General considerations

Patients with atherosclerotic disease commonly have other underlying disease processes, some of which may contribute to the development of disease and increase the morbidity and mortality rates associated with surgery. Among the underlying conditions are chronic tobacco use with chronic obstructive pulmonary disease, diabetes, peripheral neuropathy, hypertension, dyslipidemia, obesity, and advancing age.^2,5

The progression of atherosclerosis, which leads to most vascular surgical procedures, is a systemic disease that affects all arterial beds including those in the extremities, heart, kidneys, and brain.^2–4 A vital part of treatment of arterial disease is risk factor modification to include smoking cessation and control of underlying comorbidities such as diabetes, hypertension, and dyslipidemia.^2,5 Venous surgical procedures have also increased in number as a result of improvements in technology and the use of minimally invasive techniques.^5,8 This chapter is limited to care of the patient undergoing surgery on blood vessels outside the heart.

Diagnostic procedures

Noninvasive diagnostics, such as the ankle brachial index (ABI), ultrasonography, computed tomography angiogram (CTA), and magnetic resonance angiography (MRA) and imaging (MRI), have contributed greatly to the early treatment of vascular disease.5 These procedures do not usually require sedation.

The ABI is a ratio of ankle-to-brachial blood pressure. PAD is present if the ABI is 0.90 or less.^2,5Box 36.1 describes the calculation of an ABI. This test may also be used postoperatively to assess the patency of vessels following stent placement, percutaneous transluminal angioplasty (PTA), bypass graft placement, or endarterectomy. In patients with diabetes who have developed calcification of the large vessels, an ABI might not be obtainable because of the inability to fully compress the vessels to obtain a pressure. In these patients, toe-brachial index is a useful tool for assessing distal blood flow.^1,5

Box 36.1

Obtaining an Ankle Brachial Index

1. 1. Obtain the blood pressure in both arms with the patient lying supine.
   
2. 2. Obtain the blood pressure with a Doppler scan at the dorsalis pedis and posterior tibial pulses on each ankle.
   
3. 3. Calculate the ABI with the highest ankle pressure divided by the highest arm pressure. (Example: Right BP 140/80 mm Hg; left BP 146/88 mm Hg; right DP 136 mm Hg; right PT 124 mm Hg; left DP 128 mm Hg; left PT 132 mm Hg; right ABI = 136 mm Hg/146 mm Hg [0.93]; left ABI = 132 mm Hg/146 mm Hg [0.90].)

---

ABI, Ankle brachial index; BP, blood pressure; DP, Dorsalis Pedis; PT, Posterior Tibial.

Arteriography continues to be the gold standard for invasive diagnostic testing and usually requires intravenous (IV) sedation. This test requires direct injection of contrast media into the arterial bed and is used to examine the arterial supply of a specific region. Arteriography can also be done in conjunction with various treatment methods including angioplasty, cryoplasty, atherectomy, and stenting.^5,7,9

Endovascular procedures

Endovascular treatments for PAD include PTA, PTA with stent placement, atherectomy, cryoplasty, and fibrinolytic therapy.^5,7 These procedures are performed by a variety of specialists including interventional radiologists, vascular surgeons, and cardiologists. These procedures may require only local anesthetic and IV sedation depending on the patient’s condition and physician’s preferences. The procedures can also be performed alone or in conjunction with other vascular surgical procedures in the operating room and may be done with local plus IV sedation, epidural, spinal, or general anesthesia.^5,10

PTA may be performed on carotid, aortic, mesenteric, renal, iliac, femoral, popliteal, and tibial vessel stenosis. This procedure may be used alone or in conjunction with stent placement. Major complications after PTA or stenting include bleeding, hematoma, thrombus formation or embolism, and intimal tears (disruption of the inner lining of the vessel) or perforation.^5,7 Other complications may occur specific to the vascular bed being treated such as transient ischemic attack or stroke for carotid stenting and worsening renal failure in treatment of renal artery stenosis.⁵ Stents are used to compress and hold the plaque against the vessel wall. Covered stents have been shown to have higher patency rates than bare metal stents.^5,7 They can also be used to treat an intimal tear in the vessel wall. Stents and balloons with drug coating such as paclitaxel may be used for some lesions and appear to reduce in-stent stenosis as a result of their effects on smooth muscle cell proliferation. They have primarily shown promise in locations where in-stent restenosis is high and are believed to improve long-term patency rates. There are conflicting studies in regard to possible increase in mortality associated with paclitaxel. Further research is needed to determine a definitive relationship in use of paclitaxel and mortality.⁷

Atherectomy is a technique designed for removing plaque from the vessel wall with a special rotating blade and suction apparatus. Atherectomy devices may be directional, rotational, or laser. Angioplasty or stenting may follow atherectomy.⁷ Cryoplasty balloons were previously used to combine freezing and dilation of arteries with the belief that they would reduce vessel dissection and intimal hyperplasia. They have not proven to be very effective and are rarely used.⁷

After these procedures, patients are monitored for recovery from IV sedation and for bleeding and hematoma formation at the puncture site.⁵ Distal pulses are assessed bilaterally to detect any change in blood flow that may be related to formation of an embolism or thrombus for procedures that involve the abdominal vessels or extremities.⁵ These pulses should be compared with the baseline pulses documented before the procedure. Intake and output should be monitored closely, and adequate hydration should be maintained after any procedure with IV contrast. IV contrast can be toxic to the renal system, leading to contrast-induced nephropathy (CIN); this is characterized by an increase in creatinine of 25% from baseline within 48 hours of contrast administration.¹¹ This is of greater concern in patients with preexisting diabetic nephropathy, glomerular filtration rate (GFR) < 60, older age, heart failure, extremes of body mass index (BMI > 30 or < 18), anemia, high contrast dose, and hypertension. Treatments such as additional IV fluids, N-acetylcysteine, and sodium bicarbonate can be used to provide additional protection against CIN. Other treatments may include holding medications such as metformin prior to any study using contrast. Some newer studies indicate that continuing metformin for 48 hours prior to contrast administration may not increase the risk of CIN.^10,11

Bed rest is maintained for 6 to 8 hours after the procedure with the extremity in a straight position to prevent bleeding at the puncture site. If a closure device is used at the puncture site, the patient may be allowed out of bed sooner.^5,12 Any patient who undergoes an arteriogram, angioplasty, or stenting that involves the carotid or cranial circulation should undergo frequent neurologic assessment after the procedure. Special protection devices are used during carotid angioplasty and stenting to trap any free-floating particles of plaque or thrombus that may be dislodged during the procedure. These devices serve to minimize postprocedural complications such as stroke.^3,13

Fibrinolytic therapy is used when an embolus or thrombus has occluded a vessel. Special catheters are placed in the area of the thrombus, and agents such as alteplase, tenecteplase, or reteplase are used to lyse the clot.⁵ This process can be done by initial bolus and then completed via infusion and may take hours for complete lysis of the thrombus. These patients need close observation throughout the infusion for signs of bleeding, bruising, anaphylaxis, hematoma at the puncture site, and hematuria. Blood pressure should be monitored closely to decrease the risk of cerebral hemorrhage. Assessing for signs of cerebral bleeding is critical. If treatment is needed for bleeding, aminocaproic acid (Amicar) can be used to inhibit the fibrinolytic process.⁶ Frequent assessment of the limb is also needed as reperfusion occurs. As the limb reperfuses, pain may actually worsen initially as microemboli break away from the thrombus and move distally to smaller vessels. As the infusion continues, pain improves as these emboli are dissolved. Frequent laboratory work includes serial monitoring of complete blood count, fibrinogen, prothrombin time and international normalized ratio (PT/INR), and partial thromboplastin time (PTT).¹⁴ Periodic assessment in radiology is done to follow the progress of the lytic agent. The infusion is discontinued when lysis is complete, bleeding occurs that necessitates transfusion, or no response to the agent is found.^5,14 Studies completed in the past 5 years that examined monitoring of fibrinogen suggest that it may not be a significant indicator for bleeding risk, but most recommendations support the need to keep the level above 100.¹⁵

Medications used in vascular surgery

Anticoagulants are among the most commonly used medications in the treatment of the patient for vascular surgery. Unfractionated heparin can be administered before, during, and after surgery. Its actions occur at multiple points in the coagulation cascade to ultimately inactivate thrombin and prevent conversion of fibrinogen to fibrin. Heparin has a short 60- to 90-minute half-life and may be administered IV or subcutaneously. The response to heparin is measured with the activated PTT and is targeted at 1.5- to 2.5-fold greater than normal to obtain a therapeutic response and prevent thromboembolism. Therapeutic levels can only be obtained by continuous IV infusion.16 Complications associated with the use of heparin include increased risk of bleeding and heparin-induced thrombocytopenia (HIT). Platelet counts should be monitored for decrease of 40% to 50% from baseline or any decrease to less than 100,000. If HIT develops, heparin must be discontinued, and alternative anticoagulants should be used.¹⁶ Protamine is the antidote for heparin; its action occurs within 5 minutes of administration. Care must be taken to avoid overly rapid administration of protamine. When administration is too rapid, side effects can include hypotension, pulmonary hypertension, shortness of breath, and flushing. The usual target dose for reversal is 1 mg of protamine for every 90 units of heparin.¹⁶

Low-molecular-weight heparins (LMWHs), such as enoxaparin (Lovenox), dalteparin (Fragmin), and tinzaparin (Innohep), may also be used in the care of the patient for vascular surgery. These drugs are administered subcutaneously and have a significantly lower molecular weight than unfractionated heparin, which gives them improved predictability in the dose response and a longer half-life. This advantage greatly reduces the need for laboratory monitoring. If testing is needed, antifactor Xa level is the test of choice for monitoring. The LMWHs are administered subcutaneously and have a significantly lower incidence rate of HIT associated with their use; they are primarily used to prevent thromboembolism after surgery but are also approved in the treatment of deep vein thrombosis (DVT) and pulmonary embolism (PE). They may also be used to bridge patients before and after surgery who require long-term anticoagulation with warfarin (Coumadin) or other anticoagulants. The decision to bridge (use a short-acting blood thinner) is based on diagnosis and thromboembolic risk. Patients with renal disease may need a dose reduction depending on the severity of their disease. Complications are similar to those of unfractionated heparin. Laboratory testing should be monitored for signs of HIT, although it occurs much less frequently with the use of LMWH.^5,16 The decision to bridge a patient in the perioperative period is based on the risk of thrombosis and the risk of bleeding.¹⁷ Patients with a low risk of bleeding and thrombosis are usually safe not being bridged. Patients with high risk of thrombosis and bleeding are generally bridged, and the anticoagulant is held periprocedure.¹⁷ If there is a low risk of thrombosis with a high bleeding risk surgery or procedure, the recommendation is to hold the anticoagulant without bridging. For patients with a high risk of thrombosis but a low risk of bleeding or low risk of thrombosis and bleeding, anticoagulants may be continued during the procedure.¹⁷

Warfarin is an oral anticoagulant that inhibits vitamin K–dependent coagulation factors and the anticoagulant proteins C and S; it has a half-life of 36 to 42 hours. Monitoring of warfarin is done with PT/INR.¹⁶ The PT/INR is laboratory dependent, and specific methods vary among institutions. Caregivers should be familiar with institutional methods. For long-term monitoring, the INR alone is used. Warfarin is used to treat a variety of thromboembolic disorders, and it can be used to promote long-term patency of infrainguinal bypass grafts after thrombosis of previously placed grafts. Complications include increased risk of hemorrhage and skin necrosis. Patients receiving warfarin must be counseled to discontinue the drug several days before any invasive procedure to allow time for the PT/INR levels to decrease to normal. Reversal of warfarin is achieved with vitamin K, fresh frozen plasma, or prothrombin-complex concentrates.¹⁶

Additional oral anticoagulants are now available and are commonly referred to as direct oral anticoagulants (DOACs). These agents work at specific targets in the coagulation cascade. Table 36.1 summarizes all of the oral anticoagulants currently available including target of action, uses, antidotes, and special considerations for each drug. Rivaroxaban (Xarelto), apixaban (Eliquis), and edoxaban (Savaysa) are direct factor Xa inhibitors. Dabigatran is a direct thrombin inhibitor. They are currently approved for the prevention of stroke in nonvalvular atrial fibrillation. Rivaroxaban and apixaban are also approved for short-term thromboprophylaxis after elective hip or knee surgery. All three agents may be used in the treatment of DVT or PE.¹⁸ Though these agents are not currently approved for treatment of arterial disease, patients may present on these medications due to comorbidities. The VOYAGER PAD trial looked at using rivaroxaban 2.5 mg twice daily with aspirin and was found to indicate a reduction in acute limb ischemia, amputation related to vascular disease, myocardial infarction (MI), ischemic stroke, and death from other cardiovascular events.¹⁹ More research is needed to determine if this is generalizable across all populations.

IV direct thrombin inhibitors act at the active site of thrombin. These drugs provide an alternative to heparin in the patient with HIT. Current drugs available in this category include argatroban (Acova) and bivalirudin (Angiomax).²⁰

Parenteral factor X inhibitors currently include only fondaparinux (Arixtra). Fondaparinux activates antithrombin III, leading to inactivation of factor X. It is administered subcutaneously and requires no laboratory monitoring. Its primary use is prevention of DVT and treatment of acute coronary syndromes. It may be used in patients unable to use LMWH or unfractionated heparin due to HIT. There is no reversal agent for fondaparinux.^5,20

Antiplatelet agents include aspirin, cilostazol (Pletal), clopidogrel (Plavix), dipyridamole (Persantine), dipyridamole ER/aspirin (Aggrenox), prasugrel (Effient), ticagrelor (Brilinta), ticlopidine (Ticlid), and vorapaxar (Zontivity). These agents are summarized in Table 36.2. They may be used in the patient with vascular disease as a preventive measure for MI and stroke or as part of medical management for patients after placement of infrainguinal bypass grafts, carotid endarterectomy (CEA), and peripheral and carotid stenting.^5,21 These drugs exhibit an irreversible permanent effect on the platelet for its life span and produce a qualitative effect on the platelet measured with the bleeding time. Platelet counts are not affected by these agents. Cilostazol also has some vasodilatory effects and is contraindicated in patients with heart failure. Patients should be counseled regarding the discontinuation of these drugs 5 to 10 days before invasive procedures to decrease the risk of bleeding.^5,21 Patients at moderate to high risk for cardiovascular events may continue their antiplatelet agents to the time of surgery.²¹

Glycoprotein IIb/IIIa inhibitors are parenteral agents that also interfere with platelet aggregation and include abciximab (Reopro), eptifibatide (Integrilin), and tirofiban (Aggrastat). These agents are administered by IV infusion. Patients who have had drug-eluting coronary stent placement within the previous 12 months of a surgical procedure may need to be bridged with a glycoprotein IIb/IIIa inhibitor to discontinue their antiplatelet drugs for surgery or may be instructed to continue their aspirin and clopidogrel (Plavix) up to surgery.²²

Preprocedural assessment

The PAD patient often presents with multiple comorbidities and/or risk factors including advanced age, tobacco use with or without chronic pulmonary disease, diabetes mellitus, impaired renal function, coronary artery disease, hypertension, and congestive heart failure.23 Optimizing the patient’s status before interventional and surgical procedures is vital to the outcome of the postoperative course. Cardiac risk, fluid management, pharmacotherapy, renal evaluation, and medical management of other comorbidities before surgery is vital to patient safety.^23,24

The Vascular Study Group of New England Cardiac Risk Index (VSG-CRI) was developed as a means of cardiac risk prediction for patients undergoing noncardiac vascular surgery. The index includes nine variables that comprehensively evaluate cardiac risk in the vascular patient population. These variables are listed in Box 36.2. The index has been used to predict the cardiac risk in CEA, lower extremity bypass, endovascular repair of abdominal aortic aneurysm (AAA) repair, and open infrarenal AAA repair. Even though endovascular procedures may carry a lower risk of a cardiac event, patients should be stratified in the event that an endovascular procedure needs to be converted to an open procedure or additional procedures are required.²³ The American Heart Association currently recommends that patients with intermediate or high cardiac risk undergo a cardiac stress test with exercise or pharmacologic agents and an electrocardiogram. Stress echocardiograms have been shown to be twice as accurate in predicting the postoperative occurrence of cardiac events and may be the best tool for evaluating cardiac risk. Some patients may require cardiac intervention before vascular surgery. Patients considered low risk for a postoperative event will require no further intervention.²³ Surgery in patients who have undergone coronary stent placement should be delayed 4 to 6 weeks due to increased risk of stent thrombosis. Dual antiplatelet therapy should be continued before the surgery unless the bleeding risk outweighs the risk of thrombosis. For patients who have undergone placement of drug-eluting stents, surgery should be delayed for at least 6 months if possible.²³

Stay updated, free articles. Join our Telegram channel

Join