***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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    ***EXAMPLES*** 
    Input: AIM To investigate the effect of low central venous pressure ( LCVP ) on blood loss during hepatectomy for hepatocellular carcinoma ( HCC ) . METHODS By the method of sealed envelope , 50 HCC patients were r and omized into LCVP group ( n=25 ) and control group ( n=25 ) . In LCVP group , CVP was maintained at 2 - 4 mmHg and systolic blood pressure ( SBP ) above 90 mmHg by manipulation of the patient 's posture and administration of drugs during hepatectomy , while in control group hepatectomy was performed routinely without lowering CVP . The patients ' preoperative conditions , volume of blood loss during hepatectomy , volume of blood transfusion , length of hospital stay , changes in hepatic and renal functions were compared between the two groups . RESULTS There were no significant differences in patients ' preoperative conditions , maximal tumor dimension , pattern of hepatectomy , duration of vascular occlusion , operation time , weight of resected liver tissues , incidence of post-operative complications , hepatic and renal functions between the two groups . LCVP group had a markedly lower volume of total intraoperative blood loss and blood loss during hepatectomy than the control group , being 903.9+/-180.8 mL vs 2 329.4+/-2 538.4 ( W=495.5 , P<0.01 ) and 672.4+/-429.9 mL vs 1 662.6+/-1 932.1 ( W=543.5 , P<0.01 ) . There were no remarkable differences in the pre-resection and post-resection blood losses between the two groups . The length of hospital stay was significantly shortened in LCVP group as compared with the control group , being 16.3+/-6.8 d vs 21.5+/-8.6 d ( W=532.5 , P<0.05 ) . CONCLUSION LCVP is easily achievable in technique . Maintenance of CVP < or= 4 mmHg can help reduce blood loss during hepatectomy , shorten the length of hospital stay , and has no detrimental effects on hepatic or renal function Objective : To evaluate the protective effects of ischemic preconditioning in a prospect i ve r and omized study involving a large population of unselected patients and to identify factors affecting the protective effects . Summary Background Data : Ischemic preconditioning is an effective protective strategy in several animal models . Protection has also been suggested in a small series of patients undergoing a hemihepatectomy with 30 minutes of inflow occlusion . Whether preconditioning confers protection in other types of liver resection and longer periods of ischemia is unknown . Therefore , we conducted a prospect i ve r and omized study to evaluate the impact of ischemic preconditioning in liver surgery . Methods : A total of 100 unselected patients undergoing major liver resection ( > bisegmentectomy ) under inflow occlusion for at least 30 minutes were r and omized during surgery to either receive or not receive an ischemic preconditioning protocol ( 10 minutes of ischemia followed by 10 minutes of reperfusion ) . Univariate and multivariate analyses were performed to identify independent factors affecting the protective effects of ischemic preconditioning .  ATP contents in liver were measured as a possible mechanism of protection . Results : Both groups ( n = 50 in each ) were comparable regarding age , gender , duration of inflow occlusion , and resected liver volumes . Postoperative serum transaminase levels were significantly lower in preconditioned than in control patients ( median peak AST 364 U/L vs. 520 U/L , P = 0.028 ; ALT 406 vs. 519 U/L , P = 0.049 ) . Regression multivariate analysis revealed an increased benefit of ischemic preconditioning in younger patients , in patients with longer duration of inflow occlusion ( up to 60 minutes ) , and in cases of lower resected liver volume ( < 50 % ) . Patients with steatosis were also particularly protected by ischemic preconditioning .  ATP content in liver tissue was preserved by ischemic preconditioning in young but not older patients . Conclusions : This study establishes ischemic preconditioning as a protective strategy against hepatic ischemia in humans . The strategy is particularly effective in young patients requiring a prolonged period of inflow occlusion , and in the presence of steatosis , and is possibly related to preservation of ATP content in liver tissue . Other strategies are needed in older patients Objective This prospect i ve r and omized study determined the influence of closed-suction drainage on the incidence of postoperative complications after elective hepatic resection . Summary Background Data Routine drainage is no longer advocated after several intra-abdominal surgical procedures . Methods A series of 81 patients who underwent elective hepatic resection were r and omly allocated to either a nondrainage group ( n = 39 ) and a drainage group with closed-suction drainage ( n = 42 ) . Indications for resection were 42 benign lesions and 39 malignant tumors , including 19 with cirrhosis . Major hepatic resection was performed in 25 patients and minor resection , in 56 . All patients underwent ultrasonography with puncture for bacteriologic cultures of all fluid collection s within the first 5 postoperative days . Results One patient died in each group . Ultrasonography found a significantly higher rate of subphrenic collection s in the drainage group compared with the nondrainage group ( respectively , 36 % vs. 15 % , p < 0.05 ) . These collection s were more frequently infected in the drainage group ( n = 6 ) than in the nondrainage group ( n = 2 ) . After major liver resection , the rate of intra-abdominal postoperative complications ( i.e. , subphrenic fluid collection s , hematomas , and bilomas ) was similar between the two groups . Conclusion Minor liver resection is safer without drainage . Major liver resection can be performed with or without abdominal drainage BACKGROUND Two r and omized prospect i ve studies suggested that ischemic preconditioning ( IP ) protects the human liver against ischemia-reperfusion injury after hepatectomy performed under continuous clamping of the portal triad . The primary goal of this study was to determine whether IP protects the human liver against ischemia-reperfusion injury after hepatectomy under continuous vascular exclusion with preservation of the caval flow . STUDY DESIGN Sixty patients were r and omly divided into two groups : with ( n=30 ; preconditioning group ) and without ( n=30 ; control group ) IP ( 10 minutes of portal triad clamping and 10 minutes of reperfusion ) before major hepatectomy under vascular exclusion of the liver preserving the caval flow .  Serum concentrations of aspartate transferase , alanine transferase , glutathione-S-transferase , and bilirubin and prothrombin time were regularly determined until discharge and at 1 month . Morbidity and mortality were determined in both groups . RESULTS Peak postoperative concentrations of aspartate transferase were similar in the groups with and without IP ( 851 + /- 1,733 IU/L and 427 + /- 166 IU/L respectively , p=0.2 ) . A similar trend toward a higher peak concentration of alanine transferase and glutathione-S-transferase was indeed observed in the preconditioning group compared with the control group . Morbidity and mortality rates and lengths of ICU and hospitalization stays were similar in both groups . CONCLUSIONS IP does not improve liver tolerance to ischemia-reperfusion after hepatectomy under vascular exclusion of the liver with preservation of the caval flow . This maneuver does not improve postoperative liver function and does not affect morbidity or mortality rates . The clinical use of IP through 10 minutes of warm ischemia in this technique of hepatectomy is not currently recommended BACKGROUND AND AIMS Liver surgery usually involves ischemia and reperfusion ( I/R ) which results in oxidative stress and cell damage . The administration of antioxidants should diminish or prevent this damage . The purpose of this study was to investigate the effect of the antioxidant vitamin E on I/R injury . METHODS We carried out a placebo-controlled double-blind study on 68 patients undergoing elective , tumor-related , partial liver resection . 47 patients were qualified for the per protocol population based evaluation . The patients were r and omly assigned to two groups . The day before surgery one group received three infusions containing vitamin E ( 600 IU=540 mg vitamin E emulsion ) . The other group received three infusions of placebo . RESULTS Length of stay in the intensive care unit ( ICU ) was significantly shorter in the verum group than in the placebo group ( P<0.05 ) . There were signs of improvement for AUC AST ( P<0.05 ) , ALT and GLDH in the verum group after surgery . Serum vitamin E concentration increased after administration of vitamin E infusion and declined in both treatment groups after surgery ( P<0.01 ) . In the verum group vitamin E deficiency was prevented while vitamin E concentration remained low in the placebo group ( P<0.01 ) . CONCLUSIONS The findings from this study indicate that preoperative administration of vitamin E is safe and that this treatment may have beneficial effects by reducing the impact of I/R injury in liver surgery Hepatic pedicle clamping ( HPC ) is widely used to control intraoperative bleeding during hepatectomy ; intermittent HPC is better tolerated but is associated with blood loss during each period of reperfusion . Recently , it has been shown that ischemic preconditioning ( IP ) reduces the ischemia-reperfusion damage for up to 30 minutes of continuous clamping in healthy liver . We evaluated the safety of IP for more prolonged periods of continuous clamping in 42 consecutive patients with healthy liver su bmi tted to hepatectomy .  IP was used in 21 patients ( group A ) ; mean + /- SD of liver ischemia was 54 + /- 19 minutes ( range , 27 - 110 ; in 7 cases > 60 minutes ) . In the other 21 patients , continuous clamping alone was used ( Group B ) ; liver ischemia lasted 36 + /- 14 minutes ( range , 13 - 70 ; in 2 cases > 60 minutes ) . Two patients in Group A ( 9.5 % ) and 3 in Group B ( 14.2 % ) received blood transfusions . In spite of the longer duration of ischemia ( P=.001 ) , patients with IP had lower aspartate aminotransferase ( AST ; P=.03 ) and alanine aminotransferase ( ALT ; P = not significant ) at postoperative day 1 , with a similar trend at postoperative day 3 . This was reconfirmed by multiple regression analysis , which showed that although postoperative transaminases increased with increasing duration of ischemia and of the operation in both groups , the increases were significantly smaller ( P<.001 ) with the use of preconditioning . In conclusion , the present study confirms that IP is safe and effective for liver resection in healthy liver and is also better tolerated than continuous clamping alone for prolonged periods of ischemia . This technique should be preferred to continuous clamping alone in healthy liver . Additional studies are needed to assess the role of IP in cirrhotic liver and to compare IP with intermittent clamping Background The success of hepatectomy can be associated with intraoperative blood loss because massive blood loss causes a poor prognosis . This study was design ed to evaluate the effect of infrahepatic inferior vena cava ( IVC ) clamping on the bleeding amount during hepatectomy . Methods Eighty-five patients scheduled to undergo hepatic resection were r and omly assigned to the IVC clamping or an IVC nonclamping group according to age , indocyanine green retention rate at 15 minutes , operative procedure , and number of tumors by prospect i ve , r and omized method . All analyses were compared by Mann-Whitney U test . Results Forty-three patients were assigned to the IVC clamping group and 42 to the nonclamping group ( IVC clamping group vs. non-clamping ) : total blood loss ( 499 vs. 584 ml ; p = 0.567 ) , amount of bleeding during hepatectomy ( 233 vs. 285 ml ; p = 0.474 ) , amount of bleeding during hepatectomy/area of dissection ( 4.9 vs. 6.6 ml/cm2 ; p = 0.63 ) , CVP difference ( −3 cmH2O vs. −1 cmH2O ; p < 0.01 ) , and diameter of the right hepatic vein ( −2.2 cm vs. 0 ; p < 0.01 ) . Conclusions Although we had speculated that infrahepatic IVC clamping would reduce blood loss during hepatectomy , we failed to demonstrate any beneficial effects in this clinical setting with low CVP OBJECTIVES To analyze sources search ed in Cochrane review s , to determine the proportion of trials included in review s that are indexed in major data bases , and to compare the quality of these trials with those from other sources . METHODS All new systematic review s in the Cochrane Library , Issue1 2001 , that were restricted to r and omized controlled trials ( RCTs ) or quasi- RCTs were selected . The sources search ed in the review s were recorded , and the trials included were checked to see whether they were indexed in four major data bases . Trials not indexed were checked to determine how they could be identified . The quality of trials 
    Output:
    
Hepatic vascular occlusion does not decrease the blood transfusion requirements .
It decreases the cardiac output and increases the systemic vascular resistance .
In the comparison between continuous portal triad clamping and intermittent portal triad clamping , four of the five liver failures occurred in patients with chronic liver diseases undergoing the liver resections using continuous portal triad clamping .
There was no difference in any of the other important outcomes in any of the comparisons .
In elective liver resection , hepatic vascular occlusion can not be recommended over portal triad clamping .
Intermittent portal triad clamping seems to be better than continuous portal triad clamping at least in patients with chronic liver disease .
There is no evidence to support selective inflow occlusion over portal triad clamping .
The optimal method of intermittent portal triad clamping is not clear .
There is no evidence for any difference between the ischaemic preconditioning followed by vascular occlusion and intermittent vascular occlusion for liver resection in patients with non-cirrhotic livers .