Cerebral hyperperfusion syndrome following carotid endarterectomy

Three patients with a severe symptomatic carotid stenosis developed headache, epileptic seizures and focal neurologic deficits several days after carotid endarterectomy. CT of the brain revealed hypodensities, indicative of cerebral oedema with haemorrhagic components. This is caused by cerebral hyperperfusion, a complication after carotid endarterectomy as a result of increased cerebral perfusion on the side of the operated carotid stenosis. Dysfunction of the cerebral autoregulation believed to be the cause of this hyperperfusion. Sometimes these complications are incorrectly attributed to one of the better known types of stroke.     

Neuropsychometric changes in patients after carotid endarterectomy

BACKGROUND AND PURPOSE: One hundred twelve patients undergoing elective carotid endarterectomy for symptomatic and asymptomatic carotid artery stenosis were enrolled in a prospective study to evaluate the incidence of change in postoperative cerebral function. METHODS: Patients were evaluated preoperatively and postoperatively before hospital discharge and at follow-up 1 and 5 months later with a battery of neuropsychometric tests. The results were analyzed by both event-rate and group-rate analyses. For event-rate analysis, change was defined as either a decline or improvement in postoperative neuropsychometric performance by 25% or more compared with a preoperative baseline. RESULTS: Approximately 80% of patients showed decline in one or more test scores, and 60% had one or more improved test scores at the first follow-up examination. The percentage of declined test scores decreased and the percentage of improved test scores increased with subsequent follow-up examinations. Group-rate analysis was similar for group performance on individual tests. However, a decline in performance was seen most commonly on verbal memory tests, and improved performance was seen most commonly on executive and motor tests. CONCLUSIONS: Neuropsychometric evaluation of patients undergoing carotid endarterectomy for significant carotid artery stenosis demonstrates both declines and improvements in neuropsychometric performance. The test changes that showed decreased performance may be associated with ischemia from global hypoperfusion or embolic phenomena, and the improvement seen may be related to increased cerebral blood flow from removal of stenosis.     

Interpretation of embolic phenomena during carotid endarterectomy

BACKGROUND AND PURPOSE: Air and particulate emboli are a major source of morbidity during carotid endarterectomy (CEA); however, amplitude overload and poor time resolution have restricted the ability of transcranial Doppler ultrasound to differentiate between the two. METHODS: We have now overcome these two limitations by (1) rerouting embolic signals away from the audio frequency amplifier to avoid amplitude overload and (2) substituting the Wigner distribution function for the fast Fourier transform to improve time and frequency resolution. Thus, we can now accurately determine embolic duration and embolic velocity, the product of which is the sample volume length (SVL). This measurement represents the physical distance over which an embolic signal can be detected. The underlying hypothesis was that air reflected more ultrasound and would therefore be detected over a greater SVL. RESULTS: The median SVL (interquartile range) for 75 in vitro air emboli was 1.97 cm (range, 1.70 to 2.35) compared with 0.27 cm (range, 0.16 to 0.43) for 185 particulate emboli detected during the dissection phase of CEA. Off-line analysis on an additional 560 embolic signals detected during different phases of CEA suggested that 46 of 143 (32%) of emboli immediately after shunt insertion were particulate, as were 19 of 33 (58%) occurring during shunting, 28 of 78 (36%) after restoration of flow in the external carotid artery, 23 of 251 (9%) after restoration of flow in the internal carotid artery, and 55 of 55 (100%) of those emboli detected during the early recovery phase. CONCLUSIONS: This development provides objective physical criteria upon which embolus characterization (particulate/air) can be based. This could have major implications for future patient monitoring with respect to modification of surgical technique and pharmacological intervention.     

Predictive value of carotid artery stump pressures during carotid endarterectomy

The ideal method of monitoring cerebral perfusion during carotid endarterectomy remains controversial. This article reviews many of the larger studies in the literature that have attempted to evaluate the usefulness of carotid artery stump pressure. Topics discussed include stump pressure alone, regional anesthesia, stump pressure and EEG, and stump pressures and transcranial Doppler ultrasonography.     

Cerebral hemodynamics during carotid massage in patients with carotid sinus syndrome

The effect of cardioinhibition and/or vasodepression on cerebral hemodynamics assessed by transcranial Doppler has been investigated during carotid massage in 11 patients (62-87 years, mean age 72) with carotid sinus syndrome. The patients were tested in the OOO mode (n = 11) with six tested in the DDD mode. Carotid massage in the OOO mode decreased mean arterial pressure by 44% (P < 0.01) and mean cerebral blood flow velocity by 50% (P < 0.01). Although not significant, cerebrovascular resistance increased transiently by 17% during massage, then decreased by 31% upon recovery. Carotid massage in the DDD mode decreased arterial pressure by 30% (P < 0.01), cerebral blood velocity by 23% (P < 0.01), and resistance by 15% (P < 0.05). The decreased cerebral perfusion induced by cardioinhibition and/or vasodepression results from the delayed onset of cerebral autoregulation. Pacing in the DDD mode temporarily assists the critical period preceding the onset of cerebral autoregulation that plays a key role in preventing the deleterious effects of vasodepression.     

Resting ECG changes in long term survivors after carotid endarterectomy

PURPOSE: The aqueous flare intensity and pupillary size were studied before and after instillation of 10% phenylephrine and 4% pilocarpine in eyes with diabetes mellitus (DM). METHODS: Twenty-three patients with DM type I were compared with 30 age-matched controls, and 25 patients with DM type II were compared with 30 age-matched controls. Patients with DM were divided into two groups: 1) with mild-moderate nonproliferative diabetic retinopathy (NPDR), and 2) with advanced diabetic retinopathy (DR) which includes moderate-severe, severe NPDR and proliferative DR. The aqueous flare intensity and the horizontal diameter of the pupil were measured before and 60 minutes after topical instillation of 10% phenylephrine and 60 min after topical administration of 4% pilocarpine. RESULTS: Degree of induced mydriasis after phenylephrine instillation was not significantly different between diabetic groups and controls. Significantly less pronounced miosis was observed after stimulation of cholinergic receptors by pilocarpine in eyes with mild-moderate NPDR with DM type II and in eyes with advanced DR with DM type I and type II when compared to controls (p<0.05). Phenylephrine decreased flare intensity in all groups without a significant difference between groups. Pilocarpine instillation increased flare intensity in all groups as compared to flare intensity before any treatment. Also, a significantly smaller increase in flare intensity in eyes with advanced retinopathy in both DM type I and type II was found when compared to controls (p<0.05). CONCLUSION: Pharmacological response to cholinergic stimulation on pupil size and flare intensity is weaker in advanced stages of DR.     

Early results of combined carotid endarterectomy and coronary artery bypass grafting in patients with severe coronary and carotid artery disease

The management of patients with carotid artery disease who require coronary artery bypass grafting (CABG) remains controversial. Several published series from the USA (including one with prospective randomization) advocate a combined approach of carotid endarterectomy (CEA) followed immediately by coronary artery bypass surgery. However, experience of combined carotid endarterectomy and coronary bypass grafting has not been previously reported by a centre from the United Kingdom. Between 1986 and 1991 we performed this combined procedure on 18 patients who required myocardial revascularization and had co-existing severe (> 70%) carotid stenosis. Sixteen patients (89%) had angina and 11 patients (61%) had symptomatic carotid artery disease. The perioperative mortality was 5.5% and the ipsilateral perioperative stroke rate was 5.5%. These early results are encouraging and suggest that further evaluation of combined carotid endarterectomy and coronary artery bypass surgery is warranted.     

Role of transcranial Doppler and stump pressure during carotid endarterectomy

BACKGROUND AND PURPOSE: The aim of our study was to clarify the pathophysiology of perioperative cerebral complications during carotid endarterectomy in our series. METHODS: By means of transcranial Doppler ultrasonography and stump pressure measurement, we monitored 112 patients who underwent carotid endarterectomy under general anesthesia for symptomatic or asymptomatic severe carotid stenosis. RESULTS: Of 18 patients who underwent carotid endarterectomy with intra-arterial shunt, 2 (11.1%) developed an ischemic stroke. Of the other 94 patients, one suffered a nucleocapsular hemorrhage and 5 had cerebral ischemic complications. In these 5 patients, the duration of clamping was significantly longer (mean +/- SD, 16.4 +/- 1.1 versus 12.7 +/- 2.6 minutes; P = .0019), and the decrease of middle cerebral artery mean velocity on clamping was significantly greater (mean +/- SD, 56.4 +/- 4.9% versus 28.8 +/- 20.2%; P = .0031), while stump pressure was not significantly different. Microembolic signals were recorded in 70 patients (62.5%) and were not associated with cerebral ischemic complications. The 7 patients who developed cerebral ischemic complications had a significantly higher percentage of stenosis in the contralateral internal carotid artery (mean +/- SD, 82.0 +/- 17.8% versus 29.3 +/- 36.4%; P = .0018). CONCLUSIONS: The results of our study suggest that the major complications of carotid endarterectomy may be due to hemodynamic factors. Stump pressure alone is not a reliable indicator of hemodynamic changes that predict cerebral ischemia. Particulate microembolism may cause more subtle changes in cerebral parenchyma, but further studies are needed to clarify this point.     

Intraabdominal hemorrhage during combined coronary artery bypass and carotid endarterectomy

Intraabdominal complications during cardiopulmonary bypass are extremely rare, with an incidence of less than 1% in multiple retrospective studies. These complications are associated with a high mortality, and their rapid diagnosis is critical to the outcome of the patient. We present a case of spontaneous intraabdominal hemorrhage after combined carotid endarterectomy and four-vessel coronary artery bypass grafting, which was diagnosed through a diaphragmatic window.     

Correlation of neurologic complications and pressure measurements during carotid endarterectomy

There was no significant difference between the mean occluded internal carotid artery pressure in asymptomatic, transient ischemic attack or prior stroke patients. The stump pressure was not consistently elevated at the second operation in those having undergone bilateral procedures. Estimate of back bleeding from the internal carotid artery operation did not necessarily correlate with the stump pressure. Adequate back bleeding was recorded in patients with a low stump pressure, and reduced bleeding was noted in individuals with a high stump pressure. The pressure gradient across the stenosis of the bifurcation of the carotid artery was helpful in assessing the degree of stenosis present. The occluded internal carotid artery pressure seemed to be a helpful aid in indicating those patients with poor collateral flow and, therefore, at high risk of ischemic brain damage. The use of an inlying shunt in those individuals having a low stump pressure may be expected to reduce the over-all neurologic complication rate in patients undergoing carotid endarterectomy.     

Comparison of simultaneous electroencephalographic and mental status monitoring during carotid endarterectomy with regional anesthesia

PURPOSE: This study examines the accuracy of intraoperative electroencephalographic (EEG) monitoring for the detection of cerebral ischemia by comparing EEG with simultaneous mental status evaluation (MSE) during carotid endarterectomy in awake patients. METHODS: Between 1994 and 1997, 208 consecutive carotid endarterectomies were prospectively evaluated for cerebral function during surgery with simultaneous MSE and EEG monitoring. Regional anesthesia (RA), which consisted of superficial cervical block, was chosen preferentially in 75% of the cases, with general anesthesia (GA) reserved for the patients who did not fulfill the criteria for RA. When available, 8-channel EEG monitoring was performed (59% with RA and 55% with GA). RESULTS: The EEG was a reliable predictor in comparison with MSE in most but not all cases of cerebral ischemia. Significant neurologic changes were noted using MSE in 4 of 89 patients (4.5%) that were not detected using EEG (false negative results). Conversely, 6 of 89 cases (6.7%) showed unilateral slowing without associated changes in MSE (false positive results). For the awake patients, 21 of 150 cases (14%) showed MSE changes that required a shunt. By contrast, 9 of 32 GA cases (28%) showed EEG changes that would have led to shunting (P = NS). In the RA group, there were no strokes versus 3 of 58 cases (5.2%) with strokes in the GA group. Two of 150 cases (0.1%) had transient ischemic attacks in the RA group. There was 1 myocardial infarction in the GA group; no deaths occurred in this series. CONCLUSION: EEG monitoring yielded a significant number of false positive (6.7%) and false negative (4.5%) results in the detection of neurologic deficits when compared with MSE in the awake patients. In this series, the preferential use of RA resulted in less shunt use and was possibly associated with a lower stroke rate.     

Comparison of hemodynamic cerebral ischemia and microembolic signals detected during carotid endarterectomy and carotid angioplasty

BACKGROUND AND PURPOSE: There has been concern about carotid percutaneous transluminal angioplasty (PTA) carrying a greater risk of cerebral ischemia than carotid endarterectomy. We set out to compare cerebral hemodynamics and microembolization during carotid PTA and CEA. METHODS: We used transcranial Doppler to monitor the middle cerebral artery of 28 patients undergoing carotid PTA (n = 14) or carotid endarterectomy (CEA) with a shunt (n = 14). Each period during which the internal carotid artery was occluded by PTA balloon or by clamp when the shunt was not in place was timed. Individual periods were summated to give a total occlusion time. Ischemic time was defined as the period for which mean middle cerebral artery velocity fell to a third or less of baseline. Microembolic signals were counted during each procedure. RESULTS: CEA resulted in significantly longer individual and total occlusion time than PTA (mean individual occlusion time, seconds), CEA, 168 +/- 51; PTA, 20 +/- 7; P < .001; mean total occlusion time; CEA, 337 +/- 70; PTA, 26 +/- 10; P < .001. Ischemic time was also significantly longer during CEA than during PTA (CEA, 165 +/- 40; PTA, 17 +/- 5; P = .001). There were significantly more microembolic signals during PTA than during CEA (mean number of microembolic signals during CEA, 52 +/- 64; during PTA, 202 +/- 119; P = .001). There was no correlation between any of the parameters measured and periprocedural stroke, which occurred in one patient in each group. CONCLUSION: PTA results in less hemodynamic ischemia but more cerebral microembolism than CEA. In this small series, however, it is not possible to comment on the relations between ischemic time, microembolism, and stroke.     

Stump pressure: an unreliable guide for shunting during carotid endarterectomy

A correlative analysis was made between the neurological status of the awake patient and the internal carotid artery stump pressure in 125 consecutive patients undergoing carotid endarterectomy. There was no mortality in this series. Twenty-four patients lost consciousness immediately after carotid cross-clamping, even though stump pressures were above 50 mm Hg in more than one third of the cases. The majority (80.8%) of the patients tolerated cross-clamping (stump pressures were between 20 and 90 mm Hg). This study demonstrated the variability of cerebral tolerance relative to absolute stump pressure guidelines, such as 25 or 50 mm Hg; reliance on these values to determine the need for intraoperative shunting could lead to stroke at operation. Our experience also showed that assessment of the awake but tranquil patient continues to be the safest and most reliable guide to selective shunting during carotid endarterectomy.     

Carotid endarterectomy for asymptomatic carotid artery stenosis: patients with severe bilateral disease a high risk subgroup

Carotid endarterectomy if advised for asymptomatic disease must be associated with a low peri-operative morbidity and mortality and satisfactory long-term results. Over a 12 year period between 1978-1989 181 carotid endarterectomies were performed on 163 patients with asymptomatic carotid artery stenosis. There were 112 males and 51 females with a mean age of 64.9 years. All patients had a high-grade lesion (> 70% stenosis). The combined operative mortality and stroke rate was 2.8%. On long-term follow up six patients suffered a stroke. Only one patient however sustained a stroke in the same territory as the previously operated carotid artery. Four years following surgery 78% of patients were alive. Carotid restenosis or occlusion occurred in 8.3% of the remaining patients, all of whom were asymptomatic. All the immediate postoperative strokes occurred in patients with severe bilateral carotid artery disease. These patients with severe bilateral disease appear to constitute a high risk sub-group for peri-operative stroke. The role of 'normal pressure-hyperperfusion breakthrough' syndrome as the presumed aetiology of two of the postoperative cerebral haemorrhages is discussed.     

Incidence, timing, and causes of cerebral ischemia during carotid endarterectomy with regional anesthesia

PURPOSE: Controversy exists regarding the best technique to identify cerebral ischemia during carotid endarterectomy (CEA). Regional anesthesia allows continuous evaluation of neurologic function and therefore can help determine the incidence, timing, and causes of cerebral ischemia. METHODS: The timing and clinical manifestations of any neurologic event during CEA and as long as 30 days afterward was determined by review of operative reports, hospital charts, and outpatient records of consecutive patients who underwent CEA under regional anesthesia over a 68-month period. RESULTS: Two hundred patients underwent CEA; indications were asymptomatic stenosis > 60% in 25%, transient ischemic attack with stenosis > 50% in 52%, and prior stroke with stenosis > 50% in 23%. Eight patients (4%) were converted to general anesthesia for non-ischemic reasons. Of the remaining 192 patients, 183 (95.5%) underwent the procedure with regional anesthesia and no shunt, 2% had cerebral ischemia and underwent shunt placement, and 2.5% had cerebral ischemia, were converted to general anesthesia, and underwent shunt placement. Cerebral ischemia developed in nine patients after carotid cross-clamping, manifested by loss of consciousness in four, confusion in two, dysarthria and confusion in one, and decreased contralateral motor strength in two. Immediate cerebral ischemia developed in four of the nine patients within 1 minute of cross-damping; all four underwent shunt placement. In five of the nine patients, cerebral ischemia occurred between 20 and 30 minutes after cross-clamping; all occurred during relative intraoperative hypotension (average reduction of 35 mm Hg in the systolic pressure). All awake patients in whom ischemic symptoms developed immediately regained and maintained normal neurologic function with shunt placement. Five of 26 patients (19%) with contralateral occlusion required a shunt; none had postoperative ischemia. The mean carotid cross-clamp time was 27 minutes. Postoperative (30 day) complications included a 0.5% stroke rate, a 0.5% rate of postoperative transient ischemic attack, a 0.5% rate of worsening of preexisting acute stroke, and a 0.5% rate of myocardial infarction (no deaths). Of the nine patients who had intraoperative ischemic changes, none had a postoperative neurologic deficit; the three patients who had postoperative neurologic changes had no intraoperative ischemic symptoms. CONCLUSIONS: CEA with regional anesthesia allows continuous neurologic monitoring and can be performed safely even when contralateral occlusion coexists; intraoperative shunting for ischemia is necessary in 4.5% of all cases and in 19% of patients with contralateral occlusion. Intraoperative ischemia was flow-related in our patients; it occurred early from ipsilateral carotid clamping and late from reduced collateral flow as a result of hypotension. Monitoring should be continued throughout cross-clamping to identify late cerebral ischemia. Postoperative cerebral ischemia is not associated with intraoperative ischemia, if corrected.     

Clinical findings and hemodynamic changes associated with severe occlusive carotid artery disease

OBJECTIVE: The purpose of the study was to evaluate the ophthalmologic findings and to analyze the retrobulbar hemodynamics of patients with severe (greater than 70% stenosis) occlusive carotid artery disease (OCAD) by means of color Doppler imaging (CDI). DESIGN: A case-controlled study. PARTICIPANTS: Fifty-six consecutive patients with severe OCAD and an age- and sex-matched control group consisting of 56 healthy patients without OCAD were studied. INTERVENTION: All 112 patients underwent a complete ophthalmologic examination. Color Doppler imaging of both orbits was performed by one masked investigator. MAIN OUTCOME MEASURES: Peak systolic velocity, end diastolic velocity, and the resistive index of the ophthalmic, central retinal, and temporal short posterior ciliary arteries were measured. The authors compared the hemodynamic parameters measured in patients with severe OCAD with those obtained in the control group. The hemodynamic parameters of patients with asymmetric OCAD (stenosis > 70% in one internal carotid artery and stenosis < 50% in the contralateral artery) were also compared. In an attempt to determine risk factors associated with the ocular ischemic syndrome (OIS), the authors compared patients with severe OCAD and OIS with patients with severe OCAD without OIS. RESULTS: Peak systolic and end diastolic velocities in the ophthalmic, central retinal, and temporal short posterior ciliary arteries were significantly lower in patients with severe OCAD (P < 0.01). The mean resistive indices in the central retinal and temporal short posterior ciliary arteries were higher in the group with severe OCAD (P < 0.01). Similar results were obtained in the analysis of 25 patients with asymmetric carotid stenosis. Younger age (P = 0.012), severe bilateral OCAD (P = 0.01), high-grade carotid stenosis (P = 0.013), and reversed ophthalmic artery flow (P = 0.038) were significant risk factors for OIS. CONCLUSIONS: Patients with severe OCAD show hemodynamic changes that suggest reduced retrobulbar blood flow. Patients with severe bilateral OCAD, high-grade carotid stenosis, and reversed ophthalmic artery flow may have a greater risk of developing OIS.     

Repair of carotid endarterectomy with a collagen-impregnated fabric graft

Saphenous vein patch closure of carotid endarterectomies may decrease the risk of acute postoperative occlusion and recurrent stenosis. However, the disadvantages of a vein patch include postoperative rupture and pseudoaneurysm formation. OBJECT: The authors sought to assess the effectiveness of collagen-impregnated fabric grafts as substitutes for saphenous vein grafts. METHODS: In this report the authors prospectively analyzed 290 consecutive carotid endarterectomies in which a secondary closure was accomplished using a knitted double-velour graft. The 30-day major neurological morbidity and mortality rate was 1.7%. There were no postoperative occlusions or wound hematomas. The rate of recurrent carotid artery stenosis was less than 1%, and the graft site in one patient became infected. CONCLUSIONS: For surgeons who prefer a secondary closure of carotid endarterectomies, the synthetic graft may prove to be a viable alternative to a saphenous vein.