Continuing Education Activity

Peripheral vascular bypass (PVB) refers to surgical revision of blood flow to restore perfusion distal to an occluded or otherwise disrupted arterial segment. Peripheral vascular bypass procedures can involve any arteries excluding those in the heart or the brain. This activity describes the different types of peripheral vascular bypass surgery and highlights the role of the interprofessional team in the management of patients undergoing this procedure.

Objectives:

• Describe the indications for peripheral vascular bypass.
• Review the contraindications to peripheral vascular bypass.
• Outline potential complications of peripheral vascular bypass.
• Explain interprofessional team strategies for enhancing care coordination and communication to advance the management of patients with peripheral vascular disease and improve outcomes.

Introduction

Peripheral vascular bypass (PVB) refers to the surgical revision of blood flow to restore perfusion distal to an occluded or otherwise disrupted arterial segment. PVB procedures can involve any of the arteries excluding those in the heart or the brain. These open surgical procedures are typically done by vascular surgeons, cardiologists, or interventional radiologists.[1][2][3]

Anatomy and Physiology

PVB procedures can be accomplished via anastomosis with any of the main arteries except those located in the head.[4][5][6]

Arteries within the upper extremity and chest that may require bypass include:

• Subclavian artery – located between the anterior and medial scalene muscles
• Axillary artery – originating at the lateral aspect of the first rib
• Brachial artery – a continuation of the axillary artery as it passes the inferior margin of the teres major muscle, which bifurcates at the level of the antecubital fossa in to the radial and ulnar arteries
• Radial artery – located on the lateral aspect of the ventral lower arm
• Ulnar artery – located on the medial aspect of the ventral lower arm

Arteries often bypassed within the lower extremity include:

• Common Femoral Artery – a continuation of the external iliac artery, running into the thigh distal to the inguinal ligament
• Superficial Femoral Artery – the continuation of the common femoral artery after it gives off the profunda femoris artery
• Popliteal artery – a continuation of the superficial femoral artery after passing through the abductor canal, running dorsally and medially in the popliteal fossa and then bifurcating into the anterior tibial, posterior tibial, and peroneal arteries.
• Anterior Tibial Artery – courses through the anterior compartment of the leg, having originated posterior to the tibia at distal aspect of the popliteus muscle
• Posterior Tibial Artery – courses through the posterior compartment of the leg, having originated at the tibial-peroneal trunk from the popliteal artery
• Peroneal (Fibular) Artery – courses through the lateral compartment of the leg, originating at the tibial-peroneal trunk from the popliteal artery

Arteries often bypassed with the abdomen include:

• Abdominal Aorta – a continuation of the thoracic aorta after passing through the diaphragm at the level of T12
• Common Iliac – arises from the bifurcation of the aorta at the level of the 4 Lumbar Vertebrae
• External Iliac – a continuation of the common iliac, following the medial aspect of the psoas major muscles

Indications

PVB is applied in the management of certain traumatic arterial injuries, or aneurysms, and most commonly for peripheral arterial disease (PAD). PAD is the result of atherosclerotic plaque causing stenosis of the arteries supplying the lower extremities. Symptoms of PAD range from asymptomatic, to demand ischemia or claudication, to Critical Limb Ischemia (CLI), characterized by severe disability and tissue loss. For these patients, PVB is considered if they have severe disease burden that is not amenable to endovascular therapy, or they have failed therapy previously. Lesions that are not responsive include severe stenosis and hostile vascular anatomy which would make endovascular treatment technically challenging. [7][8]

Contraindications

The contraindications for PVB are similar to those for other surgeries. Many patients with the peripheral vascular disease have other comorbidities, including cardiac and respiratory dysfunction. Patients with a history of previous cardiac intervention (stenting, angioplasty or coronary artery bypass) or low ejection fraction have a high perioperative mortality. The same holds true for patients with respiratory illness, such as chronic obstructive pulmonary disease. Thus, any patient undergoing PVB should have and thorough cardiac and respiratory work-up prior to surgery. [9][10][11]

Equipment

The equipment used in PVB surgery involves many of the same surgical tools as other procedures. However, there are some unique instruments worth mentioning.

Tunneler: Used to tunnel bypass conduits through deep tissue

DeBakey Clamps: Used to clamp large vessels temporarily

Bulldog Clamps: Used to clamp medium-sized vessels temporarily

Vessel loops: Rubber loops used to easily identify vessels and to temporarily occlude them if needed

Doppler: Ultrasound probe that identifies audio waveforms of blood flow

Castro-Viejo: Precision needle driver for passing suture

Prolene Suture: This is the favored suture material for vascular anastomoses. It is a permanent monofilament suture.

Heparin: Anticoagulation. Given systemically or locally to prevent clotting during vascular clamping

Preparation

Vascular surgery is considered a high-risk procedure and most procedures carry a >5% risk of an acute cardiac event. Direct reconstruction of aorta iliofemoral disease is associated with a 2.8% perioperative mortality while extra-anatomic bypass confers an 8.8% mortality. Mortality increases in patients with a chronic obstructive pulmonary disease, advanced age, pre-existing cardiac disease, diabetes, renal failure and need dialysis, and tobacco use. Under this pretense, accurate risk stratification is warranted in patients undergoing PVB.

Technique

Methods

PVB procedures can vary depending on patient anatomy and location of the arterial obstruction. However, for most cases, there are common configurations to redirect the flow. The key to a functional bypass is to establish the proximal and distal anastomoses in disease-free regions.

• Unilateral aortoiliac disease: An iliofemoral bypass, which connects the ipsilateral or contralateral iliac artery to the common femoral artery (CFA), can be employed.
• Bilateral aortoiliac disease: An aortobifemoral bypass connects the abdominal aorta with bilateral CFA to bypass the occlusion. If a patient fails this intervention or has a contraindication for the procedure, an axillary-femoral bypass may be considered. In this procedure, the axillary artery first connected to the ipsilateral CFA, which is then connected to the contralateral CFA.
• Superficial femoral artery (SFA) disease: Bypass to the above knee popliteal artery.
• Popliteal artery disease: Femoral-Popliteal Bypass.

Conduits for bypass include artificial grafts (polyteraflouroethylene and Dacron) and autologous saphenous vein (reversed, non-reversed, and in situ). For most infra-inguinal bypasses, an autologous vein graft is preferred. Aortoiliac bypasses require conduits with a larger lumen. Thus synthetic grafts are commonly used.

Complications

Patients undergoing PVB are at risk for wound infection, bleeding, pneumonia, conduit occlusion, and peripheral nerve damage. These patients often have also a higher prevalence of cerebrovascular and coronary artery disease which significantly increases their risk for stroke and myocardial infarction surgery. Indicators for potential adverse outcomes include smoking, pulmonary disease, female sex, diabetes mellitus, previous bypass history, and advanced age. Conduit related complications can be divided into immediate and long-term. Immediate including acute thrombosis and bleeding. Long-term including infection and occlusion secondary to intimal hyperplasia.  

Clinical Significance

Postoperatively, the patient's distal flow to posterior tibial and dorsalis pedis should be assessed. If the pulses are not palpable, a doppler should to used for identification. Patients should be discharged on a statin, along with aspirin and/or clopidogrel. If they have a synthetic conduit, dual therapy should be considered. Follow-up should include periodic evaluations of symptoms, pedal pulses, and Ankle-Brachial Index. Duplex ultrasound is the best non-invasive technique to assess graft patency.

Enhancing Healthcare Team Outcomes

PVB can help perfuse obstructed limbs. However, peripheral vascular disease is a progressive disorder with no cure. Clinicians including pharmacists and nurses should instead educate patients on prevention of PVD. This means discontinuing smoking, maintaining a healthy body weight, controlling diabetes, lowering cholesterol and remaining physically active. These lifestyle changes have more durable benefits than most bypass procedures.

PVB is not a benign procedure and is associated with serious complications that also include death.