Aortic Bifemoral (Aortobifemoral) Bypass Technique

Updated: Jul 21, 2017
  • Author: Shabir Bhimji, MD, PhD; Chief Editor: Vincent Lopez Rowe, MD  more...
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Technique

Approach Considerations

Depending on the patient, continuous electrocardiographic (ECG) monitoring, arterial line monitoring, and a central venous line or a Swan-Ganz (pulmonary artery) catheter can be used. Routine use of the pulmonary artery catheter has not been associated with a decline in mortality.

Perform the operation using a combination of general and epidural anesthesia. Prepare the entire chest and abdomen up to the knees.

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Aortobifemoral Bypass

Aortic bifemoral (aortobifemoral) bypass may be performed via either a transperitoneal or a retroperitoneal approach. The procedure takes 3-4 hours. (See the images below.)

Image shows aorta iliac bypass. Image shows aorta iliac bypass.
Image shows bypass of aneurysmal portion of aorta. Image shows bypass of aneurysmal portion of aorta.

Operative exposure

Make two small longitudinal incisions in the groin to expose the common femoral artery at its bifurcation. If the bifurcation of the femoral artery is high, it may be necessary to cut the inferior segment of the inguinal ligament. Perform gentle dissection to develop a tract from the groin into the retroperitoneal space to the anterior iliac artery and the lateral circumflex vein. Pack the groin wounds with moist gauze. [1, 2, 3]

Make a midline abdominal incision that extends from the xiphoid to just below the umbilicus. Carefully examine the abdomen. Lift the transverse colon superiorly, then collect the small bowel to the right side and place it in a bowel bag.

Alternatively, obtain exposure of the aorta through a retroperitoneal approach via an incision made along the course of the left 10th or 11th rib and extended anteriorly. Once the retroperitoneal space is entered, it is the surgeon’s choice whether to proceed by elevating the left kidney and all of the abdominal contents or by traversing along a plane anterior to the left kidney toward the aorta.

Once the retractors are placed, perform sharp dissection on the right side of the inferior mesenteric vein (IMV). Carry the dissection directly onto the wall of the aorta. Avoid lateral dissection; damage can occur to the inferior vena cava (IVC) on the far right and the inferior mesenteric artery (IMA) on the left. The origin of the IMA is usually visible on the left side of the aorta; it is not dissected, but its location is noted.

Minimally dissect distally over the aortic bifurcation, and do not attempt to ligate the lumbar veins. Preserve all preaortic nerves and the sacral plexus in the distal aorta with minimal dissection. Carefully isolate both common iliac arteries. Proximally, carry the dissection up to the duodenum and identify both renal arteries. Make room in the proximal aorta for placement of a clamp.

Never dissect underneath the proximal aorta if the left renal vein has not been visualized anteriorly. In at least 10% of cases, the left renal vein runs posterior to the aorta and can easily be damaged by a retrograde clamp. If this ever happens, the bleeding can be torrential and difficult to control.

Heparin, 100 units/kg, is administered by the anesthesiologist 5 minutes before the aorta is clamped. Before clamping the proximal aorta, the anesthesiologist must be ready to manage any surge in blood pressure. [1, 2, 3]

Proximal anastomosis

Today, many choices of aortic grafts are available for aortofemoral bypass, but in most cases, Dacron or expanded polytetrafluoroethylene (ePTFE) is chosen. The standard graft size used by most surgeons is 14 × 7 mm. Some surgeons prefer to match the graft to the size of the patient or the aorta, but doing so does not appear to yield any differences in long-term results. [29, 1, 2]

Once the proximal clamp is applied just below the renal vessels, do not attempt to dissect posterior to the aorta. Divide the aorta about 1.5 cm distal to the clamp. Remove a small oblique segment of anterior aorta to allow visualization of the inner aorta. Cut the prosthetic graft so that only about 3 cm of the trunk remains with the bifurcated segment. [28]

If the aortic disease is at the level of the renal arteries, place the proximal clamp above the renal vessels. Exposure is often improved if the left renal vein is retracted in a vessel loop. It is crucial to visualize both renal arteries before placing the clamp. Sometimes, a change must be made in the graft anastomosis. To prevent postoperative renal dysfunction, the proximal anastomosis should be completed in less than 30 minutes. [24]

Perform the proximal aortic anastomosis in either an end-to-side or an end-to-end fashion. Perform an end-to-side anastomosis when there is an aberrant renal artery that supplies a large portion of the kidney or a large mesenteric artery that must be preserved. Another indication is a male patient who does not want to develop libido after surgery and who has significant disease of the external iliac vessels or a hypoplastic aorta. [1, 2, 3]

An end-to-end anastomosis is indicated if there is coexisting aortic aneurysmal disease or complete aortic occlusion that extends up to the renal arteries. Most surgeons prefer an end-to-end anastomosis, believing that it yields much better hemodynamic results than an end-to-side anastomosis does. However, there is no solid evidence that one technique is superior to the other in this regard; the final choice is strictly personal. Some evidence suggests that intraoperative atheroembolic episodes may be less frequent with end-to-side anastomoses.

Perform the proximal anastomosis with a 3-0 polypropylene suture, starting in the posterior wall and continuing to the front with both needles. Take large bites of the native aorta to ensure that the anastomosis will be secure. Moisten and tighten the suture before tying it. Use a nerve hook to identify any loose sutures. To assess the patency of the proximal anastomosis, clamp the distal graft and gently release the proximal aortic clamp. Repair all leaks at this stage.

A single-center, long-term, prospective randomized study monitored grafts in 99 patients after open surgical repair of abdominal aortic aneurysms. After 6 years, ePTFE grafts were the least likely to dilate as compared with polyester grafts. However, the overall differences between the grafts were not significant. Even though ePTFE grafts are reliable and durable, all prosthetic grafts used in vascular surgery must be monitored on a regular basis to ensure that there is no expansion. [30]

Distal anastomoses

Once the proximal anastomosis is done, recheck it, then carefully tunnel the graft limbs into the groin area. [1, 2, 3]  Pass a long curved clamp from each groin, and bring the graft into the retroperitoneum on each side. Take care when creating the tunnel. Structures that can be injured here include the colon, the ureters, and the iliac veins. Once the grafts on both sides of the groin have been laid out, place the proximal aortic clamp more distally.

The distal anastomoses in the two sides of the groin are usually made at the bifurcation of the common femoral artery and onto the proximal deep femoral artery, regardless of the status of the superficial femoral artery. Some surgeons perform the distal anastomosis to the external iliac artery, but unless the external iliac is completely free of disease, a distal repair may be required in the future to improve runoff.

Place clamps on the proximal common femoral artery, superficial femoral artery, and deep femoral artery. Create a small (1.0-1.5 cm) arteriotomy, and carry a beveled anastomosis out to the graft. Do not narrow any of the vessels during the anastomosis. If there is any doubt about backflow, perform an embolectomy or choose a more distal target vessel on the deep femoral artery. Do not unnecessarily ligate any branches of the femoral artery. Most surgeons have to perform some degree of endarterectomy on the femoral vessels.

Perform the anastomosis with a 5-0 polypropylene suture. Before tying the anastomosis, carry out flushing maneuvers to remove emboli and air bubbles. Before removing any clamps, notify the anesthesiologist to resuscitate the patient. Gently remove the clamp from the proximal aorta, then remove one clamp at a time from each groin. Usually, there is a slight drop in blood pressure from the buildup of lactate and metabolites while the femoral artery was clamped.

Once blood pressure has stabilized, check all of the sites to confirm that the anastomoses are good. Obtain complete hemostasis, and feel the pulses in both groins. The color of the sigmoid colon should be pink. Before reversing the anticoagulation, confirm the presence of pulses or Doppler signals in the feet.

Closure

Give protamine to reverse the heparin, and count all instruments and sponges. Carefully return the bowel, and close the peritoneal layer. Close the abdominal wall with a 1-0 monofilament suture. Before closing the groin, assess the pulses again in both groins. If there is any concern about pulses, on-table angiography is highly recommended. Perform groin closure in three layers, and cover the entire graft.

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Complications

Overall, complications from aortic surgery appear to be more common in institutions where the procedure is performed sporadically. Many postoperative complications are caused by inexperience and lack of technical skill on the part of the surgeon. [31]

Myocardial infarction

Myocardial infarction (MI) is a well-known complication after aortic bifemoral bypass. Accordingly, all high-risk patients undergo preoperative screening for significant coronary artery disease (CAD). Patients without a history of CAD and an abnormal ECG can undergo surgery without cardiac work-up. Patients with an abnormal ECG who are at risk for CAD usually undergo a treadmill test, dipyridamole thallium screening, echocardiography, or coronary angiography.

Some patients who have isolated lesions of the coronary arteries undergo stenting before the aortic procedure. Individuals who are not candidates for coronary bypass surgery are usually at high risk for anesthesia and should only undergo an extra-anatomic bypass. The Swan-Ganz catheter is widely used to monitor patients, but it does not reduce morbidity, and it may even provide misleading information in some patients with CAD.

Patients who have symptomatic carotid artery disease should undergo endarterectomy before the aortic procedure. Asymptomatic patients with internal carotid artery disease can undergo aortic surgery. [1, 2, 3]

Respiratory dysfunction

Patients with significant pulmonary disease can have problems postoperatively. Most smokers should quit smoking at least 4 weeks before surgery and should undergo chest physiotherapy and a trial of bronchodilators and antibiotics if there is evidence of lung infection. These patients may benefit from preoperative incentive spirometry, early extubation, and aggressive chest physiotherapy. Epidural anesthesia may help. [1, 2]

Renal dysfunction

Renal failure is not common after aortic bifemoral bypass. Worsening of kidney function is more likely if there is preexisting renal failure, if the aorta is clamped above the renal arteries, or if the renal vein is ligated or damaged. Other factors that can worsen renal injury include the use of contrast dye, dehydration, and embolism. [1]

Bleeding and coagulopathy

In patients who receive multiple transfusions, coagulopathies can occur. Accordingly, the coagulation parameters must be normal before surgery. Rarely, heparin-induced thrombocytopenia may occur, which may result in unexplained thrombosis. [1, 2]

Sexual dysfunction

When extensive dissection is performed over the distal aorta and left common iliac artery, decreased sexual function may result. If the periaortic sympathetic fibers are damaged, retrograde ejaculation can occur.

Precise surgical technique is the only way to prevent this disturbing side effect. On the distal aorta, dissection should be limited to the right side. If severe iliac artery disease is present, an end-to-side anastomosis is preferred to maintain retrograde flow to the external iliac branches. Some surgeons perform iliac artery endarterectomy to improve erectile function, but the results are not consistent, and there is a risk of nerve injury. [1, 2]

Ureteral obstruction

When dissection is carried out very lateral or posterior to the aorta, damage to the ureter is a risk. Other causes of ureteral damage may include ischemia, accidental grasping, and injury during tunneling. The dense fibrosis from the prosthesis reaction can also cause ureteral obstruction.

Mild hydronephrosis from edema occurs in 10% of cases and usually resolves spontaneously. Early hydronephrosis usually necessitates reoperation. Delayed hydronephrosis is often associated with fibrosis. Computed tomography (CT) is often required to identify the dense adhesions. Ureteral complications call for consultation with a urologist and may necessitate kidney decompression, adhesiolysis, or ureter reimplantation. [1, 2, 3]

Sigmoid colon ischemia

Clinically significant ischemia is seen in 1-2% of individuals and is typically detected by colonoscopy. The sigmoid colon is perfused by the IMA and collateral branches from the internal iliac artery and the deep femoral artery. Sigmoid colon ischemia can occur when antegrade flow though a large IMA is decreased during surgery, when the collateral flow is poor because of superior mesenteric artery (SMA) disease, or when perfusion pressure is diminished.

Operative trauma involving damage to the collaterals is one of the most common causes of sigmoid colon ischemia. If the large IMA is present with little antegrade flow, one must consider an end-to-side aortic anastomosis with preservation or reimplantation of the IMA. Routine reimplantation is not required in all patients. The best way to avoid bowel complications is to observe the sigmoid colon after surgery. If the colon appears ischemic, the IMA may have to be reconstructed. Sometimes, the SMA must be reconstructed to improve flow to the colon.

Any patient who presents postoperatively with fever, left-lower-quadrant pain, or bloody diarrhea should undergo sigmoidoscopy and early decompression of the colon. Transmural colon ischemia accrues a mortality in excess of 60%. [32]

Important predictors of colon ischemia include systemic hypotension, the surgeon's relative inexperience or lack of sufficient technical skill, prolonged operating times, long cross-clamp times, ligation of the internal iliac artery, and patient-related factors such as age, kidney disease, and atherosclerosis. Besides infarction, other colon complications include strictures and fibrosis. [1, 2, 3]

Emboli and "trash foot"

"Trash foot" occurs when emboli are washed downstream and end up in the distal leg. The showering emboli may produce distal toe gangrene even in the presence of intact pulses. The best way of managing trash foot is to prevent it by employing proper surgical technique and gentle manipulation of the aorta.

Paralysis/paraplegia

Paraplegia may occur after aortic bifemoral bypass, but it is very rare. Causes include severe hypotension, reduction of pelvic blood flow because of interruption of internal iliac flow, and emboli. The degree of paralysis is variable and may involve peripheral nerve roots, reduction in tendon reflexes, and patchy sensory loss. The level of injury is often difficult to discern, and the condition may have to be differentiated from cauda equina syndrome.

Treatment of paraplegia is supportive, but in most cases, the injury is permanent. Although a few patients with incomplete paralysis may show improvement over the years, such a result is a rarity. Lower motor neurons typically recover better than upper motor neurons do. [1, 2, 3]

Ileus

Ileus is common after surgery. It may take a few days for bowel activity to return to normal. In a few patients, a nasogastric tube may be required to decompress the stomach.

Graft occlusion

Graft occlusion usually occurs many years after the operation and may present as unilateral claudication or rest pain. Recurrence of symptoms is a sure sign that one of the distal limbs of the graft is narrowed or occluded. Treatment may include thrombolytic agents, thrombectomy, femorofemoral bypass, or distal bypass to improve the outflow of the graft limb. [33]

Anastomotic pseudoaneurysm

A pulsatile mass may occur in the groin, possibly indicating the presence of a pseudoaneurysm. The pseudoaneurysm may have resulted from an infection or from anastomotic failure. Surgical repair is required for all groin pseudoaneurysms, regardless of etiology. [1, 2, 3]

Aortoenteric fistula

Aortoenteric fistula is a rare but lethal complication that results from infection of the proximal aortic graft suture line into the fourth part of the duodenum. This may present initially as a small herald intestinal bleed, which is followed by massive blood loss. The traditional treatment consists of emergency surgery with removal of the aortic grafts, suture closure of the proximal aorta, and placement of an extra-anatomic bypass. Alternative treatments include reconstruction with femoral vein grafts or cryopreserved grafts. The mortality is significant. [15, 2, 34]

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