Many patients with carotid artery
atherosclerosis have significant. medical risk factors. These include
symptomatic coronary artery disease, myocardial infarction within 6
months, severe peripheral arterial disease, rheumatic heart disease,
congestive heart failure, severe hypertension (blood pressure> 180/110
mmHg), and chronic obstructive pulmonary disease. Other factors to
consider are diabetes, hyperlipidemia, and obesity. Previous
publications have documented that the operative risks are higher in
certain groups of patients with significant medical risk factors.
In patients without significant risk factors, the combined operative
morbidity and mortality is 1 to 2 percent. The major medical risk
relates to cardiac disease, and when this is present, the operative risk
is significantly higher.
Whenever there is a concern about the
patient's cardiac status, a cardiologist is called for consultation.
Often a thallium-persantin exercise tolerance test will be performed;
evidence of significant myocardial ischemia represents a relative
contraindication to surgery. In some cases, coronary angiography may be
recommended, and adverse findings may suggest monitoring with a
pulmonary artery catheter or even deferral of endarterectomy.
Occasionally, severe symptomatic coronary and carotid occlusive disease
may warrant a combined coronary artery bypass and carotid
endarterectomy.
Many patients will be on several drugs for
treatment of the factors noted above. In general these drugs are
continued. Patients receiving diuretic medication should have the serum
potassium value checked prior to operation, and any deficiency should be
treated. It is important that patients with severe hypertension be
treated because the incidence of postoperative hypertension and
morbidity is higher in this group. This is particularly true for those
patients who have an associated cerebral infarction and are at risk to
develop a cerebral hemorrhage.
Other indications for intraoperative
monitoring with a pulmonary artery catheter include left ventricular
failure, a recent myocardial infarction, severe mitral valvular
disease, and persistent angina after a coronary artery bypass. Patients
with symptomatic heart block undergo placement of a temporary
intravenous pacer.
Carotid Endarterectomy
Anaesthetic Management
Preoperative medication is kept to a minimum
because of the fragile cardiovascular state of many of these patients.
Preferable, general endotracheal anaesthesia. This technique provides good
airway control, maintenance of normal arterial blood gases, maximum
patient comfort, optimal surgical exposure, and some protection against
cerebral ischemia.
On a few occasions,
carotid endarterectomy is undertaken with regional block in patients with a strong
medical contraindication to general endotracheal anaesthesia (severe
pulmonary or cardiac failure). This can be done successfully, especially
in a cooperative patient, but the precision of surgery is reduced,
especially when ischemia leads to movement in an agitated patient.
A radial intra-arterial cannula is inserted
percutaneously for direct blood pressure recording and for blood gas
measurement. The Paco2 level is kept between 30 and 39 mmHg. If there is
any indication of low blood volume or hypotension, central venous
pressure (CVP) is monitored, and the patient is given fluid or colloid
to raise the CVP to 8 to 10 cmH2O. A vasopressor intravenous (IV)
infusion is prepared, usually with 10 mg of phenylephrine hydrochloride in 250 ml of
saline, and administered through a paediatric microdrip set as needed to
maintain an adequate blood pressure.
Brain Protection and Monitoring
The best method of maintaining adequate
cerebral circulation during the operation is to combine the benefits of
general anaesthesia with the maintenance of adequate blood volume and a
normal or slightly elevated arterial pressure. At the time of carotid
occlusion for carotid endarterectomy, the arterial pressure is elevated
to an average systolic level of 170 mmHg if there is no cardiac
contraindication.
The most effective method of monitoring the
intracranial circulation during the time of vascular occlusion for the
endarterectomy is continuous EEG recording with a full set of leads from
both sides of the head. A high degree of correlation has been
found between CBF measurements during carotid occlusion and changes in
the EEG. If a significant EEG abnormality occurs, with severe slowing
or loss of amplitude, a shunt should be placed promptly.
The question of whether a temporary shunt is
indicated during carotid endarterectomy has been the subject of many
articles. Some surgeons routinely use a shunt for cerebral protection.
Others never use a shunt, and some use a shunt selectively when
monitoring indicates a need for it. The use of a shunt carries
with it a possible risk of embolization and of injury to the intima,
although rarely seen, and it does make the technical removal
of the distal end of the plaque in the ICA a little more difficult.
Everything should be done to reduce the morbidity of the operation to as
low a level as possible. Every patient should be monitored. In only a
small percentage of patients will a shunt be needed (about 10 percent in
some series), but when it is indicated, it should be used. In some
patients, the surgeon will know preoperatively that a shunt will be
needed. These include patients in whom the vertebrobasilar circulation
depends on the carotid artery or in whom there are multiple occlusions
of major extracranial vessels.
Operative Technique
The
patient is placed in the supine position with a thyroid bag inflated
under the shoulders. The head is extended slightly, placed on a firm
head holder, and turned away from the side of the operation. The
opposite calf (if nonischemic) is prepared and draped for possible saphenous vein harvesting. The entire operation is done using a
headlight and magnifying loupes, with use of microsurgical instruments
for improved precision of plaque removal and arteriotomy closure. We
prefer loupes and a headlight for greater mobility and an improved line
of sight up the internal and external carotid arteries, especially with
a high-lying bifurcation and plaque.
Some surgeons have recommended the use of
the operating microscope for carotid endarterectomy. This may prove to be especially valuable for more
proximal lesions in which the oblique upward line of sight is not
important. Whether loupes or the microscope are employed, meticulous
endarterectomy and closure are crucial.
The incision is made along the lower
anterior border of the sternocliedomastoid muscle and just below the level of
the angle of the jaw and should be curved over the muscle posteriorly
and superiorly toward the mastoid process. If necessary,
this incision will allow maximum exposure to the base of the skull and
helps avoid retraction on the lower branch of the facial nerve near the
angle of the jaw.
After the initial incision and throughout
the exposure, careful attention is paid to meticulous haemostasis. This
is done to permit nonreversal of intraoperative heparinization and
postoperative continuation of heparinization, in most cases. To avoid
unwanted bleeding, bipolar cauterization of all bleeders, even to the
most minute, is recommended.
After the skin incision is made, the
platysma is incised. The external jugular vein is ligated, small
transverse cervical nerves divided, and the great auricular nerve
identified and spared at the upper end of the exposure. Deep dissection
is continued along the anterior border of the sternocliedomastoid muscle.
Self-retaining retractors are used to aid the exposure. The medial
blades must be kept on the subcutaneous tissue and platysma. If they are
placed too deeply against the paratracheal muscles, there may be
tracheal and nerve injury.
The internal jugular vein is identified just
medial and deep to the sternocliedomastoid muscle. The dissection then extends
along the medial border of the internal jugular vein; medial draining
branches are ligated as necessary. The descendens hypoglossal nerve is
often seen in the tissue just medial to the internal jugular vein and
overlying the CCA. This nerve is reflected medially.
By opening the carotid sheath, the CCA is
exposed medial to the internal jugular vein in the lower part of the
incision. A vascular loop is placed around this vessel, which maintains
its exposure and facilitates the further dissection. On rare occasions
the vagus nerve lies anteriorly on the CCA, and one must be alert for
this possibility.
The dissection is then extended superiorly
along the medial border of the internal jugular vein. The descendens
hypoglossi is kept medially and leads one to the hypoglossal nerve,
which may swing low into the neck across the carotid bifurcation or lie
high beneath the edge of the posterior belly of the digastric muscle.
Sometimes it lies just beneath the common facial vein and may be
adherent to this vessel. In some patients, nerve branches will come
around the lateral side of the CCA to enter the descendens hypoglossi.
Usually these branches are from the cervical plexus, but on rare
occasions they seem to come from the vagus nerve. Vagal branches are
preserved; they may be laryngeal. The descendens hypoglossi may be
sacrificed for better exposure, without noticeable loss of function.
This branch may be confirmed when bipolar stimulation causes contraction
of the strap muscles (this is possible only when one or two twitches are
evident on twitch monitoring). To give adequate exposure it may be
necessary to remove a group of lymph nodes that are commonly present
over the region of the carotid bifurcation.
When the carotid bifurcation is exposed, the
region of the carotid sinus is blocked with lidocaine hydrochloride to avoid a carotid sinus reflex bradycardia and
hypotension. Care is taken to leave the region of the distal common
carotid artery, carotid bifurcation, and proximal ICA adherent to the
posterior tissue. This avoids undue manipulation of the area, reducing
the possibility of dislodging an embolus, lessening the chance of
carotid sinus stimulation, and avoiding possible injury to the superior
laryngeal nerve.
The superior thyroid artery is identified on
the medial wall of the distal CCA or proximal ECA and a mini loop is
placed around it. The ECA is exposed to the level of the first major
branching of this vessel, and a maxiloop is placed at this point. If the
arteriogram shows an ascending pharyngeal artery coming off the region
of the bifurcation, this will have to be exposed and controlled separately.
The distal ICA is carefully exposed, staying
in the tissue plane between the hypoglossal nerve or descendens
hypoglossi medially and the internal jugular vein laterally. If one follows these guidelines, the distal ICA can be nicely
exposed. As the hypoglossal nerve swings medially, an arterial branch
often comes across the inner side of the curve of the nerve and passes
posteriorly. This fairly constant sternocliedomastoid artery, often
accompanied by a vein, is ligated. The hypoglossal nerve can, if
necessary, be reflected gently medially with a 4-0 suture through the transected descendens hypoglossi stump. If the carotid bifurcation is
located high in the neck, dissection is carried along the medial border
of the internal jugular vein and beneath the parotid gland. Up to 2 cm
of distal ICA exposure can be obtained by dissection of the posterior
belly of the digastric muscle, with firm retraction by a Cushing
retractor attached to the drapes by elastics and an Allis clamp. (The drapes are clamped with towel
clips to an IV pole which is stabilized by sand bags under its wheels.)
Subluxation of the jaw by wiring of the teeth can give an additional I
to 2 cm of distal exposure in selected cases. It may be necessary to
retract the posterior belly of the digastric muscle. On occasion the
occipital artery must be divided to free the hypoglossal nerve in order
to expose the distal ICA. The exposure of the distal ICA is carried to a
point at least 1 cm above the distal end of the plaque. In the majority
of cases the atheromatous plaque extends several millimetres further up
the posterior wall of the ICA than it does on the anterior wall. Great
care is taken in exposing this vessel to avoid any undue pressure or
manipulation of the artery. The vagus nerve may be closely adherent to
the posterior wall of the artery; occasionally it will be lateral or
superficial to the artery. It must be carefully dissected free before
placing the loop around the vessel. Pump tourniquets are placed on the
loops on the common and ICAs to use in case a shunt is needed.
With a marking pen. the proposed arteriotomy
is marked on the common and ICAs. The line is smooth and stays lateral.
away from the bifurcation. Marking in this way avoids zigzag cuts if
the arteriotomy is extended later on. A mark is made for a possible
external carotid arteriotomy. Transverse hash marks are made at the
expected distal end and distalmost possible end of the arteriotomy, and
the external diameters are measured.
If the distal artery is very small «4 mm in
diameter). or if there is a tendency to kink (or if severe irregularity
of the wall is disclosed after endarterectomy). we believe there is a
higher likelihood of thrombosis, which warrants selective placement of
a saphenous patch graft. Therefore, in case of a kinked or very small
distal ICA, it is preferable next harvest the saphenous vein at the ankle.
An incision is made
longitudinally about 1 cm anterior and 1 cm proximal to the medial malleolus. After the saphenous
vein is identified, the incision is carried proximally at least 10 cm.
Haemostasis is obtained and Weitlaner retractors are placed. The vein is
marked with a marking pen. Making every effort to avoid trauma to the
vein, the surgeon opens the adventitia and dissects beneath the distal
vein, placing a miniloop around it. By gently lifting the vein,
attachments are put on stretch and divided sharply. Two or three large
side branches are ligated with 4-0 silk and divided; small branches are
coagulated with bipolar current. Finally the vessel is ligated distally
and proximally, and excised. It is immediately irrigated gently (from
distally) with heparinized saline. With a Potts scissors, the vein is
opened along the longitudinal marking and placed in a bath of
heparinized saline. The wound is closed with interrupted 3-0 coated Vicryl in the subcutaneous tissue and running 3-0 nylon in the skin.
The
patient is given an IV bolus of 5000 to 7000 units of heparin. The blood
pressure is raised to at least 170 mmHg systolic, if there is no cardiac
contraindication.
The common carotid artery is then occluded
with an appropriate vascular clamp (usually an angled Fogarty
hydro-grip), care being taken to avoid injury to the underlying vagus
nerve. We prefer to use Sugita temporary aneurysm clips to occlude the
other arteries, but on occasion a large ICA or ECA will require the use
of a small bulldog clamp. Care must also be taken to avoid injury to the
vagus nerve at this point because it lies in the tissue adjacent to the
ICA. The clip on the ECA is placed at or just below the first major
bifurcation.
A longitudinal incision is made along the
previously placed mark in the distal CCA with a no. 15 knife blade. The incision is carried through the wall of the artery until
the shiny yellow surface of the atheromatous plaque is seen. A Penfield
no. 4 dissector is then used to develop the plane between the atheroma
and the outer arterial wall. Often the atheroma is
adherent to a relatively thin outer wall at the bifurcation. It is best
to separate the plaque for a few millimeters and then extend the
incision superiorly with a Potts scissors before attempting further
dissection. The distal end of the incision extends up the ICA to
approximately the distal end of the plaque. The proximal extent of the
arteriotomy is usually I to 2 cm below the bifurcation. A thin layer of
thickened intima will usually extend proximally in the common carotid
artery and does not need to be of concern as long as one is proximal to
the stenosis.
The atheromatous plaque is then separated
carefully from the outer arterial wall in the CCA. A right-angled clamp
is placed around the plaque, and the plaque is cut off and bevelled with
curved microscissors at the proximal end of the arteriotomy in the
common carotid artery. The plaque is kept intact and is
removed first from the origin of the superior thyroid artery and the
proximal ECA. In some patients it is necessary to temporarily open the
clamp on the ECA to remove the plaque, which may extend quite far
distally. Additional bits of atheroma may be removed circumferentially
with a Jacobson haemostat. The line of sight provided by loupes and a
headlight is very helpful for this step. Once this removal has been
accomplished, the atheroma is carefully dissected from the outer wall of
the ICA, keeping gentle traction on the intact plaque. Often there is a
very clean dissection plane. Great care is taken as the distal end of
the plaque is reached. Usually the plaque will extend
distally several millimeters further along the posterior wall of the
artery. Care must be taken to remove this portion of the atheroma. Once
the plaque has been separated, it usually comes away cleanly at the
junction with normal intima and does not leave an intimal flap.
The
plaque may "feather" away from the wall, becoming ever
thinner, then vanishing. Or it may extend along the posterior wall like
a yellow tongue, with a clear-cut dissection margin. In both of these
situations, there is no tendency to distal irregularity or intimal flap
formation. Sometimes the plaque seems to extend further distally,
without a clear-cut margin. In this case the surgeon should consider a
circumferential bevelling incision of the thin plaque with the curved
microscissors. When done properly. this results in a very smooth inner
wall, without a significant shelf effect. Tiny distal irregularities,
either longitudinal or transverse, may be excised flush with the
microscissors (more cleanly than by avulsion). The distal artery is
inspected under loupes or microscope, with jets of irrigation to reveal
any possible tendency to intimal flap formation. Further revision of
the endarterectomy margin can be made. Only occasionally do we use 6-0
double-armed tacking stitches to improve such a situation.
The area of the endarterectomy is irrigated
with heparinized saline and inspected with the help of the headlight and
magnification. There are almost always some loose fragments adherent to
the wall, which are excised or removed by peeling them in a
circumferential fashion with a Jacobson haemostat. The final inspection
is made of the distal end of the endarterectomy in the ICA and ECA.
visualizing the area directly using a headlight and fine suction.
The arteriotomy is then closed with a
continuous 6-0 Prolene suture beginning
at the distal end of the arteriotomy on the ICA and progressing down
onto the CCA. The 6-0 suture permits very thin bites and interbite distance (0.3 to 0.4 mm) with virtually no arterial narrowing.
To avoid fracture. the surgeon should never handle the brittle suture
with instruments. Seven tight square throws are needed on the distal
knot to prevent untying. The suture must be snugged down with each
stitch to maintain a taut suture line. Each stitch must include, under
direct vision, both the medial and intimal layers on both lateral and
medial sides. As one reaches the bifurcation, the lumen becomes larger
and the wall thicker, and a larger bite and interbite distance (0.6-0.8
mm) are appropriate. In the CCA, a 10 to 12 mm artery warrants even
larger bites and intervals (1.0 to 1.2 mm). Just before the final
sutures are placed, backflow is allowed from both the ICA and the ECA so
that air and any debris are flushed out of the area of the
endarterectomy. If the backflow is poor, the arteriotomy is reopened and
the problem corrected. In this situation there may be an intimal flap or
narrowing at the distal end of the suture line. After the last suture is
placed, backflow through the superior thyroid artery is permitted to
exclude air from the lumen during the final tying of the suture. When
the closure is completed, a rubber dam is placed over the suture line
and held by a sponge with gentle pressure. Blood flow is allowed first
into the ECA to wash out any further residual debris. and then into the
ICA. Bleeding from the suture line is usually not a problem and is
easily controlled by gentle pressure on the rubber dam. One should not
be in any hurry to close small areas of leak from the suture line
because most will clot with gentle pressure and patience. Surgicel is placed
on the suture line. If the hemorrhage persists, the surgeon may place an
additional stitch at the point of leakage, with tiny bites to avoid
narrowing: a small flap of periarterial tissue may be used.
Once flow has been re-established. the
endarterectomy site is checked. The exposed arteries and the superficial
temporal artery are palpated gently. If there is a thrill in the ICA.
the clamps are replaced and the artery reopened to correct the problem.
If one is concerned about narrowing of the internal carotid lumen, a
patch can be used. If there is a poor pulse or thrill in the ECA or if
the STA is absent, the ECA may be obstructed. Microdoppler may be used
for confirmation in that a separate arteriotomy and endarterectomy may
be needed.
Not reversing the heparin may protect against thrombus formation,
particularly during the first hour after the closure. Occasionally
with extended cross-clamping of over 1 h, additional heparin may be
needed. Rarely, bleeding at the time of closure demands (partial)
reversal with protamine sulfate.
Activated clotting time (ACT) determinations during carotid
endarterectomy is performed. Because the test is done in the operating room by the
anaesthesiologist, with results within 5 min, data can be used to guide
repetition of heparin administration or the use of protamine sulfate.
Ready vac drain No
10 is left for 24 hours. If the dressing is dry in the recovery room, heparin is
restarted at 500 units/h for 48 hours. This program seems to reduce the
risks of embolization and with this protocol wound haematoma is rare.
Special Technical Problems
Insertion of a Patch Graft
With the routine use of magnification for
the endarterectomy, we have found that in most cases the arterial
incision can be closed with a continuous 6-0 Prolene running suture.
When the ICA appears to be too small for satisfactory closure (~4 mm in
diameter) or it appears that closure will compromise the lumen
(particularly with a tendency to kink or with a markedly irregular
wall), we have no hesitation in using a patch graft. In most patients
with recurrent stenosis, a patch graft is used because of the scar
formation in the wall of the artery. Some surgeons use a patch routinely.
The patch is made
from a collagen-impregnated knitted Dacron graft. This graft material is convenient, handles well,
avoids needle hole leakage, and has not been associated with blow
out. The patch is cut to fit the arteriotomy. The graft is usually
about 4 mm in width near the distal end and tapers over 6 to 8 mm to a
blunt distal end and gradually to a long 2-mm tail.
Double-armed sutures of 6-0 Prolene are used. One arm of the suture is placed through the
distal end of the graft from the inner to the outer surface and the
other arm is placed at the distal end of the arteriotomy from inside the
lumen to the outer wall. Sutures are placed from the outside through the
graft and then from the arterial wall lumen to the exterior, in order to
accurately suture the intima and media. Four to five sutures are placed
on one edge, then a similar number on the other to maintain smooth
symmetry. Note that one edge will be done backhand. The graft should
extend about 8- to 10-mm above the end of the remaining thickened
intima to confer adequate expansion of the lumen at this critical spot.
Note that in placing a patch graft, the bite size and interbite distance
are larger (about 0.8 to 1.0 mm) than in primary closure. This is done
to exclude the irregular wall edge from the lumen, and it can be done so
because the patch offers extra material for adequate lumen maintenance.
When suturing reaches the bifurcation, the tail of the graft is pulled
taut and transected. The end of the patch is sewn to one side of the
arteriotomy and tied. The other limb of suture is used for continuous
closure of the CCA. If there is concern about a possible blowout, a 10-mm diameter Gore-tex
sleeve is placed around the entire graft and carotid artery.
Use of a Shunt
When the EEG demonstrates ischemic
changes after crossclamping (slowing, voltage loss), these can be
reversed to prevent stroke by the use of a shunt. However, a shunt
can cause intimal dissection or emboli, which can cause a stroke.
Meticulous technique can prevent these problems.
Argyle
carotid shunt catheters are in common use. The advantage of these sterile
polyethylene catheters is that the surgeon has four sizes (nos. 8,
10, 12, and 14 French) immediately available that are the correct
length (15 cm) and have smooth ends. Shunts are prepared by filling
with heparinized saline and temporary cross-clamping with a
haemostat. After arterial clamps and clips are placed, a rapid
arteriotomy incision is made. including through the plaque, starting
a few millimeters more proximally on the common carotid artery than
usual and extending a few millimeters more distally on the ICA. The shunt tube is first passed distally into the ICA;
the surgeon visualizes the intima distal to the plaque so that a
flap is not dissected by the tip of the catheter. A tape and
tourniquet gently keep the arterial wall snug around the shunt.
Rarely a Sundt-Kees clip graft can be used to provide a better view
higher up. The shunt is checked to be certain there is satisfactory
backflow of blood. The catheter is again temporarily occluded and
is then passed proximally into the CCA, and the tourniquet is
"tightened. The plaque can then be dissected and removed as
previously described. Great care is taken to ensure a smooth ending
to the plaque removal. especially at the distal end. Sometimes the
shunt will have to be removed temporarily to ensure a satisfactory
margin. The arteriotomy is closed with two sutures that begin at
either end. All but about 3 mm in the central portion of the
arteriotomy is closed. The catheter is clamped and removed, and the
closure of the arteriotomy is completed.
Complete lCA Occlusion
When the angiogram indicates a complete
ICA occlusion, changes in the operative approach are indicated.
Great care is taken to avoid hypotension. An incision is made on the
ICA distal to the plaque after occluding the common and external
carotid arteries. In the majority of patients a thrombus will be
found. but in a few the lumen of the ICA will be open distal to the
atheromatous plaque. If there is a long-standing occlusion, the
artery may be a firm fibrous cord without backflow, and ligation
with 0-0 silk is indicated.
If the thrombus can be removed and
backflow established. the endarterectomy is completed as described.
In some patients with complete occlusion of the ICA, the ECA may
supply significant collateral flow to the brain. In some of these
patients, flow can be maintained in the ECA by the application of a
Satinsky clamp across the bifurcation at the origin of the ICA or by
the use of a common to external carotid artery shunt.
Certain techniques may help in opening the
completely occluded artery. If a thrombus is encountered in the ICA, an
effort is made to withdraw it gradually with forceps using a
hand-overhand technique. Thrombi as long as 20 cm have been removed.
If this technique fails. a smooth-ended suction catheter (a shunt tube
attached to suction) is introduced into the internal carotid lumen until
resistance is felt. Suction is then applied. and this may withdraw the
thrombus. If this method fails. a no. 3 Fogerty catheter is passed
gently as far as the base of the skull. inflated. and withdrawn. Care
is required to avoid injuring the distal ICA with subsequent
development of a carotid-cavernous fistula. Measurements on the
angiogram from the internal carotid origin to the base of the skull may
help in determining the safe length of catheter that may be inserted. An
intraoperative angiogram is recommended to document restoration of flow
without an intimal flap or distal thrombus. If good backflow with
satisfactory angiography cannot be achieved. the ICA is doubly ligated
with 0-0 silk sutures. When flow is re-established, anticoagulation
should be continued in the postoperative period.
Postoperative Management
Systolic blood pressure is generally
maintained in the range of 100 to 150 mmHg. with efforts to avoid both
hypotension and hypertension. If hypotension develops. the
electrocardiogram (ECG) is checked. Mild hypotension will usually
respond to the administration of IV fluid or colloid. A phenylephrine
drip is available if needed. If the hypotension does not immediately
respond to volume replacement, a CVP catheter is inserted. If the CVP
is maintained in the range of 5 to 10 cm with judicious utilization of
fluid, this problem will generally resolve. On occasion, bradycardia may
develop and the administration of atropine may be necessary. The blood
pressure and pulse usually return to a normal level within a few hours.
Control of hypertension is also important.
There is a significant incidence of postoperative hypertension.
Patients who develop postoperative systolic readings that are
persistently above 170 mmHg require treatment with rapid-acting IV
antihypertensive medication until long-acting medications become
effective. Intracerebral hemorrhage with
postoperative hypertension was encountered. as previously reported, but since the
institution of careful postoperative blood pressure control, this
complication has been rare.
In most cases, we use low-dose heparin for
48 h as described and then switch to aspirin. In patients with severe
irregularity of the luminal wall after endarterectomy, we use
therapeutic heparinization (partial thromboplastin time, 55 to 65 s)
and then warfarin therapy for 3 months (prothrombin time, 15 to 17 s).
In these cases, the dissection was difficult, the endarterectomy plane
seemed roughened, the plaque was particularly long, or a complete
occlusion was reopened. A special circumstance when anticoagulation
should probably be continued is when the patient has a severely
stenotic contralateral ICA stenosis.
Results
The mortality rate
in de novo cases
is 1 percent, the incidence of
major stroke 1 percent, and the incidence of minor stroke 1 percent.
Virtually all other patients return to their previous level of activity.
Several reports of patients who have had elective carotid endarterectomies for TIAs have documented similar low morbidity and
mortality rates when the operation is done by an experienced person in a
center performing a significant number of
operations. For patients who have had a previous
stroke there is a slight increase in risk.
Reports of surgical treatment for
asymptomatic carotid atherosclerosis include those of Thompson et
al., who reported two strokes among 167 operations for asymptomatic
bruit, and Moore et al., who reported no complications in 78
operations for asymptomatic carotid ulcerations.
Among patients with
crescendo TIAs, acute mild to moderate deficit, or fluctuating or
progressive stroke, enjoyed an excellent or good outcome. In this
group there is 2 percent death due to a cardiopulmonary complication. There
is 4 percent where the neurological deficit become worse after the
operation, but there is also several spectacular recoveries in the
immediate postoperative period after operation for both stenosis and
occlusion. In another report of emergency carotid endarterectomy, 7
patients with crescendo TIAs all made a full recovery, and of 17
patients with stroke in evolution, none were worse, 4 were unchanged, 12
made a good recovery, and 1 died. Encouraging results in selected cases
have also been reported from other centres.
Complications
Cerebral Ischemia and Infarction
The EEG electrodes are left on the
patient until the patient awakens in the recovery room. If a
neurological deficit is found as the patient awakens and a
significant EEG change has occurred after leaving the operating
room, the patient is returned immediately for exploration of the
artery. If the deficit is present with no change in the EEG, a
bedside ultrasound examination is performed immediately to look for
occlusion and a CT scan is performed to look for hemorrhage. If
these studies are normal, angiography is done. If studies show that the
endarterectomy site is normal and that blood volume and blood
pressure are maintained, a decision is made regarding
anticoagulation. If the neurological deficit is mild and
nonprogressive, usually no abnormality is found on angiography. In
such patients it is assumed that an embolus was dislodged sometime
during the dissection.
If the patient develops a substantial
neurological deficit after an initial good recovery, it often
indicates occlusion at the site of the operation. If the superficial
temporal pulse is lost or the ultrasound shows occlusion, the
patient should be taken immediately to the operating room to
ascertain the status of the artery. If the deficit is mild and
highly focal, a CT scan is done to look for hemorrhage, and if this
study is normal, an angiogram is performed. The usual reason for
postoperative carotid occlusion is a residual plaque or an intimal
flap, but on rare occasions the problem may be associated with an
ICA kink or an unrecognized hypercoagulable state.
Transient Ischemic Attacks
A small number of patients will have one
or more transient ischemic episodes in the postoperative period.
Usually it is a single attack, but if there is more than one it
usually does not recur after 10 to 14 days and does not signify a
serious problem in the operated artery.
Noninvasive studies are done to
ascertain whether there is a hemodynamic lesion. Most patients will not have evidence of stenosis. They are treated
with antiplatelet or anticoagulant therapy and usually do not have
further problems. If TIAs persist or a significant abnormality is
present on the noninvasive tests, angiography is indicated and may
demonstrate a lesion that needs reoperation.
Intracerebral Hemorrhage
Typical
hypertensive hemorrhage occurs in the basal ganglia 4 days after
surgery when the patient's blood pressure is 200/100 mmHg. Aggressive control of postoperative
hypertension reduce the incidence of this complication.
However, occasionally even with a mild elevation in blood pressure,
a hemorrhage may occur.
Intracerebral hemorrhage is also of concern when postoperative
heparin or antiplatelet therapy is used and in patients who have
had previous cerebral infarction.
Cranial Nerve Injury
If the incision is carried too near the
angle of the jaw or retraction is too vigorous. the mandibular
branch of the facial nerve can be stretched, causing weakness of the
lower lip. This is an annoying problem; it causes a cosmetic change
and may cause the patient to drool from the corner of the mouth.
Spontaneous recovery almost always occurs. This problem is avoided by curving the incision away from the angle of the jaw
toward the mastoid process and being careful with placement of the
self-retaining retractors.
Injury to the vagus or recurrent laryngeal
nerve with vocal cord paresis has been reported to occur in about 1
percent of patients undergoing carotid endarterectomy.
Traction or pressure on the nerve is the usual cause. As noted in the
discussion of operative technique, the vagus nerve can lie on the
anterior surface of the common carotid artery and may be encountered
early in the dissection. Another area where the vagus nerve is
susceptible to injury is in dissection of the ICA, to which it may
adhere. The majority of patients will show spontaneous recovery within a
year.
Injury to the hypoglossal nerve is generally
avoided by following the steps outlined in "Operative Technique." When
it does occur, it is usually due to excessive traction on the nerve.
Nothing need be done. Usually there are no symptoms, and a majority of
the patients will have a spontaneous recovery within a few months.
Other Complications
Cardiopulmonary complications have been
reduced by following the guidelines described under "Preoperative
Medical Evaluation". Other neurological complications include seizures
and headaches. When a headache occurs, it generally subsides in a day
or so.
Recurrent Stenosis
Recurrent stenosis occurs in a small
percentage of patients who have had a carotid endarterectomy. There
seem to be three groups of patients in which this problem arises:
1.Patients in whom surgical technique has
contributed to the problem. This includes failure to remove the distal
tongue of the plaque, narrowing of the lumen during the arteriotomy
closure, and damage to the intima by vascular clamps.
2.Patients who have a tendency to
excessive scar formation.
3.Patients who develop a combination of
fibrosis, recurrent atherosclerosis, and, at times, an associated
thrombus.
Symptomatic stenosis may recur within a few months of the
operation. This usually relates to one of the problems in surgical
technique or to the thickened fibrosis of the arterial wall, which is
grossly and histologically distinct from the typical atherosclerotic
plaque. Fortunately, this tendency to excessive scar formation is a rare
happening. Recurrent stenosis that occurs after 2 years usually has
significant atheroma formation as well as fibrosis.
Reoperation is often difficult because of
the dense periarterial scar and the fibrosis of the vessel wall. Great
care is required to avoid injury to the internal jugular vein and the
vagus and hypoglossal nerves. The thickened intima is often densely
adherent to the arterial wall, particularly in the region of the
previous suture line. In most patients it is necessary to use a patch
graft to repair the artery. In some instances where myofibrointimal
hyperplasia is the problem, no dissection plane can be developed, and
patch grafting alone is the best procedure.
