***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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    Input: Objective To determine the prevalence of deep vein thrombosis ( DVT ) among patients requiring prolonged mechanical ventilation in the intensive care unit . Design Prospect i ve cohort study . Setting Medical intensive care unit of a university-affiliated urban teaching hospital . Patients Patients requiring mechanical ventilation for > 7 days . Interventions All patients admitted to the medical intensive care unit requiring prolonged mechanical ventilation  underwent duplex ultrasonography of their lower extremities and upper extremities every 7 days . The main outcome identified was the presence of DVT . Secondary outcomes included hospital mortality , hospital and intensive care unit lengths of stay , and the occurrence of pulmonary embolism . Measurements and Main Results A total of 110 patients requiring mechanical ventilation for > 7 days were enrolled . Prophylaxis against DVT was employed in 110 of the patients ( 100 % ) . A total of 26 patients ( 23.6 % ) developed DVT . Patients with DVT were statistically more likely to have underlying malignancy ( 30.8 % vs. 8.3%;p = .004 ) and longer duration s of central venous catheterization ( 26.9 ± 22.2 days vs. 14.5 ± 12.1 days;p = .024 ) compared with patients without DVT . There were no statistically significant differences in hospital mortality or lengths of stay in the hospital and intensive care unit for patients with and without DVT . Patients documented to have DVT by using duplex ultrasonography had a statistically greater frequency of subsequent pulmonary embolism during their hospitalization ( 11.5 % vs. 0.0%;p = .012 ) . Conclusion The occurrence of DVT is common among patients requiring prolonged mechanical ventilation in the intensive care unit setting despite the use of prophylaxis measures . These data suggest that alternative strategies for the prevention of DVT should be evaluated . Additionally , early detection methods should be considered to reduce the potential morbidity associated with untreated DVT in this high-risk population BACKGROUND Deep vein thrombosis ( DVT ) is a major complication in intensive care units ( ICU ) but dedicated guidelines on its management are still lacking . OBJECTIVES AND METHODS This study investigated the effect of a 1-year educational program for the implementation of DVT prophylaxis on the incidence of  inferior limb DVT in a mixed-bed ICU that admits high-risk surgical and trauma patients , investigated during a first retrospective phase [ 126 patients , SAPS II score 42 ( 28 - 54 ) ] and a following prospect i ve phase [ 264 patients , SAPS II score II 41 ( 27 - 55 ) ] . The role of baseline and time-dependent DVT risk factors in DVT occurrence was also investigated during the prospect i ve phase . RESULTS The educational program on implementation of DVT prophylaxis was associated with a significant decrease in DVT incidence from 11.9 % to 4.5 % ( P < 0.01 ) and in the mean length of ICU stay ( P < 0.01 ) . Combined with pharmacological prophylaxis , the use of elastic compressive stockings  significantly also increased in the prospect i ve phase ( P < 0.01 ) . The duration of mechanical ventilation , vasopressor administration and neuromuscular block were significantly different between DVT-positive and DVT-negative patients ( P < 0.01 ) . Multivariate analysis identified neuromuscular block as the strongest independent predictor for DVT incidence . CONCLUSION One-year ICU-based educational programs on implementation of DVT prophylaxis were associated with a significant decrease in the incidence of DVT and also in the length of stay in ICU BACKGROUND Deep venous thrombosis ( DVT ) in severely injured patients is a life-threatening complication . Effective and safe thromboprophylaxis is highly desirable to prevent DVT . Low-dose heparin ( LDH ) and sequential compression device ( SCDs ) are the most frequently used methods . Inappropriate use of these methods because of the nature or site of critical injuries ( eg , brain lesion , solid visceral or retroperitoneal hematoma , extremity fractures ) may lead to failure of DVT prophylaxis . STUDY DESIGN A prospect i ve study was performed to evaluate the efficacy of a policy of aggressive use of LDH and SCDs in patients who are at very high risk for DVT . From January 1996 to August 1997 , 200 critically injured patients were followed by weekly Doppler examinations to detect DVT  at the proximal lower extremities . Only 3 patients did not receive any thromboprophylaxis . SCDs were applied in 97.5 % and LDH was administered to 46 % of the patients ; 45 % had both . RESULTS DVT was found in 26 patients ( 13 % ) . The majority ( 58 % ) developed DVT within the first 2 weeks , but new cases were found as late as 12 weeks after admission . The incidence of DVT was the same among patients who had SCDs only or a combination of LDH and SCDs . Mechanism of injury , type and number of operations , site of injury , Injury Severity Score , and the incidence of femoral lines were not different between patients with and without DVT . Differences were found in the severity of injury to the chest and the extremities and the need for high-level respiratory support . Patients with DVT had prolonged ICU and hospital stays ( on average , 34 and 49 days , respectively ) and a high mortality rate ( 31 % ) . CONCLUSIONS The incidence of DVT remains high among severely injured patients despite aggressive thromboprophylaxis . A combination of LDH and an SCD showed no advantage over SCD alone in decreasing DVT rates . Risk factors in this group of patients who are already at very high risk are hard to detect ; Doppler examinations are justified for surveillance in all critically injured patients . Current methods of thromboprophylaxis seem to offer limited efficacy , and the search for more effective methods should continue OBJECTIVE To evaluate the incidence of deep venous thrombosis in critically ill , Intensive Care Unit patients of Chinese ethnicity . DESIGN Prospect i ve , observational study . SETTING Intensive Care Unit in a Hong Kong teaching hospital . PATIENTS Consecutive adult Chinese medical patients not receiving pharmacological or mechanical prophylaxis for deep venous thrombosis . MAIN OUTCOME MEASURES  Compression and duplex Doppler ultrasound examinations of the lower limbs within 24 hours of admission and twice weekly thereafter during their Intensive Care Unit stay . After discharge , a 1-week follow-up investigation was also performed . Demographic data and risk factors for deep venous thrombosis were prospect ively recorded . RESULTS Over a 9-month study period , 80 patients were investigated .  Deep venous thrombosis was detected by ultrasound examination in 15 ( 19 % ) of the patients ( 95 % confidence interval , 14 - 23 % ) . Nine of 15 had isolated below-knee deep venous thrombosis , and of these , five had bilateral involvement . Characteristics of patients with or without deep venous thrombosis were similar . Of the 15 patients who had a positive ultrasound examination , only four ( 27 % ) had clinical signs of deep venous thrombosis . Of the 65 patients without a positive ultrasound examination  , only two ( 3 % ) had positive clinical signs ( P=0.01 ) . This yielded a moderate positive likelihood ratio of 9 ( 95 % confidence interval , 2 - 43 ) and a small negative likelihood ratio of 0.76 ( 95 % confidence interval , 0.56 - 1.03 ) . There were no cases of pulmonary embolism . Hospital mortality in those with and without deep venous thrombosis was 33 % and 28 % , respectively . CONCLUSIONS In the absence of prophylaxis , the incidence of deep venous thrombosis in Chinese medical Intensive Care Unit patients is lower than that reported in similar Caucasian patients , but higher than expected . As clinical features are not able to reliably exclude the presence of deep venous thrombosis , early routine prophylaxis for deep venous thrombosis in Chinese medical Intensive Care Unit patients should be considered PURPOSE Acute and chronic illness , immobility , and procedural and pharmacologic interventions may predispose patients in the intensive care unit ( ICU ) to venous thromboembolic ( VTE ) disease . The purpose of this study was to observe potential risk factors and diagnostic tests for VTE , and prophylaxis against VTE in medical-surgical ICU patients . MATERIAL S AND METHODS In a prospect i ve observational study , 93 consecutive patients admitted to a mixed medical-surgical ICU were followed . We recorded demographics , admitting diagnoses , APACHE II score , VTE risk factors , antithrombotic , anticoagulant and thrombolytic agents , diagnostic tests for deep venous thrombosis ( DVT ) and pulmonary embolus ( PE ) , and clinical outcomes . RESULTS Patients were 65.5 ( 15.5 ) years old with an APACHE II score of 21.1 ( 9.0 ) ; 44 ( 47.3 % ) were female . Admission diagnoses were medical ( 58 , 67.4 % ) and surgical ( 35 , 37.6 % ) . The duration of ICU stay was 3 days ( interquartile range : 1 , 8.5 days ) and the ICU mortality rate was 20.4 % ( 19 of 93 ) . We observed 8 VTE events among 5 of 93 patients ( incidence 5.4 % [ 0.8 to 10.0 ] ) ; 2 patients had DVT and PE before admission , 1 had DVT as an admitting diagnosis , 1 had DVT on day 2 and PE on day 3 , and 1 had PE on day 2 . Over 804 ICU patient-days , 2 of 5 ultrasound examinations diagnosed DVT and 2 of 3 ventilation-perfusion lung scans diagnosed PE . Of 64 patients in whom heparin was not contraindicated and who were not anticoagulated , subcutaneous heparin prophylaxis was prescribed for 40 ( 62.5 % ) patients . ICU-acquired VTE risk factors were mechanical ventilation ( odds ratio [ OR ] 1.56 ) , immobility ( OR 2.14 ) , femoral venous catheter ( OR 2.24 ) , sedatives ( OR 1.52 ) , and paralytic drugs ( OR 4.81 ) , whereas VTE heparin prophylaxis ( OR 0.08 ) , aspirin ( OR 0.42 ) , and thromboembolic disease stockings ( OR 0.63 ) were associated with a lower risk . Only warfarin ( OR 0.07 , P = .01 ) and intravenous heparin ( OR 0.04 , P<.01 ) were associated with a significantly decreased risk of VTE . CONCLUSIONS Several ICU-acquired risk factors for VTE were documented in this medical-surgical ICU .  VTE prophylaxis was underprescribed , and VTE diagnostic tests were infrequent . Further research is required to determine the incidence , predisposing factors , attributable morbidity , mortality , and costs of VTE in medical-surgical ICU patients , the optimal diagnostic test strategies , and the most cost-effective approaches of prophylaxis Objective Predicting patients who are harboring asymptomatic deep venous thrombosis ( DVT ) , or who are at particular risk of developing DVT , is a desirable clinical goal since prevention or early treatment of DVT might reduce the risk of fatal pulmonary embolism . Thus validation of simple laboratory tests that reliably predict venous thromboembolism ( VTE ) would be clinical ly very important . Tests that might be useful for these applications include markers of hypercoagulability ( predicting patients at risk of DVT ) and D-dimer ( predicting which patients may have acute DVT ) . Methods In a prospect i ve cohort study we measured a panel of hypercoagulability markers at the time of ICU admission , and six commercial D-dimer assays were performed serially during the ICU stay in medical-surgical ICU patients who were screened for DVT with biweekly lower limb compression ultrasonography . Ultrasonography was also performed at the time of any clinical ly suspected DVT events . We matched cases with DVT with controls without DVT for length of stay in the ICU to generate receiver operating characteristics ( ROC ) curves . Results One hundred ninety-seven patients were enrolled .  Blood was collected on a total of 763 occasions ( median number of occasions per patient : 3 , range 1–21 ) . None of the assays predicted DVT , as indicated by the areas under the ROC curves , that did not differ significantly from 50 % . Conclusion In critically ill patients , neither tests of hypercoagulability nor D-dimer levels predict patients at risk of DVT and thus they should not be used to guide diagnostic testing for DVT Patients undergoing major orthopedic surgery are at an increased risk of thromboembolism even after the acute postoperative phase . Therefore , prolonged thromboprophylaxis is currently recommended and widely used . The length of hospital stay after major orthopedic surgery is steadily decreasing and most patients are transferred to specialized rehabilitation centers in the early postoperative phase . Consequently , thromboprophylaxis is usually given during the rehabilitation period . Previously there have been no systematic studies of how many patients with asymptomatic thrombosis are transferred to a reh 
    Output:
    
A diagnosis of DVT upon ICU admission appears to affect clinical ly important outcomes including duration of ICU and hospital stay and hospital mortality .