***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: PURPOSE : Routine deep venous thrombosis prophylaxis is controversial in Asian patients , because deep venous thrombosis incidence was considered negligible . Because of recent reports of significantly higher incidences , a r and omized , controlled trial was conducted to assess the effectiveness and complications of enoxaparin prophylaxis ( low molecular weight heparins ) in major colorectal surgery . METHODS : Three hundred twenty consecutive patients were r and omly assigned to control or low molecular weight heparins groups . Patients in the low molecular weight heparins group were given perioperative enoxaparin starting 12 hours before surgery . The surgeon ( blinded ) assessed for difficulties related to possible enoxaparin administration . Independent blinded observers performed daily clinical assessment s and Doppler studies ( at the 3rd and 5th postoperative day ) . Deep venous thrombosis was confirmed by duplex ultrasound , and pulmonary embolism was confirmed by lung scans or postmortem examinations . RESULTS : Deep venous thrombosis developed in 5 of 169 ( 3 percent ) controls and 0 of 134 low molecular weight heparins patients ( P=0.045 ) . Three of the deep venous thrombosis patients had pulmonary embolism , which was fatal in one patient . The surgeons were unable to perceive any increased surgical difficulties in the low molecular weight heparins group . The bleeding-related complications were significantly higher in the low molecular weight heparins patients ( controls , n=3 ( 1.8 percent ) ; low molecular weight heparins , n=9 ( 6.7 percent ) ) . However , apart from one subdural hematoma and two abdominal hemorrhages needing re-exploration , which also occurred in one of the controls , these complications were minor bruises at the wounds , drains , or injection sites . CONCLUSION : Deep venous thrombosis prophylaxis is needed in Asian patients undergoing major colorectal surgery In a prospect i ve , r and omized multicentre trial the efficacy and safety of the low molecular weight heparin ( LMWH ) fraction Fraxiparin ® and unfractionated calcium heparin ( Calciparin ® ) were compared for the prevention of postoperative deep vein thrombosis . Of 1909 patients included in the trial 1896 underwent abdominal surgery  and received either one daily subcutaneous injection of 7500 anti‐X a units Fraxiparin or 5000 units calcium heparin three times a day subcutaneously . Elastic compression stockings were worn by both groups of patients in the postoperative period . Before r and omization the patients were stratified in two subgroups with or without malignant disease . To assess the rate of deep vein thrombosis ( DVT ) , 125I‐labelled fibrinogen leg scanning was performed daily for 7 postoperative days . Positive results were confirmed by phlebography whenever possible . Venous thrombosis occurred in 27 of 960 patients ( 2.8 per cent ) given Fraxiparin and in 42 of 936 patients ( 4.5 per cent ) given calcium heparin ( P = 0.034 ) . The rates of proximal vein thrombosis were 0.4 per cent ( 4 patients ) and 1.4 per cent ( 13 patients ) respectively ( P<0.05 ) . Pulmonary embolism occurred in 2 of 960 patients ( 0.2 per cent ) treated with Fraxiparin and in 5 of 936 patients ( 0.5 per cent ) treated with calcium heparin . The two treatments were equally well tolerated . Intra‐ and postoperative blood loss , the number of wound haematomas as well as frequency and volume of transfusions were similar in both groups . The present trial demonstrates that a single daily subcutaneous injection of Fraxiparin is more effective than the established low dose subcutaneous heparin prophylaxis with 5000 units three times per day in preventing postoperative DVT after abdominal surgery in patients wearing compression stockings A r and omized multicentre double-blind study was organized to evaluate the efficacy and the safety of Clivarin ( reviparin-sodium ) ( anti-Xa/anti-IIa ratio : 3 - 5 International units ) for the prevention of post-operative thromboembolism in patients undergoing general surgery . 1,351 patients were r and omly allocated to receive subcutaneously either 5,000 U of unfractionated heparin ( UFH ) twice a day or 1,750 anti-Xa IU of reviparin-sodium once a day ( morning ) followed by a placebo injection ( evening ) for at least 6 days . Deep vein thrombosis ( DVT ) was detected with the 125I-fibrinogen technique confirmed by phlebography if necessary . After r and omization thrombotic risk factors were equally distributed in each group . More than 50 % of the patients had a cancer . The incidence of DVT and of pulmonary embolism was 4.8 % ( CI 95 % : 3.3 - 6.7 % ) in the reviparin-sodium group and 4.4 % ( CI 95 % : 2.9 - 6.2 % ) in the UFH group , a non-significant difference . The number of transfusions required was equivalent in the two groups . However , post-operative bleeding complications , including wound haematomas and internal bleeding , were less frequent in the reviparin-sodium group ( P < 0.01 ) . Therefore , for the first time , this study demonstrates that an unusual low dose of a low molecular weight heparin retains its antithrombotic efficacy by comparison with UFH and that the tolerance of this low dose is better In a prospect i ve , double-blind , r and omized multicenter trial the efficacy and safety of low molecular weight heparin and unfractionated heparin were compared for the prevention of  postoperative deep vein thrombosis in patients undergoing abdominal surgery . Six hundred and seventy-three patients were r and omly allocated to the two prophylaxis groups ; 20 of these , however , did not undergo surgery and did not receive any prophylaxis . Of the remaining 653 patients 323 received one subcutaneous injection of 3,000 anti-Xa units of low molecular weight heparin and 330 received subcutaneously 5,000 U heparin three times a day . Treatment was initiated 2 h preoperatively and continued for 7 to 10 days . The occurrence of DVT was determined by the 125I-labelled fibrinogen uptake test and phlebography . Venous thrombosis was diagnosed in 24 of 323 patients ( 7.4 % ) treated with low molecular weight heparin and in 26 of 330 patients ( 7.9 % ) treated with low-dose heparin .  DVT of proximal veins was detected in four patients of the low molecular weight heparin group and in three patients of the low-dose heparin group . During the observation period three pulmonary emboli - one fatal and two non-fatal - occurred in patients receiving prophylaxis with low-dose heparin . No pulmonary embolism was found in patients treated with low molecular weight heparin . Both prophylactic schemes were well tolerated . Intra- and postoperative blood loss , incidence of wound hematoma , frequency and volume of intra- and postoperative blood transfusion were similar in both groups with a slight advantage for the low molecular weight heparin group . ( ABSTRACT TRUNCATED AT 250 WORDS The effect of low-dose heparin prophylaxis on  venous thrombosis and bleeding after major elective surgery was studied in a prospect i ve controlled study of 820 patients . The total incidence of venous thrombosis detected with leg-scanning using fibrinogen labeled with radioactive iodine ( 125I ) was reduced from 16.0 % in the control group to 4.2 % in treated patients . More important , the incidence of popliteal or femoral vein thrombosis was reduced from 2.9 % to 1.0 % . Prophylaxis result ed in a slight increase in bleeding-minor wound hematoma , mean volume of blood transfused , and a post-operative hematocrit fall in treated patients . However , increased bleeding was clinical ly minor , and prophylaxis was well tolerated Abstract . The efficacy of low-molecular-weight heparins ( LMWH ) alone versus a combination of Daflon 500 mg with LMWH in preventing postoperative symptomatic thromboembolism was investigated . A total of 1372 patients aged 40 years or older undergoing major abdominal , pelvic , or abdominal wall surgery were r and omized into four groups . Group A ( n = 591 ) received enoxoparin 20 mg or fraxiparin 0.3 ml . Group B ( n = 595 ) received the regimens of group A plus Daflon 500 mg . Group C ( n = 93 ) received enoxoparin 40 mg or fraxiparin 0.6 ml . Group D ( n = 93 ) received the regimens of group C plus Daflon 500 mg . Each LMWH was given subcutaneously once a day during the hospitalization and continued in groups C and D for 15 days after discharge ( high risk patients ) . Daflon 500 mg was given as two tablets every 8 hours during the day before surgery , two tablets 6 hours before surgery , and two tablets once a day on postoperative days 4 to 15 . Daily clinical examination was performed ; and phlebography or  perfusion lung  scanning ( or both ) were used in symptomatic patients to confirm deep vein thrombosis ( DVT ) or pulmonary embolism ( PE ) . The wound was examined on a daily basis for hematomas . The diagnosis of PE was established in two patients of group A and in three patients of group C ; symptomatic DVT was established in one patient in group A and three patients of group C. Neither DVT nor PE were established in Daflon 500 mg groups . These data suggest that the combination of Daflon 500 mg and LMWH is more effective than LMWH alone for preventing symptomatic thromboembolism The prophylactic effect of a semisynthetic heparin analogue ( SSHA ) on  deep vein thrombosis  was investigated in a prospect i ve double‐blind multicentre trial . 440 major general surgical and gynaecological patients were r and omized to one of three treatment groups : 50 mg SSHA , 37.5 mg SSHA and 5000 units sodium heparin subcutaneously 12‐hourly . Deep venous thrombosis ( DVT ) was diagnosed with the fibrinogen uptake test and verified with phlebography . Bleeding complications and other side‐effects were carefully monitored . There were no significant differences between the three treatment groups of patients in age , sex , type of operation or risk factors . A DVT was diagnosed in 16 patients ( 12 per cent ) in the SSHA 50 mg group , in 21 patients ( 15 per cent ) in the SSHA 37.5 mg group and 21 patients ( 14 per cent ) in the heparin‐treated group . No significant differences were found in the number of patients who bled unexpectedly in the postoperative period , required transfusion or developed wound haematomas . Blood loss at operation was similar in all three groups . Three pulmonary emboli were diagnosed by pulmonary scintigraphy , one in each group Objective To compare the effectiveness and safety of low-dose unfractionated heparin and a low-molecular-weight heparin as prophylaxis against venous thromboembolism after colorectal surgery . Methods In a multicenter , double-blind trial , patients undergoing resection of part or all of the colon or rectum were r and omized to receive , by subcutaneous injection , either calcium heparin 5,000 units every 8 hours or enoxaparin 40 mg once daily ( plus two additional saline injections ) . Deep vein thrombosis was assessed by routine bilateral contrast venography performed between postoperative day 5 and 9 , or earlier if clinical ly suspected . Results Nine hundred thirty-six r and omized patients completed the protocol and had an adequate outcome assessment . The venous thromboembolism rates were the same in both groups . There were no deaths from pulmonary embolism or bleeding complications . Although the proportion of all bleeding events in the enoxaparin group was significantly greater than in the low-dose heparin group , the rates of major bleeding and reoperation for bleeding were not significantly different . Conclusions Both heparin 5,000 units subcutaneously every 8 hours and enoxaparin 40 mg subcutaneously once daily provide highly effective and safe prophylaxis for patients undergoing colorectal surgery . However , given the current differences in cost , prophylaxis with low-dose heparin remains the preferred method at present Deep vein thrombosis and its sequel , pulmonary embolus , are possibly the greatest threats to recovery after surgical operation . In a r and omized , controlled clinical trial in which the 125I-fibrinogen uptake test , Doppler ultrasound , and phlebography were used for diagnosis , it was found that low doses of calcium heparinate administered subcutaneously and sodium pentosan polysulfate intramuscularly were effective in preventing deep vein thrombosis ( DVT ) , postoperatively . The incidence of DVT was as follows : 9 % in the group treated with heparinate ; 15 % in the group treated with sodium pentosan polysulfate ; nad 51 % in the un 
    Output:
    
This level 1 evidence report shows that bleeding complications requiring a change in care occur less than 3 % of the time and seem reduced with lower-dose prophylaxis .
Given these findings , most patients undergoing general surgery could receive pharmacologic prophylaxis safely