Carotid artery surgery without a temporary indwelling shunt. 1,917 consecutive procedures

Importance of cerebral angiography and intraoperative neuromonitoring in carotid endarterectomy

It is an increasingly common practice to indicate a carotid endarterectomy procedure based on the information provided by non-invasive tests like Duplex ultrasound, MR angiography or CT angiography, thereby obviating the performance of a conventional cerebral angiography. We present a case of symptomatic left carotid artery 80% stenosis in which cerebral angiography showed absence of the right A1 segment and bilateral anterior cerebral artery territories that filled only from a left injection. Just 90seconds after carotid artery clamping at the neck, brain oximetry and somatosensory evoked potentials significantly dropped, that recovered after immediate clamp removal. Endarterectomy was dismissed and a carotid stent was successfully placed. This case highlights the importance of knowing the dynamics of cerebral blood circulation distal to the stenosis. If endarterectomy had been attempted, unawareness of the information provided by the cerebral angiography would have likely result in severe bi-hemispheric ischemia.

Preoperative digital carotid compression as a predictor of the need for shunting during carotid endarterectomy

This study prospectively attempted to assess the need for shunting by preoperative digital compression of the proximal common carotid artery and correlated these findings with intraoperative assessment while performing carotid endarterectomy under local anaesthesia. Preoperative digital compression is highly predictive of the need for shunting intra-operatively and can be used as a valuable test in carefully chosen patients. This may help in decreasing the need for advanced neurological monitoring during carotid endarterectomy.

Shunting during carotid endarterectomy

BACKGROUND

The use of shunting during carotid endarterectomy (CEA) is controversial. While some surgeons advocate routine shunting, others prefer selective shunting or no shunting. Several large series have documented excellent results of CEA with routine shunting or without shunts. Others reported similar results with selective shunting using transcranial Doppler (TCD), electroencephalogram (EEG) monitoring, carotid stump pressure (SP), cervical block anesthesia (CBA), and somatosensory evoked potential (SSEP). In this study, we review the available evidence supporting shunting, nonshunting, and selective shunting during CEA.

METHODS

An electronic PubMed/MEDLINE search was conducted to identify all published CEA studies between January 1990 and December 2010, that analyzed the perioperative outcome of routine shunting, routine nonshunting, routine versus selective shunting, selecting shunting versus avoiding a shunt, and selective shunting based on EEG, TCD, SP, CBA, and SSEP.

RESULTS

The mean reported perioperative stroke rate for CEAs with routine shunting was 1.4% and for routine nonshunt was 2%. Meanwhile, the mean perioperative stroke rates for selecting shunting were 1.6% using EEG, 4.8% using TCD, 1.6% using SP, 1.8% using SSEP, and 1.1% for CBA. Similar results were noted for perioperative stroke and death rates.

CONCLUSIONS

The use of routine shunting and selective shunting was associated with a low stroke rate. Both methods are acceptable, and the individual surgeon should select the method with which they are more comfortable.

Carotid endarterectomy, carotid artery shunting and outcome: an historical perspective

PURPOSE OF REVIEW

Carotid endarterectomy is now celebrating its 50th anniversary! Yet, despite millions of these operations having been performed, there is little agreement about the best methods of surgical technique, cerebral protection, anesthetic technique and monitoring methods. In this time of evidence-based medicine, carotid endarterectomy fares badly, with only the indications for the surgery having been subjected to the appropriate methodology of clinical trials and biostatistics for proper evaluation. This review is designed to look back over the history of carotid endarterectomy in order to understand the evolution of current practices.

RECENT FINDINGS

Within the past 5 years, despite the publication of many papers dealing with issues surrounding carotid shunting, no randomized controlled trials evaluating this aspect of carotid artery surgery have appeared. One must probe further into the past to understand how so much can be written yet so little learned!

SUMMARY

Current evidence is not able to support the hypothesis that shunting during carotid artery surgery reduces the risk of perioperative stroke or death or that its use is associated with an increase in perioperative or long-term complications. Routine, selective or no shunting protocols during carotid artery surgery remain a matter of local custom and tradition.

The evolution of extracranial carotid artery surgery as seen by one surgeon over the past 40 years

Carotid endarterectomy is one of the most common vascular and neurosurgical operations. Controversies regarding its indications and safety have required several decades before general resolution, while its methodology is still debated. The first operations are described with particular emphasis on the epic successful procedure in 1954 by Eastcott and Rob. Early procedures were on patients with frank strokes with poor results. The development of carotid endarterectomy was slow because neurologists were unsure of its effectiveness and safety as the mortality and stroke results recorded by untrained surgeons were unacceptable. It was not until some 35 years after its introduction that randomised controlled trials, both in North America and Europe, defined its indications and demonstrated its benefits for both symptomatic and asymptomatic carotid stenosis. Clamping of the carotid vessels, required during endarterectomy, may result in various degrees of cerebral ischaemia. Methods to determine which patients need shunting are compared. The author has employed local neck block anesthesia since 1972, which is the only method that provides constant neurological assessment for selective shunting during carotid cross clamping. Evidence is presented showing that local anaesthesia also reduces complications of general anaesthesia, especially myocardial infarction. The technique of neck block, conventional endarterectomy and two varieties of eversion endarterectomy for carotid disease are described. Each of these techniques of endarterectomy is advantageous in certain circumstances, suggesting that vascular surgeons should ideally be proficient in each. Likewise, the management of early stroke after operation, stenotic or occluded external carotid the presence of retinal Hollenhorst plaques, and the totally occluded internal carotid, is presented. Finally, observations on some famous figures who suffered from cerebrovascular complications secondary to carotid disease and what effect it may have had on world history is discussed.

Systematic review of the risks of carotid endarterectomy in relation to the clinical indication for and timing of surgery

BACKGROUND AND PURPOSE

Reliable data on the risk of carotid endarterectomy (CEA) in relation to clinical indication and timing of surgery are necessary to target CEA more effectively, to inform patients, to adjust risks for case mix, and to understand the mechanisms of operative stroke.

METHODS

We performed a systematic review of all studies published from 1980 to 2000 inclusive that reported the risk of stroke and death resulting from CEA. Pooled estimates of risk by type of presenting ischemic event and time since the last event were obtained by Mantel-Haenszel meta-analysis.

RESULTS

Of 383 published studies, only 103 stratified risk by indication. Although the operative risk for symptomatic stenosis overall was higher than for asymptomatic stenosis (odds ratio [OR], 1.62; 95% confidence interval [CI], 1.45 to 1.81; P<0.00001; 59 studies), risk in patients with ocular events only tended to be lower than for asymptomatic stenosis (OR, 0.75, 95% CI, 0.50 to 1.14; 15 studies). Operative risk was the same for stroke and cerebral transient ischemic attack (OR, 1.16; 95% CI, 0.99 to 1.35; P=0.08; 23 studies) but higher for cerebral transient ischemic attack than for ocular events only (OR, 2.31; 95% CI, 1.72 to 3.12; P<0.00001; 19 studies) and for CEA for restenosis than primary surgery (OR, 1.95; 95% CI, 1.21 to 3.16; P=0.018; 6 studies). Urgent CEA for evolving symptoms had a much higher risk (19.2%, 95% CI, 10.7 to 27.8) than CEA for stable symptoms (OR, 3.9; 95% CI, 2.7 to 5.7; P<0.001; 13 studies), but there was no difference between early (<3 to 6 weeks) and late (>3 to 6 weeks) CEA for stroke in stable patients (OR, 1.13; 95% CI, 0.79 to 1.62; P=0.62; 11 studies). All observations were highly consistent across studies.

CONCLUSIONS

Risk of stroke and death resulting from CEA is highly dependent on the clinical indication. Audits of risk should be stratified accordingly, and patients should be informed of the risk that relates to their presenting event.

Patient satisfaction after carotid endarterectomy using a selective policy of local anesthesia

BACKGROUND

Patient satisfaction after carotid endarterectomy has not been specifically studied or reported. Results of carotid endarterectomy using either local or general anesthesia have been widely reported, and outcomes are not significantly different for either technique. Patient satisfaction data were obtained in order to determine whether patients preferred one method of anesthesia over another. Data regarding outcome may be added to the surgical literature as benchmark data when comparing operative carotid endarterectomy to newer techniques.

METHODS

During a 30-month period, 186 consecutive carotid endarterectomies were performed on 169 patients by a single surgeon with assistance from senior surgical residents. All patients were offered local anesthesia using a cervical block technique with intraoperative supplementation. Patients for whom local anesthesia was inappropriate or who declined were operated on using general endotracheal anesthesia. Results of operation were tabulated including indication for operation, method of anesthesia, intraoperative and postoperative complications, and mortality, and completion of a patient satisfaction survey form either on postoperative visit or by telephone questionnaire.

RESULTS

Of 169 patients who underwent carotid endarterectomy, 151 (89%) completed the satisfaction survey form. One hundred fourteen (62%) had local anesthesia and 71 patients (38%) had general anesthesia. There was 1 stroke (0.5%) and 1 death (0.5%) in the series. Perioperative complications including temporary cranial nerve injury, neck hematoma, myocardial infarction, and restenosis were noted and not significantly different in either the general anesthesia or local anesthesia group. Patient satisfaction data including intraoperative discomfort, postoperative pain, attentiveness of the operating room staff, and length of stay were all tabulated. There was no statistically significant difference in satisfaction between the general anesthesia group and the local anesthesia group (chi-square and Fisher's exact test). Additionally, satisfaction with the procedure was extremely high.

CONCLUSIONS

Patient outcome and perception of pain and recovery were not statistically significantly different in patients undergoing carotid endarterectomy using local anesthesia compared with general anesthesia. Overall patient satisfaction was extremely high. Patients should be offered carotid endarterectomy using an anesthesia technique with which the surgeon and patients are both comfortable, having confidence that the outcome is not related to anesthesia technique and that patients will be highly satisfied.

Continuous electroencephalographic monitoring and selective shunting reduces neurologic morbidity rates in carotid endarterectomy

PURPOSE

The role of continuous electroencephalographic (EEG) monitoring during carotid endarterectomy was evaluated in this retrospective review.

METHODS

We analyzed data from 902 consecutive carotid endarterectomy procedures performed with vein patch angioplasty. In 591 operations from 1980 to 1988 we did not use intraoperative EEG monitoring or shunting (non-EEG group). Continuous intraoperative EEG monitoring and selective shunting were used in 311 procedures from 1988 to 1994 (EEG group). The patients' mean age was higher in the EEG group (68.8 years; range, 41 to 87 years) than in the non-EEG group (66.2 years; range, 34 to 90 years; p < 0.001). There was also a significantly higher incidence of hypertension (56.2% vs 41.9%) and redo operations (5.4% vs 2.54%) in the EEG group than in the non-EEG group (p < 0.05). The operative technique was identical in both groups. We defined a significant EEG change as a greater than 50% reduction of the amplitude of the faster frequencies, a persistent increase of delta activity, or both.

RESULTS

In the EEG group, acute EEG changes occurred in 40 patients (12.8%); 31 (77.5%) unilateral and ipsilateral to the operated carotid artery, and nine (22.5%) bilateral. In five patients (12.5%) the changes correlated with an intraoperative episode of hypotension, and after normal blood pressure was restored the EEG returned to normal. In 35 procedures (87.5%) a carotid shunt was inserted. In 33 of those patients the EEG returned to baseline, in one patient there was a significant improvement, and in one patient the EEG changes persisted. Postoperative hospital strokes occurred in one patient (0.32%) in the EEG group and in 13 patients (2.19%) in the non-EEG group (p < 0.05). All strokes (n = 14) were ipsilateral to the operated carotid artery. Of the 13 strokes in the non-EEG group nine were major and four were minor. The one stroke in the EEG group was embolic in origin and occurred before carotid cross-clamping; it was associated with profound EEG changes that did not reverse after placement of a shunt. In the total group (n = 902), intraoperative EEG monitoring was inversely associated with postoperative stroke (p < 0.05).

CONCLUSION

The overall neurologic morbidity rate was significantly lower in the EEG group than in the non-EEG group, therapy demonstrating the value of intraoperative EEG monitoring in carotid endarterectomy.

Inadequate cerebral perfusion is an unlikely cause of perioperative stroke

The purpose of this study was to determine the importance of hypoperfusion ischemia as a cause of stroke during carotid endarterectomy (CEA). A retrospective analysis of 128 consecutive CEA procedures were examined in patients at risk for hypoperfusion ischemia, namely, patients with occlusion of the contralateral carotid artery. All procedures were performed under general anesthesia without the use of a temporary indwelling shunt. Sixty-one percent of patients had cerebrovascular symptoms preoperatively and 39% were asymptomatic. The degree of stenosis of the carotid artery was 80%-99% in 67% (86/128) of patients, 60%-79% in 25% (32/128), 20%-59% in 7% (9/128), and 0-19% in 0.8% (1/128). The perioperative mortality was 0.8% (1/128), the incidence of permanent neurologic morbidity was 1.6% (2/128), and the incidence of transient neurologic morbidity was 3.9% (5/128). In conclusion, these data suggest that hypoperfusion ischemia is a rare cause of stroke during CEA even in patients with occlusion of the contralateral carotid artery and that CEA can be performed safely even in patients with contralateral occlusion without the use of a temporary indwelling shunt.

Recent developments in cerebral monitoring--near-infrared light spectroscopy. An overview

A recent development has been the resurgence of interest in the concept of near-infrared light spectroscopy as a method of monitoring cerebral perfusion. Although this technique has been in use for 40 years, the principle has been primarily employed in peripheral pulse oximetry. Infrared light of wavelengths 600-1300 nanometres (nm) penetrate human tissue to a depth of several centimetres. Within the human brain this light is attenuated by the chromophores oxyhaemoglobin, deoxyhaemoglobin and also oxidised cytochrome a3. Positioning a near-infrared light source and a photodetector in a side by side configuration detects light attenuated and reflected in a parabolic path through the scalp, skull and brain tissue.

A systematic review of the risks of stroke and death due to endarterectomy for symptomatic carotid stenosis

BACKGROUND AND PURPOSE

Carotid endarterectomy reduces the risk of carotid territory ischemic stroke ipsilateral to a recently symptomatic severe carotid stenosis. However, the benefit is limited by the risks of stroke and death associated with the operation. Although reported surgical risks vary enormously, there has been no systematic review of the published literature.

METHODS

We performed a systematic review of mortality and the risk of stroke and/or death due to endarterectomy for symptomatic carotid stenosis in studies published since 1980.

RESULTS

Fifty-one studies fulfilled our criteria. Overall mortality was 1.62% (95% confidence interval [CI], 1.3 to 1.9), and the risk of stroke and/or death was 5.64% (95% CI, 4.4 to 6.9). However, there was significant heterogeneity of risk of stroke and/or death (P < .001). The risk varied systematically with the methods and the authorship of the study. The risk of stroke and/or death was highest in studies in which patients were assessed by a neurologist after surgery (7.7%; 95% CI, 5.0 to 10.2) and lowest in studies with a single author affiliated with a department of surgery (2.3%; 95% CI, 1.8 to 2.7). After correcting for study methodology, there was no temporal trend in the risk of stroke and/or death between 1980 and 1995.

CONCLUSIONS

The reported risks of endarterectomy for symptomatic carotid stenosis show significantly greater variability than would be expected by chance. However, much of this variability can be accounted for by differences in methodology and authorship. The 5.6% overall risk of stroke and/or death is consistent with present guidelines.

A systematic comparison of the risks of stroke and death due to carotid endarterectomy for symptomatic and asymptomatic stenosis

BACKGROUND AND PURPOSE

There is some evidence that carotid endarterectomy reduces the risk of ipsilateral carotid territory ischemic stroke in patients with severe asymptomatic carotid stenosis. However, the benefit of endarterectomy is dependent on a low risk of stroke and/or death due to surgery. Whether the low operative risks reported in recent clinical trials and cited in recent guidelines are widely generalizable to clinical practice is unclear. Is endarterectomy for asymptomatic carotid stenosis really safer than surgery for recently symptomatic stenosis?

METHODS

We performed a systematic review comparing the risks of stroke and death due to carotid endarterectomy, performed by the same surgeons or in the same institutions, for symptomatic and asymptomatic stenosis in studies published since 1980.

RESULTS

Twenty-five studies fulfilled our criteria. Mortality within 30 days of endarterectomy was 1.31% for asymptomatic stenosis and 1.81% for symptomatic stenosis (odds ratio [OR], 0.69; 95% confidence interval [CI], 0.49 to 0.99). The risks of fatal stroke were 0.47% and 0.91%, respectively (OR, 0.57; 95% CI, 0.34 to 0.98). The overall risk of stroke and/or death was 3.35% for asymptomatic and 5.18% for symptomatic stenosis (OR, 0.61; 95% CI, 0.51 to 0.74).

CONCLUSIONS

Mortality and the risk of stroke and/or death due to carotid endarterectomy are significantly lower for asymptomatic than symptomatic stenosis. These findings are consistent across virtually all studies and are likely to be widely generalizable.

Simplified Shunt for Carotid Artery Surgery

Use of intraluminal shunts is an established method for augmenting cerebral blood flow during carotid artery surgery. However, many undesirable complications such as embolization of atheromatous plaque and scuffing of the intima have been described after their use. We describe a simplified shunt, which provides sufficient cerebral blood flow and is devoid of the various known complications.

Technical issues in carotid artery surgery 1995

In reviews in the 1980s, we discussed both indications for and surgical techniques in carotid endarterectomy. Significant changes in the practice of extracranial cerebrovascular reconstruction have occurred over the past few years. The newest indications and cooperative study data have recently been discussed by Camarata and Heros in this topic review series. In this article, we aim to review the advances in operative monitoring and surgical techniques of the last decade. We would be remiss, however, not to note that the latest Asymptomatic Carotid Atherosclerosis Study data, released in September 1994, indicate that carotid endarterectomy is significantly superior to medical therapy for asymptomatic stenosis of > 60%. These data, along with the North American Symptomatic Carotid Endarterectomy Trial results, will revitalize and lend scientific validity to carotid artery reconstruction.

Intraoperative urokinase infusion for embolic stroke during carotid endarterectomy

Embolic stroke is an infrequent complication of carotid endarterectomy. Somatosensory evoked potential monitoring detected delayed acute neurological deterioration during endarterectomy performed on a 71-year-old woman. Intraoperative arteriography performed via an indwelling shunt revealed thrombus within the middle cerebral artery and distal branches. A microcatheter was placed into the internal carotid artery via the arteriotomy and advanced into the middle cerebral artery. Urokinase was infused into and around the thrombus until almost complete thrombolysis had been achieved. The patient recovered quickly and was discharged without neurological deficit.

Carotid endarterectomy in awake patients: its safety, acceptability, and outcome

PURPOSE

The purpose of this study was to determine the safety and efficacy of performing carotid endarterectomy procedures with the patient receiving cervical block anesthetic.

METHODS

Over the last 14 years, 654 carotid endarterectomy procedures were performed with patients receiving regional anesthetic. Intraluminal shunts were placed on demand, if neurologic changes with clamping of the carotid artery developed in the patient. During the same period, 419 cases were done with the patients receiving general anesthetic. Choice of anesthetic was based on surgeon and patient preference.

RESULTS

In the regional anesthetic group the indications for operation included transient ischemic attack (311), asymptomatic hemodynamically significant stenosis (146), amaurosis fugax (106), stroke (86), restenosis (3), and aneurysm (2). Shunts were used in 46 of 654 cases (7%). Conversion from regional to general anesthetic was required in seven patients (1.1%). The operative mortality rate was 0.76% (5 of 654). Permanent nonfatal neurologic deficits occurred in 0.76% (5 of 654), and temporary neurologic deficits occurred in 1.07% (7 of 654).

CONCLUSIONS

On the basis of these results, we believe regional cervical block anesthetic is an acceptable option to the routine use of shunts performed with the patient receiving general anesthetic during carotid endarterectomy. In addition, the ability to continuously assess the awake patient receiving cervical block may contribute to a decrease in perioperative stroke and mortality rates while simplifying functional cerebral monitoring during carotid endarterectomy.

Correlation of contralateral stenosis and intraoperative electroencephalogram change with risk of stroke during carotid endarterectomy

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 less than 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 less than 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.

Stump pressure, the contralateral carotid artery, and electroencephalographic changes

Electroencephalographic (EEG) monitoring and measurement of stump pressure are the most widely employed methods of assessing the risk of cerebral ischemia during carotid endarterectomy. The status of the contralateral carotid artery has also been thought to influence the need for placing a shunt. The relationship of EEG monitoring, stump pressure, and the contralateral carotid artery has not been completely delineated. We retrospectively reviewed these three variables in 113 patients undergoing 124 carotid endarterectomies. The contralateral artery was classified as occluded, stenotic (greater than 50% decrease in diameter), or nonstenotic. There was a 48% incidence of EEG changes with contralateral occlusion, 18% with stenosis, and 21% with nonstenotic arteries (p = 0.014). There was a 73% incidence of EEG changes when the stump pressure was less than 25 mm Hg, 32% when the stump pressure was 25 to 50 mm Hg, and 2% when the stump pressure was greater than 50 mm Hg (p less than 0.001). There was no significant difference in the mean stump pressure for patients with occlusion (43.8 mm Hg), stenosis (44.7 mm Hg), or nonstenotic contralateral arteries (51.3 mm Hg). All patients with contralateral occlusion and a stump pressure less than 25 mm Hg had EEG changes. No patient with a stump pressure greater than 50 mm Hg and a patent contralateral artery had EEG changes. Although the incidence of EEG changes in the majority of patients was not accurately predicted by the stump pressure and the status of the contralateral carotid artery, stump pressure less than or equal to 50 mm Hg was sensitive, identifying 97% of patients with EEG changes.

Perioperative stroke. Part I: General surgery, carotid artery disease, and carotid endarterectomy

Although stroke, defined as a focal neurological deficit lasting more than 24 hr, is uncommon in the perioperative period, its associated mortality and long-term disability are high. No large-scale data are available to identify the importance of recognized risk factors for stroke in the perioperative period. A review of the literature shows that the incidence and mechanism of its occurrence are influenced by the presence of cardiovascular disease and the type of surgery. The most common cause of perioperative stroke is embolism. In non-cardiac surgery, the incidence of perioperative stroke is higher among the elderly. Properly administered, controlled hypotension is associated with minimal risk of stroke. Cerebral vasospasm may be the cause of focal cerebral ischaemia in eclamptic patients, and the aggressive treatment of hypertension may exacerbate the neurological damage. The risk of stroke associated with carotid endarterectomy is closely related to the preoperative neurological presentation, and the experience of the surgical/anaesthetic team. Symptomatic cerebrovascular disease, acute stroke, asymptomatic carotid lesions, preoperative assessment of risk, local and general anaesthesia, cerebral protection and monitoring during carotid endarterectomy are discussed with reference to reducing the risk of perioperative stroke. Adequate monitoring and protection have minimized the risk of ischaemia from carotid clamping, and the major mechanism of stroke is embolization.

Surgical reconstruction of the internal carotid artery with contralateral occlusion without use of shunt

Between 1979 and 1989, 133 carotid artery reconstructions were performed in 130 patients with contralateral internal carotid artery occlusion. These 133 reconstructions represent 7.3% of 1815 revascularizations of the internal carotid artery for atheromatous lesions performed during the same period. There were 113 men (87%) and 17 women (13%) whose mean age was 64.8 years (range 38 to 83 years). Forty-two patients (32%) had coronary artery disease and 77 (59%) were hypertensive. Nineteen patients (14%) were asymptomatic; 16 (12%) had symptoms of isolated vertebrobasilar insufficiency; 19 (14%) had ipsilateral carotid symptoms (on the side of operation); 67 (51%) had contralateral symptoms (on the side of occlusion); and 12 (9%) had bilateral carotid symptoms. All procedures were performed under general anesthesia without the use of a shunt. Nine patients (6.8%) died in the postoperative period (eight of neurologic and one of respiratory causes). Twelve patients (9%) sustained a cerebral vascular accident (eight ipsilateral and four contralateral). Four of these cerebral vascular accidents were diagnosed upon awakening, the remaining eight occurred after an initial uneventful recovery. Combined neurologic mortality and morbidity was 9.8%. Patients with occlusive lesions of the contralateral carotid artery undergoing internal carotid artery reconstruction are at high risk for postoperative cerebral vascular accidents. It is in this group of patients that the various methods of monitoring and cerebral protection should be evaluated.

Pre- and intraoperative transcranial Doppler: prediction and surveillance of tolerance to carotid clamping

We report 91 patients (mean age 70 years) operated upon, prospectively for a total of 100 carotid revascularizations (nine bilateral). Eighty-five of these patients had pre-, intra-, and postoperative transcranial Doppler investigations. Preoperatively, these 85 patients (92 procedures) were classified into two groups based on the results of their Doppler examinations: Group A (65 patients, 72 procedures), those who did not require an intraoperative indwelling shunt and Group B (20 patients, 20 procedures), those who did. The shunt was inserted only when the mean stump (back) pressure was less than 50 mmHg after cross-clamping. Group A all had satisfactory collaterality with a functional anterior and one or two posterior communicating arteries. Group B had no communicating arteries (anterior or posterior) identified by transcranial Doppler. In 17 of 20 patients in this group, the stump pressure was less than 50 mmHg and a shunt was placed. The overall prediction based on Doppler examination of whether or not patients would need a shunt during operation for the two groups A and B (i.e., 92 procedures) was correct in 95.6% (88/92) of cases. Moreover, six hemodynamically significant stenoses (four in the cavernous portion, two in the middle cerebral artery) were disclosed. Sensitivity and specificity of transcranial Doppler as correlated with arteriographic findings were 70 and 90%. Preoperative transcranial Doppler can measure the velocities of the principal cerebral arteries and the collateral capacity of the circle of Willis, and can forecast tolerance to carotid cross-clamping. Intraoperatively, the velocity of flow in the middle carotid artery was correlated with stump pressure, which allowed for surveillance of the shunt.

Balloon test occlusion of the internal carotid artery with monitoring of compressed spectral arrays (CSAs) of electroencephalogram

We used the compressed spectral arrays (CSAs) of the electroencephalogram (EEG) to monitor cerebral blood flow related events in balloon test occlusion of the internal carotid artery (balloon Matas test). Reliability of the CSAs was examined in 22 patients subjected to the test. Of 9 patients who underwent subsequent permanent carotid occlusion, in 6 there was no change on CSAs and/or in neurological conditions. In 2 patients, there was a slowing on CSAs prior to the appearance of neurological deterioration during clinical testing. CSAs transformed these EEG changes into a succinct graphic display. In 1 of the 2, for whom the Matas test was repeated 1 year later, there was a change from positive to negative and delayed cerebral infarction occurred after carotid occlusion. In the other patient, an ischemic insult occurred during the balloon occlusive procedures. The third patient had a fatal delayed ischaemic complication 3 days after surgical ligation of the cervical carotid artery, despite the negative balloon Matas test. Complications in these 3 patients were presumably related to thromboembolic mechanisms. The balloon Matas test monitored by CSAs is useful for detecting change in brain functions attributed to an inadequate blood flow. However, this test is unreliable for predicting thrombo-embolic complications.

Results of microsurgical carotid endarterectomy. A prospective study with transcranial Doppler and EEG monitoring, and elective shunting

100 consecutive carotid endarterectomies in a total of 93 patients were performed using the operative microscope. Cerebral perfusion and activity were monitored with simultaneous transcranial Doppler (TCD) and EEG. Thiopentone for cerebral protection was given prior to carotid clamping in 11 cases when an insufficient collateral circulation was suspected on the basis of the pre-operative TCD or angiography and if temporary intraluminal shunting was to be avoided because of a high bifurcation, long stenosis or associated carotid artery kinking. A temporary intraluminal shunt was inserted electively if the mean middle cerebral artery flow velocity fell after cross-clamping below 30-40%. Direct closure of the arteriotomy was preferred over a patch graft, which was performed only in cases with concomitant stricture of the arterial wall. No peri-operative strokes occurred in the present series. Two patients died due to medical complications in the post-operative period. During the mean follow-up of 15 months, 1 patient suffered a lethal stroke ipsilateral to the treated carotid artery and another patient had a minor contralateral stroke. Two patients died of unrelated causes during follow-up. Two patients suffered a single reversible neurologic deficit corresponding to the treated carotid territory. Four other patients had a single contralateral hemispheric or retinal reversible ischaemic attack during follow-up.

Carotid eversion endarterectomy revisited

Carotid eversion endarterectomy appears to be a safe and anatomically acceptable alternative to the standard carotid bifurcation endarterectomy, as evidenced by the absence of permanent neurologic morbidity and mortality in 98 operations. Preliminary clinical, angiographic, and noninvasive laboratory parameters suggest that there is a significant reduction of both residual technical defects and early recurrent stenosis. Specifically, no perioperative thrombosis or early restenosis was encountered in the 98 endarterectomies. Furthermore, only two technical defects have been noted, and one of these occurred in one patient who required a longitudinal arteriotomy and attendant suture line when the common carotid artery was transected too proximally and the eversion maneuver could not be accomplished. Serial long-term clinical and noninvasive laboratory follow-up evaluation, in addition to indicated postoperative angiography, will continue in an effort to assess the durability of a technical approach to carotid endarterectomy that may minimize residual defects and early restenosis.

Carotid endarterectomy: to shunt or not to shunt

Because of controversies in the cerebrovascular literature regarding the use of an intraluminal shunt in carotid endarterectomy, we report a randomized prospective study of 118 consecutive symptomatic patients receiving surgery within a single neurosurgical practice. Over 4 years, 138 carotid endarterectomies were performed in the 118 patients, 63 operations with intraluminal shunting and 75 without. Standard rationale for surgery included ipsilateral cerebral infarction in 38% of the operations and ipsilateral transient ischemic attacks in 36%. Unilateral angiographic stenosis of greater than 90% was seen in 58% of the operations; there were no ipsilateral occlusions. Surgery was performed under general anesthesia with barbiturate induction and mild blood pressure elevation. The 30-day complication rate included a mortality rate of 0.7% with a 5.1% incidence of postoperative neurologic deficit and a 1.4% rate of myocardial infarction. In the 24 hours after surgery there were no cerebral infarctions in the shunted group and six in the unshunted group. This 8% rate in the unshunted group compared with 0% in the shunted group was significant at p = 0.023 with a power of 0.95 by Fisher's exact test and chi 2 analysis. This suggests that in our neurosurgical practice (resident training program) the use of an intraluminal shunt during carotid endarterectomy significantly reduces the risk of intraoperative neurologic deficit without increasing the incidence of other complications.

The value of continuous intra-operative EEG monitoring during carotid endarterectomy

In a retrospective study, an evaluation was made of the intra-operative EEG findings and clinical results of 100 consecutive carotid endarterectomies carried out in 90 patients over the period 1977 to 1983. There was no operation-associated mortality; the peri-operative morbidity was 5%. All operations were performed maintaining the systemic blood pressure some 20% above the patients normal value. No interval shunt was used. The surgical policy was not influenced by EEG findings in any of the procedures. There was no relationship between carotid-clamping time and intra-operative EEG changes, nor was there a relationship between EEG changes and clinical outcome. It is most likely that neurological deficit following carotid endarterectomy, if operation is performed during elevated systemic blood pressure, is not due to haemodynamic disturbances, as a consequence of critical reduction of cerebral blood flow during internal carotid artery clamping, but to micro-embolism. From this assumption, it can be concluded that peri-operative complications of carotid endarterectomy cannot be reduced by intra-operative EEG monitoring.

Preoperative evaluation of patients with extracranial carotid disease. Plethysmographic criteria for the use of a shunt, and for avoidance of surgery

Eighty five angiographically studied patients (mean age 52) with carotid artery disease were preoperatively evaluated for the type and adequacy of their collateral circulation by the use of supraorbital photo-electric plethysmography (SPP). According to certain criteria we identified the candidates for surgery with or without shunt or for conservative treatment. Sixty patients presented evidence of extracranial collateral mainly from the ipsilateral superficial temporal artery (49 of 60), 11 patients revealed evidence of intracranial collateral mainly from the contralateral internal carotid artery (9 of 11), while in the rest, 14 patients, the source of the collateral circulation was undeterminable. Furthermore, an adequate circle of Willis was found in 67 patients and an inadequate one in the rest 7 (4 of 60, and 3 of 14). The majority of the surgically treated patients (74 of 81) were subjected to surgery without shunt (91%) while only 7 necessitated the use of a shunt (9%). No neurological complication was encountered and the single death (1.3%) was not directly related to the surgery itself. According to the present study, the careful preoperative determination of the collateral circulation, with the simple technique of SPP and the identification of patients at high risk under certain criteria could help the surgeon to decide about the advisability of a shunt or not and about the avoidance of surgery as well. This technique may be valuable where other more sophisticated forms of monitoring, such as EEG, evoked potentials or blood flow, are not readily available.

Role of EEG monitoring and cross-clamping duration in carotid endarterectomy

The usefulness of electroencephalographic (EEG) monitoring as well as the significance of the period of cross clamping in carotid endarterectomy have not been completely defined. In particular, the clinical importance of major EEG changes has not been fully investigated and some recent studies seem to indicate that the method has little value. As to the duration of cross clamping, there is strong evidence that occlusion times of about 15 minutes are tolerated under general anesthesia, but no information is available regarding longer periods of occlusion. The authors describe a consecutive series of 141 carotid endarterectomies in which the patients with EEG changes were shunted only when occlusion was anticipated to last longer than 30 minutes. Early major EEG changes (during the first 4 minutes) occurred in 14% of the cases. In the absence of EEG changes, long occlusion periods of 40 to 50 minutes were well tolerated. In contrast, the 20 patients with major persistent EEG changes did not tolerate protracted occlusion and three of them had immediate postoperative neurological complications. It seems that, in these circumstances, the incidence of neurological deficit is a function of the duration of cross clamping: these three patients had undergone occlusion for 15 to 30 minutes. Their deficits partially resolved. On the basis of these results it is concluded that: EEG recording is a reliable monitoring system in carotid artery cross clamping. No major strokes due to temporary carotid artery occurred in the series. The clinical significance of major persistent EEG changes is not negligible. Cross clamping for longer than 15 minutes in the presence of significant EEG alterations is potentially dangerous.

Risks of carotid endarterectomy. Toronto Cerebrovascular Study Group

An objective, retrospective review of 358 carotid endarterectomies performed in the neurosurgical teaching units of the University of Toronto in the year 1982 demonstrated a perioperative stroke rate of 3.9% and a death rate of 1.5%. Most (82%) surgical neurological complications occurred after the immediate post-operative period (24 hours). This high incidence of delayed stroke suggests that most perioperative strokes are embolic rather than hemodynamic. Careful operative technique and the use of anticoagulants and antiplatelet agents may be more important in preventing postoperative deficits than intraoperative monitoring and intraluminal shunting. Our figures and those of current published data indicate that a 5-6% combined morbidity and mortality should be expected in carotid endarterectomy. These data are critical both to decision making with the individual patient as well as in the planning of future carotid surgery trials.

Significance of EEG changes at carotid endarterectomy

Visually apparent EEG changes associated with clamping the internal carotid artery appeared in 55 of 176 consecutive patients (31%) undergoing carotid endarterectomy without shunt. Attenuation of higher frequency activity was the most common change. Changes were moderate in 33 patients (19%) and major in 22 (12.5%). Major changes usually commenced earlier than less severe alterations. EEG changes resolved within 10 minutes of clamp release in 36 of 55 patients (65%) after an average clamp time of 36.25 minutes. Changes occurred more commonly when pre-operative EEGs were abnormal contralateral to clamping and when the contralateral carotid artery was more than 90% stenosed. Of the inhalational anesthetics employed with nitrous oxide and oxygen, isoflurane was associated with the lowest incidence of clamp-associated EEG change. Post-operative strokes occurred in 2 of 22 patients (9%) with major clamp-associated EEG changes, none of 33 patients with moderate changes and none of 121 without changes. However, the mechanism of this relationship remains in doubt.

The validity of internal carotid back pressure measurements during carotid endarterectomy for unilateral carotid stenosis

Peri-operative neurological deficits in 212 patients undergoing carotid endarterectomy for unilateral carotid stenosis were examined to determine whether the internal carotid back pressure (ICBP) correctly predicted the need for a protective shunt during temporary carotid occlusion. Three strokes occurred in 149 patients who were not shunted. In one of these the ICBP indicated the need for a shunt, but shunting was not possible for technical reasons and a stroke due to hypoperfusion occurred. In another patient a stroke occurred as a result of embolism. There was only one patient where the ICBP possibly incorrectly predicted that a shunt would not be necessary. Four strokes due to various causes occurred in the 63 shunted patients. Shunting was not withheld from these patients in order to prove that ICBP would correctly predict their vulnerability to hypoperfusion since to have done so would be unethical. The results indicate that in patients with unilateral carotid stenosis the ICBP is an accurate indicator of which patients can undergo carotid endarterectomy without the need for shunting.