Carotid surgery: The past is prologue
1997; Elsevier BV; Volume: 25; Issue: 1 Linguagem: Inglês
10.1016/s0741-5214(97)70329-x
ISSN1097-6809
Autores Tópico(s)Intracranial Aneurysms: Treatment and Complications
ResumoI feel very honored indeed to be chosen as the Homans Lecturer this year, especially at the time of the 50th anniversary of the Society for Vascular Surgery, yet I have a sense of deep humility when I look back over the list of previous Homans lecturers. It is also a real privilege to present a lecture named for one of the great vascular surgeons of the 20th century, Dr. John Homans. I am deeply grateful to the officers and council for selecting me. John Homans, the man for whom this lecture is named, was a Boston surgeon and a charter member of The Society for Vascular Surgery. He was born in Boston in 1877, the fourth John Homans to practice medicine in Boston. He attended Harvard College and the Harvard Medical School and trained at the Massachusetts General Hospital. He later spent a year at the Johns Hopkins Hospital under Harvey Cushing. When the Peter Bent Brigham Hospital opened in 1913, Harvey Cushing, now Surgeon-in-Chief, chose John Homans at age 36 to be a member of his original surgical staff, where he remained for the rest of his career. Basically a general surgeon, he developed a special interest in vascular diseases, especially in venous disease. He described bland thrombosis in the legs as a cause of pulmonary embolism, as differentiated from thrombophlebitis. He was the first to advocate femoral and iliac vein ligation to prevent pulmonary embolism. At the suggestion of Harvey Cushing, he wrote a Textbook of Surgery which became a classic. During 15 years it was adopted as a standard textbook in 65 medical schools and went through six editions, the last in 1945. In 1939 he published another classic textbook, Circulatory Diseases of the Extremities. John Homans was a real character, a raconteur of rare ability with a ready and salty wit. He was one of my teachers when I was a medical student at the Peter Bent Brigham Hospital. He was sparkling, unpredictable, and colorful. He was a keen observer, had a logical mind, and his conclusions were based on clear thinking coupled with the facts of the matter. He died in Boston in 1954 at age 77 of a myocardial infarction. He was a true pioneer in vascular surgery.1Elkin DC John Homans Lecture.N Engl J Med. 1951; 245: 997-1000Crossref PubMed Scopus (4) Google Scholar, 2Thompson JE The founding fathers.Surgery. 1977; 82: 801-808PubMed Google Scholar Because this is the 50th anniversary of The Society for Vascular Surgery, I thought it would be appropriate and of interest to recount some of the problems we faced in the early days of carotid surgery some 40 years ago. Some of these problems are still unsolved, while many have been resolved. A brief excursion into the history of carotid surgery before 1951 is relevant. As Thomas Carlyle said, “History is the essence of innumerable biographies.” The word “carotid” is derived from the Greek term “Karótide” or “Karos,” meaning to stupefy or plunge into deep sleep. The ancient Greeks were aware of the significance of the carotid arteries. The 31st metope from the south side of the Parthenon in Athens shows a centaur applying left carotid compression to the neck of a Lapith warrior.3Thompson JE Historical perspective of carotid artery disease.in: Advances in vascular surgery. Vol 1. Mosby–Year Book, St Louis1993: 3-15Google Scholar Ambroise Paré in the 16th century was familiar with the carotid phenomenon and called the carotid arteries the soporales or sleepy arteries.4Paré A The Workes of That Famous Chirurgion Ambrose Parey.4th English ed. 1678Google Scholar The first operations on the carotid arteries were quite naturally ligation procedures for hemorrhage or trauma. Hebenstreit of Germany in 1793 reported a case of carotid ligation for hemorrhage, and the patient is said to have lived.5Hebenstreit EBG Zusatze zu Benj. Bell's Abhandlung von den Geschwuren und deren Behandlung.1793Google Scholar John Abernethy in London in 1798 ligated the carotid artery for trauma, but the patient died of cerebral causes.6Abernethy J Surgical observations.in: Surgical works. 2. 1804: 193-209Google Scholar The first authentic successful ligation of the carotid artery on record was performed by David Fleming, a young British naval surgeon on October 17, 1803, on a servant who tried to commit suicide by cutting his throat. The patient survived.7Coley RW Case of rupture of the carotid artery, and wounds of several of its branches, successfully treated by tying the common trunk of the carotid itself.Med Chir J Rev. 1817; 3: 1-4Google Scholar, 8Keevil JJ David Fleming and the operation for ligation of the carotid artery.Br J Surg. 1949; 37: 92-95Crossref Scopus (13) Google Scholar The first successful ligation of the carotid artery in the United States was performed by Dr. Amos Twitchell of Keene, N.H., on October 18, 1807, on a cavalry soldier who had been accidentally shot at a regimental review. The patient made an uneventful recovery. Amos Twitchell, who died in 1850, became the leading surgeon in his area of New England.9Twitchell A Gunshot wound of the face and neck: Ligature of the carotid artery.New Engl Quart J Med Surg. 1842; 1: 188-193Google Scholar Sir Astley Cooper of London was the first to ligate successfully the carotid artery for cervical aneurysm, on June 22, 1808, and the patient lived until 1821.10Cooper A Second case of carotid aneurysm.Med Chir Trans. 1809; 1: 222-223Google Scholar, 11Cooper A Account of the first successful operation performed on the common carotid artery for aneurysm in the year 1808 with the postmortem examination in the year 1821.Guy's Hosp Rep. 1836; : 53-59Google Scholar Progress was slow during the ensuing 100 years. It was believed by most physicians, including William Osler, that strokes were caused by intracranial vascular disease.12Osler W The Principles and Practice of Medicine.7th ed. D. Appleton and Company, New York1909Google Scholar This concept is a reflection of how things work in the world of science. We think that discoveries are made, their importance is quickly recognized, and appropriate changes are adopted promptly. Not so. Such was the case with extracranial carotid disease. Autopsies had revealed massive brain infarcts, but it was not recognized that these lesions could be due to extracranial carotid disease because the carotid arteries were not examined during routine autopsies for fear of disfigurement. This failure need not have occurred because a number of physicians had described occlusive lesions in the extracranial vasculature and had related these to the clinical phenomena observed.3Thompson JE Historical perspective of carotid artery disease.in: Advances in vascular surgery. Vol 1. Mosby–Year Book, St Louis1993: 3-15Google Scholar In a landmark paper, J. Ramsay Hunt of New York City in 1914 had called attention to the importance of extracranial lesions in cerebrovascular disease.13Hunt JR The role of the carotid arteries in the causation of vascular lesions of the brain, with remarks on certain special features of the symptomatology.Am J Med Sci. 1914; 147: 704-713Crossref Google Scholar In 1927 Egas Móniz had introduced cerebral arteriography and thus laid the groundwork of a practical method for the diagnosis of occlusive lesions.14Mońiz E L'encephalographic artérielle son importance dan la localization des tumeurs cerebrales.Rev Neurol (Paris). 1927; 2: 72-90Google Scholar In two papers, in 1951 and 1954, C. Miller Fisher, working in Montreal but later in Boston, made significant contributions; he noted that with severe stenosis of the carotid bifurcation the distal vessels could be entirely free of disease, and suggested that surgical correction should be possible.15Fisher M Occlusion of the internal carotid artery.Arch Neurol Psychiat. 1951; 65: 346-377Crossref Scopus (369) Google Scholar, 16Fisher M Occlusion of the carotid arteries.Arch Neurol Psychiat. 1954; 72: 187-204Crossref Scopus (183) Google Scholar The first successful reconstruction of the carotid artery for frank stroke was performed by Carrea, Molins, and Murphy in Buenos Aires on October 20, 1951, after reading Fisher's article, and was reported in 1955. This was an end-to-end anastomosis between the proximal left external carotid artery and the distal internal carotid artery after partial resection of the stenosed area, together with cervical sympathectomy. The patient lived for 23 years and died of a myocardial infarction in 1974.17Carrea R Molins 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 Lat Am. 1955; 1: 71-78Google Scholar On January 28, 1953, Strully, Hurwitt, and Blankenberg in New York City first attempted thromboendarterectomy of a totally occluded cervical internal carotid artery but were unable to obtain retrograde flow.18Strully KJ Hurwitt ES Blankenberg HW Thromboendarterectomy for thrombosis of the internal carotid artery in the neck.J Neurosurg. 1953; 10: 474-482Crossref PubMed Scopus (53) Google Scholar The first successful carotid endarterectomy was performed by Michael E. DeBakey on August 7, 1953, and was reported several years later. The patient was a 53-year-old school bus driver who had had recurring transient ischemic attacks (TIAs) and a mild stroke; he lived for 19 years without further strokes, dying of myocardial infarction in 1972.19DeBakey ME Successful carotid endarterectomy for cerebrovascular insufficiency.JAMA. 1975; 233: 1083-1085Crossref PubMed Scopus (224) Google Scholar The operation that gave the greatest impetus to the development of carotid surgery was that of Eastcott, Pickering, and Rob, performed on May 19, 1954, at St. Mary's Hospital in London and reported in November of 1954.20Eastcott HHG Pickering GW Rob CG Reconstruction of internal carotid artery in a patient with intermittent attacks of hemiplegia.Lancet. 1954; 2: 994-996Abstract Scopus (526) Google Scholar A 66-year-old woman, having suffered 33 TIAs, underwent resection of the carotid bifurcation, followed by end-to-end anastomosis between the common carotid and the distal internal carotid arteries. Hypothermia to 28° C was used for cerebral protection. The patient was relieved of her symptoms and lived 20 years, dying in 1974 at age 86. The second operation at St. Mary's was an endarterectomy, done in June 1954. My first carotid endarterectomy was performed on April 16, 1957, 39 years ago.21Thompson JE Kartchner MM Austin DJ et al.Carotid endarterectomy for cerebrovascular insufficiency (stroke): follow-up of 359 cases.Ann Surg. 1966; 163: 751-763Crossref PubMed Scopus (42) Google Scholar With increasing experience the various procedures just described were abandoned with the exception of endarterectomy, which has become the standard operation. Table I lists in chronologic order some of the early procedures that were performed for the treatment of extracranial cerebrovascular disease.Table IThe first carotid reconstructions for cerebrovascular insufficiency, listed in chronologic orderAuthorDate of operationDegree of stenosisProcedureRestoration of flowCarrea, Molins, & Murphy17Carrea R Molins 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 Lat Am. 1955; 1: 71-78Google ScholarOctober 20, 1951PartialEnd-to-end anastomosis external carotid to internal carotidYesStrully, Hurwitt, & Blankenberg18Strully KJ Hurwitt ES Blankenberg HW Thromboendarterectomy for thrombosis of the internal carotid artery in the neck.J Neurosurg. 1953; 10: 474-482Crossref PubMed Scopus (53) Google ScholarJanuary 28, 1953TotalThromboendarterectomy followed by ligation and resectionNoDeBakey19DeBakey ME Successful carotid endarterectomy for cerebrovascular insufficiency.JAMA. 1975; 233: 1083-1085Crossref PubMed Scopus (224) Google ScholarAugust 7, 1953TotalThromboendarterectomyYesEastcott, Pickering, & Rob20Eastcott HHG Pickering GW Rob CG Reconstruction of internal carotid artery in a patient with intermittent attacks of hemiplegia.Lancet. 1954; 2: 994-996Abstract Scopus (526) Google ScholarMay 19, 1954PartialEnd-to-end anastomosis common carotid to internal carotidYesJune, 1954PartialThromboendarterectomyYesDenman, Ehni, & Duty22Denman FR Ehni G Duty WS Insidious thrombotic occlusion of cervical arteries treated by arterial graft, a case report.Surgery. 1955; 38: 569-577PubMed Google ScholarJuly 14, 1954TotalResection with homograftYesLin, Javid, & Doyle23Lin PM Javid H Doyle EJ Partial internal carotid artery occlusion treated by primary resection and vein graft.J Neurosurg. 1956; 13: 650-655Crossref PubMed Scopus (15) Google ScholarDecember, 1955PartialResection with saphenous vein graftYesMurphey & Miller24Murphey F Miller JH Carotid insufficiency: diagnosis and surgical treatment.J Neurosurg. 1959; 16: 1-23Crossref PubMed Scopus (14) Google ScholarFebruary 6, 1956TotalThromboendarterectomyYesFebruary 24, 1956PartialThromboendarterectomyYesCooley, Al-Naaman, & Carton25Cooley DA Al-Naaman YD Carton CA Surgical treatment of arteriosclerotic occlusion of common carotid artery.J Neurosurg. 1956; 13: 500-506Crossref PubMed Scopus (54) Google ScholarMarch 8, 1956PartialEndarterectomyYesLyons & Galbraith26Lyons C Galbraith JG Surgical treatment of atherosclerotic occlusion of the internal carotid artery.Ann Surg. 1957; 146: 487-496PubMed Google ScholarAugust 9, 1956PartialSubclavian-carotid nylon bypass graftYes Open table in a new tab In the early 1950s most of us were general or thoracic surgeons who were interested in the burgeoning field of vascular surgery. As such we had had little or no experience with cerebrovascular insufficiency. My attention was called to carotid disease and strokes by the neurosurgeons in our hospital, who had been influenced by Dr. Francis Murphey of Memphis and Dr. William Fields in Houston. Thus began a joint endeavor with the neurosurgeons. Eventually the chief of neurosurgery asked us to take over the carotid project, which we did, but with the continued advice and help of the neurosurgeons and neurologists, who saw all the patients in consultation. It soon became obvious that all strokes were not alike. We learned that there were transient episodes, strokes with all degrees of severity, and patients with carotid lesions that were asymptomatic. It was obviously necessary to classify patients into specific groups. Thus various classifications were developed in different centers, by DeBakey and his colleagues,27DeBakey ME Crawford ES Cooley DA et al.Cerebral arterial insufficiency: one to 11-year results following arterial reconstructive operation.Ann Surg. 1965; 161: 921-945Crossref PubMed Scopus (143) Google Scholar by DeWeese et al.,28DeWeese JA Rob CG Satran R et al.Surgical treatment for occlusive disease of the carotid artery.Ann Surg. 1968; 168: 85-94Crossref PubMed Scopus (49) Google Scholar and by others. The one we came to use had four categories: frank stroke, TIAs, chronic ischemia, and asymptomatic bruit or stenosis. There are many subsets in the frank stroke category. Although simple, this classification has served us well over the years.21Thompson JE Kartchner MM Austin DJ et al.Carotid endarterectomy for cerebrovascular insufficiency (stroke): follow-up of 359 cases.Ann Surg. 1966; 163: 751-763Crossref PubMed Scopus (42) Google Scholar There have been many classifications proposed since the 1950s, including the NINCDS,29National Institute of Neurological Communicative Disorders Stroke A classification and outline of cerebrovascular disease.Stroke. 1975; 6: 564-616Crossref PubMed Google Scholar the Marseilles classification of Courbier,30Basis for a classification of cerebral arterial diseases. Excerpta Medica, Amsterdam1985Google Scholar the CHAT,31Hye RJ Dilley RB Browse NL Bernstein EF Evaluation of a new classification of cerebrovascular disease (CHAT).Am J Surg. 1987; 154: 104-110Abstract Full Text PDF PubMed Scopus (6) Google Scholar and that of the Joint council of the SVS/ISCVS.32Baker JD Rutherford RB Bernstein EF Courbier R Ernst CB Kempczinski RF et al.Suggested standards for reports dealing with cerebrovascular disease.J Vasc Surg. 1988; 8: 721-729PubMed Google Scholar It is important to classify patients with cerebrovascular insufficiency into specific clinical categories. Only in this way can proper selection of patients for surgery be made and results of different methods of therapy within the same category be compared. The outcome early and late is also related to the initial classification.33Thompson JE Carotid surgery, 1982: the state of the art.Br J Surg. 1983; 70: 371-376Crossref PubMed Scopus (48) Google Scholar When we became involved with carotid surgery, all the carotid arteriographic scans in our hospital were performed by the neurosurgeons and later by some of the neurologists, who were very skillful and had low complication rates. At first these were done through a cutdown in the mid-neck. As experience grew, percutaneous punctures low in the neck were done. It was soon learned that unilateral arteriograms were inadequate, so bilateral pictures were obtained. We also found that stenoses as well as total occlusions could cause symptoms. It also became clear that intracranial views were necessary. As x-ray equipment improved, serial films were possible using the Schönander unit. General anesthesia was used in all cases. At that time getting pictures of the vertebral and arch vessels was a problem. Retrograde techniques using needles and short catheters through the common carotid, subclavian, axillary, and brachial arteries were developed. One technique that was tried for a short while was a direct suprasternal notch puncture of the aortic arch with a long #17 gauge needle. This gave good pictures, but also resulted in bleeding into the upper mediastinum, so the technique was abandoned. With the advent of the retrograde femoral Seldinger technique, carotid punctures were abandoned and selective arteriographic scans using local anesthesia took over. Recent developments have included digital subtraction angiography, magnetic resonance arteriography, and color-flow duplex ultrasound. In the early days it was not clear which patients should undergo surgery. The ones most frequently seen were those who had frank strokes of any degree of severity, including those with coma and hemiplegia. Arteriograms appropriate to the clinical picture were obtained, and total carotid occlusion was a frequent finding. Such severe cases were promptly operated on. Data began to accumulate, however, regarding the outcome of operation on such patients. Thus Wylie et al. in 1964 reported an operative mortality rate of 60% in a small series.34Wylie EJ Hein MF Adams JE Intracranial hemorrhage following surgical revascularization for treatment of acute strokes.J Neurosurg. 1964; 21: 212-218Crossref PubMed Scopus (242) Google Scholar DeWeese et al. in 1968 reported an operative mortality rate of 34% when such patients underwent surgery within 24 hours.28DeWeese JA Rob CG Satran R et al.Surgical treatment for occlusive disease of the carotid artery.Ann Surg. 1968; 168: 85-94Crossref PubMed Scopus (49) Google Scholar In 1966 we reported our results in 45 operated patients with acute profound strokes. Nine patients died, an operative mortality rate of 20%; all nine underwent surgery within 26 hours of onset of the stroke.21Thompson JE Kartchner MM Austin DJ et al.Carotid endarterectomy for cerebrovascular insufficiency (stroke): follow-up of 359 cases.Ann Surg. 1966; 163: 751-763Crossref PubMed Scopus (42) Google Scholar Blaisdell et al. in 1969, reporting for the Joint Study, had an operative mortality rate of 42%, while those who did not undergo surgery had a 20% mortality rate. Patients who underwent surgery more than 14 days after onset had a lower mortality rate of only 17%.35Blaisdell FW Clauss RH Galbraith JG et al.Joint study of extracranial arterial occlusion. IV. A review of surgical considerations.JAMA. 1969; 209: 1889-1895Crossref PubMed Scopus (273) Google Scholar The recommendation from these studies was that it was inadvisable to perform emergency operation on patients with acute profound strokes or rapidly progressing strokes because of the hazard of producing intracerebral hemorrhage and edema in ischemic brain tissue, with subsequent death, after surgical revascularization. If operation was to be considered, a delay of at least 2 weeks or more was necessary for stabilization. In 1986 Meyer et al. at the Mayo Clinic reported performing emergency endarterectomy on 34 patients with acute carotid occlusion who had profound deficits. Despite restoring flow in 94% of these patients, the operative mortality rate was 21% and only 38% were improved.36Meyer FB Sundt Jr, TM Piepgras DG et al.Emergency carotid endarterectomy for patients with acute carotid occlusion and profound neurological deficits.Ann Surg. 1986; 203: 82-88Crossref PubMed Scopus (193) Google Scholar So the problem of the acute profound stroke remains unsolved. There is controversy whether to perform emergent, urgent, or elective surgery on patients with fluctuating or unstable strokes, slowly progressing strokes, and crescendo TIAs. With careful clinical judgment and experience, outcome with emergent or urgent operations can be excellent, as reported by a number of surgeons.37Goldstone J Moore WS A new look at emergency carotid artery operations for the treatment of cerebrovascular insufficiency.Stroke. 1978; 9: 599-602Crossref Scopus (49) Google Scholar, 38Whittemore AD Mannick JA Surgical treatment of carotid disease in patients with neurologic deficits.J Vasc Surg. 1987; 5: 910-913PubMed Scopus (14) Google Scholar, 39Greenhalgh RM Carotid stenosis with unstable fluctuating neurologic deficit.in: Common problems in vascular surgery. Year Book Medical Publishers, Chicago1989: 13-21Google Scholar It soon became obvious that the subject of acute profound strokes could not be divorced from the subject of total carotid occlusion because a large proportion of the former are caused by the latter. In the early days we operated regularly on patients with totally occluded arteries. We soon learned, however, that only 40% of these arteries could be opened by carotid endarterectomy. In 112 patients we found that those who underwent surgery within 6 hours of onset of occlusion had 100% restoration of flow. Much to our amazement, patients who underwent surgery after a month still had a 20% patency rate. Chronic occlusion in the absence of symptoms is not an indication for surgery. Chronic occlusion in the presence of symptoms may occasionally justify surgery. If the occlusion is associated with a profound stroke, operation is not indicated. Clinical considerations of the stroke itself are the most important criteria determining operability.40Thompson JE Austin DJ Patman RD Endarterectomy of the totallly occluded carotid artery for stroke: results in 100 operations.Arch Surg. 1967; 95: 791-801Crossref PubMed Scopus (56) Google Scholar After an early learning period, it soon became clear that the principal role of carotid endarterectomy was prevention of strokes in patients with TIAs, mild deficits, and asymptomatic but significant carotid stenoses, rather than treatment of severe strokes.41Thompson JE Austin DJ Patman RD Carotid endarterectomy for cerebrovascular insufficiency: long-term results in 592 patients followed up to thirteen years.Ann Surg. 1970; 172: 663-679Crossref PubMed Scopus (233) Google Scholar Much progress has been made in carotid surgery over the past 40 years. How do we assess the outcome? In the words of Norman Hertzer, “Results mean everything.”42Hertzer NR Presidential address: outcome assessment in vascular surgery—results mean everything.J Vasc Surg. 1995; 21: 6-15Abstract Full Text Full Text PDF PubMed Scopus (65) Google Scholar The goals of carotid surgery are to relieve symptoms, prevent strokes, and by so doing improve the quality of life, and hopefully to lengthen survival. The evaluation parameters include operative mortality rates, operation-related deficits, long-term strokes, long-term stroke deaths, and long-term survival.43Thompson JE Talkington CM Carotid endarterectomy.in: Advances in surgery. Vol 26. Mosby–Year Book, St. Louis1993: 99-131Google Scholar Of primary concern is the operative mortality rate after endarterectomy. At the outset these elderly patients constituted a high-risk group. Operative mortality data for the first 6 years of our group's experience beginning April 16, 1957, showed that in 272 operations the procedure mortality rate for frank strokes was 8.7%. For TIAs it was 1.7%, and for chronic ischemic and asymptomatic patients it was zero, for an overall mortality rate of 4.8%. After this analysis, we abandoned emergency operation on acute profound strokes, used general anesthesia in most cases, and adopted the routine use of a temporary inlying shunt. The operative mortality rate thus progressively declined. For the next 27 years with 1696 operations, the operative mortality rate for frank strokes was 3.3%, for TIAs 1.2%, and for asymptomatic patients 0.3%, for an overall mortality rate of 1.47%.43Thompson JE Talkington CM Carotid endarterectomy.in: Advances in surgery. Vol 26. Mosby–Year Book, St. Louis1993: 99-131Google Scholar Thus the 33-year experience with 1968 operations gives an overall figure of 1.9%. In a recent 4-year experience, the operative mortality rate for frank strokes has dropped to 1.78%. In a 1988 survey of 15,960 carotid endarterectomies performed for all indications, Hertzer44Hertzer NR Presidential address: carotid endarterectomy—a crisis in confidence.J Vasc Surg. 1988; 7: 611-619Abstract Full Text Full Text PDF PubMed Scopus (34) Google Scholar found the overall average operative mortality rate to be 1.4% and the perioperative stroke rate to be 2.2%. In a number of individual series the operative mortality rate has been less than 1% and the perioperative stroke rate less than 2%.45Nunn DB Carotid endarterectomy in patients with territorial transient ischemic attacks.J Vasc Surg. 1988; 8: 447-452PubMed Scopus (20) Google Scholar Thus in the hands of well-trained, experienced vascular surgeons, with proper selection and timing, carotid endarterectomy can be performed safely with low mortality and morbidity rates. In the early experience about 70% of the operative deaths were from cerebral causes. Once we stopped operating on patients with profound strokes and improved our techniques, deaths from cerebral causes declined markedly, so in recent years operative death has been largely a result of cardiac causes, with an occasional fatality caused by stroke. Another problem we faced at the beginning was how to operate on these patients safely without making their deficits worse or producing new deficits, if they were asymptomatic or had TIAs. At first we tested the patient by compressing the carotid in the neck to see if any symptoms developed. If the patient could stand 20 minutes of carotid compression, he could usually tolerate carotid clamping long enough for performance of endarterectomy. Another maneuver was to operate with the patient under local anesthesia and to test the patient by temporary clamping of the carotid for 5 to 10 minutes, as is still done. If the patient could not tolerate carotid clamping, then we had a problem. Early methods of cerebral protection during carotid clamping included general anesthesia, induced hypertension, hypercapnia, hypocapnia, and hypothermia. General anesthesia is indeed helpful by increasing the tolerance of the brain to ischemia and reducing cerebral metabolic demands for oxygen. Except for general anesthesia, the other methods were abandoned. The use of a temporary bypass shunt thus came to be the most reliable method for cerebral support. The external shunt was the first technique to be used. As far as I can determine, the case described by Cooley in 195625Cooley DA Al-Naaman YD Carton CA Surgical treatment of arteriosclerotic occlusion of common carotid artery.J Neurosurg. 1956; 13: 500-506Crossref PubMed Scopus (54) Google Scholar was the first reported use of an external shunt during carotid endarterectomy. The shunt consisted of a polyvinyl tube with a 14-gauge needle at its lower end and a 16-gauge needle at its upper or internal carotid end. I first used an external shunt similar to Cooley's using 13-gauge needles on January 6, 1958, and continued to use the external shunt until October 1960, when I first used an intraluminal inlying shunt at the suggestion of Stanley Crawford. I have continued to use the inlying shunt first selectively and then routinely since that time. We described our use of this type of shunt before this Society in 1961.46Thompson JE Austin DJ Surgical treatment of arteriosclerotic occlusions of the carotid artery in the neck.Surgery. 1962; 51: 74-83PubMed Google Scholar The shunt solved the problem of cerebral protection during carotid endarterectomy. Over the years extensive discussion has centered on the necessity for routine use of the shunt. Some surgeons have employed it routinely, such as Javid and ourselves, some use it selectively on the basis of an assessment of cerebral collateral circulation, and a few state they rarely or never use it. Methods presently available to determine the adequacy of collateral blood flow during carotid clamping are: (1) determination of cerebral blood flow by the xenon method; (2) temporary carotid occlusion under local anesthesia; (3) determination of stump pressure in the occluded distal internal carotid artery; (4) electroencephalographic monitoring; (5) transcranial Doppler monitoring; and (6) somatosensory evoked potential monitoring. I am fully aware that shunting is not necessary i
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