***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: A multicenter retrospective audit of  carotid endarterectomies performed during 1981 was completed with 46 institutions contributing 3,328 cases . Overall , there was a 2.5 % risk of transient neurological dysfunction following surgery and a 6 % risk of stroke or death . The intra-institutional combined major morbidity and mortality varied from 21 % to 0 . Those institutions with greater than 700 beds had a statistically lower incidence of stroke or death than did other institutions . The incidence of stroke or death postoperatively was significantly lower for patients who were operated on for amaurosis fugax or for unspecified reasons . Those patients who were operated on for a progressing stroke had a higher incidence of stroke but this group was at greatest risk for stroke without surgery . The incidence of postoperative stroke or death was related to the type of arterial repair ; vein patch grafting was statistically better than both fabric patch grafting and primary closure . When all patients who were not monitored during surgery were compared to all patients who had  electroencephalographic ( EEG ) monitoring , there was found to be a significant statistical difference in favor of the EEG group . Endarterectomy combined with coronary artery bypass or simultaneous bilateral endarterectomies had a statistically significant higher incidence of stroke or death than did unilateral carotid endarterectomy OBJECTIVE To compare the extent of subtle cerebral damage ( SCD ) in patients undergoing carotid endarterectomy with or without shunt placement .  DESIGN Prospect i ve , r and omised study . PATIENTS AND METHODS We assessed a consecutive series of 96 patients undergoing endarterectomy for severe unilateral left carotid stenosis who had been r and omly assigned to receive a shunt ( 48 ) or not ( 48 ) . Eligibility criteria included age up to 80 years and Mini-Mental State Examination score > 24 points . Patients underwent neuropsychological testing before surgery . Serum concentrations of S100 protein , neuron-specific enolase ( NSE ) and interleukin-6 ( IL-6 ) were measured intraoperatively before and after carotid clamping . Finally , each patient underwent neuropsychological testing 3 weeks after surgery . RESULTS Patients with and without shunt had similar serum concentrations of S100 protein , NSE and IL-6 as well as similar neuropsychological test scores , all p>0.05 . CONCLUSIONS There was no difference in subtle cerebral damage between patients r and omized to receive a shunt or not A prospect i ve study was undertaken to determine the efficacy of performing carotid endarterectomy without an intraluminal shunt . During a two-year period , 240 patients , ranging in age from 36 to 89 years , underwent 309 consecutive carotid endarterectomies .  The indication for operation was transient ischemic attacks in 151 ( 63 % ) patients , asymptomatic carotid bruit in 67 ( 28 % ) , and previous stroke in 22 ( 9 % ) . Internal shunts were not used in any patients and all arteriotomies were patched with a preclotted knitted Dacron@ velor patch . Systemic heparinization was used during the procedure . The early postoperative mortality was 0.64 % ( 2/309 ) . Both deaths were caused by myocardial infa rct ion . The incidence of stroke after operation was 1.29 % ( 4/309 ) . Neither carotid clamp time nor the presence of contralateral disease correlated with the occurrence of postoperative stroke . According to results of angiography , 22 patients had total occlusion of the contralateral internal carotid artery with satisfactory intracranial circulation . No postoperative strokes occurred in this subgroup . Results of this study revealed that equally good or superior results may be obtained without a temporary shunt in performing carotid endarterectomy Because of controversies in the cerebrovascular literature regarding the use of an intraluminal shunt in carotid endarterectomy , we report a r and omized prospect i ve 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 .  St and ard rationale for surgery included ipsilateral cerebral infa rct ion 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 infa rct ion . In the 24 hours after surgery there were no cerebral infa rct ions 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 One hundred and thirty-one patients undergoing 142 carotid endarterectomy procedures were r and omized to have their operation performed either with or without intra-operative electroencephalographic ( EEG ) monitoring . Patients with EEG monitoring were shunted if both the internal carotid back pressure ( ICBP ) was less than 50 mmHg and ipsilateral change was evident on the EEG after clamping . Patients without EEG monitoring were shunted if ICBP was less than 50 mmHg . There one postoperative death ( 0.7 % ) with neurological deficits occurring in five patients ( 3.5 % ) . There were significantly fewer neurological deficits ( P = 0.02 ) in patients with no EEG change ( one of 59 ) compared with those with EEG change ( two of 13 ) . There was a highly significant increase ( P = 0.005 ) in incidence of neurological deficit ( two of five patients ) when ICBP was considered ' adequate ' at 50 mmHg or greater but EEG change occurred . No neurological deficit occurred in 14 patients who were not shunted with ICBP less than 50 mmHg but with no EEG change . There was no difference in the incidence of neurological deficit in patients with low and high ICBP when both 50 and 55 mmHg were used as the cut-off points . It is concluded that  EEG monitoring  is useful in identifying patients requiring shunting during carotid endarterectomy . Use of a shunt is recommended if there is EEG change regardless of ICBP ; conversely , if ICBP is low but there is no EEG change it would appear safe to proceed without shunting BACKGROUND Among patients with substantial carotid artery narrowing but no recent neurological symptom ( stroke or transient ischaemia ) , the balance of surgical risks and long-term benefits from carotid endarterectomy ( CEA ) was unclear . METHODS During 1993 - 2003 , 3120 asymptomatic patients with substantial carotid narrowing were r and omised equally between immediate CEA ( half got CEA by 1 month , 88 % by 1 year ) and indefinite deferral of any CEA ( only 4 % per year got CEA ) and were followed for up to 5 years ( mean 3.4 years ) . Kaplan-Meier analyses of 5-year risks are by allocated treatment . FINDINGS The risk of stroke or death within 30 days of CEA was 3.1 % ( 95 % CI 2.3 - 4.1 ) . Comparing all patients allocated immediate CEA versus all allocated deferral , but excluding such perioperative events , the 5-year stroke risks were 3.8 % versus 11 % ( gain 7.2 % [ 95 % CI 5.0 - 9.4 ] , p<0.0001 ) . This gain chiefly involved carotid territory ischaemic strokes ( 2.7 % vs 9.5 % ; gain 6.8 % [ 4.8 - 8.8 ] , p<0.0001 ) , of which half were disabling or fatal ( 1.6 % vs 5.3 % ; gain 3.7 % [ 2.1 - 5.2 ] , p<0.0001 ) , as were half the perioperative strokes . Combining the perioperative events and the non-perioperative strokes , net 5-year risks were 6.4 % versus 11.8 % for all strokes ( net gain 5.4 % [ 3.0 - 7.8 ] , p<0.0001 ) , 3.5 % versus 6.1 % for fatal or disabling strokes ( net gain 2.5 % [ 0.8 - 4.3 ] , p=0.004 ) , and 2.1 % versus 4.2 % just for fatal strokes ( net gain 2.1 % [ 0.6 - 3.6 ] , p=0.006 ) . Subgroup-specific analyses found no significant heterogeneity in the perioperative hazards or ( apart from the importance of cholesterol ) in the long-term postoperative benefits . These benefits were separately significant for males and females ; for those with about 70 % , 80 % , and 90 % carotid artery narrowing on ultrasound ; and for those younger than 65 and 65 - 74 years of age ( though not for older patients , half of whom die within 5 years from unrelated causes ) . Full compliance with allocation to immediate CEA or deferral would , in expectation , have produced slightly bigger differences in the numbers operated on , and hence in the net 5-year benefits . The 10-year benefits are not yet known . INTERPRETATION In asymptomatic patients younger than 75 years of age with carotid diameter reduction about 70 % or more on ultrasound ( many of whom were on aspirin , antihypertensive , and , in recent years , statin therapy ) , immediate CEA halved the net 5-year stroke risk from about 12 % to about 6 % ( including the 3 % perioperative hazard ) . Half this 5-year benefit involved disabling or fatal strokes . But , outside trials , inappropriate selection of patients or poor surgery could obviate such benefits OBJECTIVES To investigate the in vivo haemodynamic performance and neurological outcome of two types of carotid shunt . DESIGN R and omised single surgeon study of consecutive symptomatic patients . SETTING 163 consecutive patients undergoing carotid endarterectomy for symptomatic carotid disease were r  and  omised to the Javid or Pruitt shunt . CHIEF OUTCOME MEASURES Middle cerebral artery velocity ( MCAV ) , preoperatively , during clamping , during shunting and post-restoration of flow , embolic episodes , neurological outcome . MAIN RESULTS The MCAV preoperatively , at carotid clamping , and postoperatively was the same for both groups ( p > 0.15 ) . During shunting the MCAV was significantly lower in the Pruitt group , p < 0.005 , 59 % of the Javid and 34 % of the Pruitt shunts maintained MCAV at preoperative levels p < 0.005 , chi 2 = 8.92 . The Javid shunt produced significantly more emboli ( 73 % of cases ) at declamping than the Pruitt ( 41 % ) , p < 0.0002 , chi 2 = 14.7 . Four Javid patients and one Pruitt had disabling thromboembolic strokes ; overall thromboembolic stroke rate 3.7 % . The difference in stroke rates was not statistically significant ( p = 0.14 ) . CONCLUSIONS The Pruitt shunt was unable to maintain preoperative MCAV in 66 % of cases , the Javid shunt had a higher incidence of emboli on declamping . These factors may lead to an increased risk of stroke ; however , the numbers required for statistical confirmation would be large BACKGROUND Without strong evidence of benefit , the use of carotid endarterectomy for prophylaxis against stroke rose dramatically until the mid-1980s , then declined . Our investigation sought to determine whether carotid endarterectomy reduces the risk of stroke among patients with a recent adverse cerebrovascular event and ipsilateral carotid stenosis . METHODS We conducted a r and omized trial at 50 clinical centers throughout the United States and Canada , in patients in two predetermined strata based on the severity of carotid stenosis--30 to 69 percent and 70 to 99 percent . We report here the results in the 659 patients in the latter stratum , who had had a hemispheric or retinal transient ischemic attack or a nondisabling stroke within the 120 days before entry and had stenosis of 70 to 99 percent in the symptomatic carotid artery . All patients received optimal medical care , including antiplatelet therapy . Those assigned to surgical treatment underwent carotid endarterectomy performed by neurosurgeons or vascular surgeons . All patients were examined by neurologists 1 , 3 , 6 , 9 , and 12 months after entry and then 
    Output:
    
No significant difference was found between the groups in terms of postoperative neurological deficit between selective shunting with and without near-infrared refractory spectroscopy monitoring , However , this analysis was inadequately powered to reliably detect the effect .
There was no significant difference between the risk of ipsilateral stroke in participants selected for shunting with the combination of electroencephalographic and carotid pressure assessment compared with pressure assessment alone , although again the data were limited .
No method of monitoring in selective shunting has been shown to produce better outcomes