***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: The efficacy of low-dose heparin in preventing fatal postoperative pulmonary embolism has been investigated in a multicentre prospect i ve r and omised trial . 4121 patients over the age of forty years undergoing a variety of elective major surgical procedures were included in the trial ; 2076 of these were in the control group and 2045 patients received heparin .  The two groups were well matched for age , sex , weight , blood-group , and other factors which could predispose to the development of venous thromboembolism . 180 ( 4 - 4 % ) patients died during the postoperative period , 100 in the control and 80 in the heparin group : 72 % of deaths in the control and 66 % in the heparin group had necropsy examination . 16 patients in the control group and 2 in the heparin group were found at necropsy to have died due to acute massive pulmonary embolism ( P smaller than 0 - 005 ) . In addition , emboli found at necropsy in 6 patients in the control group and 3 in the heparin group were considered either contributory to death or an incidental finding since death in these patients was attributed to other causes . Taking all pulmonary emboli together , the findings were again significant ( P smaller than 0 - 005 ) . Of 1292 patients in whom the 125-I-fibrinogen test was performed to detect deep-vein thrombosis ( D.V.T. ) 667 were in the control group and 625 in the heparin group . The frequency of isotopic D.V.T. was reduced from 24 - 6 % in the control group 7 - 7 % in the heparin group ( P smaller 0 - 005 ) . In 30 patients D.V.T. was detected at necropsy ; 24 in the control and 6 in the heparin group ( P smaller 0 - 005 ) . 32 patients in the control group and 11 in the heparin group developed clinical ly diagnosed D.V.T. which was confirmed by venography ( P smaller than 0 - 005 ) . In addition , 24 patients in the control and 8 in the heparin group were treated for clinical ly suspected pulmonary emoblism . The difference in the number of patients requiring treatment for D.V.T. and /or pulmonary embolism in the two groups was again significant ( P smaller than 0 - 005 ) . 9 patients were found at necropsy to have died from haemorrhage ; 5 were in the control and 4 in the heparin group . A careful objective analysis of operative and postoperative bleeding in 1475 patients showed no statistically significant difference in the blood-transfusion requirements or in the fall in the postoperative haemoglobin level either in the individual operative groups or in the group as a whole . However , the difference in the number of patients who developed wound haematoma in the heparin and control groups was significant ( P smaller 0 - 01 ) . The results of the trial indicate that this form of prophylaxis can now be recommended for use on a large scale in " high-risk " patients undergoing major surgery Venous thromboembolism is a serious complication following gynecologic surgery and is particularly common in patients with malignancy . A previous study of subcutaneous low-dose heparin given as one dose preoperatively and every 12 hours postoperatively failed to show a benefit in gynecologic oncology patients . In the present study , two more intense regimens of low-dose heparin were evaluated . Three hundred four patients were assigned r and omly to receive no prophylaxis ( controls ) , subcutaneous heparin 5000 units 2 hours before surgery and every 8 hours postoperatively ( low-dose heparin ) ( regimen I ) , or 5000 units heparin subcutaneously every 8 hours preoperatively ( between two and nine doses ) and every 8 hours postoperatively ( regimen II ) . All patients had thromboembolism surveillance with the fibrinogen uptake test and clinical evaluation . Eighty-four percent had a malignancy . Thromboemboli were diagnosed in 19 of 103 control patients , ten of 104 regimen I patients , and six of 97 regimen II patients , a statistically significant difference ( P < .008 ) . When compared with the control group , the study groups had no evidence of increased bleeding complications or alteration of laboratory coagulation indicators . ( Obstet Gynecol 75 : 684 , 1990 Summary Background Data : The epidemiology of venous thromboembolism ( VTE ) after cancer surgery is based on clinical trials on VTE prophylaxis that used venography to screen deep vein thrombosis ( DVT ) . However , the clinical relevance of asymptomatic venography-detected DVT is unclear , and the population of these clinical trials is not necessarily representative of the overall cancer surgery population . Objective : The aim of this study was to evaluate the incidence of clinical ly overt VTE in a wide spectrum of consecutive patients undergoing surgery for cancer and to identify risk factors for VTE . Methods : @RISTOS was a prospect i ve observational study in patients undergoing general , urologic , or gynecologic surgery . Patients were assessed for clinical ly overt VTE occurring up to 30 ± 5 days after surgery or more if the hospital stay was longer than 35 days . All outcome events were evaluated by an independent Adjudication Committee . Results : A total of 2373 patients were included in the study : 1238 ( 52 % ) undergoing general , 685 ( 29 % ) urologic , and 450 ( 19 % ) gynecologic surgery . In-hospital prophylaxis was given in 81.6 % and postdischarge prophylaxis in 30.7 % of the patients . Fifty patients ( 2.1 % ) were adjudicated as affected by clinical ly overt VTE ( DVT , 0.42 % ; nonfatal pulmonary embolism , 0.88 % ; death 0.80 % ) . The incidence of VTE was 2.83 % in general surgery , 2.0 % in gynecologic surgery , and 0.87 % in urologic surgery . Forty percent of the events occurred later than 21 days from surgery . The overall death rate was 1.72 % ; in 46.3 % of the cases , death was caused by VTE . In a multivariable analysis , 5 risk factors were identified : age above 60 years ( 2.63 , 95 % confidence interval , 1.21–5.71 ) , previous VTE ( 5.98 , 2.13–16.80 ) , advanced cancer ( 2.68 , 1.37–5.24 ) , anesthesia lasting more than 2 hours ( 4.50 , 1.06–19.04 ) , and bed rest longer than 3 days ( 4.37 , 2.45–7.78 ) . Conclusions : VTE remains a common complication of cancer surgery , with a remarkable proportion of events occurring late after surgery . In patients undergoing cancer surgery , VTE is the most common cause of death at 30 days after surgery A prospect i ve study of a series of 77 patients on adjuvant radiochemotherapy following surgery for high- grade gliomas was conducted to evaluate the risk of deep vein thrombosis and identify risk factors . We found a 20.8 % risk of deep vein thrombosis at 12 months ( st and ard error = 4.8 % ) and a 31.7 % risk ( st and ard error = 7.4 % ) at 24 months ( Kaplan-Meier method ) . Twenty patients ( 26 % ) developed deep vein thrombosis with a maximum incidence within the first 7 months after surgery when chemotherapy was still being administered , often with corticosteroids . The risk factors identified were histology ( glioblastoma versus anaplastic astrocytoma , P = 0.032 , log rank test ; 0.0485 L-ratio ) and the presence of paresis ( P = 0.010 , log rank test ; 0.0161 L-ratio ) . A borderline tendency was found for an association between the deep vein thrombosis site and the side of paresis ( P = 0.103 , Fisher 's exact test ) . Four patients ( 5 % ) had massive pulmonary embolism , which was fatal in 3 ( 4 % ) BACKGROUND Hemato-oncology patients treated with intensive chemotherapy usually require the placement of a central venous catheter ( CVC ) . CVCs are frequently complicated by catheter-related central venous thrombosis ( CVT ) , which has been associated with an increased risk of pulmonary embolism and catheter-related infection . OBJECTIVES To determine the efficacy and safety of thromboprophylaxis with s.c . low-molecular-weight heparin ( nadroparin ) administered once daily in a r and omized placebo-controlled , double-blind trial in patients with hematologic malignancies . PATIENTS AND METHODS Consecutive patients with hematologic malignancies requiring intensive chemotherapy including autologous stem cell transplantation were eligible . The patients were r and omized to receive nadroparin 2850 antifactor Xa units once daily or placebo s.c . for 3 weeks . Venography was performed on day 21 after CVC insertion . Secondary outcomes were bleeding and catheter-related infection . RESULTS In total , 113 patients were r and omized to nadroparin or placebo , and 87 patients ( 77 % ) underwent venography . In total , 11 venographically proven catheter-related CVTs were diagnosed . The frequency of catheter-related CVT was not significantly different between study groups , namely four catheter-related CVTs in the placebo group [ 9 % ; 95 % CI : 0.002 - 0.16 ] vs. seven catheter-related CVTs in the nadroparin group ( 17 % ; 95 % CI : 0.06 - 0.28 ) . In addition , no difference in the incidence of catheter-related infection or bleeding was observed between the groups . CONCLUSION This study showed that the actual risk for catheter-related CVT in patients with hematologic malignancies is lower than suggested in earlier studies in cancer patients . Although prophylactic administration of nadroparin appeared to be safe in this group of patients with a high risk of bleeding , it can not be recommended for the prevention of catheter-related CVT or catheter-related infection in patients with hematologic malignancies BACKGROUND An intravenous course of st and ard ( unfractionated ) heparin with the dose adjusted to prolong the activated partial-thromboplastin time to a desired length is the st and ard initial in-hospital treatment for patients with deep-vein thrombosis , but fixed-dose subcutaneous low-molecular-weight heparin appears to be as effective and safe . Because the latter treatment can be given on an outpatient basis , we compared the two treatments in symptomatic out patients with proximal-vein thrombosis but no signs of pulmonary embolism . METHODS We r and omly assigned patients to adjusted-dose intravenous st and ard heparin administered in the hospital ( 198 patients ) or fixed-dose subcutaneous low-molecular-weight heparin administered at home , when feasible ( 202 patients ) . We compared the treatments with respect to recurrent venous thromboembolism , major bleeding , quality of life , and costs . RESULTS Seventeen of the 198 patients who received st and ard heparin ( 8.6 percent ) and 14 of the 202 patients who received low-molecular-weight heparin ( 6.9 percent ) had recurrent thromboembolism ( difference , 1.7 percentage points ; 95 percent confidence interval , -3.6 to 6.9 ) . Major bleeding occurred in four patients assigned to st and ard heparin ( 2.0 percent ) and one patient assigned to low-molecular-weight heparin ( 0.5 percent ; difference , 1.5 percentage points ; 95 percent confidence interval , -0.7 to 2.7 ) . Quality of life improved in both groups . Physical activity and social functioning were better in the patients assigned to low-molecular-weight heparin . Among the patients in that group , 35 percent were never admitted to the hospital at all , and 40 percent were discharged early . This treatment was associated with a mean reduction in hospital days of 67 percent , ranging from 29 percent to 86 percent in the various study centers . CONCLUSIONS In patients with proximal-vein thrombosis , treatment with low-molecular-weight heparin at home is feasible , effective , and safe BACKGROUND The finding of a decrease in contralateral breast cancer incidence following tamoxifen administration for adjuvant therapy led to the concept that the drug might play a role in breast cancer prevention . To test this hypothesis , the National Surgical Adjuvant Breast and Bowel Project initiated the Breast Cancer Prevention Trial ( P-1 ) in 1992 . METHODS Women ( N=13388 ) at increased risk for breast cancer because they 1 ) were 60 years of age or older , 2 ) were 35 - 59 years of age with a 5-year predicted risk for breast cancer of at least 1.66 % , or 3 ) had a history of lobular carcinoma in situ were r and omly assigned to receive placebo ( n=6707 ) or 20 mg/day tam 
    Output:
    
Marik PE , And rews L , Maini B. The incidence of deep venous thrombosis in ICU patients .
Cook D , Meade M , Guyatt G , et al. Dalteparin versus unfractionated heparin in critically ill patients .