Carotid endarterectomy: Its procedural development and technical update

Seminars in Cerebrovascular Diseases and Stroke Vol. 2 No. 4 2002

Carotid Endarterectomy: Its Procedural Development and Technical Update W I L L I A M H. B A K E R

MaywoodlL

ABSTRACT Technical requirements for performance of carotid endarterectomy are described. Patient selection is emphasized, and issues about use of shunts and patch angioplasty are described. Special management considerations--including the anatomically high carotid bifurcation, intraarterial thrombi, and postoperative stroke--are carefully reviewed. Finally, clinical activities designed to decrease length of stay for carotid endarterectomy are reported. Forty percent of patients are now being discharged home on the day of operation. Key words: carotid endarterectomy, length of' stay, operative technique, patient selection.

Carotid reconstruction was first performed almost a half century ago. In 1954 in England, Eastcott et al 1 excised a symptomatic internal carotid atheroma. 1 In 1955, Carrea et al 2 bypassed a symptomatic lesion by transposing the distal internal carotid artery to the proximal external carotid artery. DeBakey 3 first performed a carotid endarterectomy in 1953 and reported this case, with a 19-year follow-up, in 1975. In the interim, the popularity of the operation has waxed and waned considerably. Initially, it was thought that carotid endarterectomy would dramatically decrease the incidence of stroke. The operation was performed on many unsuitable candidates by untrained surgeons, and the results were predictable. The joint study of extracranial arterial occlusion headed by Fields, 4 a neurologist, documented that patients did well after an endarterectomy of a solitary symptomatic lesion. They also documented that operating on patients with an acute stroke, particularly those with severe neurological deficits, were fraught with excessive stroke and death rates. 5 With the publication of the extracraniaMntracranial arterial by-

pass demonstrating no benefit from surgery, the result was a decrease in the number of carotid endarterectomies performed in this country. 6 The Rand Corporation study showed an almost 10% combined stroke and death rate in numerous areas in this country, further decreasing the popularity of endarterectomy. 7 However, The North American Symptomatic Carotid Endarterectomy Trial* and the Asymptomatic Carotid Atherosclerosis Study (ACAS) 9 in this country, as well as studies performed in Europe, have shown that stroke is best prevented in both symptomatic and asymptomatic patients by carotid endarterectomy. The details of these studies and their nuances have been previously addressed in this issue.

Preoperative Evaluation Patients presenting to a carotid surgeon require a complete history and physical examination. These patients are elderly. All physicians agree that carotid atheroma is an indication of generalized atherosclerosis, including coronary artery disease. In this clinic, fit patients who exercise regularly and who have a stable electrocardiogram do not undergo additional cardiac testing. Their respective internists evaluate patients with a history compatible with angina pectoris or with electrocardiograms suggesting recent change. Treatment is optimized before considering surgery for patients with elements of congestive heart failure. Likewise, patients

From the Division of Vascular Surgery, Department of Surgery, Loyola University Medical Cente~ Maywood, IL. Address reprint requests to William H. Baker, MD, Division of Vascular Surgery,/Department of Surgery, Loyola University Medical Center, 2160 S First Ave, EMS 110-3215, Maywood, IL 60153. E-mail: wbaker @wpo.jLluc.edu. Copyright 2002, Elsevier Science (USA). All rights reserved. 1528-9931/02/0204-0003535.00/0 doi: 10.1053/scds.2002.130314

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Carotid Endarterectomy: Development and Update * with cardiac arrhythmias are medically managed before consideration of endarterectomy. All patients suspected of having carotid stenosis are first evaluated with duplex ultrasonography. In our laboratory, we have established criteria that have a 95% positive predictive value. In addition, the technologists exactly locate the site of the carotid bifurcation in relationship to the bony landmarks, document the amount and extent of atherosclerosis in the proximal common carotid artery, and document that the distal internal carotid artery is free of atherosclerosis. Our diagnostic criteria are based on peak systolic velocity rather than end diastolic velocity. These criteria were established a decade ago when our duplex findings could be compared with contrast arteriography. 1~Assuming the carotid duplex examination to unequivocally identify a significant stenosis, no further diagnostic imaging is required. This policy has been in force for more than a decade and is our current protocol. Others do not feel comfortable relying on a single duplex examination. These centers, in addition to duplex ultrasonography, obtain a magnetic resonance angiogram (MRA) and/or contrast angiography. The MRA tends to overestimate the degree of stenosis and is sometimes inaccurate in differentiating a 99% stenosis from a 100% occlusion. MRA's advantages include the following: it is noninvasive, it does not require contrast material, and it does not produce stroke. The "gold standard" of all time is contrast angiography. Multiple views can be obtained to precisely identify a stenosis. Digital subtraction techniques decrease the need for large amounts of contrast material. The main disadvantage is that angiography is invasive and requires the use of a probing catheter within the carotid system. Thus, there is an incidence of stroke, which was published by the ACAS as being 1.2%. Both MRA and contrast angiography add to the expense of medical care.

Description of the Operation Once the patients' carotid stenosis is suitably documented and the patient pronounced fit for surgery, the operation is scheduled electively. Relatively few patients with a 99% stenosis and/or crescendo transient ischemic attacks (TIAs) will be scheduled urgently, and rare patients with an acute occlusion will be operated emergently. In our clinic, all patients will have good intravenous access and a radial artjery catheter to monitor blood pressure. Central monitoring catheters are usually not required. The operation does not require a special operating suite. /

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Position /' ,' /

The patient is placed supine on the operating room table with the shoulders elevated by a roll. The neck is

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extended to the patient's maximum. It should be mentioned that many of these patients have cervical osteoarthritis, and the surgeon must take care to not overextend the neck and to insure that the patient's head is comfortably supported.

Anesthetic General anesthetic is used as a routine in our institution, although a cervical block and local anesthesia are both satisfactory. General anesthesia has the advantage of absolutely controlling the airway and depressing the cerebral metabolic rate. The disadvantages of general anesthesia are well known and include decreased cardiac contractility. The disadvantage with local anesthesia is obvious to anybody who has spent an hour awake in the dentist's chair. Cervical block allows the surgeon to dissect down to the carotid vessels, but--in g e n e r a l ~ a local anesthetic is sometimes needed within the carotid sheath. Deep cervical block should not be used in patients with respiratory problems because temporary phrenic paralysis may result. The advantage of local anesthesia is that the patient can be monitored minute by minute, especially when the carotid artery is clamped.

Dissection Most surgeons use an incision that parallels the sternocleidomastoid muscle, whereas we prefer a more cosmetically pleasing incision that travels more transversely in a natural skin crease. Subplatysmal flaps are created so as not to injure the marginal mandibular nerve. Posteriorly, the greater auricular nerve must be protected lest the patient experience an irksome numbness of the earlobe. The dissection is continued immediately adjacent to the sternocleidomastoid muscle, avoiding the more medially situated lymph nodes that contain bothersome small blood vessels. When the internal jugular vein is encountered, this vein is cleaned anteriorly from lateral to medial, thus exposing the facial vein(s). These veins are divided between ligatures exposing the carotid bifurcation. The carotid artery is dissected anteriorly over the bifurcation. The common carotid artery is isolated away from the offending atheroma lower down in the neck. The preoperative duplex examination, as well as the appearance of the artery in the operating room, determines this limit. Distally, the internal carotid artery is encircled where it becomes soft and bluish in color. The vagus nerve laterally and the hypoglossal nerve medially are usually easily identified and dissected out of harm's way. Sometimes the hypoglossal nerve is tethered by a small occipital artery and vein that lead from the external carotid artery laterally over the sternocleidomastoid. Division of these vessels facilitates medial retraction of

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this nerve. The spinal accessory nerve is rarely seen coursing along the internal carotid artery toward the sternocleidomastoid. The ansahypoglossal lies immediately anterior to the carotid. Division of this nerve usually results in no disability.

To Shunt Or Not To Shunt When the carotid is clamped, blood flow to the ipsitateral cerebral hemisphere is decreased. If this decrease falls below a critical level, a neurological deficit may result. Thus, carotid surgeons always consider the use of a temporary indwelling shunt, a plastic tube that allows adequate cerebral blood flow during the endarterectomy. Some carotid endarterectomists always use a temporary shunt. They state that its routine practice facilitates its consistent use, and the presence of a plastic tube within the field is no longer an impediment. Most other surgeons recognize that this shunt is bothersome and choose to use the shunt selectively. Those surgeons who employ regional or local anesthesia follow the patient's clinical course when the artery i s clamped. Those surgeons using general anesthesia rely on either electroencephalography or stump pressures (internal carotid artery back pressure) for this judgment. In our clinic, we use a stump pressure of 50 mm/Hg when the contralateral carotid is occluded 11 and an absolute stump pressure of 25 mm/Hg regardless of the status of the contralateral internal carotid artery. 12 Each individual surgeon may have his or her own criteria. These criteria should be based on the end point of neurological deficit. After the patient has been given intravenous heparin and the clamps applied, the dissection is completed laterally so that the artery rotates anteriorly and medially. If this dissection is completed before the arteries are clamped, there is a risk of embolization. In our clinic, we employ an arterotomy that extends from the distal common carotid artery to the end of the atheroma in the internal carotid artery (Fig 1). In general, the hard atherosclerotic lesion is easily separated from the more pliable normal carotid wall. Proximally, the thickened intima is sharply severed with a scissors at a point proximal to the atheroma leaving but a slightly thickened common carotid artery intima. The external carotid artery plaque is teased out in a more or less blind fashion. The internal carotid artery dissection is completed under direct vision. A posterior plaque of atherosclerosis usually becomes superficial and comes away from the underlying intima with ease (Fig 2). If this end point does not break off cleanly and sharply, the endarterectomist must ensure that either the remaining intima is picked away or is tacked down with longitudinally oriented tacking sutures. It should be emphasized that the sutures tack down normal intima, not retained atheroma. Once all of the small fronds and atherosclerotic material have been excised and picked off,

Fig. 1. The carotid artery has been opened longitudinally. The proximal common carotid artery intima has been sharply severed. The external carotid artery atheroma has been teased out of the external carotid artery orifice. The surgeon separates the internal carotid artery atheroma (see Fig 2). Reproduced by permission from "Operative Techniques in Vascular Surgery," edited by John H. Bergan, MD, and James S. T. Yao, MD, 1980, Grune and Stratton, Inc.

the arterotomy is closed with a patch. Rarely does a patient have a large carotid artery that may be closed primarily. The patch material used in this clinic is Dacron. Use of Teflon tends to result in increased bleeding through the needle holes. Whereas vein is quite acceptable, we see little advantage to its use in this position.

Intraoperative Surveillance To ensure that a technically perfect operation has been performed, we interrogate the endarterectomized carotid artery with duplex ultrasonography in the operating room. 13 A relatively small probe is placed inside a sterile plastic sheath and placed directly on the artery. We pay particular attention to the proximal end point to ensure there is not any retained atheroma of significance. The external carotid artery is interrogated. We are content to leave an occasional frond in this artery, but we would reopen

Carotid Endarterectomy: Developmentand Update 9 William H. Baker 283

Fig 2. An enlargement of the distal internal carotid artery end point. The atheroma extends beyond the "normal" intima. The surgeon must ensure that the site of atheroma separation and the edge of the intima are both adherent. Reproduced by permission from "Operative Techniques in Vascular Surgery," edited by John H. Bergan, MD, and James S. T. Yao, MD, 1980, Grune and Stratton, Inc.

this vessel to extract a large atheroma. The endarterectomized internal carotid artery is examined for retained large fronds and thrombus. The distal end point should be barely visible. Obviously, a stenosis is not tolerated.

Closure of the Wound After the above interrogation reveals a satisfactory technical result, the wound is inspected and hemostasis achieved. We do not drain these wounds. The platysma is closed with interrupted absorbable suture, and absorbable suture is used in a subcuticular closure of the skin. Ideally, the patient is awakened in the operating room, a quick neurological examination is performed, and the patient is transported to the recovery room.

Alternative Methodology As an alternative to the standard endarterectomy as outlined above, evers'ion endarterectomy is becoming more and more popular. 14 In this technique, the dissection is completed as before. The need for a shunt remains. The internal carotid artery is severed obliquely at its base, and this incision is carried proximally down the common carotid artery. The common carotid atheroma is excised, and endarterectomy of the external carotid artery again is

achieved in a similar fashion as listed above. The distal internal carotid artery is then peeled back from the atheroma and the endarterectomy completed to directly observe the end point. The distal intima should be adherent, as in all techniques. All fronds and other miscellaneous material can be picked off the artery as the internal carotid artery is rolled back to its original position. The internal carotid artery may be opened to allow it to fit to the enlarged opening of the common carotid artery, and this reanastomosis is completed with a continuous suture. Should the common carotid artery be larger than the internal carotid, the proximal common carotid artery may be closed primarily. Eversion endarterectomy can be performed in less time than the conventional carotid endarterectomy because of the ease of closure. The use of a shunt is allegedly no different, although the shunt must be placed after the atheroma has been excised. Tacking sutures are difficult to employ using this technique. If indeed there is extreme difficulty with the distal end point, an interposition graft may be required. Immediate stroke and death rates using this technique are comparable with the immediate stroke and death rate using the standard technique. The advantage of eversion endarterectomy is not in the immediate results but in the late results. Recurrence rates in most series are lower than found in the older series of standard carotid endarterectomies. A prospective study comparing this technique with standard carotid endarterectomy employing patch angioplasty will be required to definitively answer which technique is better over time.

The High Bifurcation or Extended Atheroma An occasional patient has a very high bifurcation and/or an extensive atheroma that disappears up behind the mandible. These patients in general require a variation in technique. 15 If this situation is known in advance, the anesthesiologist is asked to place a nasotracheal rather than an oral tracheal tube. This allows the jaw to close a little bit more and thus moves the mandible out of the surgeon's way. The mandible may also be subluxed anteriorly, giving the surgeon an extra centimeter or so of exposure. This allows the surgeon to carry his or her dissection up past the tip of the stylohyoid under direct vision. The digastric muscle can be severed and the stylohyoid trimmed without observing ill effects. The glossalpharyngeal nerve should be watched for and protected. Using all of these methods, the dissection can be carried quite a way up toward the base of the skull. Lesions right at the base of the skull in general will require, in addition, a higher-placed incision with or without a resection or portion of parotid gland and subsequent protection of the facial nerve.

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Partial Thrombosis of the Internal Carotid Artery Some patients with crescendo TIAs have a 95% or higher stenosis with thrombus either at or just distal to the stenosis. The distal tip of the thrombus may not be identified. In these patients, a slight variation of technique is required, a6 The dissection is carried down to the internal carotid artery. The common carotid artery is encircled as before. The internal carotid artery is cleaned anteriorly but not circled (Fig 3). The external carotid is cleaned anteriorly and posteriorly but not circumferentially, lest the bifurcation be manipulated. The patient is given heparin; the Common and external carotid arteries are clamped; the lateral dissection is completed so that the artery rotates anteriorly and medially; and a routine arterotomy is performed. The back bleeding from the clamped internal carotid artery should

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force the known thrombus completely out of the arterotomy. Once the thrombus extrudes through the arterotomy, only then is the internal carotid artery clamped. The remainder of the operation is standard.

Postoperative Stroke Postoperative neurological deficit is a devastating and most feared complication of this operation. Traditionally, all patients experiencing postoperative stroke were returned immediately to the operating room to correct an occluded internal carotid artery. However, in a review of our material, the following was noted. 17 When we began to use intraoperative duplex, we noted that patients who awoke with a stroke in the operating room did not have an occluded internal carotid artery. Rather, these patients usually had their symptoms on the basis of prolonged interoperative ischemia or embolization. Contrary to this, those patients who awoke neurologically intact and later developed a neurological deficit after a lucid interval, often had an occluded internal carotid artery. Thus, late neurological deficit patients are returned to the operating room as before, whereas patients with an immediate neurological deficit are rarely reoperated. Should these patients with a delayed neurological deficit have a repeat duplex examination in the recovery room? Clearly, additional surgery would be avoided if indeed the study were unequivocally normal and if the study can be performed in an expeditious manner. If a neurological deficit occurs in the evening or at night, duplex nltrasonography is not available in our institution. Even during the day it may require several minutes to move the machine from the Peripheral Vascular Laboratory to the recovery room. In our opinion, an undue delay is not warranted. It is our preference to return these patients immediately to the operating room so that flow can be restored through a temporary indwelling shunt well within an hour of the onset of their neurological deficit.

ICU Care

J Fig. 3. A carotid with a partially occluding thrombus. The common carotid artery and external carotid artery are clamped. Backflow through the open internal carotid artery forces the thrombus out of the arterotomy. The internal carotid artery is controlled only after the/thrombus has been completely extracted. Reproduced by permission Saletta C, and Baker WH "Carotid Endarterectomy. Tectmical Modifications in Patients With Internal Carotid Artery Throlnbus." The American Surgeon. Volume 19, (5):238-240, 1983. JP Lippincott and Company.

Patients are rarely sent to the intensive care unit in our institution. We established long ago that relatively few cardiac complications occur. 18 Earlier in my career, the patient's blood pressure was strictly monitored so it was maintained within 10% of his or her high and low recorded blood pressure. With the advent of same-day admission, we no longer have a good record of patients' "normal" blood pressure, and thus I suspect that our compulsiveness regarding blood pressure management is less than before. Regardless, patients who have problems with heart rate, hypotension, or hypertension--or who require monitoring because of known cardiac disease--are still sent to the intensive care unit. In general, this represents 10% of our carotid endarterectomy population.

Carotid Endarterectomy:Developmentand Update 9 William H. Baker 285 Our current routine is to monitor these patients in the recovery room for 1 or 2 hours, as is the rule with inost general surgical patients. Assuming the patient is neurologically stable and has neither hypotension, hypertension, nor arrhythmia, the patient is transferred to a general surgical bed for the remainder of his or her hospitalization. The patient is allowed to ambulate with assistance, to use the bathroom, and to begin eating light meals. Mild analgesics (acetaminophen, aspirin) are usually all that is required to control incisional pain.

Discharge From the Hospital Hospitalization post carotid endarterectomy has traditionally been required because of the dire complications of neurological deficit and neck hematoma, which m a y require operative intervention. We recently reviewed our experience in this r e g a r d J 9 Neurological deficit most often becomes manifest in the operating room, in the recovery r o o m , or at least within 8 hours o f surgery. Interestingly, neck hematomas present at exactly the same intervals. Thus, after the aforementioned review, our protocol has changed 9 A l l patients, are discharged from the recovery room to a surgical floor bed. If after 8 hours the patient continues to be stable and comfortable, the patient is discharged home that day. There are obvious exceptions to this rule. If the patient is elderly and infirm, a night of hospitalization is necessary. Some patients live more than an hour away from the hospital, and we believe that these patients should stay for the evening. Of course, other medical problems arise that necessitate hospitalization. Regardless, almost all patients are discharged the morning after surgery. What are the results of our current policy? Over the course of the last several years, more and more ;patients are being discharged the same day. Whereas initially there was a great reluctance on the part of patients and physicians alike for same-day discharge, this reluctance 9 is being overcome. Currently, 40% of our patients go home the same day as surgery.

Conclusion Carotid endarterect0my remains the "gold standard" of treatment of carotid atherosclerosis. Carotid angioplasty and stenting is becoming more and more popular. As to which technique will become the new standard is a matter of conjecture. Should carotid angioplasty and stenting 9 / prove eqmvalent, this technique may become the preferred treatment. It is our obligation to ensure that carotid endarterectomy is performed with ultimate safety and excellent long-term results. The operation should be performed economically in these especially troubled finan-

cial times. We should raise the bar so that the standards of patient care are maintained at an optimal level.

References 1. Eastcott HHG, Picketing CW, Rob CG: Reconstruction of the internal carotid artery in a patient with intermittent attacks of hemiplegia. Lancet 2:994-996, 1954 2. Carrea R, Milins M, Murphy G: Surgical treatment of spontaneous thrombosis of the internal carotid artery in the neck. Carotid-carotideal anastomosis. Report of a case. Acta Neurol Latinoam 1:71-78, 1955 3. DeBakey ME: Successful carotid endarterectomy for cerebrovascular insufficiency. Nineteen year follow up. JAMA 233:1083-1085, 1975 4. Fields WS, Maslenikov V, Meyer JS, et al: Joint Study of Extracranial Arterial Occlusion. V. Progress report of prognosis following surgery or nonsurgical treatment for transient cerebral ischemic attacks and cervical carotid artery lesions. JAMA 211:1993-2003, 1970 5. Blaisdell WF, Clauss RH, Galbraith JG, et al: Joint study of extracranial arterial occlusion. IV. A review of surgical considerations. JAMA 209:1889-1895, 1969 6. The EC/IC Bypass Study Group: Failure of extracranialintracranial arterial bypass to reduce the risk of ischemic stroke. Results of an international randomized trial. N Engl J Med 313:1191-1200, 1985 7. Winslow CM, Solomon DH, Chassin MR, et al: The appropriateness of carotid endarterectomy. N Engl J Med 318:721-727, 1988 8. North American Symptomatic Carotid Endarterectomy Trial Collaborators: Beneficial effect of carotid endarterectomy in symptomatic patients with high-grade carotid stenosis. N Engl J Med 324:445-453, 1991 9. Executive Committee for the Asymptomatic Carotid Atherosclerosis Study: Endarterectomy for asymptomatic artery stenosis. JAMA 273:1421-1428, 1995 10. Horn M, Michelini M, Greisler HE et al: Carotid endarterectomy without arteriography: The preeminent role of the vascular laboratory. Ann Vasc Surg 8:221-224, 1994 11. Baker WH, Littooy FN, Hayes DB, et al: Carotid endarterectomy without a shunt: The control series. J Vasc Surg 1:50-56, 1984 12. Littooy FN, Halstuk KS, Mamdani M, et al: Factors influencing morbidity of carotid endarterectomy without a shunt. Am Surg 50:350-353, 1984 13. Baker WH, Koustas G, Burke K, et al: Intraoperative duplex scanning and late carotid artery stenosis. J Vasc Surg 19:829-833, 1994 14. Chang BB, Darling RC III, Patel M, et al: Use of shunts with eversion carotid endarterectomy. J Vasc Surg 32: 655-662, 2000 15. Meyer FB, Kasperbauer JL: Exposure of the distal internal carotid artery, in Loftus CS, Kresowik TF: Carotid Artery Surgery. Thieme, 2000, pp 257-263

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16. Saletta C, Baker WH: Carotid endarterectomy. Technical modifications in patients with internal carotid thrombus. Am Surg 49:238-240, 1983 17. Sheehan MK, Littooy FN, Greisler HP, et al: The effect of intraoperative duplex scan upon the treatment of post carotid endarterectomy stroke. Surgery 2002; 132:761-766

18. Morasch MD, Hirko MK, Hirasa T, et al: Intensive care after carotid endarterectomy: A prospective evaluation. J Am Coll Surg 183:387-392, 1996 19. Sheehan MK, Baker WH, Littooy FN, et al: Timing of post carotid complications: A guide to safe discharge planning. J Vasc Surg 34:13-16, 200l