***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 r and omized , prospect i ve , double‐blind multicentre trial , the effect of conventional low‐dose heparin 5000 units twice daily , was compared with that of a low molecular weight heparin fragment ( 4000–5000 ) 5000 anti‐factor Xa units once daily . Four hundred and thirty‐two patients fulfilled the inclusion criteria and were analysed for development of deep vein thrombosis ( 125I‐labelled fibrinogen test ) and haemorrhagic complications . Thrombosis occurred in a 4.3 per cent of patients in the low‐dose heparin group and in 6.4 per cent of patients in the heparin fragment group , a difference which is not significant . There was a significant delay in the onset of thrombosis in the heparin fragment group . Mortality did not differ between the groups , nor did peroperative blood loss or transfusion requirements or infectious complications . Haemorrhagic complications occurred significantly more often in the fragment group ( 11.6 per cent ) than in the conventional heparin group ( 4.6 per cent ) . Patients in the heparin fragment group experienced local pain following the subcutaneous injection significantly less often Abstract Heparin ( 1 IU kg -1 h -1 ) given intravenously for 3 - 5 days during and after operation in a double-blind r and omised study , significantly reduced the frequency of deep-vein thrombosis detected by 125 I-fibrinogen uptake , and pulmonary embolism . 22 % ( 11/50 ) control patients and 4 % ( 2/45 ) patients receiving heparin had deep-vein thrombosis or pulmonary embolism .  Heparin administration was not associated with any increase in preoperative or postoperative bleeding 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 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 Fourty patients who underwent general surgery have been enrolled in a double-blind controlled trial which evaluated the efficacy and safety of Fragmin , a new low molecular weight heparin , chosen to be the 1st OMS International St and ard for LMWH . Fragmin 2500 UI anti-Xa once daily and unfractionated heparin 5000 UI twice daily were administered to prevent postoperative deep venous thrombosis . Prophylaxis began two hours before surgery and continued for the next 5 postoperative days . The incidence of isotopic venous thrombosis , thromboembolic disorders and bleeding complications have been evaluated . Results have shown a similar efficacy and safety profile of the two drugs , although Fragmin doses are markedly inferior to unfractionated heparin 's . Moreover , Fragmin has the advantage of a single daily administration , with a better patients ' compliance and an easier and less expensive nursing care The potential antithrombotic effect of a new low molecular weight heparinoid , Org 10172 , was examined in a r and omized , double-blind , placebo-controlled , dose-ranging pilot study of the prevention of deep venous thrombosis ( DVT ) in 45 high-risk patients having major thoracic or abdominal surgery for cancer .  Org 10172 was given in doses of 500 , 750 or 1000 U bd subcutaneously . DVT occurred in 9 of 14 patients given placebo and in 4 of 11 patients given 500 U bd but in none of the 20 patients given 750 or 1000 U bd . Operative blood loss and post-operative bleeding were not significantly different between the groups but one patient given 1000 U bd had major post-operative bleeding . Average mid-interval and trough plasma anti-Xa levels reached 0.26 and 0.20 U/ml respectively following the highest dose . It is concluded that Org 10172 is a potentially useful antithrombotic agent and that the effective and safe dose appears to be between 500 and 1000 U bd for prevention of DVT in high-risk patients 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 polysulf 
    Output:
    
Studies of general surgery contain considerable numbers of colorectal patients .