament. It is about 5-8 cm in length and then bifurcates in to the superficial femoral and profunda femoris arteries

·      The inguinal ligament is a good external landmark to estimate where the CFA is. It is critical to emphasize that the inguinal ligament does not correspond to the groin crease and this is especially true in obese patients. An imaginary line is drawn from the ASIS to the pubic tubercle. The artery generally runs a third of the way from the pubic tubercle to the ASIS. A metallic instrument can be placed in this area to mark it externally and a fluoroscopic image can be obtained to identify the relation of the instrument to the medial third of the femoral head. This imaginary line also marks the superior-most extent of the access

·      The CFA is most often accessed in a retrograde fashion in between the inguinal ligament and femoral bifurcation. This allows for a multitude of potential diagnostic and therapeutic procedures in most parts of the body.

 

Can the CFA be accessed antegrade?

·      Yes. Sometimes antegrade CFA access is used when performing an intervention distal on the ipsilateral leg. The advantage of antegrade access is better pushability and torquability of wires, catheters, and sheaths when performing complex peripheral intervention where no other proximal procedures are needed.

·      Antegrade access is more challenging than retrograde access, however. This is particularly true in patients with a very short CFA, short distance between the inguinal ligament and the femoral bifurcation because the needle requires a steeper angle of entry to allow for cannulation well above the femoral bifurcation.

·      Obtaining antegrade access is especially difficult in obese patients and will usually require an assistant to retract the pannus to allow proper needle placement. I would say antegrade access is relatively contra-indicated in morbidly obese patients with large pannus. Ultrasound guidance remains key here as well.

 

What are some other commonly accessed arteries for endovascular procedures?

·      The tibial vessels can be accessed percutaneously for retrograde recanalization for severe LE PAD. It is usually performed using micropuncture kits which we will discuss a little later. It is usually done with ultrasound guidance and uses small sheaths and wires. The PT and AT are more commonly used because they are easier to access.

·      The radial artery is commonly used in coronary interventions and is increasingly being used by vascular surgeons. It is easily palpable over the distal radius and can be cannulated with ease. Hemostasis is straightforward using compression. In the rare setting of radial occlusion, the hand rarely becomes ischemic because most people are ulnar dominant. It can accommodate sheaths up to 6 French.

·      The brachial artery can be accessed percutaneously over the olecranon process with the arm supinated. Ultrasound guidance allows for visualization of the brachial bifurcation. It can accommodate 6-7 Fr sheaths. Hemostasis is critically important as bleeding can result in a hematoma that results in median nerve compression, which is a surgical emergency.

 

Let’s not forget about venous access. What are some of the most commonly accessed veins?

·      The CFV is commonly accessed for procedures involving the IVC and iliac vessels and their branches for conditions such as May-Thurner, pelvic congestion syndrome, and IVC filter placement. Treatment of PE can also be performed through the CFV. The CFV can easily be compressed over the femoral head and is located medial to the CFA. Ultrasound guidance should be used to prevent arterial injury and backwalling.

·      The internal jugular vein can be accessed using US guidance (to prevent carotid injury; IJ is lateral to the carotid). IJ access is used most commonly for central venous catheters as well as IVC placement and filter retrieval. It is also an excellent access to treat pulmonary embolism via thrombolysis or thrombectomy. The IJ can be utilized to perform ovarian and internal iliac vein embolization. IJ is also the preferred access to perform TIPS, which is often of less interest to vascular surgeon.

·      The popliteal vein can be accessed with the patient in the prone position or the distal femoral vein in the supine position to diagnose and treat DVTs of the extremity veins. Ultrasound is also helpful to avoid arterial access and especially if the vein is thrombosed

·      Arm veins (cephalic/basilic) can be also readily accessed for vein mapping or fistula interventions.

 

Let’s move on to access technique. Historically, there are two types of puncture needles: single-wall and double-wall. Can you talk about the differences?

·      Double wall needles were commonly used back in the day for femoral access. They have an outer hollow blunt-tipped needle and an inner sharp stylet. The needle was inserted through and through the artery and the stylet removed and the blunt hollow needle pulled back until blood is returned. These aren’t favored anymore because they cause unnecessary backwalling of the artery. Double wall access kits are used in treating endoleaks from both a transcaval and translumbar routes to allow access into the aneurysm sack and needle removal to avoid puncturing the endograft.

·      Single wall needles are typically the choice for diagnostic procedures. 18-gauge needles accommodate an 0.035 in wire and 21 gauge accommodates a 0.018 in wire.

 

Can you describe the micropuncture technique for percutaneous access?

·      Micropuncture technique is the most commonly used method for percutaneous access nowadays. The advantage of the micropuncture technique is the use of a small needle which can be removed and repositioned with a negligible risk of bleeding and minimal amount of manual compression needed.

·      Ultrasound is used to cannulate the artery with a 21-gauge needle. It is best to visualize the needle entering the artery and to be intraluminal without being against the wall Blood return is then seen and a floppy tip micropuncture (0.018) wire is inserted under fluoroscopic guidance to make sure the wire passes into the vessel easily. A 4 Fr introducer sheath is placed over the wire gently to avoid kinking the wire. The inner cannula of the sheath is removed, and a 0.035 guidewire is placed under fluoroscopic guidance. It is important to remember that there are two types of introducer sheath depending on amount of subcutaneous scar tissue containing either a soft or a stiffened cannula. The 4 Fr is removed over the wire while holding manual pressure and desired sheath (usually 5 or 6 Fr) is placed for definitive access. The side port is then aspirated for arterial blood and flushed with heparinized saline.

 

With any invasive procedure, there are risks of complications. What are some of the complications of percutaneous vascular access?

·      Hematomas are the most common complication and have an incidence of about 3%. Most of these hematomas are clinically insignificant but retroperitoneal hemorrhage from a high puncture above the inguinal ligament can be life-threatening. These may require conversion to open and direct repair of the vessel or covered stent placement (especially if the puncture is above the inguinal ligament). Proximal balloon occlusion can be helpful to control hemorrhage while the vessel is being repaired.

·      Groin hematomas are not uncommon and are usually self-limiting. An expanding hematoma that is seen early can be treated with simple manual pressure at the bedside. If the hematoma is large and compressing surrounding structures or threatening skin integrity or if the patient is hemodynamically unstable, then surgical evacuation may be necessary

·      Pseudoaneurysms are an uncommon complication with an incidence of about 0.6%. Most pseudoaneurysms are treated with ultrasound-guided compression or thrombin injection. Thrombin injection requires a narrow neck into the pseudoaneurysm. If the pseudoaneurysm is >2cm, compresses surrounding structures, threatens skin integrity, or has failed thrombin injection, then surgical repair is required.

·      Thrombosis of the CFA is a known complication but fortunately is rare with an incidence of 0.2%. This can result from manual compression of the CFA that has severe atherosclerotic disease or prior groin reconstruction. This generally requires a cutdown, endarterectomy, thrombectomy, and patch angioplasty.

·      Lastly, AV fistula can form and are usually between the femoral artery and vein with an incidence of 0.5-0.9%). These usually occur from a low puncture of the CFA bifurcation or profunda. They are usually asymptomatic and detected on exam (palpable thrill) and confirmed with duplex imaging. If the fistula is small, it generally can be observed with close duplex surveillance. If it enlarges or becomes symptomatic, then repair is indicated. Covered stent grafts can be placed with minimal morbidity, making this optimal for high risk patients. Open surgery also is highly successful. Deciding between non-operative, endovascular, or open treatment is up for debate and is up to the clinical judgement of the surgeon.