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Patients presenting for carotid endarterectomy (CEA)
are often elderly, have advanced cerebrovascular
disease, and frequently have significant coexisting
diseases involving other organ systems. Anesthetic
management of these patients requires both an
understanding of the physiologic stress imposed by
the surgical procedure (disruption of the major
cerebral hemispheric blood supply) and an
appreciation of the physiologic constraints imposed
by the coexisting diseases.
I. Guidelines for
Several prospective, randomized studies have
reported superior outcome for medically stable
patients who have symptomatic, high-grade carotid
stenoses (70% to 99%) after CEA combined with best
medical therapy compared to medical treatment alone.
On the basis of these studies, both the American
Heart Association and the Canadian Neurosurgical
Society have formulated guidelines for performing
CEA (Table -1).
Subgroup analyses of the results of these
multicenter trials have expanded the selection
criteria for patients likely to benefit from CEA to
include older patients and those who have complex
carotid disease (e.g., tandem
extracranial-intracranial stenoses). As a result,
anesthesiologists can expect to care more frequently
for older patients and those at increased risk for
Endovascular treatment for carotid stenosis ”carotid
angioplasty and stenting (CAS)” has been developed
over the past several years. Although CAS are
increasingly used in clinical practice, the utility
and durability are still undergoing clinical trials
which will better define indications.
CEA remains the preferred surgical intervention for
the prevention of stroke among patients who have
extracranial cerebrovascular disease.
Cerebral blood flow (CBF)
The brain is highly active metabolically but is
essentially devoid of oxygen and glucose reserves,
making it dependent on the continuous delivery of
oxygen and glucose by cerebral circulation.
Table -1. Surgery
guidelines for carotid endarterectomy
Appropriate candidate for CEA
Symptomatic 70-99% stenosis with
||Stable medical and
Uncertain candidate for CEAa
Symptomatic <70% stenosis withb
||Stable medical and
Asymptomatic >60% stenosis with
Inappropriate candidate for CEA
Asymptomatic <60% stenosis
Symptomatic or asymptomatic with
stenoses more severe than the extracranial
diabetes mellitus, hypertension, congestive
heart failure, or unstable angina pectoris
||A major neurologic
deficit or decreased level of consciousness
The percentage stenosis
should be defined by cerebral angiography
and the NASCET method. The surgeon's rate of
surgical complications (stroke or death)
should be <6% for CEA in cases of
symptomatic stenoses (appropriate or
uncertain candidates), and <3% in cases of
asymptomatic stenoses (uncertain
aGuidelines uncertain =
insufficient evidence to support a
bGuideline for symptomatic
<70% stenosis expected to be clarified this
year with publication of NASCET results for
this group of patients.
TIA, transient ischemic attack; CEA, carotid
endarterectomy; NASCET, North American
Symptomatic Carotid Endarterectomy Trial.
CBF is provided by the internal carotid arteries
(approximately 80%) and the vertebral arteries
(approximately 20%), which anastomose at the base of
the brain to form the circle of Willis.
Patients who have advanced occlusive cerebrovascular
disease may be dependent on other collateral
channels to maintain adequate CBF.
Normally, CBF is autoregulated to match the brain's
metabolic requirements and maintain normal neuronal
CBF is related to cerebral perfusion pressure (CPP)
and cerebrovascular resistance (CVR) according to
the equation CBF = CPP/CVR.
The following factors affect CBF:
1. CPP equals mean arterial blood pressure (MAP)
minus intracranial pressure or central venous
pressure, whichever is higher.
2. CVR is a function of blood viscosity and the
diameter of the cerebral resistance vessels.
Optimization of CBF during CEA is hampered by the
fact that the only factors readily amenable to
intraoperative manipulation are arterial blood
pressure and arterial carbon dioxide tension (Paco2),
which impact on CPP and CVR, respectively.
Carbon dioxide tension Paco2
Within the range of Paco2 from 20 to 80
mm Hg, CBF changes by 1 to 2 mL/100 g/minute for
every 1 mm Hg change in Paco2.
The most common approach to ventilatory management
during CEA is to maintain normocapnia. This is
achieved by ventilation to a Paco2 that
produces a normal pH in the absence of coexisting
CBF remains remarkably constant within the range of
MAP from 50 to 150 mm Hg. Beyond this range, the
limit of vasomotor activity is exceeded and CBF
directly depends on changes in CPP.
In patients who have preexisting chronic
hypertension, both the upper and lower limits of
autoregulation are shifted to higher pressures.
In patients who have cerebrovascular disease, the
CBF response to changes in Paco2 during
carotid cross-clamping is impaired. Under these
conditions, improvement in CBF is likely to depend
largely on increases in CPP, emphasizing the
relatively greater importance of blood pressure
control during CEA surgery.
During CEA, blood pressure should be maintained
within the normal preoperative range. Mild increases
in systolic blood pressure of up to 20% above normal
at the time of cross-clamping are acceptable, but
hypotension and severe hypertension should be
The patient's state of health is determined from the
medical history, pertinent physical examination, and
Coexisting diseases are assessed and optimized.
Common coexisting diseases include coronary artery
disease, arterial hypertension, peripheral vascular
disease, chronic obstructive pulmonary disease,
diabetes mellitus, and renal insufficiency.
For patients who have diabetes, perioperative blood
glucose should be carefully managed to avoid both
hypo- and hyperglycemia. Current evidence suggests
that hyperglycemia adversely affects outcome after
temporary focal or global cerebral ischemia.
Cardiac complications are a major source of
mortality after CEA. Preoperative factors reported
to correlate with increased perioperative cardiac
morbidity include poorly controlled hypertension,
congestive heart failure, and recent myocardial
Cerebral angiograms should also be reviewed to
identify patients at increased risk from the
presence of significant contralateral carotid artery
disease or poor collateral circulation.
A risk stratification scheme for perioperative
complications has been proposed for patients
undergoing CEA (Table -2).
CEA can be safely performed under
general anesthesia, regional anesthesia, or local
anesthetic infiltration. Experienced centers report
similar morbidity and mortality, and available
evidence is insufficient to establish the definitive
superiority of any one technique.
Superficial and deep cervical plexus blocks are the
most commonly used regional anesthetic techniques
1. A superficial cervical plexus block is performed
by injecting a local anesthetic subcutaneously along
the posterior border of the sternocleidomastoid
muscle where the cutaneous branches of the plexus
fan out to innervate the skin of the lateral neck.
2. A deep cervical plexus block is a paravertebral
block of the C2-4 nerve roots. This technique
involves injecting local anesthetic at the vertebral
foramina (transverse processes) of the C2-4
vertebrae to block the neck muscles, fascia, and
greater occipital nerve.
3. Many regional anesthesia textbooks describe the
techniques in detail and should be reviewed before
performing the blocks.
Intraoperative monitors include the following:
1. Intra-arterial cannula for blood pressure
2. Continuous electrocardiogram (ECG)
3. Pulse oximetry
4. Capnography sampled via nasal prongs for
monitoring respiratory rate
Supplemental oxygen should be provided through a
mask or nasal prongs positioned to avoid the site of
Carefully titrated sedation using small, repeated,
intravenous doses of fentanyl, 10 to 25 mcg, and/or
midazolam, 0.5 to 2 mg, should render the patient
comfortable and cooperative during the operation.
Propofol is a reasonable alternative administered as
intermittent intravenous bolus doses, 0.3 to 0.5
mg/kg, or as a low-dose continuous infusion, 10-50
mg/kg/hr. The potential advantages of using
dexmedetomidine, an alpha2-agonist, include
supplemental sedation, modest analgesia, minimal
respiratory depression, and preserved cognitive
function. Careful attention is necessary during
administration to avoid hemodynamic instability
(i.e., transient hypertension, hypotension, and
Table-2. Preoperative risk
stratification for patients undergoing CEA
Total Morbidity and Mortality (%)
Neurologically stable, no major medical or
Neurologically stable, significant
angiographic risk, no major medical risk
Neurologically stable, major medical risk, ±
major angiographic risk
Neurologically unstable, ± major medical or
Type of Risk
Myocardial infarction (<6 mo)
Congestive heart failure
hypertension (>180/110 mm Hg)
obstructive pulmonary disease
deficit (<24 hr)
Frequent daily TIA(s)
Multiple cerebral infarcts
Contralateral ICA occlusion
Proximal or distal plaque extension
Presence of soft thrombus
TIA, transient ischemic
attack; ICA, internal carotid artery.
Equipment should be immediately available to convert
to a general anesthetic if intraoperative conditions
Advantages of regional
anesthesia include the following:
1. Superior neurologic monitoring associated with an
2. Potential to minimize interventions such as shunt
insertion based on the presence or absence of
neurologic symptoms at cross-clamping
3. Less expensive
4. Reports of more rapid recovery and shorter
Disadvantages of regional
anesthesia include the following:
1. Requirement of an operating room staff committed
to working with patients under regional anesthesia,
which necessitates patience, gentle technique, and
reinforcement of the block as needed
2. Lack of airway and ventilatory control
3. Potential need to deal with complications in an
awake patient: stroke or transient cerebral
ischemia, cross-clamp intolerance, seizure, airway
obstruction, hypoventilation, confusion, agitation,
4. Complications associated with cervical plexus
blocks: local anesthetic toxicity, inadvertent
injection into either the subarachnoid space or the
vertebral artery, and phrenic or recurrent laryngeal
General anesthesia represents the most common
anesthetic technique for CEA.
Intraoperative monitors are the same as for regional
1. Monitoring central venous and pulmonary artery
pressure is used infrequently. A central venous
catheter facilitates the management of
intraoperative fluid administration and provides
central access for drug administration or
resuscitation. A pulmonary artery catheter may be
helpful in patients who have high-risk
cardiovascular disease (e.g., unstable angina, poor
left ventricular function, recent myocardial
infarction). Care should be exercised to avoid
carotid puncture when inserting these catheters into
the jugular vein.
The key consideration during the induction of
anesthesia is the maintenance of stable hemodynamic
conditions during intubation, positioning, and
Thiopental, midazolam, propofol, and etomidate are
all appropriate induction drugs and should be
supplemented with opioid.
All of the nondepolarizing neuromuscular-blocking
drugs facilitate tracheal intubation.
Succinylcholine is a reasonable alternative.
However, its use is contraindicated in patients who
have had a recent paretic cerebral infarct.
General anesthesia is usually maintained with a
combination of volatile anesthetic (typically
isoflurane, desflurane, or sevoflurane) and opioid.
Neuromuscular blockade is maintained throughout the
procedure. Propofol infusion is a reasonable
alternative. The use of remifentanil, an
ultrashort-acting opioid, has also become popular as
an adjunct to general anesthesia for CEA. Its short
duration of action facilitates titration of
anesthesia and promotes early emergence,
particularly when used in combination with
short-acting volatile anesthetic drugs such as
desflurane and sevoflurane.
The administration of nitrous oxide is controversial
as a result of reports of potential adverse effects
on cerebral metabolism and increased risk of
Blood pressure is maintained at preoperative levels.
Small bolus doses of vasopressor (e.g.,
phenylephrine, 40 to 60 mcg, or ephedrine, 5 to 7.5
mg) can be administered to support blood pressure if
necessary. Some anesthesiologists use infusions of
phenylephrine to maintain or increase blood
pressure, especially during cross-clamping. However,
evidence suggests that this practice may be
associated with an increased risk of myocardial
Ventilation is adjusted to maintain normocapnia.
Advantages of general
anesthesia include the following:
1. Is potentially more comfortable for patients and
operating room staff
2. Facilitates intraoperative control of
ventilation, airway, and sympathetic responses
3. Facilitates management of complications (e.g.,
cross-clamp intolerance and transient cerebral
ischemia) through the use of induced hypertension or
pharmacologic suppression of electroencephalographic
4. Reduces the need for expedience in performing
surgery because patient tolerance is not a factor
5. May provide some cerebral protection
Disadvantages of general
anesthesia include the following:
1. There is the need for an alternate method for
monitoring cerebral function.
2. In the absence of a completely reliable cerebral
function monitor, it is possible that some
remediable complications will not be detected before
the occurrence of irreversible neuronal injury
(e.g., cross-clamp intolerance, kink in carotid
3. Prolonged emergence might confuse postoperative
4. It is more expensive.
Before cross-clamping, heparin, 75 to 100 U/kg, is
Carotid cross-clamping is often associated with an
increase in blood pressure of up to approximately
20% above preoperative levels. Excessive increases
can reflect cerebral ischemia. This should be
considered before controlling the increase in blood
1. The purpose of neurologic monitoring is to
identify patients at risk for adverse neurologic
outcome owing to the development of cerebral
ischemia, particularly during carotid
2. An awake patient represents the least expensive
and most sensitive neurologic function monitoring
3. Because patients are not awake during general
anesthesia, various other techniques are available
to monitor neurologic function. EEG, carotid stump
pressure measurements, transcranial Doppler (TCD),
cerebral oximetry, and CBF measurements are used
most commonly, either individually or in combination
(i.e., EEG and TCD). The use of SEP with carotid
protocol is helpful in detecting early shifts in
latency and amplitude.
4. Each of these techniques can identify significant
reductions in cerebral perfusion. However,
controversy continues regarding the reliability of
these techniques, individually or in combination, to
predict outcome accurately.
5. Interventions available but unproven in clinical
trials in response to evidence of cerebral ischemia
include the following:
(1) Increasing CPP by administering systemic
vasopressor drugs (e.g., phenylephrine)
(2) Reducing the risk of ischemia by pharmacologic
suppression of cerebral metabolic requirements
(e.g., thiopental, propofol)
(3) Restoring internal carotid artery blood flow by
inserting a carotid shunt
Emergence should be designed to avoid excessive
coughing or straining and surges in systemic blood
pressure, which might open the freshly closed
Heparin is usually partially reversed at the time of
Many surgeons prefer patients to be awake and their
tracheas extubated at the conclusion of the
procedure to facilitate neurologic examination in
the early postoperative period.
The intra-arterial cannula is maintained during the
initial postoperative period to permit continuous
blood pressure monitoring.
All patients receive supplemental oxygen
postoperatively. Pulse oximetry monitors the
adequacy of oxygenation. Bilateral CEA is associated
with the abolition of the ventilatory and
cardiovascular responses to hypoxemia. Providing
supplemental oxygen and closely monitoring
ventilatory status are particularly important in
Postoperative hemodynamic instability occurs in >40%
of patients after CEA and is postulated to be
related to carotid baroreceptor dysfunction.
CEA performed using a carotid sinus nerve-sparing
technique is associated with a higher incidence of
postoperative hypotension, most likely because of
increased exposure of the carotid sinus after
removal of the atheromatous plaque. Associated with
a marked decrease in systemic vascular resistance,
hypotension can be prevented or treated with local
anesthetic blockade of the carotid sinus nerve, the
administration of intravenous fluid or, if
necessary, the administration of vasopressor drugs
such as phenylephrine.
Hypertension after CEA is less well understood and
has been reported to be more common in patients who
have preoperative hypertension and in patients who
undergo CEA with denervation of the carotid sinus.
Mild increases in postoperative blood pressure of up
to 20% above preoperative levels are acceptable, but
marked increases are treated with antihypertensive
Other causes of hemodynamic instability after CEA
include myocardial ischemia or infarction,
arrhythmias such as atrial fibrillation, hypoxia,
hypercarbia, pneumothorax, pain, confusion, and
distention of the urinary bladder.
In most hospitals, patients are discharged from the
postanesthetic care unit to an environment in which
intensive neurologic and cardiovascular monitoring
is available (e.g., intensive care unit or
neurosurgical observation unit).
Major postoperative complications
after CEA include stroke, myocardial infarction, and
Approximately two-thirds of strokes associated with
CEA occur in the postoperative period. Most of these
appear to be related to surgical factors resulting
in either carotid occlusion (e.g., thrombosis,
intimal flap) or emboli originating at the surgical
Intraoperative strokes represent approximately
one-third of strokes that occur in the perioperative
period. Most intraoperative strokes happen at the
time of carotid cross-clamping and are either
technical (i.e., shunt malfunction) or embolic,
rather than hemodynamic, in origin.
Monitoring intraoperative neurophysiologic function
is directed to identifying a relatively small group
of patients who develop hemodynamically induced
ischemia, which is potentially reversible with early
recognition and intervention.
It is likely that, beyond using current anesthetic
and monitoring techniques and meticulously
manipulating hemodynamic and ventilatory parameters,
the anesthesiologist has little ability, at present,
to affect the incidence of stroke and the outcome
Myocardial infarction represents the major cause of
mortality after CEA. The incidence of fatal
postoperative myocardial infarction is 0.5% to 4%,
and the proportion of total perioperative mortality
(within 30 days of operation) attributed to cardiac
causes is estimated to be at least 40%.
On the basis of the high incidence of coronary
artery disease among patients undergoing CEA,
routine coronary angiography has been advocated.
However, little evidence supports the premise that
routine preoperative coronary angiography improves
cardiac outcome after CEA. It seems more reasonable
to assume that all patients presenting for CEA have
atherosclerotic disease involving the coronary
arteries and to gauge perioperative risk in relation
to the patient's functional status.
High-risk patients including those who have unstable
angina, recent myocardial infarction, or recent
heart failure may be considered more appropriate
candidates for CEA staged or combined with a
coronary artery bypass graft (CABG) procedure.
Existing evidence is insufficient to formulate firm
recommendations regarding the staging of CEA with
CABG surgery. The risk of stroke is similar if CEA
precedes or is combined with CABG. This risk is
lower than when CABG is performed before CEA.
However, the incidence of myocardial infarction and
death is higher when CEA precedes CABG. Pending
results from well-designed prospective studies,
recommendations from the Canadian Neurosurgical
Society suggest that CEA should precede CABG if
possible. When the patient's cardiac condition is
too unstable to permit a prior CEA, combined surgery
should be considered.
Stroke and myocardial infarction represent the major
causes of perioperative mortality associated with
Patient selection, the experience of the surgeon,
and the institution where the surgery is performed
affect operative risk.
On the basis of these considerations, the American
Heart Association Stroke Council has recommended
that the combined risk for either death or stroke
associated with CEA should not exceed 3% for
asymptomatic patients, 5% for symptomatic (transient
cerebral ischemia) patients, 7% for patients who
have suffered a previous stroke, and 10% for
patients undergoing reoperation for recurrent
An increase in CBF occurs frequently after CEA.
Typically the magnitude of this increase is
relatively small (<35%). However, in severe cases,
increases in CBF can exceed 200% of preoperative
levels and are associated with an increase in
morbidity and mortality.
Clinical features of this hyperperfusion syndrome
include headache (usually unilateral), face and eye
pain, cerebral edema, seizures, and intracerebral
Patients at greatest risk include those who already
have a preoperative reduction in hemispheric CBF
owing to bilateral high-grade carotid stenoses,
unilateral high-grade carotid stenosis with poor
collateral cross-flow, or unilateral carotid
occlusion with contralateral high-grade stenosis.
The syndrome is thought to result from restoration
of perfusion to an area of the brain that has lost
its ability to autoregulate as the result of a
chronic decrease in CBF. The restoration of CBF
leads to a state of hyperperfusion that persists
until autoregulation is reestablished, usually over
a period of days.
Patients at risk for this syndrome should be
monitored closely in the perioperative period, and
blood pressure should be meticulously controlled.
Other complications associated with CEA include
hematoma formation and cranial nerve palsies.
Hematoma formation can lead to airway compromise
owing to mass effect, which might require opening
the wound acutely to reestablish the airway before
emergent reoperation. Cranial nerve palsies are
typically temporary and could manifest themselves as
vocal cord paralysis and altered gag reflex.
Neuroradiology-Carotid Angioplastic Stenting
Carotid angioplasty with or without the use of
endovascular stenting is a relatively new technique
for the treatment of carotid stenosis. Its safety
and efficacy relative to CEA, particularly with
respect to perioperative and long-term neurologic
outcome, are currently the subject of several
CAS techniques have been progressively modified as
new technologies become available to include
self-expanding stents and cerebral-protection
Advocates suggest that the technique offers
advantages in patients who have high-risk medical
conditions and those who have surgically
inaccessible carotid disease (e.g., previous neck
irradiation, intracranial stenosis).
CAS can be performed under either general anesthesia
or sedation. No evidence is available to recommend
one technique over the other.
Advantages of general anesthesia include the
(1) Provides better airway control
(2) Provides better quality of the images
(3) Facilitates control of blood pressure, Paco2
(4) Facilitates treatment of neurologic emergencies
Advantages of an awake, sedated patient include the
(1) Awake cerebral function monitoring
(2) Identification of intraoperative complications
(3) Rapid emergence and postoperative neurologic
(4) Less expensive
Preoperative assessment is the same as for patients
scheduled for CEA.
For patients undergoing CAS, factors affecting the
selection of the awake (sedation) technique include
the presence of gastroesophageal reflux and evidence
Monitoring should be consistent with operating room
standards including intra-arterial blood pressure
measurement, pulse oximetry, ECG, and capnography.
Central venous access is optional depending on the
patient's medical condition.
Hemodynamic changes typically associated with
carotid distension at the time of angioplasty or
stent expansion, especially bradycardia and
asystole, can be profound. A small dose of atropine
or glycopyrrolate is often administered to attenuate
this response. The immediate availability of
external pacing equipment is prudent.
Here, we are focusing on the
anesthetic management of patients undergoing CEA. It
also includes a brief overview of the current status
of CAS. Physiologic concepts that form the basis for
current recommendations regarding the choice of
anesthetic technique, drugs, monitoring, and
hemodynamic and ventilatory management are
discussed. Newer anesthetic drugs facilitate the
titration of anesthesia in relation to the patient's
responses to changing intraoperative conditions and
promote rapid emergence and early assessment after
CEA. Expanded criteria defining appropriate
candidates for CEA suggest that the anesthesiologist
will increasingly be called upon to care for
patients who are older and present with significant
complex needs. The management of coexisting disease,
particularly the risk of cardiac complications,
continues to represent important perioperative
challenges for the anesthesiologist.