Peripheral Vascular Bypass (Peripheral Bypass Surgery)

Overview of Peripheral Vascular Bypass

Peripheral vascular bypass (PVB) is a surgery that redirects blood flow in order to supply blood beyond a blocked or damaged part of an artery. This can involve any artery in the body, except those in the heart or the brain. The surgery is usually performed by vascular surgeons, who specialize in treating blood vessel disorders.

Most people with peripheral artery disease (PAD), which happens when arteries get narrow, do not show symptoms and don’t have a high risk of losing a limb. So they usually don’t need this surgery. However, some people with PAD have symptoms like muscle pain (known as claudication) or pain at rest. A significant number of these symptomatic patients can suffer from chronic limb-threatening ischemia (CLTI) – a severe condition where the tissues in the limbs do not get enough blood flow and are at risk of damage or death. These individuals may need a peripheral vascular bypass surgery.

Anatomy and Physiology of Peripheral Vascular Bypass

A procedure known as PVB (Peripheral Vascular Bypass) involves connecting a blocked artery to a healthier one to improve blood flow. However, it’s important to note, this can’t be performed on any arteries in the head.

The main arteries that might require this procedure are located in the upper body and chest area:

• The Subclavian artery, which is found between two muscles in your neck known as the anterior and medial scalene muscles.
• The Axillary artery, which starts on the outer side of the first rib.
• The Brachial artery, which is an extended part of the Axillary artery. This artery continues down to your elbow, where it splits into the radial and ulnar arteries.
• The Radial artery, which is on the outside of the forearm.
• The Ulnar artery, which is on the inner side of your forearm.

The following list includes arteries in the lower body, commonly involved in the PVB procedure:

• The Common Femoral Artery, which is a continuation of the external iliac artery and runs into the thigh just below the crease at the top of the leg (inguinal ligament).
• The Superficial Femoral Artery, which continues on from the common femoral artery after it branches off to another artery called the profunda femoris artery.
• The Popliteal artery, which becomes the continuation of the superficial femoral artery after passing through a canal formed by muscles in the thigh, running along the back and towards the inside of the knee. It then splits into the anterior tibial, posterior tibial, and peroneal arteries.
• The Anterior Tibial Artery, which moves through the front compartment of the leg, starting from behind the shin bone (tibia) at the bottom of the popliteus muscle.
• The Posterior Tibial Artery, which passes through the back compartment of the leg. It starts at the point where the tibial-peroneal trunk branches off from the popliteal artery.
• The Peroneal (Fibular) Artery, which moves through the outer compartment of the leg. It also originates from the tibial-peroneal trunk at the popliteal artery.

In the abdomen, we often see bypasses for the:

• Abdominal Aorta, which is a continuation of the thoracic aorta (the main blood vessel descending from the heart) after it passes through the diaphragm (the muscle below the lungs) at the level of T12 (the last thoracic vertebra).
• Common Iliac, which comes from the aorta’s split at the level of the 4th lumbar vertebra.
• External Iliac, which is the continuation of the common iliac. It travels along the inner part of the psoas major muscles (large muscles on either side of the spine).

Why do People Need Peripheral Vascular Bypass

Peripheral Vascular Bypass (PVB) is a treatment method often used for certain artery issues such as injuries, aneurysms, and a condition called Peripheral Arterial Disease (PAD). PAD happens when plaque builds up in arteries that supply blood to your legs. This can lead to narrower arteries and trouble with blood flow. Depending on how severe it is, people might not experience any symptoms or they might have difficulty walking due to poor blood supply (known as claudication), or even severe disability and tissue loss, a condition known as Critical Limb Ischemia (CLI).

In cases of PAD where the disease is severe and hasn’t responded to other treatment methods, or if previous treatments haven’t worked, PVB might be a good option. This can be true for situations where the arteries are very narrow or where the structure of the blood vessels makes other treatments difficult.

However, in PAD patients who have claudication, the decision to perform PVB is usually based on whether it will significantly improve their ability to walk. This is mainly considered for patients whose disease affects the more major vessels closer to the hip or knee. As such, it is not usual to have PVB for more minor vessels, like those around the ankle.

It’s important to underline that, in patients suffering from CLI who show symptoms like pain at rest and tissue loss, improving the blood supply through measures such as PVB is often recommended. If not, the disease may progress to a point where amputation becomes a possibility. There are situations where managing the symptoms without the need to improve blood supply may be appropriate, but these are generally in lesser advanced stages of the disease.

Moreover, CLI often involves multiple locations of narrowed arteries, including those in the thigh and calf. A PVB can address this by creating a new route for blood from a major artery in the groin to a smaller one in the foot. However, in patients with diabetes who also have PAD, sometimes a shorter bypass is more appropriate, such as one originating from an artery in the thigh or knee.

When a Person Should Avoid Peripheral Vascular Bypass

There are certain conditions that could prevent patients from being suitable for a specific operation known as PVB (paravertebral block), a type of anesthetic technique. This situation is similar to other types of surgeries.

Often, these patients have a condition called peripheral vascular disease, which affects blood circulation. They also frequently have other health issues at the same time, like heart and lung problems.

People who previously had heart procedures, like stenting, angioplasty, or coronary artery bypass, or have a low ejection fraction (which means the heart isn’t pumping blood as well as it should) could have a high risk of complications during and after the surgery. The same goes for patients with chronic obstructive pulmonary disease (COPD), a progressive lung disease that makes it hard to breathe.

Therefore, it’s crucial for anyone who is having a PVB procedure to undergo a comprehensive heart and lung assessment before the surgery. This helps doctors ensure the patient can safely have the operation.

Equipment used for Peripheral Vascular Bypass

The tools used during a PVB surgery, which is a type of procedure, include several common instruments, but a few specific tools are important to know.

* A “tunneler” is used to create pathways in deep tissues so tubes or “bypass conduits” can be inserted.
* “DeBakey Clamps” are used for temporarily pinching-off or blocking large blood vessels.
* “Bulldog Clamps” are used in the same way but for the medium-sized vessels.
* “Vessel loops” are rubber loops used to easily identify and, temporarily block blood vessels if necessary.
* A “Doppler” is an ultrasound device that lets the doctors listen to the sound of blood flow.
* “Castro-Viejo” is a special tool for passing threads or “sutures,” used with high precision.
* “Prolene Suture” is the preferred thread material for connecting or ‘anastomosing’ blood vessels. It does not dissolve and is considered a permanent suture.
* “Heparin” is a medicine that thins the blood, reducing the chance of clots. It can be given throughout the body or only to the area of surgery during the time vessels are clamped.
These instruments help in ensuring a successful surgery and a swift recovery.

Preparing for Peripheral Vascular Bypass

Vascular surgery, or surgery on the blood vessels, is seen as high risk because there’s more than a 5% chance of a heart issue occurring during the operation. Different types of this surgery can have different risks. For example, reconstructing aorta-iliofemoral disease, a condition affecting the main artery and the arteries in the thigh and pelvic region, is linked with about 2.8% mortality rate. On the other hand, bypass surgery done outside the main blood vessels has even higher risks at an 8.8% mortality rate.

Certain factors increase the risk of death during these surgeries. This includes chronic obstructive pulmonary disease (a type of lung disease), old age, heart disease, diabetes, kidney failure, and tobacco use. It is important to predict the risks accurately before surgery. Even though most patients undergo general anesthesia, using local or regional anesthesia – numbing of a specific part of the body instead of making the patient unconscious – can have several benefits. These advantages include a stable heart rate and blood pressure during surgery and better pain relief after surgery. Also, studies have shown that using these numbing methods can help prevent long-term pain after surgery more efficiently.

According to a few retrospective studies, which are studies that look back at past events, older patients with a history of lung disease are often numbed locally. The injury to the heart muscle after non-heart-related surgery, also known as MINS, can predict heart risks in patients who are having vascular surgery. MINS is significant when a certain protein in the blood, troponin T (a sign of heart damage), is at or above 0.03 ng/mL.

Patients with MINS are much more likely to die within 30 days after surgery. Almost 75% of these patients show no symptoms and do not show clear signs of reduced blood flow to the heart. Rise in troponin level after surgery predicts a 26% drop in survival over five years post-surgery. However, if a patient suffers a significant heart attack after surgery, it predicts a 55% reduction in five-year survival.

Therefore, it is important to manage heart medications like beta blockers, angiotensin-converting enzyme inhibitors, alpha-agonists (for instance, clonidine), and antiplatelet drugs. Patients with chronic kidney disease (CKD), a condition where the kidneys gradually lose function, are at a higher risk of kidney damage because of the contrast agents (dyes used to enhance imaging) used in procedures. Thus, it is necessary to check patient’s creatinine level (a marker of kidney function) before surgery.

Patients receiving an angiography, an imaging test that uses dyes to look at your blood vessels, should be hydrated enough. So, it is recommended to hydrate them with 1mL/kg/hour of saline solution intravenously – through a vein – for 6 to 12 hours before and during the procedure. Hydration should also continue for 6 to 12 hours post-surgery.

How is Peripheral Vascular Bypass performed

A procedure called Peripheral Vascular Bypass (PVB), can help improve blood flow if a person’s artery is blocked. This procedure is tailored to a patient’s unique body structure, and the specifics of where the block is located. The goal of this procedure is to create a new path for blood to flow by connecting healthy blood vessels before and after the problematic area.

There are specific approaches depending on where in the body the blockage is located:

1. If the problem is in a person’s aortoiliac (main blood vessel in the stomach area that splits into two to go to each leg), the surgeon can create a bypass by linking a vessel from the same or the opposite side of the blocked area to the main artery in the leg.

2. If both the main vessel in the belly and the branches guiding the blood flow to both legs are blocked, a bypass can be created from the stomach area to both legs. If this cannot be done, a bypass can be created by connecting the artery under the collarbone to the main artery in the leg.

In the procedure, the patient is laid on their back with their arms outstretched. The area from the chest to the knees is cleaned and sterilized. The surgeon makes cuts in both groins to isolate the leg arteries. It’s very important that the ends of these arteries are healthy so they can be sealed off for the operation. The stomach is usually accessed through a cut in the middle, but depending on the patient, other angles can be used.

After isolating the main stomach artery below the level of the kidneys, a blood-thinning medication is given. The surgeon then blocks the blood flow to the lower part of the aorta (the largest artery in the body running through the heart and abdomen), which is then divided and a part of it is removed near another artery coming off it. Then the opening of the aorta is stitched closed. A graft (tube made of special material) is then linked to the upper part of the aorta using stitches.

The limbs of the graft are flushed (cleaned and opened) and passed through tunnels created in the body to the groin cuts. The arteries in the legs are blocked with special clamps, then opened so the graft can be attached to them with stitches. A cleaning process is done before completion, and then the same procedure is done on the other leg. Once finished, blood flow is restored, starting with the main leg artery, then to a major branch, and lastly to the smaller branches.

Stomach layers are closed properly to keep the new pathway separate from the rest organs in the area. Synthetic grafts or a patient’s own veins can be used to create these bypasses. For blockages in lower part of the body, surgeons usually prefer to use the patient’s own veins. But for blockages in bigger vessels, synthetic grafts are commonly used.

Possible Complications of Peripheral Vascular Bypass

Patients getting peripheral vascular bypass (PVB) surgery must be aware of certain risks like wound infection, bleeding, lung infection, blockage in surgical tubes, and damage to the nerves around the surgical area. There’s also a higher chance for these patients to have pre-existing conditions such as stroke or heart disease. Such conditions can significantly heighten the risk for a heart attack or stroke during surgery.

Certain factors make some people more likely to have complications. These include things like smoking, lung disease, being a woman, having diabetes, a history of previous bypass surgeries, and being older.

There are also complications linked to the surgical tube used in the bypass, and these can happen soon after surgery or much later. Problems that might happen soon after surgery include clot formation and bleeding. Over the longer term, there could be issues such as infection and blockage due to excessive growth of the inner lining of the blood vessels.

What Else Should I Know About Peripheral Vascular Bypass?

To check your body’s blood flow to the areas behind your shinbone and on the top of your foot, your doctor may need to feel for pulses. If these pulses cannot be easily felt by hand, a special tool called a Doppler may be used for this purpose.

After this, your doctor may prescribe you a type of medicine called a statin, alongside other medications such as aspirin and/or clopidogrel. These medications help regulate blood flow and prevent clotting. If a synthetic tube was used in your treatment to redirect blood flow, you may need both of these medications.

Regular check-ups with your doctor are important after your treatment. During these visits, your doctor will ask about any symptoms you may have, feel for the pulses on top of your foot, and conduct a test comparing the blood pressure in your ankle and arm.

An imaging method called a duplex ultrasound is preferable to check if the graft (synthetic tube) is working properly. This method is non-invasive, meaning it doesn’t require any surgical procedures.