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Anesthesia for endovascular aortic repair

Anesthesia for endovascular aortic repair
Literature review current through: Jan 2024.
This topic last updated: Jul 06, 2022.

INTRODUCTION — Endovascular aortic repair (EVAR) has become a standard approach to treatment for thoracic and abdominal aortic aneurysms, accounting for well over one-half the patients who would otherwise undergo an open surgical repair. Since EVAR does not require intrathoracic or intraabdominal exposure of the aorta, or aortic cross-clamping, perioperative morbidity and mortality are reduced compared with open repair. Also, EVAR has made treatment possible for some patients with comorbidities who might not otherwise be candidates for aortic repair.

Vascular access for EVAR is achieved via access to the femoral or iliac vessels, either percutaneously or via small incisions; thus, the procedure may be accomplished with the aid of local/regional anesthetic techniques with monitored anesthesia care (MAC), neuraxial anesthesia, or general anesthesia.

This topic will review the preoperative anesthesia consultation and each of these anesthetic options for thoracic or abdominal EVAR. Separate topics review anesthetic management for open repair of the abdominal aorta or the descending thoracic aorta. (See "Anesthesia for open abdominal aortic surgery" and "Anesthesia for open descending thoracic aortic surgery".)

SURGICAL TECHNIQUES — Significant advances in imaging technology allows for accurate three-dimensional reproduction of any aortic aneurysm, which provides optimal preprocedural planning and stent choice and stent production commissioned to a particular specification even with complex anatomy [1]. Such advances together with increased clinical experience have reduced the need for different approaches to descending thoracic aneurysms versus abdominal aneurysms. Further details are available in separate topics:

(See "Endovascular repair of abdominal aortic aneurysm".)

(See "Endovascular devices for abdominal aortic repair".)

(See "Endovascular repair of the thoracic aorta".)

(See "Endovascular devices for thoracic aortic repair".)

PREANESTHETIC ASSESSMENT — Most patients with thoracic and/or abdominal aortic aneurysm are older and have major cardiovascular and other comorbidities (eg, coronary artery disease, hypertension, obesity, diabetes, hyperlipidemia, smoking, and chronic obstructive pulmonary disease) [2]. Many have had recent intravenous (IV) contrast for angiography, with consequent risk of contrast-induced nephropathy (CIN). Although EVAR is associated with lower perioperative morbidity and mortality compared with open surgical repair, risk for conversion to open intraabdominal or intrathoracic repair is present [3,4]. Thus, preoperative evaluation is as thorough for EVAR as for open repair [5]. (See "Anesthesia for open abdominal aortic surgery", section on 'Preanesthetic consultation' and "Anesthesia for open descending thoracic aortic surgery", section on 'Preanesthetic assessment'.)

Risks that affect anesthetic management will be briefly summarized here, while further details are available in separate topics:

(See "Endovascular repair of abdominal aortic aneurysm", section on 'Preoperative risk assessment'.)

(See "Endovascular repair of the thoracic aorta", section on 'Medical risk assessment'.)

Particular emphasis is placed on the cardiovascular and renal systems:

Cardiovascular assessment – We obtain a preoperative electrocardiogram (ECG), as recommended by professional societies, as a useful baseline if the postoperative ECG is abnormal [5-8]. We obtain additional cardiac testing selectively in patients with changes in cardiac symptoms and functional status. (See "Evaluation of cardiac risk prior to noncardiac surgery", section on 'Initial evaluation' and "Evaluation of cardiac risk prior to noncardiac surgery", section on 'Testing to further define risk'.)

Either abdominal or thoracic EVAR are procedures associated with intermediate risk for a perioperative cardiovascular event (at least 1 percent) [3,5]. Notably, patients with known preexisting right ventricular dysfunction have a higher risk for major postoperative cardiac complications including cardiovascular mortality, nonfatal cardiac arrest, myocardial infarction, development of congestive heart failure, and stroke after major vascular surgery, including endovascular aortic surgery [9].

Renal assessment – We obtain a creatinine level in the immediate preoperative period to compare with previous measurements to determine if the intravascular contrast dye used in preoperative imaging decreased creatinine clearance. Then we allow sufficient time between the last contrast dye load and the time of the currently planned procedure when possible (typically two weeks), and we obtain consultation with a nephrologist. (See "Prevention of contrast-associated acute kidney injury related to angiography".)

Severe renal dysfunction after elective abdominal or thoracic EVAR occurs in 0.7 to 2 percent of patients. This is primarily due to the administration of IV contrast agents, but also influenced by dislodgement of embolic debris by manipulation of intravascular catheters and wires near the renal arteries, or impingement of the renal ostia by the graft. Patients undergoing emergency endovascular therapy for a ruptured aneurysm have a higher incidence of renal as well as other complications. (See "Complications of endovascular abdominal aortic repair", section on 'Contrast-induced nephropathy' and "Complications of endovascular abdominal aortic repair", section on 'Renal ischemia' and "Endovascular repair of the thoracic aorta".)

Medication management – We continue chronically administered beta-blockers, statins, and antihypertensives in the perioperative period, similar to other noncardiac surgical cases with high cardiovascular risk. (See "Management of cardiac risk for noncardiac surgery", section on 'Beta blockers' and "Management of cardiac risk for noncardiac surgery", section on 'Statins' and "Perioperative medication management", section on 'Cardiovascular medications'.)

INTRAOPERATIVE MONITORING — In addition to standard noninvasive monitoring, including electrocardiography (ECG) with leads II and V5, with computerized ST-segment trending to detect myocardial ischemia and/or arrhythmias, pulse oximetry (SpO2), and intermittent noninvasive blood pressure (BP) cuff measurements (table 1), cardiovascular monitoring and neuromonitoring may be employed. We use continuous ECG monitoring. (See "Basic patient monitoring during anesthesia" and "Anesthesia for noncardiac surgery in patients with ischemic heart disease", section on 'Monitoring for myocardial ischemia'.)

Cardiovascular monitoring

Arterial blood pressure measurements – Direct intra-arterial pressure monitoring is usually employed, although there are no studies demonstrating benefit compared with noninvasive blood pressure measurements. Arterial BP monitoring for descending aortic surgery is optimally established in the right arm for descending aortic surgery since the left innominate artery may be occluded if the stent covers the left subclavian artery. Also, the left arm may occasionally be used for vascular access.

After deployment of the stent, the surgeon may wish to monitor distal limb pressure to check for adequate flow. Pressure tubing connected to the distal limb artery is passed from the sterile surgical field to the anesthesiologist, to be attached to a monitored pressure transducer.

Transesophageal echocardiography – Transesophageal echocardiography (TEE) is often used in thoracic aortic, emergency, or complex EVAR procedures to evaluate aortic anatomy (eg, atherosclerotic lesions, thrombi, dissection), assist with positioning and deployment of the endograft precisely at the target location, then confirm correct positioning, and detect endoleaks [10-16]. Use of TEE requires general anesthesia for patient comfort and preoperative assessment of esophageal pathology for safety.

If hemodynamic instability develops, TEE can be used to rapidly determine the etiology by assessing:

Systolic and diastolic ventricular function (see "Intraoperative transesophageal echocardiography for noncardiac surgery", section on 'Ventricular function'),

Adequacy of ventricular filling (ie, preload) (see "Intraoperative transesophageal echocardiography for noncardiac surgery", section on 'Volume status'), and

Vascular resistance (see "Intraoperative transesophageal echocardiography for noncardiac surgery", section on 'Systemic vascular resistance')

This information can then be used to guide decision-making about volume expansion, inotropic and/or vasopressor support, or vasodilator therapy [17-19].

TEE is also used to monitor for new regional wall motion abnormalities, potentially providing a sensitive and specific indicator of myocardial ischemia (figure 1) [20,21]. However, there are no data demonstrating that TEE monitoring reduces risk of adverse perioperative cardiovascular events in patients undergoing vascular surgery [6,17,22,23]. (See "Intraoperative transesophageal echocardiography for noncardiac surgery", section on 'Major vascular surgery'.)

Further details regarding use of TEE monitoring during noncardiac surgery are presented elsewhere. (See "Intraoperative transesophageal echocardiography for noncardiac surgery".)

Central venous catheter (CVC) – It is usually unnecessary to measure central venous (or pulmonary artery) pressure or cardiac output, either invasively or noninvasively. However, large bore intravenous access must be obtained for either abdominal or thoracic EVAR procedures because of the possibility of hemorrhage and the need for transfusion. If obtaining such access is challenging, or use of vasoactive infusions is likely, the reliable vascular access and the information obtained with a CVC can be helpful, particularly in thoracic EVAR cases.

Neuromonitoring for spinal cord ischemia — A surgical decision to use cerebrospinal fluid (CSF) drainage as a protective strategy to minimize spinal cord ischemia necessitates spinal cord monitoring with somatosensory evoked potentials (SSEPs) and/or motor evoked potentials (MEPs) (table 2). (See 'Monitoring and management of spinal cord ischemia' below and "Endovascular repair of the thoracic aorta", section on 'Minimizing spinal ischemia'.)

Somatosensory evoked potentials – Monitoring of SSEPs involves electrical stimulation of distal nerves of the lower extremity (eg, the posterior tibial and peroneal nerves), then recording the resultant cortical electrical potentials via scalp electrodes to monitor continuity of lateral and posterior column function (figure 2). (See "Neuromonitoring in surgery and anesthesia", section on 'Somatosensory evoked potentials'.)

Considerations for anesthetic management when SSEPs are used to monitor for spinal cord ischemia are discussed separately [24-26]. (See "Anesthesia for open descending thoracic aortic surgery", section on 'Somatosensory evoked potentials (SSEPs)'.)

Motor evoked potentials – Transcranial monitoring of MEPs involves electrical stimulation of the scalp overlying the motor cortex, which generates waves that travel down the corticospinal tract to the nerve root and the peripheral nerve, which results in muscle action potentials in a peripheral muscle group (eg, the anterior tibialis), where the evoked response is recorded (figure 3). (See "Neuromonitoring in surgery and anesthesia", section on 'Motor evoked potentials'.)

Considerations for anesthetic management when MEPs are used to monitor for spinal cord ischemia are discussed separately [24-26]. (See "Anesthesia for open descending thoracic aortic surgery", section on 'Motor evoked potentials (MEPs)'.)

ANESTHETIC MANAGEMENT — EVAR has been performed safely with local anesthesia, neuraxial anesthesia, or general anesthesia [2].

Anesthetic goals — Anesthetic goals may vary according to surgical needs during EVAR but typically include:

Facilitating the patient's ability to lie still comfortably for one to three hours

Assuring adequate hydration to reduce risk of contrast nephropathy

Managing anticoagulation (initiation, monitoring, and reversal)

Measuring serial hematocrits; preparation for massive transfusion (rare)

Controlling systemic blood pressure (BP), including administering pharmacologic agent(s) to rapidly decrease mean arterial pressure (MAP) when necessary (eg, at the time of device deployment)

Controlling temperature including active patient warming when necessary

Anesthetic choices — Thoracic or abdominal EVAR can be performed using local/regional anesthetic techniques together with monitored anesthesia care (MAC), neuraxial anesthesia, or general anesthesia. In all cases, the patient must remain immobile during positioning of modular graft components.

We prefer local/regional or neuraxial anesthesia for most EVAR procedures performed using routine surgical access to the aorta via the femoral or iliac arteries (see 'Local/regional anesthesia' below and 'Neuraxial anesthesia' below). As graft technology and imaging technology have evolved (eg, grafts have become smaller, more flexible, and are specifically designed for complex anatomy) and surgeon experience has increased, use of local/regional anesthesia with MAC is typically selected for primary repair candidates and is well-tolerated. For less common procedures requiring retroperitoneal vascular access via a 3 to 5 inch lower flank incision extended down to directly expose the iliac artery (eg, when direct access to the iliac artery is necessary due to femoral artery pathology), neuraxial or general anesthesia is typically necessary. General anesthesia may be selected for complex repairs that require extended duration to provide patient comfort and immobility.

Potential advantages of local/regional or neuraxial anesthesia – Compared with general anesthesia, potential advantages of these techniques in an awake patient include (table 3) [27,28]:

Shorter intensive care unit (ICU) and hospital stays

Avoidance of general anesthetics having myocardial depressant effects

Less alteration of pulmonary mechanics

Less catecholamine release because of avoidance of the sympathetic stimulation of laryngoscopy, as well as emergence excitation and the stimulation of extubation

Early detection of anaphylactic and anaphylactoid reactions because of immediate complaint of symptoms (eg, pruritus due to hives; flushing; dyspnea; wheezing due to bronchospasm; stridor; swollen lips, tongue, and uvula; or syncope)

Detection of aneurysm rupture by the patient's report of retroperitoneal pain

Decreased intraoperative blood loss with neuraxial anesthesia, due to lower average mean arterial pressures

Possible decreased in-hospital and 30-day mortality compared with general anesthesia, although these improved outcomes are only suggested in aggregate meta-analyses but not in direct randomized trials

A summary of available data comparing local/regional or neuraxial anesthesia versus general anesthesia is presented:

Elective abdominal EVAR cases – For elective abdominal EVAR procedures, meta-analyses of randomized and nonrandomized studies suggest that local/regional or neuraxial anesthesia techniques are at least equivalent to general anesthesia, and may confer some benefit with respect to hospital length-of-stay and morbidity [27-30]. A 2020 meta-analysis that included 12 observational studies with 12,024 abdominal EVAR patients (1664 with local/regional anesthesia ad 10,360 with general anesthesia) noted shorter surgical time, shorter hospital stays in those receiving local/regional anesthesia, but no differences in 30-day mortality or in cardiac, renal, or vascular complications [30]. Similarly, a 2012 meta-analyses of abdominal EVAR cases that included 10 nonrandomized studies of 13,459 patients also noted shorter surgical times and hospital stays, with lower likelihood of ICU admission, but no differences in mortality for patients receiving local/regional or neuraxial anesthesia compared with those receiving general anesthesia [29]. In a review of 1206 abdominal EVAR cases (788 general anesthesia; 246 neuraxial anesthesia; 82 local/regional anesthesia), there were no differences among groups in surgical time, length-of-stay, or morbidity or mortality [31]. Interpretation of data from these studies is limited by the absence of randomized trials, as well as the small total number of events and heterogeneity among studies (eg, nonstandardized anesthetic techniques, inclusion of emergencies in some studies).

Emergency abdominal EVAR cases – For emergency EVAR repair of ruptured abdominal aortic aneurysm, a 2021 meta-analysis included eight studies with 3116 patients; 867 received local/regional anesthesia, while 2249 received general anesthesia [28]. Lower mortality (in-hospital plus 30-day) was noted in the local/regional anesthesia group compared with the general anesthesia group (16.4 versus 25.4 percent, unadjusted odds ratio [OR] 0.47, 95% CI 0.32-0.68). In a 2018 meta-analysis that included 39,744 patients from 22 nonrandomized studies undergoing either elective or emergency abdominal EVAR, local/regional anesthesia appeared to confer lower risk for 30-day mortality in emergency abdominal EVAR cases compared with general anesthesia, but the trends in elective surgery were less clear [27]. Notably, mortality did not differ in comparisons between neuraxial versus general, or neuraxial versus local anesthesia in this study.

Thoracic EVAR cases – Similarly, for thoracic EVAR, there are no randomized trials comparing anesthetic techniques. In one single-center prospective study that included 400 consecutive elective or emergency thoracic EVAR cases, multivariate analysis revealed that general anesthesia was a risk factor for mortality compared with neuraxial anesthesia (hazard ratio [HR] 1.59, 95% CI 1.02-2.50) [32]. Selection bias was likely since general anesthesia was used most commonly in this center's early experience, but with increasing experience, general anesthesia was used only when the patient was unable to cooperate during the procedure. Also, changes in stent technology (eg, decreased size and increased flexibility) have improved the likelihood of success with local or neuraxial anesthesia in the years since this study was performed [32]. (See "Endovascular repair of the thoracic aorta".)

Potential advantages of general anesthesia – General anesthesia has advantages and may be preferred for patients with (table 3):

Elimination of concerns regarding anxiety, claustrophobia, discomfort, and/or ability to remain motionless and cooperate

Elimination of concerns regarding inability to lay flat due to significant chronic obstructive pulmonary disease, congestive heart failure, back pain, or other reasons

Less risk of patient movement during painful stimuli (eg, during manipulation of sheaths or device delivery systems inside the iliac vessels or ischemic limb pain caused by prolonged attempts at contralateral limb cannulation)

Complete and satisfactory suspension of respiration during stent deployment

Decreased bowel peristalsis if opioids are administered in sufficient doses [33], which may improve the quality of intraoperative imaging

Notably, conversion from regional or neuraxial anesthesia to general anesthesia occasionally becomes necessary. Notably, with increasing experience and improving technology, intraoperative conversion from EVAR to open aortic repair is less than 1 percent. However, emergency conversion to general anesthesia rarely occurs due to aneurysm rupture, vascular injury, or inability to deliver or seal the device (ie, endoleak), but in many reports the incidence of conversion is zero [34,35].

Specific anesthetic techniques

Local/regional anesthesia — Femoral or iliac arterial access to accomplish EVAR is accomplished with skin infiltration with local anesthetic. MAC is provided by the anesthesiologist. Short-acting agents such as midazolam boluses, an opioid (eg, infusion of remifentanil), or infusion of a sedative-hypnotic agent such as propofol or dexmedetomidine may be administered to provide sedation, analgesia, and/or anxiolysis as necessary, but allow rapid recovery. Notably, progression from a "light," level of sedation to "deep," sedation (or unconsciousness) can occur suddenly, particularly in the older patient. Vigilant monitoring and constant communication with the patient is required to avoid airway obstruction, hypoxemia, or aspiration.

Although placement of older devices with a much larger diameter occasionally required supplementation by ilioinguinal and iliohypogastric nerve blocks [36], this is rarely necessary with the smaller, more flexible grafts that are currently used. Bilateral transversus abdominis plane blocks have also been successfully used as analgesia adjuvants in the past [34]. (See "Abdominal nerve block techniques", section on 'Ilioinguinal and iliohypogastric nerve block' and "Transversus abdominis plane (TAP) blocks procedure guide".)

Neuraxial anesthesia — Effective neuraxial anesthetic techniques include single-dose spinal, continuous spinal, or epidural anesthesia. The typical goal is to provide neuraxial anesthesia at dermatomal levels T6 through L3, lasting three to four hours [37]. If hypotension develops due to sympathetic blockade after a neuraxial block, this should be immediately treated to avoid insufficient myocardial or cerebral blood flow since many patients undergoing EVAR have concomitant coronary or cerebrovascular atherosclerotic disease (see 'Hemodynamic management' below). Short-acting agents providing a "light," level of sedation may be administered to supplement the neuraxial anesthetic, similar to MAC for patients who have local/regional anesthesia. (See 'Local/regional anesthesia' above.)

General anesthesia — For general anesthesia, anesthetic agents and dosing are selected with the primary goad of avoiding (or immediately treating) significant fluctuations in BP. (See 'Hemodynamic management' below.)

Induction – Induction is similar to that for patients undergoing open abdominal aortic aneurysm surgery or other patients with likely ischemic heart disease undergoing noncardiac surgery. (See "Anesthesia for open abdominal aortic surgery", section on 'Induction' and "Anesthesia for noncardiac surgery in patients with ischemic heart disease", section on 'Induction'.)

Maintenance – Goals during maintenance of anesthesia are to maintain hemodynamic stability while avoiding interference from anesthetic agents with any neuromonitoring techniques if these are planned. Maintenance of anesthesia can be achieved with a volatile anesthetic agent, a total intravenous (IV) anesthetic technique, or with a combination of volatile and IV agents. Details are discussed in separate topics. (See "Neuromonitoring in surgery and anesthesia", section on 'Anesthetic effects on neuromonitoring' and "Anesthesia for noncardiac surgery in patients with ischemic heart disease", section on 'Maintenance'.)

Emergence – Goals during emergence from general anesthesia are to maintain hemodynamic control and avoid wide swings in BP as anesthetic agents are discontinued and the trachea is extubated. Administration of a short-acting beta blocker (eg, esmolol) and/or vasodilator (eg, nicardipine, nitroglycerin, nitroprusside) is often necessary to blunt the transient sympathetic stimulation that occurs during arousal and extubation. (See 'Hemodynamic management' below.)

Fluid and blood management — Restoring and maintaining adequate intravascular volume status is accomplished with IV crystalloid (ie, normal saline or a balanced isotonic crystalloid solution) administered before, during, and continuing for several hours after contrast administration to reduce the risk of contrast-induced nephropathy (CIN). (See "Intraoperative fluid management", section on 'Crystalloid solutions'.)

If angiography with contrast has been performed shortly before urgent surgery, measures to avoid CIN include avoidance of intravascular volume depletion. Typically, for outpatients undergoing contrast angiography, 3 mL/kg of IV crystalloid solution is administered over one hour preprocedure, then 1 to 1.5 mL/kg/hour is administered during and for four to six hours after angiography. For inpatients, 1 mL/kg/hour is administered for 6 to 12 hours preprocedure, then for 6 to 12 hours during and after angiography. Normal saline or a balanced isotonic crystalloid solution is typically selected rather than sodium bicarbonate because bicarbonate provides no additional benefit to saline, needs to be compounded, and is more expensive [38]. (See "Prevention of contrast-associated acute kidney injury related to angiography", section on 'Fluid administration' and "Prevention of contrast-associated acute kidney injury related to angiography", section on 'Saline versus bicarbonate'.)

If angiography was not performed, the calculated fluid deficit is quickly replaced at the beginning of the procedure (see "Intraoperative fluid management", section on 'Hypovolemia'). The duration of administration of fluid should be directly proportional to the degree of renal impairment (ie, longer for individuals with more severe renal impairment). Mild hypervolemia (approximately 5 ml/kg ideal body weight positive fluid balance) may be helpful to avoid increases in serum creatinine in patients without congestive heart failure or ejection fraction <40 percent [39].

Similar to other surgical procedures, we transfuse autologous, salvaged, or allogeneic red blood cells when hemoglobin is <7 to 8 g/dL (approximately equivalent to a hematocrit ≤21 to 24 percent). We use a higher target of <9 to 10 g/dL in selected patients with increased risk of spinal cord malperfusion or if myocardial or spinal cord ischemia is detected [40]. (See 'Monitoring and management of spinal cord ischemia' below and "Intraoperative transfusion and administration of clotting factors", section on 'Red blood cells'.)

Hemodynamic management — Generally, we maintain systolic and mean arterial BP values within 20 percent of the patient's baseline, with a MAP of not less than 90 mmHg when there are concerns for spinal cord perfusion based on prior thoracic aortic replacement and/or data from ongoing SSEP monitoring [40]. Hypotension with systolic BP <90 mmHg or <40 percent below preoperative levels for ≥10 minutes is avoided, as this may contribute to development of postoperative renal insufficiency [41], or insufficient myocardial or cerebral blood flow in these patients who often have concomitant coronary or cerebrovascular atherosclerotic disease. We also avoid any hypertensive episodes which may cause aneurysm rupture. (See "Hemodynamic management during anesthesia in adults", section on 'Blood pressure targets' and "Anesthesia for noncardiac surgery in patients with ischemic heart disease", section on 'Prevention of ischemia'.) [42,43].

The anesthesiologist should have sympathomimetic, vasodilator, and short-acting beta blocker medications readily available throughout the perioperative period to rapidly treat hypotension or hypertension, or arrhythmias. Specifically, we suggest that bolus doses of the following drugs be immediately available: phenylephrine (eg, 100 mcg/mL, administered in 100 to 200 mcg boluses), ephedrine (eg, 5 to 10 mg/mL, administered in 5 to 20 mg boluses), vasopressin (eg, 1 unit/mL, administered in 1 unit boluses), nicardipine (eg, 100 mcg/mL, administered in 100 to 500 mcg boluses), labetalol (eg, 5 to 10 mg/mL, administered in 5 to 20 mg boluses), esmolol (10 mg, administered in 10 to 50 mg boluses), and atropine (0.4 mg/mL, administered as 0.2 to 0.4 mg boluses). In addition, we prepare infusion solutions of a vasopressor and a vasodilator that are immediately available to administer (eg, phenylephrine and nicardipine or nitroglycerin (table 4 and table 5)). (See "Intraoperative use of vasoactive agents", section on 'Vasopressor and positive inotropic agents' and "Intraoperative use of vasoactive agents", section on 'Antihypertensive agents'.)

Considerations during device deployment — At the time of device deployment, the anesthesiologist may be asked to lower mean arterial BP to decrease the risk of distal migration of the stent. This may be accomplished with administration of short-acting anesthetic agents such as propofol in 10 to 30 mg increments, or short-acting vasoactive agents such as esmolol 10 to 30 mg or nicardipine 100 to 200 mcg. Furthermore, ventilation is transiently stopped at the time of device deployment in anesthetized patient (or awake patients are asked to hold their breath).

Management of anticoagulation — Prior to insertion of the endovascular graft device, systemic anticoagulation is initiated, typically with an IV heparin dose of 5000 to 8000 units. The goal is an activated coagulation time (ACT) of 200 seconds or greater. After device deployment, anticoagulation is reversed and the ACT is rechecked.

After insertion of the graft, thrombus in the aortic aneurysm remains in contact with the general circulation due to back bleeding of the lumbar arteries and other aortic branches around or through the graft, and back into the aneurysm. This thrombus has the potential to induce consumption of the coagulation factors and platelets. However, studies have noted only mild perturbations in the coagulation pathway after EVAR (eg, a decrease in platelet count or an increase in fibrin degradation products), while no cases of disseminated intravascular coagulation have been reported in this setting [44,45]. (See "Complications of endovascular abdominal aortic repair", section on 'Endoleak'.)

Temperature management — Hypothermia is prevented by using convective warming devices (eg, forced air warmers) and administering warmed IV fluids. Management of hypothermia continues into the postoperative period as necessary. (See "Perioperative temperature management".)

Monitoring and management of spinal cord ischemia

Procedure-related risks

Abdominal EVAR – The risk of spinal cord ischemia in elective abdominal EVAR in patients without prior thoracic aortic aneurysm repair is estimated to be 0.3 percent [46]. Since there are risks with lumbar cerebrospinal fluid (CSF) drainage including epidural hematoma [47,48], the technique is rarely used in abdominal EVAR cases. Although the technique may be considered in patients with prior repair of aortic aneurysm in a different aortic location such as a large descending thoracic aneurysm [49], one study found no increased risk in patients having abdominal EVAR after prior thoracic EVAR [50].

Thoracic EVAR – Spinal cord ischemia is also rare in patients undergoing thoracic EVAR (<3 percent); this incidence is similar to risks incurred with CSF drain placement [51]. A 2011 literature review found only six case reports [52]. However, the extent of the aorta that is covered by endograft is considered since risk increases if the length of aortic coverage is >20 cm [53,54], as is prior repair of abdominal aortic aneurysm [55]. One study reported that patients undergoing thoracic EVAR after prior abdominal EVAR had an incidence of spinal cord ischemia in 14.3 percent [55]. Risk is greatest if the artery of Adamkiewicz was previously excluded since that artery supplies most of the flow to the lower one-third of the anterior spinal artery.

Specific management techniques — For patients with complex aortic aneurysms undergoing EVAR after prior thoracic aortic surgery (and thus increased risk of spinal cord malperfusion), the most common practices to prevent spinal cord ischemia include BP elevation to a MAP of not less than 90 mmHg in the perioperative period and ensuring a hemoglobin goal of not less than 10 g/dL; treatment of evidence of spinal cord ischemia also includes placement of a CSF drain (table 2) [40,56]. Details of monitoring and management are discussed separately. (See "Anesthesia for open descending thoracic aortic surgery", section on 'Neuromonitoring for spinal cord ischemia' and "Anesthesia for open descending thoracic aortic surgery", section on 'Cerebrospinal fluid (CSF) pressure monitoring'.)

POSTOPERATIVE ANESTHETIC CARE — After completion of the EVAR, the patient is transferred to the post-anesthesia care unit regardless of whether general anesthesia, neuraxial anesthesia, or intravenous (IV) sedation was employed, for recovery from sedation and monitoring for myocardial or spinal cord ischemia. Management in an intensive care unit (ICU) is appropriate for some patients (eg, high risk for cardiovascular, pulmonary, renal, bleeding, or spinal cord complications). (See "Endovascular repair of abdominal aortic aneurysm", section on 'Postoperative care' and "Complications of endovascular abdominal aortic repair".)

Notably, spinal cord ischemia and paraplegia can present hours or even several days after open aortic repair or EVAR (algorithm 1) [52]. In high-risk cases, a systematic approach may be employed that includes frequent neurologic assessment, arterial pressure augmentation, somatosensory evoked potential (SSEP) monitoring, cerebrospinal fluid (CSF) drainage if necessary to treat developing neurologic deficits, and imaging the spine using computed tomography or magnetic resonance imaging [40,56-58]. (See "Spinal cord infarction: Treatment and prognosis", section on 'Following aortic surgery or endovascular repair'.)

However, since spinal cord ischemia is rare after EVAR procedures (see 'Procedure-related risks' above), most clinicians choose to wait for neurologic deficits to develop, and then intervene with immediate placement of a CSF drain [40]. This approach balances the risk of placement of an intrathecal catheter for CSF drainage with the rarity of development of postoperative paraparesis or paraplegia [47]. In one institution, detection and treatment of spinal cord ischemia using this approach in patients undergoing EVAR for a descending thoracic aneurysm limited permanent neurologic deficit to 2.7 percent, although 6.6 percent of patients had evidence of postoperative spinal cord ischemia [58]. Although having a CSF drain already in place may improve chances for good neurologic outcome in patients with delayed spinal cord ischemia [59], prophylactic use of CSF drainage undergoing thoracic EVAR is associated with moderate risk and questionable benefit [54,60].

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Aortic and other peripheral aneurysms" and "Society guideline links: Aortic dissection and other acute aortic syndromes".)

SUMMARY AND RECOMMENDATIONS

Preanesthetic assessment – Most patients with thoracic and/or abdominal aortic aneurysm are older and have major cardiovascular and other comorbidities, as well as risk of contrast-induced nephropathy (CIN) if angiography was recent. (See 'Preanesthetic assessment' above.)

We obtain a preoperative electrocardiogram (ECG) as a useful baseline if the postoperative ECG is abnormal. We perform additional cardiac testing in selected patients with changes in cardiac symptoms and functional status.

We obtain a creatinine level in the immediate preoperative period to compare with previous measurements. In consultation with a nephrologist, we ensure that sufficient time is allowed between the last contrast dye load and the time of the currently planned procedure.

We continue chronically administered beta-blockers, statins, and antihypertensives in the perioperative period.

Monitoring considerations – In addition to standard monitoring (table 1), specialized monitoring includes:

Cardiovascular monitoring (See 'Cardiovascular monitoring' above.)

-Direct intra-arterial pressure monitoring is optimally established in the right arm for descending aortic surgery since the left innominate artery may be occluded if the stent covers the left subclavian artery.

-Transesophageal echocardiography (TEE), often used in thoracic aortic, emergency, or complex endovascular aortic repair (EVAR) procedures to evaluate aortic anatomy (eg, atherosclerotic lesions, thrombi, dissection), confirm correct positioning of grafts and stents, and detect endoleaks. Use of TEE requires general anesthesia.

Neuromonitoring – A surgical decision to use cerebrospinal fluid (CSF) drainage as a protective strategy to minimize spinal cord ischemia (table 2) necessitates spinal cord monitoring with somatosensory evoked potentials (SSEPs (figure 2)) and/or motor evoked potentials (MEPs) (figure 3). (See 'Neuromonitoring for spinal cord ischemia' above.)

Anesthetic choices – Thoracic or abdominal EVAR can be performed using local/regional anesthetic techniques together with monitored anesthesia care (MAC), neuraxial anesthesia, or general anesthesia (table 3). In all cases, the patient must remain immobile during positioning of modular graft components. (See 'Anesthetic goals' above.)

We suggest local/regional or neuraxial anesthesia for most EVAR procedures performed using routine surgical access to the aorta via the femoral or iliac arteries (Grade 2C). For less common procedures requiring retroperitoneal vascular access via a 3 to 5 inch lower flank incision extended down to directly expose the iliac artery, neuraxial or general anesthesia is typically necessary. General anesthesia may be selected for complex repairs that require extended duration to provide patient comfort and immobility. (See 'Anesthetic choices' above.)

Local/regional anesthesia – For local/regional anesthesia, skin infiltration with local anesthetic may be supplemented with short-acting agents such as midazolam boluses, an opioid (eg, infusion of remifentanil), or infusion of a sedative-hypnotic agent such as propofol or dexmedetomidine to provide sedation and/or analgesia as part of MAC. (See 'Local/regional anesthesia' above.)

Neuraxial anesthesia – Effective neuraxial anesthetic techniques include single-dose spinal, continuous spinal, or epidural anesthesia. Hypotension due to sympathetic blockade should be immediately treated. Supplemental sedation and/or analgesia with short-acting agents may be administered if needed. (See 'Neuraxial anesthesia' above.)

General anesthesia – For general anesthesia, anesthetic agents and dosing are selected with the primary goal of avoiding significant fluctuations in blood pressure (BP), as well as avoiding interference with neuromonitoring techniques (if used). (See 'General anesthesia' above.)

Fluid and blood management – Restoring and maintaining adequate intravascular volume status with intravenous (IV) crystalloid (ie, normal saline or a balanced isotonic crystalloid solution) administered before, during, and continuing for several hours after contrast administration reduces the risk of CIN. We transfuse red blood cells when hemoglobin is <7 to 8 g/dL, with a higher hemoglobin target of <9 to 10 g/dL in selected high-risk patients or if myocardial or spinal cord ischemia is detected. (See 'Fluid and blood management' above.)

Hemodynamic management – Generally, we maintain systolic and mean arterial BP values within 20 percent of the patient's baseline, with a mean arterial pressure (MAP) of not less than 90 mmHg (table 4). We also avoid any hypertensive episodes which may cause aneurysm rupture. At the time of device deployment, a lower MAP may be achieved with administration of short-acting anesthetic agents or short-acting vasoactive agents (table 5). (See 'Hemodynamic management' above.)

Anticoagulation management – Prior to insertion of the endovascular graft device, systemic anticoagulation is initiated, typically with an IV heparin dose of 5000 to 8000 units. The goal is an activated coagulation time (ACT) of 200 seconds or greater. After device deployment, anticoagulation is reversed and the ACT is rechecked. (See 'Management of anticoagulation' above.)

Management of spinal cord ischemia – Perioperative rescue maneuvers for evidence of spinal cord ischemia include BP elevation to a MAP of not less than 90 mmHg, ensuring a hemoglobin goal of not less than 10 mg/dL, and placement of a CSF drain (table 2 and algorithm 1). (See 'Monitoring and management of spinal cord ischemia' above.)

Postoperative considerations – Transfer to the post-anesthesia care unit (or intensive care unit [ICU]) is necessary regardless of whether general anesthesia, neuraxial anesthesia, or IV sedation was employed, for recovery from sedation and monitoring for myocardial or spinal cord ischemia. (See 'Postoperative anesthetic care' above.)

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Topic 93506 Version 35.0

References

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