***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 examine the rate of success and complications of Doppler-guided subclavian vein catheter insertion compared with st and ard insertion in patients considered at high risk for failure . DESIGN Prospect i ve , r and omized , crossover trial . SETTING University-affiliated tertiary care medical center . PATIENTS Two hundred forty patients were enrolled in the study . Patients were stratified for 3 known risk factors : ( 1 ) prior surgery in the subclavian vein region , ( 2 ) prior radiotherapy at the attempted catheterization site , and ( 3 ) an abnormal weight-height ratio . INTERVENTIONS Subclavian vein catheterization was performed either in st and ard or Doppler-guided fashion using the Smart Needle ( Peripheral Systems Group , Mountain View , Calif ) , which is a Doppler probe at the tip of a cannulating needle . If subclavian vein catheterization was unsuccessful after 2 attempts , patients were crossed over to the other technique . MAIN OUTCOME MEASURE Successful cannulation of the subclavian vein . RESULTS The success rate , either as an initial technique or as a salvage technique , and complication rate were not significantly different with use of the Smart Needle . A subgroup of physicians had a significantly lower success rate using the Smart Needle . CONCLUSIONS Doppler guidance did not increase the success rate or decrease the complication rate of subclavian vein catheterization when compared with the st and ard technique in high-risk patients . Doppler guidance was not more useful than the st and ard technique as a salvage technique following a previous failure of catheterization . Furthermore , real-time Doppler guidance of subclavian vein catheterization is a technique that is highly operator dependent STUDY OBJECTIVE To compare the use of real-time-ultrasound guidance with the st and ard l and mark-oriented approach for obtaining femoral vein catheterization in patients requiring intravenous access during CPR . METHODS Prospect i ve , r and omized , paired subject-controlled clinical trial in the setting of an urban teaching county hospital emergency department . The study comprised a convenience sample of 20 patients presenting with apnea and pulselessness in the ED . Each patient received bilateral femoral lines , one by ultrasound guidance and one by the l and mark approach ( control ) . R and omization determined which technique and which side would be attempted first . The following parameters were recorded : time to initial flash of blood , time to completion of catheterization , number of needle passes , and rate of arterial catheterization . CPR and Advanced Cardiac Life Support protocol s were continued during both procedures . RESULTS Real-time ultrasound-guided catheterization had a higher success rate ( 90 % versus 65 % , P = .058 ) , a lower number of needle passes ( 2.3 + /- 3 versus 5.0 + /- 5 , P = .0057 ) , and a lower rate of arterial catheterization ( 0 % versus 20 % , P = .025 ) than the st and ard l and mark-oriented approach . Ultrasound was also slightly faster in time to blood flash and in time to catheterization . An incidental finding of interest was that real-time ultrasound demonstrated the presence of femoral vein pulsations during CPR . CONCLUSION Real-time ultrasound-guided femoral vein catheterization was faster and produced a lower rate of inadvertent arterial catheterization and a higher rate of success during CPR than the st and ard l and mark-oriented approach . Also , ultrasound demonstrated that palpable femoral pulsation during CPR is venous rather than arterial BACKGROUND Central venous access is a m and atory part of patient management in many clinical setting s and is usually achieved with a blind , external l and mark-guided technique . The purpose of this study is to evaluate whether an ultrasound technique can improve on the external l and mark method . METHODS We prospect ively evaluated an ultrasound-guided method in 28 patients undergoing femoral vein cannulation for acute haemodialysis access and compared the results with 38 patients in whom an external l and mark-guided technique was used .  External l and mark-guided technique was done by manual localization of the femoral artery in the femoral triangle inferior to the inguinal ligament with needle insertion medial to the artery . Ultrasound-guided cannulation was performed in the same location with the aid of an ultrasound device ( Site-Rite , Dymax Corp. , USA ) with a 7.5 MHz transducer covered by a sterile sheath . RESULTS Cannulation of the femoral vein was achieved in all patients ( 100 % ) using ultrasound and in 34 patients ( 89.5 % ) using the l and mark-guided technique . The vein was entered on the first attempt in 92.9 % of patients using ultrasound and in 55.3 % using the l and mark technique ( P < 0.05 ) . Average access time ( skin to vein ) was similar but total procedure time was 45.1 + /- 18.8 s by the ultrasound approach and 79.4 + /- 61.7 s by the l and mark approach ( P < 0.05 ) . Using ultrasound , puncture of the femoral artery occurred in 7.1 % of patients , and haematoma in 0 % . Using external l and mark technique , puncture of the femoral artery occurred in 15.8 % of patients , and haematoma in 2.6 % . CONCLUSIONS Ultrasound-guided cannulation of the femoral vein reduces the time required for the procedure , reduces the number of passes needed to puncture the vein , and minimizes complications such as arterial puncture or haematoma BACKGROUND : Percutaneous cannulation of the femoral vein , in the pediatric age group , can be technically challenging , especially when performed by residents in training . We examined whether the use of real-time ultrasound guidance is superior to a l and mark technique for femoral vein catheterization in children undergoing heart surgery . METHODS : Patients were prospect ively r and omized into 2 groups . In group LM , the femoral vein was cannulated using the traditional method of palpation of arterial pulse . In group US , cannulation was guided by real-time scanning with an ultrasound probe . The time to complete cannulation ( primary outcome ) , success rate , number of needle passes , number of successful cannulations on first needle pass , and incidence of complications were compared between the 2 groups . RESULTS : Forty-eight pediatric patients were studied . The time to complete cannulation was significantly shorter ( 155 [ 46–690 ] vs 370 [ 45–1620 ] seconds ; P = 0.02 ) in group US versus group LM . The success rate was similar in both groups ( 95.8 % ) . The number of needle passes was smaller ( 1 [ 1–8 ] vs 3 [ 1–21 ] ; P = 0.001 ) and the number of successful cannulations on first needle pass higher ( 18 vs 6 ; P = 0.001 ) in group US compared with group LM . The incidence of femoral artery puncture was comparable between the 2 groups . CONCLUSIONS : Ultrasound-guided cannulation of the femoral vein , in pediatric patients , when performed by senior anesthesia residents , is superior to the l and mark technique in terms of speed and number of needle passes , with remarkable improvement in first attempt success Central venous cannulation allows accurate monitoring of right atrial pressure and infusion of drugs during the anaesthetic management of infants undergoing cardiopulmonary bypass . In this prospect i ve , r and omized study , we compared the success and speed of cannulation of the internal jugular vein in 45 infants weighing less than 10 kg using three modes of identification : auditory signals from internal ultrasound ( SmartNeedle , SM ) , external ultrasound imaging ( Imaging Method , IM ) and the traditional palpation of the carotid pulsation and other l and marks ( L and marks Method , LM ) . The cannulation time , number of attempts with LM and SM techniques were greater than those with IM technique . The incidence of carotid artery puncture and the success rate were not significantly different among the three groups . In infants , a method based on visual ultrasound identification ( IM ) of the internal jugular vein is more precise and efficient than methods based on auditory ( SM ) and tactile perception ( LM ) Objective : To determine whether ultrasound ( US ) increases successful central venous catheter ( CVC ) placement , decreases site attempts , and decreases CVC placement complications . Design and Setting : A prospect i ve observational cohort study evaluating a transition by the Pediatric Critical Care Medicine service to US-guided CVC placement .  Medical and surgical patients in a 21-bed quaternary multidisciplinary pediatric intensive care unit had CVCs placed by attendings , fellows , residents , and a nurse practitioner . Patients : Ninety-three patients were prospect ively enrolled into the l and mark ( LM ) group and 119 into the US group .  Interventions : After collection of prospect i ve LM data , training with US guidance was provided . CVCs were subsequently placed with US guidance . Measurements and Main Results : Operator information , disease process , emergent/routine , sites attempted , and complications were recorded . Procedure time was from initial skin puncture to guidewire placement . There was no difference overall in success rates ( 88.2 % LM vs. 90.8 % US , p = 0.54 ) or time to successful placement ( median seconds 269 LM vs. 150 US , p = 0.14 ) between the two groups . Median number of attempts were fewer with US for all CVCs attempted ( 3 vs. 1 , p < 0.001 ) as were attempts at > 1 anatomical site ( 20.7 % LM vs. 5.9 % US , p = 0.001 ) . Use of US was associated with fewer inadvertent artery punctures ( 8.5 % vs. 19.4 % , p = 0.03 ) . Time to successful placement by residents was decreased with US ( median 919 seconds vs. 405 seconds , p = 0.02 ) . More internal jugular CVCs were placed during the US period than during the LM period ( 13.4 % vs. 2.1 % ) . Conclusions :  US-guided CVC placement in children is associated with decreased number of anatomical sites attempted and decreased number of attempts to gain placement . Time to placement by residents was decreased with US , but not the time to placement by other operators . US guidance increased the use of internal jugular catheter placement and decreased artery punctures . US guidance did not improve success rates Objective : Subclavian vein catheterization may cause various complications . We compared the real-time ultrasound-guided subclavian vein cannulation vs. the l and mark method in critical care patients . Design : Prospect i ve r and omized study . Setting : Medical intensive care unit of a tertiary medical center . Patients : Four hundred sixty-three mechanically ventilated patients enrolled in a r and omized controlled IS RCT N-registered trial ( IS RCT N-61258470 ) . Interventions : We compared the ultrasound-guided subclavian vein cannulation ( 200 patients ) vs. the l and mark method ( 201 patients ) using an infraclavicular needle insertion point in all cases . Catheterization was performed under nonemergency conditions in the intensive care unit . R and omization was performed by means of a computer-generated r and om-numbers table and patients were stratified with regard to age , gender , and body mass index . Measurements and Main Results : No significant differences in the presence of risk factors for difficult cannulation between the two groups of patients were recorded . Subclavian vein cannulation was achieved in 100 % of patients in the ultrasound group as compared with 87.5 % in the l and mark one ( p < .05 ) . Average access time and number of attempts were significantly reduced in the ultrasound group of patients compared with the l and mark group ( p < .05 ) . In the l and mark group , artery puncture and hematoma occurred in 5.4 % of patients , respectively , hemothorax in 4.4 % , pneumothorax in 4.9 % , brachial plexus injury in 2.9 % , phrenic nerve injury in 1.5 % , and cardiac tamponade in 0.5 % , which were all increased compared with the ultrasound group ( p < .05 ) . Catheter misplacements did not differ between groups . In this study , the real-time ultrasound method was rated on a semiquantitative scale as technically difficult by the participating physicians . Conclusions : The present data suggested that ultrasound-guided cannulation of the subclavian vein in critical care patients is superior to the l and mark method and should be the method of choice in these patients OBJECTIVE To compare ultrasound (US)-guided vs. l and mark-guided techniques for central venous access ( CVA ) in the emergency department . METHODS This was a prospect i ve study of consecutive patients enrolled at a university teaching hospital with an annual census of approximately 100,000 . On even days patients had CVA with ultrasonic assistance ; patients presenting on odd days had CVA via traditional l and mark techniques . Ultrasound users were emergency medicine faculty or residents who completed a one-hour training session . A data collection tool with 17 variables was completed for each central line placed . Variables were compared using the independent t-test , Fisher 's exact test , and the non-parametric Mann-Whitney U test . RESULTS Between August 1 , 2000 , and February 1 , 2001 , data for 122 subjects ( n = 51 for US , and n 
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No evidence was found of a difference in inadvertent arterial puncture or other complications .
On the basis of available data , we conclude that two-dimensional ultrasound offers small gains in safety and quality when compared with an anatomical l and mark technique for subclavian ( arterial puncture , haematoma formation ) or femoral vein ( success on the first attempt ) cannulation for central vein catheterization .