***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 
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    Input: BACKGROUND Coronary artery bypass surgery with cardiopulmonary bypass carries a significant risk of perioperative brain injury . At least 1 % to 5 % will suffer a stroke , and at 3-months postoperatively approximately 30 % are reported to have cognitive impairment assessed by neuropsychologic testing . In off-pump surgery cardiopulmonary bypass is not used and instrumentation on the ascending aorta is reduced . The main aim of this study was to assess if off-pump surgery reduces intraoperative cerebral embolization . METHODS This was a prospect i ve and r and omized study of two comparable groups with regard to age , sex , years of education , preoperative cognitive functioning , and surgical characteristics . Fifty-two patients ( 29 off-pump ) were monitored by the use of transcranial Doppler ultrasound for cerebral microembolization during surgery . Preoperative and postoperative clinical , cerebral magnetic resonance imaging , and neuropsychologic examinations were also carried out . RESULTS There was a significant reduction in the number of cerebral microemboli during off-pump compared with on-pump surgery ( 16.3 [ range 0 to 131 ] versus 90.0 [ range 15 to 274 ] , p < 0.0001 ) . No significant difference with regard to the incidence of neuropsychologic performance ( decline in 29 % off-pump , 35 % on-pump ) or neuroradiologic findings at 3 months was found , and there was no association between the number of cerebral microemboli and cognitive outcome . CONCLUSIONS This study clearly demonstrates that off-pump surgery leads to a reduction in intraoperative cerebral microembolization . A significant reduction in the number of off-pump patients with cognitive decline or ischemic brain lesions on cerebral magnetic resonance imaging could not be demonstrated in this relatively small patient population Background and Purpose — The aim of this study was to assess the first multifrequency transcranial Doppler system that was specially developed to automatically detect and discriminate between solid and gaseous cerebral microemboli . Methods — The multifrequency transcranial Doppler instrumentation insonates simultaneously with 2.5 and 2.0 MHz . Differentiation between solid and gaseous microemboli is based on the principle that solid microemboli reflect more ultrasound at the higher than at the lower frequency , whereas the opposite is the case for gaseous microemboli . In the in vitro studies , 159 plastic spheres ( 50 or 80 & mgr;m in diameter ) and 105 gas bubbles ( 8 to 25 & mgr;m ) were studied in a pulsatile closed-loop system containing irodinium or pig blood . In vivo studies were carried out for 1 hour in 15 patients with mechanical heart valves and in 45 patients with carotid stenosis . This gave a total of 60 hours of online automatic monitoring in patients . Results — In the in vitro studies , 152 of the 159 ( 95.6 % ) plastic spheres were classified as solid , and 7 ( 4.4 % ) were classified as uncertain solid . Of the 105 gas bubbles , 99 ( 94.3 % ) were classified as gaseous and 6 ( 5.7 % ) as uncertain gaseous . Thus , correct classification was made for 251 ( 95.1 % ) of the 264 embolic events studied . A comparison between the automatic multifrequency discrimination and the known embolic classification gave a & kgr ; value of 0.897 ( P < 0.0001 ) . The multifrequency Doppler classified 433 ( 84.2 % ) of the 514 emboli detected in the mechanical heart valve patients as gaseous , 74 ( 14.4 % ) as solid , and 7 ( 1.4 % ) as uncertain ( 3 uncertain solid , 4 uncertain gas ) . Thirty-two emboli were detected in 17 ( 38 % ) of the 45 carotid stenosis patients ; 30 ( 93.7 % ) were classified as solid and 2 ( 6.3 % ) as uncertain solid . Conclusions — This study has shown that multifrequency transcranial Doppler can be used to automatically differentiate between solid and gaseous microemboli online . Most detected microemboli in this initial study of mechanical heart valves were classified as gaseous , whereas most were classified as solid in the patients with carotid stenosis OBJECTIVE To analyze the frequency and severity of sub clinical cerebral complications associated with  coronary artery bypass grafting ( CABG ) .  DESIGN A prospect i ve controlled study using preoperative and postoperative magnetic resonance imaging ( MRI ) of the brain , quantitative electroencephalography ( QEEG ) , and detailed neuropsychological and neurologic examinations as potentially sensitive indicators of sub clinical cerebral injury associated with CABG . SETTING Multimodality evaluation in a tertiary care unit ( Kuopio University Hospital , Kuopio , Finl and ) . PATIENTS Thirty-eight patients undergoing elective CABG and 20 control patients undergoing other major vascular surgery , mostly operations on the abdominal aorta .  MAIN OUTCOME MEASURES Coronary artery bypass grafting-associated cerebral complications assessed preoperatively and postoperatively by  brain MRI , QEEG , detailed neurologic examination , and a neuropsychological test battery that evaluates cognitive functions in major areas known to be vulnerable to organic impairment ( learning and memory , attention , flexible mental processing , and psychomotor speed ) . RESULTS There were no major neurologic complications . A mild hemisyndrome developed in 1 patient who underwent CABG and in 1 control patient . Overall , there was no decline in mean cognitive performance 3 months after surgery . Electroencephalographic slowing of 0.5 Hz or more in at least 2 channels occurred in 11 patients who underwent CABG and in 1 control patient ( P=.03 ) . The postoperative brain MRI scan revealed new small ischemic lesions in 8 patients ( 21 % ) in the CABG group but in none of the control group ( P=.03 ) . These new cerebral MRI lesions did not explain deterioration in neuropsychological test performance or the QEEG slowing . CONCLUSIONS Coronary artery bypass grafting causes more QEEG alterations and small ischemic cerebral lesions that are detectable by MRI than does other major vascular surgery . The effect is mainly sub clinical , because no statistically significant deterioration in mean neuropsychological test performance was detected Background and Purpose Microemboli have been implicated in the etiology of neuropsychological deficits after cardiopulmonary bypass . This study examined the incidence of high‐intensity transcranial signals ( microemboli ) and their relation to changes in neuropsychological performance after surgery . Methods Transcranial Doppler ultrasonography was used to measure middle cerebral artery blood flow velocity and detect microemboli . The number of high‐intensity transcranial signals was determined and related to a neurological examination and absolute changes in neuropsychological performance as well as the number of patients considered to exhibit a neuropsychological deficit . Data were available on 100 consenting patients undergoing routine cardiopulmonary bypass . Fifty of the patients were r and omly assigned to a procedure that included a 40‐&mgr;m arterial line filter , and 50 had the procedure without any arterial line filter . Results Significantly more patients were found to have neuropsychological deficits in the group without the arterial line filter at both 8 days ( P<.05 ) and 8 weeks ( P<.03 ) after surgery . In addition , more “ soft ” neurological signs were found in the nonfiltered group 24 hours after surgery ( P<.05 ) . More high‐intensity transcranial signals were found in the nonfiltered group , and the number of high‐intensity transcranial signals was found to be related to the likelihood of a patient having a neuropsychological deficit at 8 weeks . Conclusions These data suggest that neuropsychological deficits after routine cardiopulmonary bypass are related to the number of microemboli delivered during surgery . Furthermore , the numbers of microemboli may be reduced by including a 40‐&mgr;m filter on the arterial line . ( Stroke . 1994;25:1393‐1399 . BACKGROUND Neurologic and clinical morbidity after  coronary artery bypass grafting ( CABG )  can be significant . By avoiding cardiopulmonary bypass , off-pump CABG ( OPCAB ) may reduce morbidity . METHODS Sixty patients ( 30 CABG and 30 OPCAB ) were prospect ively r and omized . Neurocognitive testing was performed before the operation and 2 weeks and 1 year after the operation . Neurologic testing to detect stroke and (99m)Tc-HMPAO whole-brain single photon emission computed tomography scanning to assess cerebral perfusion were performed before the operation and 3 days afterward . Bilateral middle cerebral artery transcranial Doppler scanning was performed intraoperatively to detect cerebral microemboli . All examiners were blinded to treatment group . Clinical morbidity and costs were compared . RESULTS Coronary artery bypass grafting was associated with more cerebral microemboli ( 575 + /- 278.5 CABG versus 16.0 + /- 19.5 OPCAB ( median + /- semiinterquartile range ) and significantly reduced cerebral perfusion after the operation to the bilateral occipital , cerebellar , precunei , thalami , and left temporal lobes ( p < or = 0.01 ) . Cerebral perfusion with  OPCAB  was unchanged . Compared with base line , OPCAB patients performed better on the Rey Auditory Verbal Learning Test ( total and recognition scores ) at both 2 weeks and at 1 year ( p < or = 0.05 ) , whereas CABG performance was statistically unchanged for all cognitive measures . Patients who underwent CABG had more chest tube drainage ( 1389 + /- 1256 mL CABG versus 789 + /- 586 mL OPCAB , p = 0.02 ) and required more blood ( 3.9 + /- 5.8 U CABG versus 1.2 + /- 2.2 U OPCAB , p = 0.02 ) , fresh frozen plasma ( 3.0 + /- 6.0 U CABG versus 0.5 + /- 2.2 U OPCAB , p = 0.03 ) , and hours of postoperative use of dopamine ( 16.3 + /- 21.2 hours CABG versus 7.3 + /- 9.7 hours OPCAB , p = 0.04 ) . These differences culminated in higher costs for CABG  ( $ 23,053 + /- $ 5,320 CABG versus $ 17,780 + /- $ 4,390 OPCAB , p < 0.0001 ) . One stroke occurred with CABG , compared with none with OPCAB ( p = NS ) . One OPCAB patient died because of a pulmonary embolus ( p = NS ) . CONCLUSIONS Compared with CABG , OPCAB may reduce neurologic and clinical morbidity as well as cost Background and Purpose — Improvements in cardiac surgery mortality and morbidity have focused interest on the neurological injury such as stroke and cognitive decline that may accompany an otherwise successful operation . We aim ed to investigate ( 1 ) the rate of stroke , new ischemic change on MRI , and cognitive impairment after cardiac valve surgery ; and ( 2 ) the controversial relationship between perioperative cerebral ischemia and cognitive decline . Methods — Forty patients ( 26 men ; mean [ SD ] age 62.1 [ 13.7 ] years ) undergoing intracardiac surgery ( 7 also with coronary artery bypass grafting )  were studied .  Neurological , neuropsychological , and MRI examinations  were performed 24 hours before surgery and 5 days ( MRI and neurology ) and 6 weeks ( neuropsychology and neurology ) after surgery . Cognitive decline from baseline was determined using the Reliable Change Index . Results — Two of 40 ( 5 % ) patients had perioperative strokes and 22 of 35 ( 63 % ) tested had cognitive decline in at least one measure ( range , 1 to 4 ) . Sixteen of 37 participants ( 43 % ) with postoperative imaging had new ischemic lesions ( range , 1 to 17 lesions ) with appearances consistent with cerebral embolization . Cognitive decline was seen in all patients with , and 35 % of those without , postoperative ischemic lesions ( P<0.001 ) , and there was an association between the number of abnormal cognitive tests and ischemic burden ( P<0.001 ) . Conclusion — We have provided a reliable estimate of the rate of stroke , postoperative ischemia , and cognitive impairment at 6 weeks after cardiac valve surgery . Cognitive impairment is associated with perioperative ischemia and is more severe with greater ischemic load Background — Reinfusion of unprocessed cardiotomy blood during cardiac surgery can introduce particulate material into the cardiopulmonary bypass circuit , which may contribute to postoperative cognitive d 
    Output:
    
Conclusion : This systematic review could neither confirm nor rule out a causal link between emboli from CPB and postoperative cognitive decline