AUTHOR(S): Redekop, Gary, M.D.; Ferguson, Gary, M.D., Ph.D., F.R.C.S.C. Division of Neurosurgery, The University of Western Ontario, London, Ontario, Canada Neurosurgery 30; 191-194, 1992 ABSTRACT: Two hundred ninety-three carotid endarterectomies were performed with electroencephalogram (EEG) monitoring and without the use of a shunt. Two hundred sixteen patients had contralateral carotid stenosis of less than 70%; 45 had contralateral stenosis of 70 to 99%; and 32 had contralateral occlusion. There were six perioperative strokes (2.0%) and two deaths (0.7%). Major EEG changes were seen in 11 of the 77 patients (14.3%) with significant contralateral stenosis or occlusion versus 11 of the 216 patients (5.1%) in those without (P < 0.025). The risk of immediate postoperative deficit was significantly higher in the subgroup with major EEG changes (4 of 22, 18.2%) than in those without such changes (5 of 271, 1.8%) (P < 0.005). The risk in patients with less than 70% contralateral stenosis (7 of 216, 3.2%) was not significantly different from those with greater contralateral stenosis or occlusion (2 of 77, 2.6%). Carotid endarterectomy can be safely performed without a temporary shunt. Contralateral stenosis or occlusion alone does not confer increased risk. Major EEG changes are infrequent, but they identify a subgroup with significantly higher risk of intraoperative stroke. KEY WORDS: Carotid endarterectomy; Carotid occlusion; Electroencephalogram; Shunt INTRODUCTION The purpose of carotid endarterectomy is to reduce the risk of future stroke. To provide maximum benefit to patients undergoing this procedure, the incidence of stroke related to the procedure must be as low as possible. Many of the technical aspects of the procedure have been refined to reduce the risk of operative complications (10,15). There has been considerable debate, however, about the best method of monitoring cerebral function during the period of carotid cross-clamping, the indications for use of an indwelling shunt, and the specific risks associated with carotid artery surgery in the presence of contralateral carotid occlusion. Intraoperative monitoring techniques that have been developed include the measurement of stump pressure in the internal carotid artery after clamping the common and external carotid arteries (7,12,14), the analysis of regional cerebral blood flow (21), and the assessment of routine (4,26) or computer-analysed (5, 23) electroencephalography (EEG). In addition, some
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surgeons prefer regional anesthesia over general, and they can then monitor mental status changes with internal carotid artery clamping in the awake patient (9) . Some authors advocate the use of shunts in all cases (1,18,20,24), whereas others recommend their selective use based on various intraoperative monitoring techniques to detect cerebral ischemia (9, 11,16,19,21,26) , or others never use them (2,3,7,14,17). The relative merits of selective shunting based on monitoring criteria and the results with this technique in a large series of patients have been documented by Sundt (21). Similar results in a large series in which no shunts were used have been reported by Whitney et al. (25). The presence of contralateral carotid artery occlusion has been considered by most surgeons to add to the surgical risk (1,9,14,15) or at least to increase the necessity for shunting (6,15,26). Several series, however, have now reported excellent results in this patient group (3,11,17-19,24,26). Patients with severe contralateral stenosis, previous ipsilateral cerebral infarction, intraluminal thrombus, or generalized vascular disease have also been considered to be at increased risk of stroke (14,15). To assess objectively the clinical significance of changes seen during intraoperative monitoring and to help answer the question of whether or not the use of shunts is necessary to achieve satisfactory results with this surgery, a series of patients was studied in whom no shunts were used, despite changes observed with intraoperative monitoring. Patients were included in this prospective series regardless of factors predictive of increased risk. This decision was made because of previous reports with excellent results in series where shunts were never used (2,17,25) and because our previous experience in London, Ontario, in which shunts were rarely used, supported these results (7). PATIENTS AND METHODS Two hundred ninety-three carotid endarterectomies were performed on 275 patients between 1978 and 1988. There were 173 men and 102 women, ranging in age from 37 to 82 years, with a mean age of 62 years. Indications for surgery are presented in Table 1. Thirty-two endarterectomies were performed on patients with contralateral carotid occlusion. The indications for surgery in this subgroup are listed in Table 2. Each patient underwent a preoperative cerebral angiogram. Operative technique has been described previously (7), including the use of general anesthesia in all patients. Intraoperative EEG monitoring was used routinely (4), with changes classified as major, moderate, or insignificant (Table 3). Shunts were not used in any patient, regardless of observed EEG changes. Clamp times ranged from 10 to 63 minutes, with a mean of 32 minutes. Statistical analyses were performed using a χ2 with Yates' continuity correction. RESULTS Two hundred sixteen patients had contralateral
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Neurosurgery 1992-98 February 1992, Volume 30, Number 2 191 Correlation of Contralateral Stenosis and Intraoperative Electroencephalogram Change with Risk of Stroke during Carotid Endarterectomy Experimental and Clinical Study
DISCUSSION Because carotid endarterectomy is performed as a prophylactic procedure to prevent the risk of future stroke, it is imperative that the perioperative morbidity and mortality be reduced to an absolute minimum. The combined stroke and death rate of 2.7% in this series of 293 patients compares favorably with results achieved in other large series, including those using shunts routinely, selectively, or not at all (2,3,10,14,17,22,24-26). Much of the controversy regarding the need for shunts to provide cerebral protection during endarterectomy is based on the question of the pathogenesis of intraoperative ischemia (7,8,13,21,22). Shunts have been advocated in the belief that hemodynamic intolerance is the major cause of stroke (1,18,20,21,24), although there is now
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substantial evidence that the majority of strokes associated with endarterectomy are thromboembolic (2,3,7,8,13,17,25) . Shunts present several difficulties, and are no guarantee against intraoperative ischemia. If a shunt is placed before the endarterectomy is complete, atheromatous debris may be embolized or an intimal dissection may be produced, both of which may result in a stroke. The shunt can also limit exposure, particularly if the carotid bifurcation is high, and it may interfere with the adequacy of the endarterectomy at its most critical point--the upper end. Various methods of intraoperative monitoring have been suggested to identify those patients who may be at risk of hemodynamic compromise. This series provides important information about the predictive value of EEG monitoring because shunts were not used in spite of any observed changes. Major EEG changes were seen more frequently in patients with significant contralateral disease (Table 4), although the presence of contralateral stenosis or occlusion alone did not confer increased risk of intraoperative stroke (Table 5). Regardless of the degree of contralateral stenosis, major EEG changes identified a small subgroup of patients with higher risk of neurological deficit in the immediate postoperative period (4 of 22). This EEG alteration may be the result of inadequate collateral circulation, and it could be seen even in the presence of a normal contralateral carotid if there were insufficient intracranial and extracranial anastomotic vessels. It could be that the routine use of shunts in this patient group would reduce the overall risk of intraoperative stroke, but the added technical difficulty and potential for embolization and dissection must be considered. Although contralateral carotid occlusion has been considered a significant risk factor by some authors (1,2,9,14,16,22) , excellent results in this subgroup have now been reported (3,11,17-19,24,26). Patterson (18) reported a series of 23 patients, using a temporary shunt in all cases. There were no perioperative strokes and no deaths. Bland and Lazar (3), in a large series of patients undergoing endarterectomy without intraoperative monitoring and without using a shunt, had 19 patients with contralateral occlusion, also without perioperative stroke or death. Whittemore et al. (26) performed 219 carotid endarterectomies, all with EEG monitoring. They noted EEG changes, which were regarded as an indication for shunting, in 10% of those with unilateral disease, 27% of those with bilateral disease, and 42% of those with unilateral stenosis and contralateral occlusion. There were 2 perioperative strokes in 200 patients with a patent contralateral carotid artery, and none in 19 patients with contralateral occlusion. The results in patients with contralateral occlusion with varying shunt indications are presented in Table 7. In the present series, there were no new neurological deficits attributable to surgery, and one patient who had a major stroke preoperatively died. It is clear that endarterectomy can be performed safely in this group with or without the use of shunts.
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stenosis of less than 70%; 45 had contralateral stenosis of 70 to 99%; and 32 had contralateral carotid occlusion. Major EEG changes were seen in 11 of the 77 patients (14.3%) with contralateral stenosis of 70% or greater or occlusion, whereas such changes were seen in only 11 of the 216 patients (5.1%) with less than 70% contralateral stenosis (P < 0.025). The difference between patients with severe contralateral stenosis and occlusion did not reach statistical significance (Table 4). New neurological deficits occurred within 30 days in 12 patients. Nine of these deficits were present immediately after the surgical procedure, whereas three were delayed in the postoperative period. Four of the nine immediate deficits and two of the three delayed deficits were minor and transient, and the patients had a rapid and full recovery. Five of the immediate deficits and one of the delayed deficits were significant, and the patients had permanent neurological impairment. Thus, the perioperative stroke rate was 6 of the 293 patients or 2.0%. Three of the intraoperative strokes occurred in patients without EEG changes or with only moderate changes, whereas two occurred in patients with major changes. There were two deaths in this series (0.7%). One patient died from a myocardial infarction, which occurred 24 hours after surgery, and one died as a result of a massive, bihemispheric infarction, which was progressing preoperatively despite anticoagulation with heparin. This patient underwent emergency endarterectomy on an ulcerated plaque with 95% stenosis in the presence of contralateral occlusion. There were no new deficits attributable to surgery, but the preoperative course was unaltered. Of the nine cases in which immediate neurological deficits were present postoperatively, four of these occurred in the 22 patients with major EEG changes (18.2%), whereas five occurred in the 271 patients without such changes (1.8%) (P < 0.005). The risk in patients with less than 70% contralateral stenosis (7 of 216, 3.2%) was not significantly different from those with greater stenosis or occlusion (2 of 77, 2.6%). There were no immediate postoperative deficits in any of the 32 patients with contralateral occlusion (Table 5). The results of EEG monitoring related to postoperative neurological deficits are presented in Table 6.
11.
12.
13.
14.
15. 16.
Received for publication, June 17, 1991; accepted, September 9, 1991. Reprint requests: Gary Ferguson, M.D., Division of Neurosurgery, University Hospital, 339 Windermere Road, London, Ontario, Canada N6A 5A5.
17.
REFERENCES: (1-26) 18. 1.
2. 3. 4. 5.
6.
7. 8. 9.
10.
Andersen CA, Rich NM, Collins GJ, McDonald PT, Boone SC: Unilateral carotid arterial occlusion: Special considerations. Stroke 8:669-671, 1977. Baker WH, Dorner DB, Barnes RW: Carotid endarterectomy: Is an indwelling shunt necessary? Surgery 82:321-326, 1977. Bland JE, Lazar ML: Carotid endarterectomy without shunt. Neurosurgery 8:153-157, 1981. Blume WT, Ferguson GG, McNeill DK: Significance of EEG changes at carotid endarterectomy. Stroke 17:891-897, 1986. Chiappa KH, Burke SR, Young RR: Results of electroencephalographic monitoring during 367 carotid endarterectomies. Stroke 10:381388, 1979. Collice M, Arena O, Fontana RA, Mola M, Galbiati N: Role of EEG monitoring and crossclamping duration in carotid endarterectomy. J Neurosurg 65:815-819, 1986. Ferguson GG: Extracranial carotid artery surgery. Clin Neurosurg 29:543-574, 1982. Ferguson GG: Carotid endarterectomy. To shunt or not to shunt? Arch Neurol 43:615617, 1986. Friedman SG, Riles TS, Lamparello PJ, Imparato AM, Sakwa MP: Surgical therapy for the patient with internal carotid artery occlusion and contralateral stenosis. J Vasc Surg 5:856-861, 1987. Giannotta SL, Dicks RE, Kindt GW: Carotid endarterectomy: Technical improvements.
Downloaded from https://academic.oup.com/neurosurgery/article-abstract/30/2/191/2752956 by Frankfurt Univesity Library user on 04 March 2018
19.
20.
21.
22.
23.
24. 25.
Neurosurgery 7:309-312, 1980. Hammacher ER, Eikelboom BC, Bast TJ, DeGeest R, Vermeulen FE: Surgical treatment of patients with a carotid artery occlusion and a contralateral stenosis. J Cardiovasc Surg (Torino) 25:513-517, 1984. Hunter GC, Sieffert G, Malone JM, Moore WS: The accuracy of carotid back pressure as an index for shunt requirements: A reappraisal. Stroke 13:319-326, 1982. Krul JM, van Gijn J, Ackerstaff RG, Eikelboom BC, Theodorides T, Vermeulen FE: Site and pathogenesis of infarcts associated with carotid endarterectomy. Stroke 20:324-328, 1989. Littooy FN, Halstuk KS, Mamdani M, Calandra D, Hayes A, Baker WH: Factors influencing morbidity of carotid endarterectomy without a shunt. Am Surgeon 50:350-353, 1984. Loftus CM, Quest DO: Technical controversies in carotid artery surgery. Neurosurgery 20:490-495, 1987. Moore DJ, Modi JR, Finch WT, Sumner DS: Influence of the contralateral carotid artery on neurologic complications following carotid endarterectomy. J Vasc Surg 1:409-414, 1984. Ott DA, Cooley DA, Chapa L, Coelho A: Carotid endarterectomy without temporary intraluminal shunt. Ann Surg 191:708-714, 1980. Patterson RH: Risk of carotid artery surgery with occlusion of the contralateral carotid artery. Arch Neurol 30:188-189, 1974. Phillips MR, Johnson WC, Scott RM, Vollman RW, Levine H, Nabseth D: Carotid endarterectomy in the presence of contralateral carotid occlusion. The role of EEG and intraluminal shunting. Arch Surg 114:1232-1239, 1979. Sachs SM, Fulenwider JT, Smith RB, Darden WA, Salam A, Perdue GD: Does contralateral carotid occlusion influence neurologic fate of carotid endarterectomy? Surgery 96:839-844, 1984. Sundt TM: The ischemic tolerance of neural tissue and the need for monitoring and selective shunting during carotid endarterectomy. Stroke 14:93-98, 1983. Sundt TM: Occlusive Cerebrovascular Disease. Diagnosis and Surgical Management. Philadelphia, WB Saunders, 1987, pp 182-231. Tempelhoff R, Modica PA, Grubb RL, Rich KM, Holtmann B: Selective shunting during carotid endarterectomy based on two-channel computerized electroencephalographic/compressed spectral array analysis. Neurosurgery 24:339-344, 1989. Thompson JE, Talkington CM: Carotid endarterectomy. Ann Surg 184:1-15, 1976. Whitney DG, Kahn EM, Estes JW, Jones CE: Carotid artery surgery without a temporary
Redistribution of this article permitted only in accordance with the publisher’s copyright provisions.
CONCLUSIONS The purpose of this report is to demonstrate the safe performance of carotid endarterectomy without an intraluminal shunt, not to condemn its use. The surgeon who obtains satisfactory results using the shunt should continue to do so. Our experience, however, confirms that excellent clinical results can be achieved without a shunt, even in patients with significant contralateral stenosis or occlusion. Our data suggest that contralateral stenosis or occlusion alone does not confer an increased risk of intraoperative stroke, although major EEG changes were observed more frequently in those patients with significant contralateral disease. Regardless of the degree of contralateral stenosis, major EEG changes identified a small subgroup with significantly higher risk of intraoperative ischemia, presumably reflecting a lack of adequate collateral flow. In this objectively identified subgroup, intraoperative shunts may prove beneficial to reduce the risk of stroke. This hypothesis remains to be proven, however, as there are added technical difficulties associated with shunt use.
COMMENT This report by Drs. Redekop and Ferguson is a major contribution to our understanding of the risks and benefits in extracranial carotid surgery. Although not all the information is new, the authors' use of a prospective trial and a diligent pursuit of one surgical treatment plan (no shunting) is laudable. The major findings in this study are worth repeating. First, it is clear that major electroencephlogram (EEG) changes during carotid surgery identify a high-risk subgroup that the surgeon should consider for intraluminal shunting. Contralateral stenosis of greater than 70% or frank contralateral occlusion appeared to make little difference in terms of additional risk, and, in point of fact, they did not add to the risk of neurological deficit reported for patients in this series. With each addition of such findings to the literature, it becomes clearer that the major cause of perioperative stroke in carotid artery surgery is embolization rather than cross-clamp ischemia. Surgical progress will be accomplished best by attention to technical details, including tacking sutures, adequate arterial inspection and repair, and prevention of particulate embolization, both during vessel dissection and reopening of the arterial tree, rather than by continued and, most likely, futile debate about the propriety of shunting. My personal preference has been to use an indwelling shunt in patients where either moderate or major EEG changes are identified. Thus, my indications for shunt use are somewhat more relaxed than Drs. Redekop and Ferguson. With my technique, because most patients with an EEG change are shunted, there is no way to correlate postoperative deficit with the presence of a major EEG change. The authors are to be congratulated for a significant contribution to the cerebrovascular literature in a welldocumented series of carotid patients. Christopher M. Loftus Iowa City, Iowa
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Redistribution of this article permitted only in accordance with the publisher’s copyright provisions.
26.
indwelling shunt: 1,917 consecutive procedures. Arch Surg 115:1393-1399, 1980. Whittemore AD, Kauffman JL, Kohler TR, Mannick JA: Routine EEG monitoring during carotid endarterectomy. Ann Surg 197:707713, 1983.
Table 2. Indications for Carotid Endarterectomy in 32 Patients with Contralateral Carotid Occlusion
Table 3. Electroencephalogram Interpretation
Table 4. Electroencephalogram Change Related to Contralateral Carotid Stenosis
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Table 1. Indications for Carotid Endarterectomy in 293 Patients
Table 5. Contralateral Carotid Stenosis Related to Immediate Postoperative Deficits
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Table 6. Electroencephalogram Changes Related to Immediate Postoperative Deficits
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Table 7. Selected Series with Carotid Stenosis and Contralateral Carotid Occlusion
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surgeons prefer regional anesthesia over general, and they can then monitor mental status changes with internal carotid artery clamping in the awake patient (9) . Some authors advocate the use of shunts in all cases (1,18,20,24), whereas others recommend their selective use based on various intraoperative monitoring techniques to detect cerebral ischemia (9, 11,16,19,21,26) , or others never use them (2,3,7,14,17). The relative merits of selective shunting based on monitoring criteria and the results with this technique in a large series of patients have been documented by Sundt (21). Similar results in a large series in which no shunts were used have been reported by Whitney et al. (25). The presence of contralateral carotid artery occlusion has been considered by most surgeons to add to the surgical risk (1,9,14,15) or at least to increase the necessity for shunting (6,15,26). Several series, however, have now reported excellent results in this patient group (3,11,17-19,24,26). Patients with severe contralateral stenosis, previous ipsilateral cerebral infarction, intraluminal thrombus, or generalized vascular disease have also been considered to be at increased risk of stroke (14,15). To assess objectively the clinical significance of changes seen during intraoperative monitoring and to help answer the question of whether or not the use of shunts is necessary to achieve satisfactory results with this surgery, a series of patients was studied in whom no shunts were used, despite changes observed with intraoperative monitoring. Patients were included in this prospective series regardless of factors predictive of increased risk. This decision was made because of previous reports with excellent results in series where shunts were never used (2,17,25) and because our previous experience in London, Ontario, in which shunts were rarely used, supported these results (7). PATIENTS AND METHODS Two hundred ninety-three carotid endarterectomies were performed on 275 patients between 1978 and 1988. There were 173 men and 102 women, ranging in age from 37 to 82 years, with a mean age of 62 years. Indications for surgery are presented in Table 1. Thirty-two endarterectomies were performed on patients with contralateral carotid occlusion. The indications for surgery in this subgroup are listed in Table 2. Each patient underwent a preoperative cerebral angiogram. Operative technique has been described previously (7), including the use of general anesthesia in all patients. Intraoperative EEG monitoring was used routinely (4), with changes classified as major, moderate, or insignificant (Table 3). Shunts were not used in any patient, regardless of observed EEG changes. Clamp times ranged from 10 to 63 minutes, with a mean of 32 minutes. Statistical analyses were performed using a χ2 with Yates' continuity correction. RESULTS Two hundred sixteen patients had contralateral
Redistribution of this article permitted only in accordance with the publisher’s copyright provisions.
Neurosurgery 1992-98 February 1992, Volume 30, Number 2 191 Correlation of Contralateral Stenosis and Intraoperative Electroencephalogram Change with Risk of Stroke during Carotid Endarterectomy Experimental and Clinical Study
DISCUSSION Because carotid endarterectomy is performed as a prophylactic procedure to prevent the risk of future stroke, it is imperative that the perioperative morbidity and mortality be reduced to an absolute minimum. The combined stroke and death rate of 2.7% in this series of 293 patients compares favorably with results achieved in other large series, including those using shunts routinely, selectively, or not at all (2,3,10,14,17,22,24-26). Much of the controversy regarding the need for shunts to provide cerebral protection during endarterectomy is based on the question of the pathogenesis of intraoperative ischemia (7,8,13,21,22). Shunts have been advocated in the belief that hemodynamic intolerance is the major cause of stroke (1,18,20,21,24), although there is now
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substantial evidence that the majority of strokes associated with endarterectomy are thromboembolic (2,3,7,8,13,17,25) . Shunts present several difficulties, and are no guarantee against intraoperative ischemia. If a shunt is placed before the endarterectomy is complete, atheromatous debris may be embolized or an intimal dissection may be produced, both of which may result in a stroke. The shunt can also limit exposure, particularly if the carotid bifurcation is high, and it may interfere with the adequacy of the endarterectomy at its most critical point--the upper end. Various methods of intraoperative monitoring have been suggested to identify those patients who may be at risk of hemodynamic compromise. This series provides important information about the predictive value of EEG monitoring because shunts were not used in spite of any observed changes. Major EEG changes were seen more frequently in patients with significant contralateral disease (Table 4), although the presence of contralateral stenosis or occlusion alone did not confer increased risk of intraoperative stroke (Table 5). Regardless of the degree of contralateral stenosis, major EEG changes identified a small subgroup of patients with higher risk of neurological deficit in the immediate postoperative period (4 of 22). This EEG alteration may be the result of inadequate collateral circulation, and it could be seen even in the presence of a normal contralateral carotid if there were insufficient intracranial and extracranial anastomotic vessels. It could be that the routine use of shunts in this patient group would reduce the overall risk of intraoperative stroke, but the added technical difficulty and potential for embolization and dissection must be considered. Although contralateral carotid occlusion has been considered a significant risk factor by some authors (1,2,9,14,16,22) , excellent results in this subgroup have now been reported (3,11,17-19,24,26). Patterson (18) reported a series of 23 patients, using a temporary shunt in all cases. There were no perioperative strokes and no deaths. Bland and Lazar (3), in a large series of patients undergoing endarterectomy without intraoperative monitoring and without using a shunt, had 19 patients with contralateral occlusion, also without perioperative stroke or death. Whittemore et al. (26) performed 219 carotid endarterectomies, all with EEG monitoring. They noted EEG changes, which were regarded as an indication for shunting, in 10% of those with unilateral disease, 27% of those with bilateral disease, and 42% of those with unilateral stenosis and contralateral occlusion. There were 2 perioperative strokes in 200 patients with a patent contralateral carotid artery, and none in 19 patients with contralateral occlusion. The results in patients with contralateral occlusion with varying shunt indications are presented in Table 7. In the present series, there were no new neurological deficits attributable to surgery, and one patient who had a major stroke preoperatively died. It is clear that endarterectomy can be performed safely in this group with or without the use of shunts.
Redistribution of this article permitted only in accordance with the publisher’s copyright provisions.
stenosis of less than 70%; 45 had contralateral stenosis of 70 to 99%; and 32 had contralateral carotid occlusion. Major EEG changes were seen in 11 of the 77 patients (14.3%) with contralateral stenosis of 70% or greater or occlusion, whereas such changes were seen in only 11 of the 216 patients (5.1%) with less than 70% contralateral stenosis (P < 0.025). The difference between patients with severe contralateral stenosis and occlusion did not reach statistical significance (Table 4). New neurological deficits occurred within 30 days in 12 patients. Nine of these deficits were present immediately after the surgical procedure, whereas three were delayed in the postoperative period. Four of the nine immediate deficits and two of the three delayed deficits were minor and transient, and the patients had a rapid and full recovery. Five of the immediate deficits and one of the delayed deficits were significant, and the patients had permanent neurological impairment. Thus, the perioperative stroke rate was 6 of the 293 patients or 2.0%. Three of the intraoperative strokes occurred in patients without EEG changes or with only moderate changes, whereas two occurred in patients with major changes. There were two deaths in this series (0.7%). One patient died from a myocardial infarction, which occurred 24 hours after surgery, and one died as a result of a massive, bihemispheric infarction, which was progressing preoperatively despite anticoagulation with heparin. This patient underwent emergency endarterectomy on an ulcerated plaque with 95% stenosis in the presence of contralateral occlusion. There were no new deficits attributable to surgery, but the preoperative course was unaltered. Of the nine cases in which immediate neurological deficits were present postoperatively, four of these occurred in the 22 patients with major EEG changes (18.2%), whereas five occurred in the 271 patients without such changes (1.8%) (P < 0.005). The risk in patients with less than 70% contralateral stenosis (7 of 216, 3.2%) was not significantly different from those with greater stenosis or occlusion (2 of 77, 2.6%). There were no immediate postoperative deficits in any of the 32 patients with contralateral occlusion (Table 5). The results of EEG monitoring related to postoperative neurological deficits are presented in Table 6.
11.
12.
13.
14.
15. 16.
Received for publication, June 17, 1991; accepted, September 9, 1991. Reprint requests: Gary Ferguson, M.D., Division of Neurosurgery, University Hospital, 339 Windermere Road, London, Ontario, Canada N6A 5A5.
17.
REFERENCES: (1-26) 18. 1.
2. 3. 4. 5.
6.
7. 8. 9.
10.
Andersen CA, Rich NM, Collins GJ, McDonald PT, Boone SC: Unilateral carotid arterial occlusion: Special considerations. Stroke 8:669-671, 1977. Baker WH, Dorner DB, Barnes RW: Carotid endarterectomy: Is an indwelling shunt necessary? Surgery 82:321-326, 1977. Bland JE, Lazar ML: Carotid endarterectomy without shunt. Neurosurgery 8:153-157, 1981. Blume WT, Ferguson GG, McNeill DK: Significance of EEG changes at carotid endarterectomy. Stroke 17:891-897, 1986. Chiappa KH, Burke SR, Young RR: Results of electroencephalographic monitoring during 367 carotid endarterectomies. Stroke 10:381388, 1979. Collice M, Arena O, Fontana RA, Mola M, Galbiati N: Role of EEG monitoring and crossclamping duration in carotid endarterectomy. J Neurosurg 65:815-819, 1986. Ferguson GG: Extracranial carotid artery surgery. Clin Neurosurg 29:543-574, 1982. Ferguson GG: Carotid endarterectomy. To shunt or not to shunt? Arch Neurol 43:615617, 1986. Friedman SG, Riles TS, Lamparello PJ, Imparato AM, Sakwa MP: Surgical therapy for the patient with internal carotid artery occlusion and contralateral stenosis. J Vasc Surg 5:856-861, 1987. Giannotta SL, Dicks RE, Kindt GW: Carotid endarterectomy: Technical improvements.
Downloaded from https://academic.oup.com/neurosurgery/article-abstract/30/2/191/2752956 by Frankfurt Univesity Library user on 04 March 2018
19.
20.
21.
22.
23.
24. 25.
Neurosurgery 7:309-312, 1980. Hammacher ER, Eikelboom BC, Bast TJ, DeGeest R, Vermeulen FE: Surgical treatment of patients with a carotid artery occlusion and a contralateral stenosis. J Cardiovasc Surg (Torino) 25:513-517, 1984. Hunter GC, Sieffert G, Malone JM, Moore WS: The accuracy of carotid back pressure as an index for shunt requirements: A reappraisal. Stroke 13:319-326, 1982. Krul JM, van Gijn J, Ackerstaff RG, Eikelboom BC, Theodorides T, Vermeulen FE: Site and pathogenesis of infarcts associated with carotid endarterectomy. Stroke 20:324-328, 1989. Littooy FN, Halstuk KS, Mamdani M, Calandra D, Hayes A, Baker WH: Factors influencing morbidity of carotid endarterectomy without a shunt. Am Surgeon 50:350-353, 1984. Loftus CM, Quest DO: Technical controversies in carotid artery surgery. Neurosurgery 20:490-495, 1987. Moore DJ, Modi JR, Finch WT, Sumner DS: Influence of the contralateral carotid artery on neurologic complications following carotid endarterectomy. J Vasc Surg 1:409-414, 1984. Ott DA, Cooley DA, Chapa L, Coelho A: Carotid endarterectomy without temporary intraluminal shunt. Ann Surg 191:708-714, 1980. Patterson RH: Risk of carotid artery surgery with occlusion of the contralateral carotid artery. Arch Neurol 30:188-189, 1974. Phillips MR, Johnson WC, Scott RM, Vollman RW, Levine H, Nabseth D: Carotid endarterectomy in the presence of contralateral carotid occlusion. The role of EEG and intraluminal shunting. Arch Surg 114:1232-1239, 1979. Sachs SM, Fulenwider JT, Smith RB, Darden WA, Salam A, Perdue GD: Does contralateral carotid occlusion influence neurologic fate of carotid endarterectomy? Surgery 96:839-844, 1984. Sundt TM: The ischemic tolerance of neural tissue and the need for monitoring and selective shunting during carotid endarterectomy. Stroke 14:93-98, 1983. Sundt TM: Occlusive Cerebrovascular Disease. Diagnosis and Surgical Management. Philadelphia, WB Saunders, 1987, pp 182-231. Tempelhoff R, Modica PA, Grubb RL, Rich KM, Holtmann B: Selective shunting during carotid endarterectomy based on two-channel computerized electroencephalographic/compressed spectral array analysis. Neurosurgery 24:339-344, 1989. Thompson JE, Talkington CM: Carotid endarterectomy. Ann Surg 184:1-15, 1976. Whitney DG, Kahn EM, Estes JW, Jones CE: Carotid artery surgery without a temporary
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CONCLUSIONS The purpose of this report is to demonstrate the safe performance of carotid endarterectomy without an intraluminal shunt, not to condemn its use. The surgeon who obtains satisfactory results using the shunt should continue to do so. Our experience, however, confirms that excellent clinical results can be achieved without a shunt, even in patients with significant contralateral stenosis or occlusion. Our data suggest that contralateral stenosis or occlusion alone does not confer an increased risk of intraoperative stroke, although major EEG changes were observed more frequently in those patients with significant contralateral disease. Regardless of the degree of contralateral stenosis, major EEG changes identified a small subgroup with significantly higher risk of intraoperative ischemia, presumably reflecting a lack of adequate collateral flow. In this objectively identified subgroup, intraoperative shunts may prove beneficial to reduce the risk of stroke. This hypothesis remains to be proven, however, as there are added technical difficulties associated with shunt use.
COMMENT This report by Drs. Redekop and Ferguson is a major contribution to our understanding of the risks and benefits in extracranial carotid surgery. Although not all the information is new, the authors' use of a prospective trial and a diligent pursuit of one surgical treatment plan (no shunting) is laudable. The major findings in this study are worth repeating. First, it is clear that major electroencephlogram (EEG) changes during carotid surgery identify a high-risk subgroup that the surgeon should consider for intraluminal shunting. Contralateral stenosis of greater than 70% or frank contralateral occlusion appeared to make little difference in terms of additional risk, and, in point of fact, they did not add to the risk of neurological deficit reported for patients in this series. With each addition of such findings to the literature, it becomes clearer that the major cause of perioperative stroke in carotid artery surgery is embolization rather than cross-clamp ischemia. Surgical progress will be accomplished best by attention to technical details, including tacking sutures, adequate arterial inspection and repair, and prevention of particulate embolization, both during vessel dissection and reopening of the arterial tree, rather than by continued and, most likely, futile debate about the propriety of shunting. My personal preference has been to use an indwelling shunt in patients where either moderate or major EEG changes are identified. Thus, my indications for shunt use are somewhat more relaxed than Drs. Redekop and Ferguson. With my technique, because most patients with an EEG change are shunted, there is no way to correlate postoperative deficit with the presence of a major EEG change. The authors are to be congratulated for a significant contribution to the cerebrovascular literature in a welldocumented series of carotid patients. Christopher M. Loftus Iowa City, Iowa
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26.
indwelling shunt: 1,917 consecutive procedures. Arch Surg 115:1393-1399, 1980. Whittemore AD, Kauffman JL, Kohler TR, Mannick JA: Routine EEG monitoring during carotid endarterectomy. Ann Surg 197:707713, 1983.
Table 2. Indications for Carotid Endarterectomy in 32 Patients with Contralateral Carotid Occlusion
Table 3. Electroencephalogram Interpretation
Table 4. Electroencephalogram Change Related to Contralateral Carotid Stenosis
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Table 1. Indications for Carotid Endarterectomy in 293 Patients
Table 5. Contralateral Carotid Stenosis Related to Immediate Postoperative Deficits
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Table 6. Electroencephalogram Changes Related to Immediate Postoperative Deficits
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Table 7. Selected Series with Carotid Stenosis and Contralateral Carotid Occlusion
