***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: BACKGROUND Unfractionated heparin and the low molecular weight heparin , dalteparin , are used for prophylaxis against venous thromboembolism in patients undergoing craniotomy . These drugs were compared in a r and omized , prospect i ve pilot study comparing intermittent pneumatic compression devices plus dalteparin to intermittent pneumatic compression devices plus heparin . METHODS One hundred patients undergoing craniotomy were r and omly allocated to receive perioperative prophylaxis with subcutaneous ( SC heparin , 5000 units every 12 hours , or dalteparin , 2,500 units once a day , begun at induction of anesthesia and continued for 7 days or until the patient was ambulating . Entry criteria were age over 18 years , no deep vein thrombosis ( DVT ) preoperatively as judged by lower limb duplex ultrasound and no clinical evidence of pulmonary embolism preoperatively . Patients with hypersensitivity to heparin , penetrating head injury or who refused informed consent were excluded . Patients underwent a duplex study 1 week after surgery and 1 month clinical follow-up . All patients were treated with lower limb intermittent pneumatic compression devices . RESULTS There were no differences between groups in age , gender , and risk factors for venous thromboembolism . There were no differences between groups in intraoperative blood loss , transfusion requirements or postoperative platelet counts . Two patients receiving dalteparin developed DVT ( one symptomatic and one asymptomatic ) . No patient treated with heparin developed DVT and no patient in either group developed pulmonary embolism . There were two hemorrhages that did not require repeat craniotomy in patients receiving dalteparin and one that did require surgical evacuation in a patient treated with heparin . Drug was stopped in two patients treated with dalteparin because of thrombocytopenia . None of these differences were statistically significant . CONCLUSION There was no significant difference in postoperative hemorrhage , venous thromboembolism or thrombocytopenia between heparin and dalteparin . The results suggest that , given the small sample size of this trial , both drugs appear to be safe and the incidence of venous thromboembolism by postoperative screening duplex ultrasound appears to be low when these agents are used in combination with intermittent pneumatic compression devices 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 % ) In a prospect i ve , r and omized , double-blind investigation of anticoagulant agents for prevention of deep vein thrombosis in patients undergoing operations at the lumbar-vertebral disc , 179 patients were r and omly allocated to two groups . 87 patients received a fixed combination of low-molecular weight heparin 1,500 U-aPTT plus dihydroergotamine 0.5 mg ( LMWH/DHE ) once a day and additionally one injection of placebo per day , 92 patients received a fixed combination of sodium heparin 5,000 U plus dihydroergotamine 0.5 mg ( HDHE ) twice a day . Treatment was initiated two hours preoperatively in both groups and continued for at least seven days . Deep vein thrombosis ( DVT ) , detected by the 125Iodine-labelled fibrinogen uptake-test , occurred in four patients treated with LMWH/DHE and in three patients with HDHE . In all seven patients phlebography was performed , confirming the diagnosis of DVT in one patient of the LMWH/DHE group and in two patients of the HDHE group , only . No increased bleeding was found in either group . Especially no neurological complications caused by epidural bleeding were observed . We therefore recommended to treat routineously all patients undergoing operations at the vertebral disc with antithrombotic agents .  The advantages of the once daily regimen with low-molecular weight heparin include better patients ' acceptance and less nursing time OBJECTIVE Prophylactic therapies have demonstrated efficacy in reducing the incidence of deep venous thrombosis ( DVT ) in neurosurgical patients . Retrospective analysis of patients undergoing neurosurgical procedures at the University of Michigan demonstrated a high incidence ( 14 % ) of postoperative DVT among patients with intracranial neoplasms treated with sequential compression device ( SCD ) prophylaxis alone . Therefore , we investigated the efficacy and safety of the low-molecular weight heparin enoxaparin in preventing DVT in patients with brain tumors . The goal of the study was to compare SCD , enoxaparin , and combined SCD/enoxaparin prophylaxis among patients requiring surgery for treatment of intracranial neoplasms . METHODS Eligible patients were r and omized to SCD , enoxaparin , or combined therapy .  Treatment was initiated before the induction of anesthesia and was continued throughout the hospital stay . Patients were screened for DVT , using duplex imaging , on four occasions in the first 1 month after surgery . The incidences of DVT and serious adverse events were compared between groups using analysis of variance and the Dunnet two-sided t test . RESULTS Sixty-eight patients completed the study .  Postoperative DVT occurred in 3 of 22 ( 13.6 % ) SCD-treated patients , 1 of 23 ( 4.3 % ) enoxaparin-treated patients , and 4 of 23 ( 17.4 % ) SCD/enoxaparin-treated patients . Differences were not statistically significant . Postoperative intracranial hemorrhage did not occur in patients in the SCD-treated group , whereas 5 of 46 patients receiving low-molecular weight heparin suffered clinical ly significant intracranial hemorrhage . The study was terminated because of the increased incidence of adverse events in the enoxaparin-treated groups . CONCLUSION Enoxaparin therapy initiated at the time of anesthesia induction increases postoperative intracranial hemorrhage By the use of 125I-labeled fibrinogen test , the incidence of postoperative deep vein thrombosis ( DVT ) and the effectiveness of prophylactic low-dose heparin treatment were investigated in 110 patients who underwent elective neurosurgical procedures . Fifty patients were appointed r and omly to a  control group and 50 to a heparin group ( 10 patients were excluded since they had DVT before surgery ) . The incidence of DVT was reduced from 34 % in the control group to 6 % in the heparin group ( p less than 0.005 ) . No statistically significant differences were observed in transfusion requirements , postoperative hemoglobin concentration , and the occurrence of postoperative hematomas between the two groups . Positive correlation was observed between DVT and motor deficit ( p less than 0.05 ) . Preoperative assessment of patients ' sensitivity to the st and ard 5000-unit dose of heparin was performed in all treated patients and is thought an important factor in improving the safety of heparin prophylaxis A r and omized , prospect i ve clinical trial of 70 patients undergoing craniotomy was performed to compare and evaluate two forms of mechanical prophylaxis of deep vein thrombosis .  Thirty-eight patients received antiembolism stockings , whereas 32 patients received external pneumatic compression . Prophylaxis was begun preoperatively and continued intraoperatively and post-operatively until the patients were ambulatory .  Impedance plethysmography  was used to detect deep vein thrombosis both preoperatively and postoperatively . Two patients , one from each group , developed thromboembolic complications postoperatively . Impedance plethysmography showed false-positive findings in two additional patients . There were no deaths . The data suggest that either form of mechanical prophylaxis is effective against the development of deep vein thrombosis in this high-risk patient population BACKGROUND Patients who have had major trauma are at very high risk for venous thromboembolism if they do not receive thromboprophylaxis . We compared low-dose heparin and a low-molecular-weight heparin with regard to efficacy and safety in a r and omized clinical trial in patients with trauma . METHODS Consecutive adult patients admitted to a trauma center who had Injury Severity Scores of at least 9 and no intracranial bleeding were r and omly assigned to heparin ( 5000 units ) or enoxaprin ( 30 mg ) , each given subcutaneously every 12 hours in a double-blind manner , beginning within 36 hours after the injury . The primary outcome was deep-vein thrombosis as assessed by contrast venography performed on or before day 14 after r and omization . RESULTS Among 344 r and omized patients , 136 who received low-dose heparin and 129 who received enoxaparin  had venograms adequate for analysis . Sixty patients given heparin ( 44 percent ) and 40 patients given enoxaparin ( 31 percent ) had deep-vein thrombosis ( P=0.014 ) . The rates of proximal-vein thrombosis were 15 percent and 6 percent , respectively ( P=0.012 ) . The reductions in risk with enoxaparin as compared with heparin were 30 percent ( 95 percent confidence interval , 4 to 50 percent ) for all deep-vein thrombosis and 58 percent ( 95 percent confidence interval , 12 to 87 percent ) for proximal-vein thrombosis . Only six patients ( 1.7 percent ) had major bleeding ( one in the heparin group and five in the enoxaparin group , P=0.12 ) . CONCLUSIONS Low-molecular-weight heparin was more effective than low-dose heparin in preventing venous thromboembolism after major trauma . Both interventions were safe Abstract Patients with high- grade glioma are at elevated risk of venous thromboembolism ( VTE ) . The relationship between VTE and survival in glioma patients remains unclear , as does the optimal protocol for chemoprophylaxis . The purpose of this study was to assessthe incidence of and risk factors associated with VTE in patients with high- grade glioma , and the correlation between VTE and survival in this population . Furthermore , we sought to define a protocol for perioperative DVT prophylaxis . This was a retrospective review of patients who underwent craniotomy for resection of high- grade glioma ( WHO grade III or IV ) at Northwestern University between 1999 and 2010 . A total of 336 patients met inclusion criteria . 53 patients developed postoperative VTE ( 15.7 % ) . Median survival was 12.0 months and was not significantly different between VTE(+ ) and VTE(− ) patients . Demographics and surgical factors were not significantly correlated with VTE development . Prior history of VTE was highly predictive of postoperative VTE ( OR 7.1 , p < .01 ) , as was seizure ( OR 2.4 , p = .005 ) . Increased duration of postoperative ICU stay was also a risk factor for VTE ( p = .025 ) . 25 patients in our study received prophylactic anticoagulation(pAC ) with either heparin or enoxaparin . Early initiation of pAC was associated with decreased incidence of VTE ( p = .042 ) . There were no hemorrhagic complications in patients receiving pAC . VTE is a common complication in high- grade glioma patients . Early initiation of anticoagulation is safe and may decrease the risk of VTE . We recommend initiation of chemoprophylaxis on postoperative day 1 in patients without contraindication CONTEXT Venous thromboembolism ( VTE ) is the most frequent complication following craniotomy for brain tumors . At Brigham and Women 's Hospital , VTE after craniotomy for brain tumor is the leading cause of deep vein thrombosis ( DVT ) and pulmonary embolism ( PE ) among patients hospitalized for conditions other than VTE . OBJECTIVE To minimize VTE among patients undergoing craniotomy for brain tumor . DESIGN R and omized , prospect i ve , double-blind clinical trial . SETTING Brigham and Women 's Hospital . PATIENTS One hundred fifty patients undergoing craniotomy for brain tumor r and omized to enoxaparin , 40 mg/d , vs heparin , 5,000 U bid , with all patients receiving graduated compression stockings and intermittent pneumatic compression . MAIN OUTCOME MEASURES The rate of DVT detected by venous ultrasonography prior to hospital discharge 
    Output:
    
This meta- analysis demonstrates a statistically significant VTE risk reduction among brain tumor patients receiving prophylaxis , with chemical prophylaxis showing the strongest risk reduction .