***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: OBJECTIVES Cardiopulmonary bypass ( CPB ) is widely regarded as an important contributor to renal failure , a well recognized complication following coronary artery surgery ( coronary artery bypass grafting ( CABG ) ) . Anecdotally off-pump coronary surgery ( OPCAB ) is considered renoprotective . We examine the extent of renal glomerular and tubular injury in low-risk patients undergoing either OPCAB or on-pump coronary artery bypass ( ONCAB ) .  METHODS Forty low-risk patients with normal preoperative cardiac and renal functions awaiting elective CABG were prospect ively r and omized into those undergoing OPCAB ( n=20 ) and ONCAB ( n=20 ) . Glomerular and tubular injury were measured respectively by urinary excretion of microalbumin and retinol binding protein ( RBP ) indexed to creatinine ( Cr ) . Daily measurements were taken from admission to postoperative day 5 . Fluid balance , serum Cr and blood urea were also monitored . RESULTS No mortality or renal complication were observed . Both groups had similar demographic makeup , Parsonnet score , functional status and extent of coronary revascularization ( 2.1+/-1.0 vs. 2.5+/-0.7 grafts ; P=0.08 ) . Serum Cr and blood urea remained normal in both groups throughout the study . A significant and similar rise in urinary RBP : Cr occurred in both groups peaking on day 1 ( 3183+/-2534 vs. 4035+/-4079 ; P=0.43 ) before reapproximating baseline levels . These trends were also observed with urinary microalbumin : Cr ( 5.05+/-2.66 vs. 6.77+/-5.76 ; P=0.22 ) . Group B patients had a significantly more negative fluid balance on postoperative day 2 ( -183+/-1118 vs. 637+/-847 ml ; P=0.03 ) . CONCLUSIONS Although renal complication or serum markers of kidney dysfunction were absent , sensitive indicators revealed significant and similar injury to renal tubules and glomeruli following either OPCAB or ONCAB . These results suggest that avoidance of CPB does not offer additional renoprotection to patients at low risk of perioperative renal insult during CABG BACKGROUND Pulmonary dysfunction is still a major problem in coronary artery bypass grafting ( CABG ) . The purpose of this r and omized study was to determine the effect of different CABG techniques on pulmonary function . METHODS Fifty eight patients with severe obstructive pulmonary disease had elective isolated coronary surgery .  The surgical methods for the patients with chronic obstructive pulmonary disease ( COPD ) were st and ard CABG in 18 patients ( group 1 ) , beating heart surgery in 19 patients ( group 2 ) , and minimally invasive direct coronary artery bypass grafting ( MIDCABG ) in 21 patients ( group 3 ) . RESULTS The earliest extubation time was from group 3 ( p < 0.001 ) . The average stay in the intensive care unit was significantly longer in group 1 ( 2.6 + /- 1.5 days ) than in groups 2 ( 1.4 + /- 0.8 days ) and 3 ( 1.1 + /- 0.8 days ) ( p < 0.05 ) . The most prevalent respiratory morbidity was atelectasis that developed in 6 patients from group 1 , in 2 patients from group 2 , and in 3 patients from group 3 . Forced expiratory volumes in 1 second ( FEV1 ) obtained in the second postoperative month were significantly lower than preoperative values only in group 1 ( p < 0.05 ) . Forced vital capacity ( FVC ) values were significantly lower than the preoperative values in all three groups ( p < 0.05 ) . CONCLUSIONS Off-pump bypass surgical procedures are more advantageous than on-pump methods for patients with COPD . These patients can be operated on using the beating heart technique or by using MIDCABG to prevent side effects of CPB on pulmonary function and effects of sternotomy OBJECTIVE Cardiopulmonary bypass ( CPB ) is associated with gut mucosal hypoxia , which may contribute to gastrointestinal complications . We examined gastric mucosal oxygenation together with whole-body oxygen flux in low-risk patients undergoing coronary artery bypass grafting ( CABG ) with and without CPB .  METHODS Fifty-four patients undergoing primary CABG by the same surgeon were r and omized into either on-pump ( ONCAB , n=27 ) or off-pump ( OPCAB , n=27 ) groups . The ONCAB group underwent mild hypothermic ( 35 degrees C ) pulsatile CPB with arterial line filtration . Each patient underwent perioperative monitoring with continuous tonometry and cardiac output devices .  Gastric intramucosal pH ( pHi ) , gastric-arterial carbon dioxide partial pressure difference ( CO(2 ) gap ) , whole-body oxygen delivery ( DO(2 ) ) and consumption ( VO(2 ) ) and whole-body oxygen extraction fraction were measured at sequential time-points intraoperatively and up to 6 h postoperatively . Anaesthetic management was st and ardized . RESULTS Both groups had similar demographic makeup and extent of revascularization ( ONCAB 2.6+/-0.9 grafts versus OPCAB 2.5+/-0.8 grafts ; P=0.55 ) . The ONCAB group had a mean ( + /-SD ) CPB time of 62+/-25 min and aortic cross-clamp time of 32+/-11 min . In both groups there was a similar and progressive drop in pHi intraoperatively . Postoperatively , there was a gradual separation between the groups with ONCAB patients showing no further decline in pHi , while further deterioration was observed in the OPCAB group up to 6 h postoperatively . There was a significant difference between the groups over time ( P=0.03 ) . There was a corresponding progressive rise in CO(2 ) gap perioperatively in both groups , with ONCAB patients demonstrating superior preservation of gastric mucosal oxygenation in the early postoperative period . Global oxygen utilization measurements showed superior DO(2 ) and VO(2 ) in the OPCAB group throughout the study . CONCLUSIONS Despite superior global oxygen flux associated with beating-heart revascularization , gastric mucosal hypoxia occurred to similar extents in both groups with worsening trends for the OPCAB patients postoperatively . The splanchnic pathophysiology during beating-heart revascularization should be further explored 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 The development of new surgical devices and techniques allows off pump coronary artery bypass grafting ( OPCAB ) without the use of CPB and cardioplegia . This study tested whether OPCAB reduces myocardial cell damage , lipid peroxidation and systemic endothelin release when compared to conventional coronary artery bypass grafting . METHODS Twenty-six patients were assigned to either the OPCAB procedure using a suction device and regular sternotomy ( n = 13 ) or were treated conventionally using extracorporeal circulation , blood cardioplegia and hypothermic arrest ( 29 - 31 degrees C ; n = 13 ) . Troponin I and creatine kinase - MB were determined for cardiac specific cell damage . Myocardial and systemic malondialdhyde levels were measured to account for oxyradical mediated lipid peroxidation . Systemic big-endothelin levels were determined as a marker for endothelial cell activation . RESULTS A significant reduction of the cardiac specific cell damage was observed in the OPCAB group vs. the CABG group over time in the absence of acute myocardial ischemia or infa rct ion . In addition , systemic and myocardial lipid peroxidation as measured by the malondialdehyde ( MDA ) levels were lower in the OPCAB group when compared to CABG . Finally , plasma levels of big-Endothelin ( big-ET ) significantly rose in the CABG but not in the OPCAB group . CONCLUSIONS The data of the present study indicate that OPCAB revascularization without the use of CPB and cardioplegic arrest reduces myocardial cell damage and lipid peroxidation . It is also associated with a reduced activation of the potent vasoconstrictor peptide endothelin . All of this may contribute to improved myocardial function and faster postoperative recovery from surgical revascularization procedures , particularly in critically ill patients BACKGROUND The performance of  coronary bypass surgery without cardiopulmonary bypass ( " off pump " ) may reduce perioperative morbidity and costs , but it is uncertain whether the outcome is similar to that involving the use of cardiopulmonary bypass ( " on pump " ) . METHODS In a multicenter , r and omized trial , we r and omly assigned 139 patients with predominantly single- or double-vessel coronary disease to on-pump surgery and 142 to off-pump surgery .  Cardiac outcome and cost effectiveness were determined one year after surgery . The uncertainty surrounding the cost-effectiveness ratio ( cost differences per quality -adjusted year of life gained ) was addressed by bootstrapping . RESULTS At one year , the rate of freedom from death , stroke , myocardial infa rct ion , and coronary reintervention was 90.6 percent after on-pump surgery and 88.0 percent after off-pump surgery ( absolute difference , 2.6 percent ; 95 percent confidence interval , - 4.6 to 9.8 ) . Graft patency in a r and omized subgroup of patients was 93 percent after on-pump surgery and 91 percent after off-pump surgery ( absolute difference , 2.0 percent ; 95 percent confidence interval , - 6.5 to 10.4 ) . On-pump surgery was associated with $ 1,839 in additional direct costs per patient ( $ 14,908 vs. $ 13,069 - -a difference of 14.1 percent ) and an increase in quality -adjusted years of life of 0.83 as compared with 0.82 ( difference , 0.01 year ; 95 percent confidence interval , - 0.03 to 0.04 ) . Off-pump surgery was more cost effective than on-pump surgery in 95 percent of bootstrap estimates . CONCLUSIONS In low-risk patients , there was no difference in cardiac outcome at one year between those who underwent on-pump bypass surgery and those who underwent off-pump surgery . Off-pump surgery was more cost effective BACKGROUND Although no r and omised controlled trial has assessed the midterm effects of coronary-artery bypass surgery on the beating heart , this technique is being used in more and more patients . We did two r and omised trials to compare the short-term morbidity associated with off-pump and on-pump myocardial revascularisation . Our aim was to pool the results to assess midterm outcomes . METHODS From March , 1997 , to November , 1999 , we r and omly allocated 200 patients to off-pump and 201 to on-pump coronary surgery .  In Beating Heart Against Cardioplegic Arrest Study ( BHACAS ) 1 , we excluded patients who had had myocardial infa rct ion in the past month or who required grafting of the circumflex artery distal to the first obtuse marginal branch . In BHACAS 2 , we included such patients . Primary outcomes were all-cause mortality and cardiac-related events at midterm follow-up ( 1 - 3 years ) . Analysis was by intention to treat . FINDINGS Analyses of combined data from both trials showed the following risk 
    Output:
    
Trial sequential analysis demonstrated overwhelming evidence supporting that off-pump bypass surgery reduces atrial fibrillation .
CONCLUSION Off-pump surgery reduces the risks of postoperative atrial fibrillation compared with on-pump surgery .