Peripheral Vascular Bypass

Anatomy and Physiology

PVB procedures can be accomplished via anastomosis with any of the main arteries except those located in the head.[5][6][7]

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 into 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 the 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 managing certain traumatic arterial injuries, or aneurysms, and most commonly for peripheral arterial disease (PAD). PAD results from 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 a severe disease burden that is not amenable to endovascular therapy or if they have failed therapy previously. Lesions that are not responsive include severe stenosis and hostile vascular anatomy, which would make endovascular treatment technically challenging.[8][9]

In PAD patients with claudication, revascularization is indicated only for those patients who will derive a functional benefit. For instance, an increase in walking distance is predicted. However, revascularization for disabling claudication is limited to those patients with the more proximal disease, specifically when the iliofemoral or femoropopliteal territory is involved. Accordingly, claudication is not usually considered a robust indication to perform a distal (e.g., femorotibial) bypass. Moreover, distal bypass to a tibial artery for the treatment of claudication is not usually indicated. Assigning the infrapopliteal vessels for the outflow of the bypass should be limited to the patients with CLTI in whom either the femoropopliteal bypass is not feasible or with the absence of direct flow into patent runoff vessels.[10]

It should be noted that in the patients with CLTI signs and symptoms, including rest pain and tissue loss, revascularization is strongly indicated otherwise, as progression to amputation is likely in such cases. Therefore, a form of intervention, either endovascular revascularization or surgical bypass, might be selected. Notwithstanding, CLTI is a considerable indication for intervention; in some patients with less significant stages of the wound, ischemia, and foot Infection stages, supportive management without revascularization is indicated. Interestingly, as the patients with CLTI are commonly affected with a multilevel arterial occlusive disease involving not only the femoropopliteal but also tibioperoneal segments, lower extremity surgical revascularization bypass addresses both by a common femoral artery to the tibial arteries bypass, however, in patients with diabetes with diffuse and significant below-the-knee disease, a shorter bypass from the superficial femoral artery or popliteal artery is indicated.[11][12][13]

Contraindications

The contraindications for PVB are similar to those for other surgeries. Many patients with 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 high perioperative mortality. The same holds for patients with respiratory illnesses, such as chronic obstructive pulmonary disease. Thus, any patient undergoing PVB should have and thorough cardiac and respiratory workup before surgery.[14][15][16]

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 are 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 greater than 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 chronic obstructive pulmonary disease, advanced age, pre-existing cardiac disease, diabetes, renal failure, and tobacco use. Under this pretense, accurate risk stratification is warranted in patients undergoing PVB. While most patients are managed under general anesthesia, local and regional anesthesia (RA) provides several possible advantages, including stable cardiovascular hemodynamic perioperative course and improved postoperative pain relief. Moreover, chronic postsurgical pain syndromes are more efficiently prevented by applying local and regional anesthesia methods.[17][18] According to several retrospective studies, older patients with a medical history of chronic obstructive pulmonary disease are more likely to be managed with regional anesthesia.[19]

Myocardial injury after noncardiac surgery (MINS) is considered an index of cardiac risk stratification in vascular surgery patients. An elevation of fourth-generation troponin T equal to or greater than 0.03 ng/mL is considered significant.[20] Patients with MINS have a significantly higher 30-day postoperative mortality. Almost 75% of the vascular surgical patients with MINS were asymptomatic without remarkable evidence of myocardial ischemia. Postoperative troponin rise predicts a 26 percent decrease in the 5-year survival post-operatively. However, the presence of a significant postoperative myocardial infarction predicts a 55 percent reduction in survival in a five-year follow-up. Management of cardiac medications, including beta blockers, angiotensin-converting enzyme inhibitors, and alpha-agonists, e.g., clonidine and anti-platelets, should be prioritized.[21]

Patients with a medical history of chronic kidney disease (CKD) are at increased risk for contrast-induced and contrast-associated nephropathy. Therefore, a baseline creatinine level and re-check in the immediate preoperative period are mandatory. The patients who are subjected to angiography should be well-hydrated. Accordingly, intravenous hydration with 1 mL/kg/hour of isotonic saline for 6 to 12 hours pre and peri-procedure are recommended. The hydration protocols should be continued for 6 to 12 hours post-operatively.[22]

Technique or Treatment

Methods

PVB procedures can vary depending on patient anatomy and the location of the arterial obstruction. However, in most cases, there are common configurations to redirect the flow. The key to a functional bypass is establishing the proximal and distal anastomoses in disease-free regions. The following technique describes the aortoiliac disease. However, the principles for surgical interventions in other anatomical involvement are consistent.

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. An axillary-femoral bypass may be considered if a patient fails this intervention or has a contraindication for the procedure. In this procedure, the axillary artery is first connected to the ipsilateral CFA, which is then connected to the contralateral CFA. For an open technique, the patient positioning is supine with arms abducted to 90 degrees. The patient should undergo prepping from the nipples to the knees. The CFA, superficial, and deep femoral arteries bilaterally are isolated through bilateral groin incisions. It is essential to be sure that the distal portions of the vessels are soft, so they are suitable for clamping. Aortic exposure is typically through a midline incision (transperitoneal approach); however, some prefer a retroperitoneal or transverse incision.

The retroperitoneum is entered, typically infracolically and after the duodenum is mobilized to the right. The aorta gets dissected below the level of the renal arteries. Most try to remain to the right of the inferior mesenteric vein to avoid violating the left mesocolon. The renal vein can be mobilized by ligation of its tributaries. Exposure of the aorta needs to be taken down to the level of the inferior mesenteric artery. Tunnels within the retroperitoneum, posterior to the ureters, are carried down to the groin incisions. On the left side, the tunnel is often brought posterior to the inferior mesenteric artery to help with keeping the graft isolated from the left mesocolon.[23]Heparin is administered (70 to 100 units/kg) with a goal of ACT of 250 to 300 seconds, and the aorta is clamped below the renal arteries and on the distal portion already exposed.[24]

The surgeon divides the aorta and a portion resected proximal to the inferior mesenteric artery. The distal aorta is oversewn. The chosen graft is anastomosed to the proximal aorta, most commonly in an end-to-end fashion using a 3-0 or 4-0 running permanent suture.

The limbs of the graft are then flushed with heparinized saline, clamped, and passed through the tunnels into the groin incisions. Clamps are applied to the CFA, and an arteriotomy is made, sometimes down to the level of the profunda, thus requiring a profundaplasty. Endarterectomy follows, if necessary. The graft is anastomosed to the CFA in an end-to-side running manner, usually with a 4-0 or 5-0 permanent suture. Before completion of the anastomosis, usual back bleeding, forward bleeding, and flushing are employed. The opposite femoral artery is addressed similarly. Blood flow is restored to the CFA, then the profunda femoris, and lastly, the superficial femoral artery. However, before unclamping, anesthesia should be notified because of the expected hypotension with reperfusion. The retroperitoneum should be closed in layers to adequately omit the graft from the GI tract. If unable to sufficiently close the retroperitoneum, an omental flap should be created.[23][25]

End-to-end anastomosis is preferred because it allows the graft to lie flatter and thus may lessen the chance of future aortoenteric fistula. This method also better allows for retrograde perfusion into the inferior mesenteric artery. However, in cases with bilateral external iliac artery occlusion, an end-to-side or formal reconstruction of one of the IIA is needed to ensure blood flow delivery to the pelvis.[24]

Conduits for bypass include artificial grafts (polytetrafluoroethylene 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 risk wound infection, bleeding, pneumonia, conduit occlusion, and peripheral nerve damage. These patients often also have a higher prevalence of cerebrovascular and coronary artery disease, significantly increasing 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

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 the 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 (MDs, DOs, NPs, and PAs), nurses, and pharmacists, operating as an interprofessional healthcare team should educate patients on preventing 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, including death.