***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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    ***EXAMPLES*** 
    Input: OBJECTIVE To determine the frequency of central venous catheter-induced  deep vein thrombosis of the femoral vein . DESIGN Prospect i ve , r and omized , controlled trial . SETTING Tertiary care center . PATIENTS Forty-five patients in a medical-surgical intensive care unit who required central venous catheterization .  INTERVENTIONS Patients were r and omized to receive central venous catheterization in either upper ( subclavian or internal jugular veins ) or lower ( femoral vein ) catheterization sites .  Lower extremity duplex ultrasound examinations  were performed before central venous catheter placement , after removal of the catheter , and 7 days after catheter removal . Ultrasound examinations were reported as positive , nondiagnostic , or negative for deep vein thrombosis . MEASUREMENTS AND MAIN RESULTS Of the 21 patients r and omized to upper access sites , none developed positive or nondiagnostic duplex ultrasound examinations . Six ( 25 % ) of 24 patients r and omized to the femoral access site developed lower extremity deep vein thrombosis ( p = .02 ) . In addition , seven ( 29 % ) patients r and omized to the lower access site sustained non-diagnostic ultrasound examinations . A total of 13 ( 54 % ) of 24 patients from the lower access group developed abnormal ultrasound examinations ( p < .001 ) . Age , duration of catheterization , coagulation profile , deep vein thrombosis prophylaxis , and Acute Physiology and Chronic Health Evaluation II scores were similar between the upper and lower access groups . CONCLUSIONS Based on the data from this study , we concluded that femoral vein catheterization is associated with a 25 % frequency of lower extremity deep vein thrombosis compared with similar patients receiving subclavian or internal jugular vein catheters . The femoral vein remains an important emergency venous access route . Physicians inserting femoral vein catheters should be aware of the risk of lower extremity deep vein thrombosis and should consider performing lower extremity duplex ultrasound examinations on removal of femoral vein catheters The function of long term indwelling venous access devices is commonly perturbed by postinsertion catheter‐related complications ( CRC ) . In an effort to assess the patterns of CRC in our community accurately , a prospect i ve analysis of  Groshong catheters in adult cancer patients was undertaken Clinical occurrence of subclavian venous thrombosis due to indwelling catheters is rare , but there is some evidence that sub clinical thrombosis frequently occurs . It is purpose of this study to report the results of a prospect i ve investigation in patients with subclavian vein catheters . Fifty-two patients admitted to the Istituto Nazionale Tumori of Milan and c and i date to infraclavicular percutaneous catheterization of the subclavian vein were evaluated . There were 26 polyvinyl chloride and 26 rubber silicone catheters , which were correctly positioned in the superior vena cava-atrium . Average duration of the intravenous stay was 12.8 days . Asymptomatic thrombosis was venographically demonstrated in 46.1 % of the polyvinyl chloride catheters and in 11.5 % of the silicone ones ( p = 0.005 ) . The average age of catheters with or without thrombosis was 10.8 and 13.8 days , respectively . Addition of heparin to the infusate ( 1 U/ml ) did not reduce the thrombosis rate in polyvinyl chloride or in silicone catheters , but risk of thrombosis was significantly higher ( p = 0.03 ) in polyvinyl chloride catheters without heparin in comparison to the silicone ones . Osmolarity of the infusional fluid , manipulation during the cannulation , colonization of the catheter tip , and duration of the intravenous stay of the catheter apparently did not influence the rate of thrombosis . Since the natural history of the thrombotic subclavian veins is not known , some caution must be paid to repeat the percutaneous cannulation of the same vein and the change the catheter over a guidewire OBJECTIVE To compare the incidence of and factors associated with vascular thrombosis after placement of heparin-bonded and st and ard femoral venous catheters . DESIGN Prospect i ve , masked , clinical study . SETTING Multidisciplinary , tertiary , pediatric intensive care unit . PATIENTS Consecutive cases ( n = 50 ) of critically ill children admitted to a pediatric intensive care unit in whom either a heparin-bonded ( n = 25 ) or a st and ard ( n = 25 ) femoral venous catheter was placed .  MEASUREMENTS AND MAIN RESULTS Patients were examined by ultrasonography within 3 days of catheter insertion , weekly while the catheter was in place , and after catheter removal for evidence of vascular thrombosis . Data were collected prospect ively regarding clinical evidence of catheter thrombosis , infusate composition , and positive blood culture results . Of 50 patients , 13 ( 26 % ) had thrombotic complications , 11 ( 44 % ) of the 25 patients in the st and ard-catheter group , in comparison with 2 ( 8 % ) of the 25 patients in the heparin-bonded catheter group ( p = 0.004 ) . In addition , there was a significantly higher incidence of positive blood culture results among patients in the st and ard-catheter group ( 24 % vs 0 % ; p = 0.009 ) . Positive catheter blood culture results were obtained in 38 % of patients with thrombosis versus 3 % without thrombosis ( p = 0.001 ) . Clinical evidence of thrombosis was found in 69 % of patients with , versus 27 % of patients without , ultrasound-proved thrombosis ( p = 0.007 ) . CONCLUSION Heparin bonding of catheters is associated with significantly fewer thrombotic complications . A reduced incidence of positive catheter-related blood culture results may be associated with the absence of thrombosis OBJECTIVES To determine the rate of lower extremity deep vein thrombosis after the use of femoral catheters in intensive care unit ( ICU ) comatose or se date d adults . Results were then compared with results of patients undergoing superior vena cava catheterization .  DESIGN Prospect i ve , r and omized , controlled , unblinded study . SETTING A mixed medical/surgical ICU in a university hospital . PATIENTS Sixty-one comatose or se date d patients admitted to the ICU who underwent central venous catheterization .  INTERVENTIONS Patients were monitored for signs of thrombotic complications . On catheter removal , a lower-extremity bilateral phlebographic examination  was performed in each patient . MEASUREMENTS AND MAIN RESULTS After r and omization , 31 patients underwent femoral vein catheterization and 30 patients underwent superior vena cava catheterization , either by axillary ( 21 patients ) or internal jugular vein ( 10 patients ) cannulation .  Single lumen polyurethane catheters were inserted for a mean duration of 7.1 + /- 4.6 ( SD ) days in the femoral vein group and 9.9 + /- 5.5 days in the superior vena cava group ( p = NS ) . No patient had clinical signs of leg venous thrombosis or pulmonary embolism during the study period . In each patient , lower extremity bilateral phlebography was performed at the time of catheter removal . Leg phlebographies were normal in 18 ( 60 % ) patients in the femoral vein group and 26 ( 84 % ) patients in the superior vena cava group . Fibrin sleeves which developed around the femoral catheters were seen in seven ( 23.3 % ) patients in the femoral vein group and in no patients in the superior vena cava cannulation group . Three patients had femoral vein thrombosis , two ( 6.6 % ) patients in the femoral vein group ( two nonobstructive thromboses , adherent to the common femoral vein wall ) and one ( 3.0 % ) patient in the superior vena cava group ( nonobstructive thrombosis which developed in the superficial femoral vein ) ( p = NS ) . Lower deep extremities thrombosis developed in five ( 16.7 % ) patients in the femoral vein group and in five ( 16 % ) patients in the superior vena cava group ( p = NS ) . CONCLUSIONS Femoral vein catheterization with a polyurethane catheter is associated with a lower rate of extremity deep vein thrombosis which is similar to the rate observed after superior vena cannulation in comatose or se date d patients .  Femoral vein thrombosis was observed at a rate of 6.6 % after femoral vein cannulation and a rate of 3 % after superior vena cava cannulation . Given the acceptable rate of this clinical ly important complication , femoral vein cannulation offers an attractive alternative to insertion via the vena cava in the critically ill PURPOSE AND METHODS Associations between thromboembolism and malignancy , usually widespread , and between thromboembolism and hormonal and /or chemotherapy have been previously reported . We performed a r and omized trial of tamoxifen 30 mg/d for 2 years ( T ) versus T plus 6 months of intravenous chemotherapy with cyclophosphamide , methotrexate , and fluorouracil ( CMF ) for postmenopausal women with involved axillary nodes and positive estrogen receptor ( ER ) or progesterone receptor ( PgR ) status following primary therapy for breast cancer . RESULTS We observed one or more thromboembolic events in 48 of 353 women ( 13.6 % ) allocated to receive T plus CMF in comparison to five of 352 women ( 2.6 % ) r and omized to receive T alone ( P < .0001 ) . Six women in the T plus CMF arm , but none r and omized to receive T alone , suffered two thromboembolic events while an study therapy . There were also significantly more women who developed severe ( grade 3 to 5 ) thromboembolic events in the T plus CMF arm than in the T arm ( 34 v five ; P < .0001 ) . Most thromboembolic events ( 39 of 54 ) occurred while women were actually receiving chemotherapy ( P < .0001 ) . Thromboembolic complications result ed in more days in hospital and more deaths than any other complication of therapy , including infection , in this trial . CONCLUSION Thromboembolism related to the addition of CMF chemotherapy to tamoxifen as adjuvant therapy in this group of women represents a relatively common and serious complication that may outweigh any benefits offered by this additional therapy Abstract A prospect i ve observational study was carried out to investigate complications of arterial and venous indwelling catheters . All patients of a mixed NICU/PICU admitted during a 12-month period were enrolled in this study with a stringent protocol of catheter prophylaxis , using heparin via continuous infusion in a dose of 100 IU/kg/day body weight or at least 100 IU/kg/day for each arterial and /or central venous catheter . Patients were regularly monitored for edema , thrombus , ischemia and catheter obstruction , i.e. complications amenable to heparinization . A total of 292 catheters in 130 patients were recorded . Patients ' weight ranged between approximately 600 g to 10,000 g. Depending on the insertion site or type of catheter the frequency of complications was as follows : edema 0–12 % ; catheter obstruction 7–24 % ; ischemia 28–40 % . No case of persistent thrombosis was detected . Conclusion A stringent protocol of heparinization leads to a low incidence of complications potentially amenable to anticoagulation STUDY OBJECTIVES To determine the frequency of and potential risk factors for  catheter-related deep venous thrombosis ( DVT ) in critically ill adult patients . DESIGN Prospect i ve , controlled , observational cohort study . SETTING A mixed medical and surgical ICU in a university hospital . PATIENTS All adult patients undergoing femoral vein catheterization .  INTERVENTIONS None . MEASUREMENTS ICU diagnosis , underlying disease , demographic data , type of catheter , complications during cannulation , use of anticoagulants , coagulation status , medications infused , and duration of catheterization were recorded .  Compression and duplex Doppler ultrasound studies of both femoral veins were performed prior to insertion , at 12 h after insertion , and daily until catheter removal . Follow-up investigation was performed at 24 h and 1 week after removal . RESULTS Of 140 cases entered into the study , 124 were evaluated . Fourteen patients developed iliofemoral vein DVTs . Two were clinical ly obvious . Twelve ( 9.6 % ) were line related ( uncannulated leg normal ) and two ( 1.6 % ) occurred only in the uncannulated leg ( p = 0.011 ; relative risk , 6.0 ; confidence interval , 1.5 to 23.5 ) . Line-related DVT can occur any time from the day after insertion to 1 week after removal . The incidence of catheter-related DVT was unrelated to number of insertion attempts , arterial punct 
    Output:
    
There was no apparent increase in bleeding events with prophylactic anticoagulation in patients with CVCs .
CONCLUSIONS In the small number of patients studied , the addition of heparin to PN did not significantly decrease the risk of catheter-related thrombosis , whereas warfarin and dalteparin did decrease the thrombosis risk in cancer patients with CVCs .
There is no apparent increase in bleeding events with prophylactic anticoagulants in patients with CVCs