General Principles of Vascular Surgery




As most vascular surgeons will attest, among the many attractions to our discipline are the vast array of instruments and procedures available to address some of the most severe medical problems known to mankind and the opportunity to apply our surgical skills to virtually every portion of the human body. Because of the many presentations of vascular disease, the vascular surgeon must have extensive knowledge, sound judgment, and in many cases exceptional technical skill to choose and then apply the best treatment for an individual. This chapter discusses some general principles in vascular surgery with a focus on open surgical procedures. The basic principles specific to endovascular repair are discussed in Chapter 2 .


Presentation and Natural History of Vascular Diseases


Essential to effective management is a thorough understanding of the anatomy, pathology, and physiologic manifestations of vascular diseases. Some conditions, such as an embolus to the popliteal artery, can cause devastation in hours if not properly diagnosed and treated. Other conditions, such as a chronic occlusion of a subclavian artery, may be tolerated for decades without causing symptoms or posing a risk to an individual.


The mechanism of causing symptoms also varies from one condition to another. Superficial femoral artery disease may cause pain to a lower extremity by reducing blood flow to the limb. However, an atherosclerotic plaque in the carotid artery is more likely to cause symptoms by showering emboli to the distal circulation than by reducing blood flow. The major risk of an aneurysm of the aorta is rupture and bleeding, whereas in other locations it may be thrombosis and ischemia. A vascular surgeon must have a thorough understanding of the pathophysiologic mechanisms of vascular disease, the natural history for various clinical conditions, the risks associate with surgical procedures, and the expected course after successful intervention. Equally important, the surgeon must have the ability to explain what are often complex issues to patients and referring physicians.




Diagnosis


Patients in their seventh decade and beyond, particularly those with heart disease, hypertension, diabetes, smoking, hypercholesterolemia, or a family history of vascular disease, are at greatest risk for atherosclerotic vascular disease. Less common conditions such as carotid dissection, fibromuscular dysplasia, entrapment syndrome, thoracic outlet syndrome, Marfan syndrome, and Ehlers-Danlos syndrome occur more often in younger adults than older ones. Congenital arteriovenous malformations and hemangiomas may be diagnosed at birth. Assessment of the patient’s general condition, family history, and social background is the first step in formulating a differential diagnosis and in reaching a definitive diagnosis.


Most vascular conditions can be diagnosed with a careful history and physical examination. A complaint of pain in the calf with walking, relieved by rest, almost always leads to the diagnosis of a chronic superficial femoral artery occlusion. A history of sudden swelling and discoloration of an upper extremity after strenuous physical activity is caused by subclavian vein thrombosis until proven otherwise. Transient loss of vision in one eye invariably leads to the diagnosis of an atherosclerotic plaque in the ipsilateral carotid artery. The physical findings for patients with arterial and venous occlusive disease, aneurysm disease, and a host of congenital vascular conditions are often striking: absence of pulses in occlusive disease, pulsating masses with aneurysmal disease, varicose veins and reflux with incompetent venous valves, and mottling of the skin with athroemboli to the extremities, to name a few.


Confirmation of a diagnosis usually begins with noninvasive laboratory tests. Ultrasound is the workhorse of every vascular laboratory. It is used to assess the size of an abdominal aorta, the severity of a carotid artery stenosis, the presence of thrombus in a femoral vein, pressure in an artery in an extremity, and many other conditions. For planning interventions, more detailed information can be obtained with magnetic resonance angiography, computed tomography, computed tomography angiography, and conventional catheter-directed angiograms. Knowing the advantages and disadvantages of each, as well as how to make the most effective use of these tests to assist in making a diagnosis, is part of the clinical skill of the vascular surgeon.




Planning a Treatment


After making the diagnosis, the first question is, “Does the patient need to be treated?” Many vascular conditions are self-limited, produce minor or no symptoms, or pose little risk during the remaining life of the individual. Good examples are the moderate asymptomatic carotid stenosis, the small (<4 cm) abdominal aortic aneurysm, and the patient with occasional intermittent claudication. Medical therapy to minimize the risk of symptoms or progression may be all that is needed. Common medications include aspirin and clopidogrel to prevent thrombus formation, statins to minimize plaque progression and instability, and antihypertensive agents for blood pressure control. Counseling to stop smoking, lose weight, and exercise are equally important. Because of the unpredictability of vascular disease, the surgeon or referring physician should set up a program for periodic evaluation.


If a condition exists that may be a risk to the patient’s life or health, such as an aneurysm that exceeds 5.4 cm in diameter or an ischemic limb resulting in pain, then the specific risks and benefits of possible treatments must be weighed against the risks of medical therapy alone. The permutations of conditions, as well as the risks and benefits of a specific treatment, are many, and the choice for one patient may often be inappropriate for another. For example, a sedentary older male with an aortic occlusion but only symptoms of moderate claudication may be best managed by medical therapy. In a younger male with a job that requires extensive walking and impotence, aortic occlusion may best be treated with open aortoiliac bypass with preservation of hypogastric artery flow. For an elderly woman with heart disease and an ischemic ulcer on her foot, the surgeon might advise treatment with an axillofemoral bypass graft. Assessment of associated medical illnesses, the expected longevity of the patient, and the prognosis for the underlying vascular condition are essential in selecting the best treatment for any given patient.


Once a choice is made, the options, the surgeon’s recommendation, and the potential risks and benefits should be clearly explained to the patient, the family if indicated, and the referring physician. In addition, it is wise to record the assessment of the situation and the particulars of the conversations, including the risks and benefits of the proposed treatment, in a letter to the referring doctor with a copy to the patient. Sending the copy to the patient eliminates misunderstanding and supplements formal informed consent.




Preoperative Assessment


Because of the association of aneurysm and occlusive disease with coronary artery disease, preoperative consideration of the cardiac status of the patient is essential. For a younger patient or someone who will undergo a relatively minor procedure, a careful history and a preoperative electrocardiogram (EKG) may be all that is necessary. For older patients who have risk factors for coronary artery disease or who are to undergo more extensive operations, the workup may include a cardiac echo to assess cardiac function, a nuclear stress test looking for foci of myocardial ischemia, or even cardiac catheterization. In some cases the planned surgery needs to be deferred until the patient first undergoes coronary revascularization. For complex cases, it is wise to have the patient evaluated by a cardiologist preoperatively and to engage the cardiologist’s help in the postoperative management.


Renal and pulmonary dysfunction can be a cause of significant morbidity for major vascular procedures, and both require careful intraoperative and postoperative management. Preoperative assessment of coagulation parameters is essential for every vascular case. The surgeon must be aware of the patient’s medications. Steroids, beta-blockers, antiplatelet agents, and medications for the management of diabetes are a few medications that may significantly affect the events in the operating room, as well as the patient’s recovery. Finally, the surgeon must pay attention to the patient’s mental state and functional capacity, as well as family support and the patient’s home situation. All are important in setting expectations and planning for disposition after the hospitalization.




Preparation in the Operating Room


Once in the operating room, a number of issues must be addressed before the surgery commences. Foremost is assuring all in the room that they are working with the correct patient, the correct side, and the correct procedure. The Universal Protocol for Preventing Wrong Site, Wrong Procedure and Wrong Person Surgery became effective July 1, 2004, for all accredited hospitals, ambulatory care, and office-based surgery facilities as mandated by the Joint Commission. The three principal components of the protocol include a preprocedure verification, site marking, and a time-out. Although this may seem trite, every experienced surgeon knows of a wrong-side surgery story, sometimes resulting in an injury to the patient, a lawsuit, and irreparable damage to a surgeon’s reputation and career. Assuring the correct operation is being performed cannot be delegated to a subordinate; it is always the responsibility of the surgeon.


Almost every major vascular surgery, open and endovascular, requires an arterial monitoring line and venous access for possible blood transfusion. Subclavian artery occlusions are not uncommon in patients with vascular disease. The anesthesiologist must be sure to monitor the arterial blood pressure from the nonaffected limb. If the anesthesia staff is having difficulty obtaining arterial access, the surgical staff should be ready to assist with a cut down on an artery or placement of a femoral artery catheter. In addition to the EKG and O 2 saturation, longer cases require monitoring of urine output and body temperature. Warming blankets may be necessary to prevent hypothermia.


The surgeon should be attentive to the placement of grounding pads, because they may obstruct the view if imaging is to be used. If the patient has a pacemaker, particularly an older model, the surgeon may need to use bipolar cautery. Defibrillators must be turned off.


Depending on the operation to be performed, other preparatory measures may include an epidural catheter for control of postoperative pain, a lumbar drain for spinal fluid drainage for thoracic aneurysmectomy, and a double lumen Carling endotracheal tube to isolate the right lung should the surgeon plan a left thoracotomy. Depending on the surgeon’s practice, an electroencephalogram or evoked potential monitoring may be desired for carotid surgery.




Positioning and Prepping the Patient


As in any surgery, the patient must be padded to assure adequate ventilation and to avoid pressure on critical areas, particularly for operations performed in the oblique, lateral, or prone position. In addition, special care must be taken for patients with lower limb ischemia to avoid contact between the heels and the operating table pad and prevent pressure sores. In the case of transaxillary first rib resection for thoracic outlet syndrome, lateral positioning of the patient and support of the arm during the operation are crucial to the ability of the surgeon to safely remove the rib without injury to the vessels or the brachial plexus.


With prepping and draping, it is important to prepare to extend the surgical field should the disease broaden beyond what was expected or should there be a need to emergently obtain proximal control of a vessel. To minimize the risk of infection, covering exposed skin with adherent antiseptic drapes is wise.


Lastly, prophylactic antibiotics are routinely given just before the incision in vascular cases. The surgical staff should be aware of the institutional directives for prophylactic antibiotics and make an explanatory note in the chart if the surgeon intends to deviate from the protocol.




Surgical Exposure


Perhaps one of the most pleasurable aspects of doing vascular surgery is the myriad of operations needed to reach most major blood vessels in the body. For many medical students, the most memorable experience of surgical clerkship is being in the operating room with a vascular surgery team and watching the team members perform surgery on the aorta, the carotid artery, a tibial artery, or a femoral artery—sometimes all in the same day. In addition to being able to operate in every part of the body, a skilled vascular surgeon needs to know multiple approaches to vessels to address various situations. For example, the posterior approach may be ideal for a popliteal aneurysm, whereas the medial approach may be better for a bypass or embolectomy. Details of the operations, including the pros and cons of surgical approaches, are discussed in subsequent chapters.




Vascular Reconstructions


For open surgery for arterial disease, most conditions can be managed with a bypass procedure, a resection with an interposition graft, or a patch repair, with or without an endarterectomy. Endarterectomy is primarily used for short segment occlusive disease, as seen at the carotid bifurcation, although endarterectomy has been used for aortoiliac and femoral artery disease. The plane for doing the endarterectomy can either be between the media and the intima or, more commonly, between the adventitia and the media.


Patch angioplasty is also useful for short segment stenoses when the focus is simply to enlarge the lumen of the vessel. Patches can be constructed from veins, synthetic materials such as Dacron or polytetrafluoroethylene (PTFE), and even the adventitia harvested from an occluded artery. Patches may be helpful in closing an arteriotomy in a severely diseased artery, a situation often encountered after an embolectomy or after passing an endograft through the femoral artery.


For long segment occlusive disease, a bypass procedure is the preferred means of reconstruction. A saphenous vein is the best conduit for lower extremity occlusive disease. If a vein is not available, PTFE grafts can be used—but not with the same expected durability. Synthetics are commonly used for bypass procedures involving the aorta and its major branches, including the arch vessels, the mesenteric and renal arteries, and the iliac arteries, because the diameter requirements are greater. For aneurysmal disease, repair with an interposition graft composed of synthetic material is performed for larger vessels and repair with a vein graft is performed for disease of smaller arteries, such as a popliteal artery aneurysm.


For bypass procedures, an end-to-side reconstruction is commonly used to preserve circulation distal to the anastomosis. A longitudinal arteriotomy is made in the native artery, and the graft is typically beveled to make an obtuse angle with the inflow or outflow tract. The suture is a fine monofilament typically beginning at the “heel” and meeting a second suture from the “toe” midway between the two. Vessels are commonly unclamped momentarily before completing the suture line for prograde flushing and retrograde backbleeding and, thus, to assure there is no thrombus proximal or distal to the clamps.


End-to-end anastomoses are commonly used in the reconstruction of aneurysmal disease and for trauma. For an aortic anastomosis, a Dacron tube is sewn in place with a heavy 2-0 or 3-0 polypropylene suture. For repair of small arteries with end-to-end anastomoses, the surgeon may choose to bevel the ends of both vessels to avoid a stenosis.

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Mar 13, 2019 | Posted by in VASCULAR SURGERY | Comments Off on General Principles of Vascular Surgery
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