Vascular Surgery: Endovascular and Open Surgery

Preoperative Assessment and Management

The goal of the preoperative assessment of the patient is to delineate the extent of underlying cardiac and noncardiac disease and medically optimize any underlying conditions. Because of the significant association of CAD, cerebrovascular disease, aortic degenerative disease, and PAD, a major focus of the preoperative assessment is to detect, evaluate, and optimize preexisting vascular comorbidities. Perioperative management must be tailored to the individual patient to protect any at-risk organ system. The association of smoking with CVD means that many patients have pulmonary comorbidities that may also increase their risk with surgery and anesthesia.

It is incumbent upon the anesthesiologist to work with the patient's surgical and medical teams to ensure medical optimization before surgery, including appropriate management of preoperative medications. As such, it is critical that the anesthesiologist recognize the potential benefits and risks of maintaining, stopping, or initiating medications in the perioperative period. As a general rule, most antihypertensive medications should be continued in the perioperative period. The preponderance of evidence suggests that patients on chronic β-blockers should be continued on the medication in the perioperative period, although β-blockers should not be instituted as new therapy on the day of surgery because of an increased risk of stroke and death. Current guidelines recommend that statin therapy should be continued in the perioperative setting, and perioperative statin therapy has been associated with the reduction of perioperative cardiac morbidity and mortality in vascular surgical patients. Management of antiplatelet agents must balance the risk of stopping medications versus the risk of bleeding in the perioperative period, particularly in the setting of recent percutaneous intervention with coronary stents. Although most recent clinical guidelines suggest that earlier discontinuation of dual-antiplatelet therapy may be considered in some cases, decisions about the duration of dual-antiplatelet therapy are best made on an individual basis based on an assessment of risk versus benefit and with input from a multidisciplinary team (surgery, anesthesiology, and cardiology).

Because of the risk of anemia, as well as a significant risk for blood loss, a complete blood count to assess starting hemoglobin and hematocrit should be obtained before vascular surgery. An active type and screen should be available, with blood products cross-matched as appropriate. A metabolic panel to assess baseline renal function is reasonable because of the likelihood of underlying renal insufficiency as well as risk for postoperative renal dysfunction. Coagulation studies should be considered for any patient who has been on anticoagulation and are mandatory if considering neuraxial manipulation either for anesthesia (e.g., spinal or epidural) or therapeutic intervention (e.g., spinal drain). A preoperative electrocardiogram (ECG) is often useful to serve as a baseline for evaluation of a perioperative insult. A preoperative echocardiogram is reasonable to assess baseline function for any patient with cardiovascular risk factors undergoing vascular surgery, particularly if there are new or worsening symptoms.

The American College of Cardiology (ACC) and American Heart Association (AHA) have released well-known guidelines regarding the perioperative cardiovascular evaluation and management of patients undergoing noncardiac surgery. The most recent recommendations from these guidelines simplify previous risk stratification before elective surgery ( Fig. 13.2 ; also see Chapter 1 ). The first step is to evaluate whether a clinical emergency exists; if so, the patient should proceed to surgery without delay with best medical optimization. The second step evaluates whether the patient has an acute coronary syndrome, which should be evaluated and optimized according to guideline-directed medical therapy before nonemergent surgery. Subsequent steps use a combination of surgical risk calculators, patient functional capacity, and clinical decision making to determine if further cardiac evaluation is warranted before surgery. In general, patients undergoing vascular surgery represent at least an intermediate (>1%) risk for an adverse perioperative cardiac event and may benefit from additional testing if it will change perioperative management (see Chapter 1 for further details).

Several observational studies previously suggested that preoperative cardiac revascularization improves patient outcomes before high-risk noncardiac surgery. The Coronary Artery Revascularization Prophylaxis (CARP) study was the first and only randomized controlled trial to evaluate outcomes following prophylactic cardiac revascularization before major vascular surgery. This study found no difference in outcomes in patients undergoing major vascular surgery who underwent routine revascularization by either coronary artery bypass grafting or percutaneous coronary intervention versus medical management. A subsequent analysis found that patients with unprotected left main disease may be the only subset of patients who benefits from prophylactic revascularization. In large part because of the CARP trial, cardiac revascularization is not typically recommended before surgery unless otherwise indicated according to current practice guidelines.

In general, most patients undergoing elective vascular surgery warrant cardiac evaluation because of their multiple comorbidities, high likelihood of concomitant CAD, and often difficult-to-quantity functional capacity related to vague symptomology (e.g., shortness of breath may be an anginal equivalent, related to concomitant pulmonary disease, or simple deconditioning) or other limiting factors (e.g., claudication before reaching 4 METs; previous amputations limiting exertion). Many vascular procedures are performed on an emergent basis, with little time for extensive workup. For urgent, but not emergent, procedures (e.g., peripheral intervention for critical limb ischemia), there may be time for limited workup and optimization. For true emergencies (e.g., ruptured aortic aneurysm), the case should proceed with best mitigation of perioperative risk ( Box 13.1 ).

Box 13.1

Strategies for Perioperative Management of Emergent Vascular Surgery Procedures

• Rapidly evaluate patient for signs and symptoms of acute coronary syndrome or equivalent (e.g., crackles or peripheral edema suggestive of decompensated heart failure; harsh systolic murmur suggestive of undiagnosed or worsened stenotic valvular disease) and treat accordingly.

• Maintain patient on preoperative antiplatelet therapy if not contraindicated, particularly if a recent coronary stent is present.

• Avoid tachycardia (will increase myocardial oxygen demand while decreasing supply). Continue preoperative β-blocker, if applicable, if hemodynamically stable.

• Avoid extremes of both hypertension (increases left ventricular wall stress) and hypotension (may compromise perfusion to vital organs).

• Avoid anemia, particularly if there is evidence of end-organ compromise.

• Assure adequate pain control to minimize sympathetic stimulation.

• Maintain normothermia.

Intraoperative Anesthetic Management

The primary anesthetic used during vascular surgery will depend on factors such as patient comorbidities, surgeon skill and comfort level, anatomic considerations, and the invasiveness of the surgical procedure. As such, anesthetic techniques for specific procedures are discussed in subsequent sections. Upon arrival to the operating room (OR), all patients should be placed on standard American Society of Anesthesiologists (ASA) monitors, including regular noninvasive blood pressure measurement, pulse oximetry, and continuous ECG. It is prudent to place an arterial catheter for invasive blood pressure monitoring for all but the most minor of vascular procedures because of the inherent risk for rapid hemodynamic changes and major blood loss. Patient comorbidities, cross-clamping on major vascular structures, and potential for hemorrhage all contribute to the hemodynamic instability frequently observed during these procedures. Invasive arterial monitoring also allows for frequent blood sampling to assess ventilation and oxygenation, ongoing blood loss and resuscitation needs, and overall metabolic milieu. Because induction of general anesthesia and endotracheal intubation are among the more hemodynamically labile periods, placing the arterial monitoring before induction of general anesthesia is wise.

Invasive monitoring with central venous or pulmonary arterial cannulation is not routine for most vascular procedures. Common exceptions include open aortic procedures or when patient comorbidities dictate utility. Large-bore intravenous (IV) access, either peripheral or central, is mandatory for any major vascular procedure because of the inherent risk of blood loss and need for resuscitation. An active type and screen and adequate blood product availability should be confirmed before undertaking any major vascular procedure.

Although transesophageal echocardiography (TEE) is the most sensitive method for detecting intraoperative myocardial ischemia, it has not supplanted clinical assessment and routine ECG for determination of patients at risk for myocardial ischemia during noncardiac surgery. The ASA, in conjunction with the Society of Cardiovascular Anesthesiologists, has released practice guidelines for the intraoperative use of TEE. In general, expert opinion has recommended that TEE should be considered in noncardiac surgery in the following circumstances: when the patient has CV pathology that may result in significant clinical compromise, when life-threatening hypotension is anticipated, and when persistent unexplained hypotension or hypoxia occurs. Furthermore, these practice guidelines recommended TEE should be strongly considered for major open abdominal aortic procedures, and TEE does not have a routine role during endovascular aortic and distal procedures.

Postoperative Management

In general, patients can undergo tracheal extubation uneventfully in the OR and recover in the postanesthesia care unit after most vascular surgical procedures. Patients undergoing major abdominal aortic procedures may benefit from close surveillance and management in an intensive care unit setting where mechanical ventilation is frequently continued after initial admission to the unit. In this case, sedation and analgesia should be provided with short-acting agents to facilitate rapid emergence and serial neurologic assessments. Common complications after major vascular surgery include myocardial ischemia, hemodynamic lability, stroke, coagulopathy, renal failure, respiratory failure, coagulopathy, hemorrhage, hypothermia, delirium, and metabolic disturbances.

Considerations for Intervention

The determination of when and how to intervene for carotid atherosclerotic disease is complex ( Box 13.2 ). The stroke risk related to the disease itself must be balanced with the inherent stroke risk due to intervention. Furthermore, surgical decision making must also take into consideration patient-specific risk factors and risk factors for open (carotid endarterectomy [CEA]) versus endovascular carotid artery angioplasty and stenting (CAS) management. Revascularization is achieved in CEA by opening the lumen of the cervical segment of the extracranial carotid artery and removing the atherosclerotic plaque (typically at the carotid bifurcation). CAS is a minimally invasive alternative, during which a stent is deployed across the atherosclerotic plaque to restore the patency of the vessel lumen.

Box 13.2

Considerations for Carotid Revascularization for Stroke Prevention

• All patients should be aggressively treated with antiplatelet therapy, statins, and β-blockade, and should receive management of comorbid conditions per current clinical practice guidelines.

• Revascularization should occur within 2 weeks of stroke or TIA for further stroke prevention.

• Revascularization is recommended for patients with symptomatic stenosis greater than 50%. The more significant the stenosis, the stronger the indication for surgical intervention.

• CEA is preferred over CAS unless there are contraindications to CEA (e.g., decompensated heart disease, previous neck surgery or radiation, contralateral vocal cord paralysis from previous surgery or an atypical and/or surgically inaccessible lesion).

• In asymptomatic stenosis greater than 60%, CEA may be considered in acceptable risk candidates (i.e., predicted combined stroke and death rates <3%) in addition to best medical therapy.

• Symptomatic patients with stenosis of <50% and asymptomatic patients with stenosis of <60% should be treated with best medical therapy and should not undergo intervention.

• Intervention is not indicated for patients with chronic total occlusion or patients with severe neurologic disability that precludes preservation of useful function.

CAS, Carotid artery angioplasty and stenting; CEA, carotid endarterectomy; TIA, transient ischemic attack.

Symptomatic carotid disease is defined as the onset of sudden and focal neurologic symptoms, either temporary or permanent, that are ipsilateral to the carotid pathology. The most important indicator of future stroke risk is the presence of symptoms within the previous 6 months. Several landmark trials have evaluated the benefit of CEA versus medical management for patients with symptomatic carotid disease. Pooled analyses of these trials found a consistent benefit was demonstrated for patients with greater than 70% stenosis, with a number needed to treat (NNT) of 6.3 to prevent one stroke over 5 years. A benefit was also demonstrated in patients with moderate (50%–69%) stenosis, although this benefit was less robust with an NNT of 22. CEA was not beneficial below 50% carotid stenosis and was found to be harmful for patients with less than 30% stenosis. There was no significant benefit of CEA with near-total occlusion of the internal carotid artery.

The role of CEA in asymptomatic carotid artery disease has also been extensively studied. A meta-analysis of the literature found a small absolute risk reduction of about 1% per year for the outcome of any stroke for patients with asymptomatic carotid disease who underwent CEA. The NNT to prevent one stroke at 3 years was approximately 33. The net benefit to CEA in asymptomatic patients is delayed because of perioperative morbidity; the early perioperative morbidity outweighs the modest reduction in stroke risk until 2 years or more after surgery. Thus asymptomatic patients must be carefully selected to have at least a 5-year expected survival to benefit from surgical intervention.

Carotid artery angioplasty and stenting is an alternative to open surgical intervention for patients with carotid atherosclerotic disease, particularly for patients considered to be poor candidates for surgery or anesthesia. Endovascular treatment of carotid disease has been extensively studied and compared to traditional CEA. The preponderance of evidence suggests similar long-term results in preventing disabling or fatal strokes between CEA and CAS; however, significant differences in short-term morbidity and mortality have been found between the two procedures, with a higher periprocedural stroke rate in patients undergoing CAS but a higher myocardial infarction (MI) rate in patients undergoing CEA. Examples of patients who are generally considered favorable candidates for CAS include those at a prohibitively elevated medical risk (e.g., contralateral occlusion, severe medical comorbidities) or surgical risk (e.g., previous radiation to the neck, history of previous neck dissection, intracranial or high extracranial location) to undergo open repair. Alternatively, severe aortic arch atheroma or significant carotid tortuosity typically increase the complication rate for CAS and are indications for CEA. The complication rate of the surgeon must also be taken into account when weighing the risk and benefits of carotid intervention for the individual patient.

Intraoperative Anesthetic Considerations and Management

Carotid revascularization can be performed under general anesthesia or under local anesthesia. The primary advantage of local anesthesia is the ability to continuously monitor neurologic function in an awake patient, which may more reliably detect cerebral ischemia than the neuromonitoring methods used under general anesthesia. Because the need for intraoperative intervention in an awake patient may be detected more promptly and reliably, it can minimize the risks of intervention such as embolic risk of shunt placement. Local anesthetic techniques may also avoid hemodynamic extremes and cardiorespiratory morbidity associated with general anesthesia. General anesthesia, on the other hand, has the benefits of increased patient comfort, decreased patient anxiety, and airway control. It also avoids the need for emergent intraoperative conversion because of complications such as seizure and airway compromise.

Patient outcomes after general versus local anesthesia have been the subject of extensive study. The largest and most well-known study is the General Anaesthesia versus Local Anaesthesia for carotid surgery (GALA) trial, which randomized more than 3500 patients undergoing CEA at 95 medical centers in 24 countries to either general anesthesia or local anesthesia. In this investigation, there were no differences in major adverse events between the two groups with respect to death, stroke, MI, length of stay (LOS), and quality of life. Patients undergoing general anesthesia were more at risk for hemodynamic instability and perioperative cognitive dysfunction; subsequent analysis, however, demonstrated that intraoperative shunting was the main risk factor variable associated with perioperative cognitive dysfunction. A recent large meta-analysis demonstrated that anesthetic technique had no effect on death, stroke, MI, postoperative cardiopulmonary complications, hospital LOS, or patient satisfaction after CEA. The available literature does not support the use of one anesthetic technique over another for carotid surgery, and survey of practice patterns suggests variability in perioperative practice for carotid surgery. The decision for general versus local anesthesia should consider both patient and surgeon preferences, as well as unique patient characteristics, that might favor one technique over another. Regardless of technique, the goals of the anesthetic are the same: maintain hemodynamic norms and ensure smooth, rapid recovery from anesthesia to allow for early neurologic assessment.