***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: Abstract Difficulties in the palpation of anatomical l and marks in pregnancy due to obesity may create problems in the regional anaesthesia . Objective of this study was to compare ultrasound examination carried out before the procedure with conventional spinal anaesthesia method with papation of bony l and marks in caesarean sections performed under spinal anaesthesia in obese pregnants . Ninety-seven obese pregnants having pre- and post-pregnancy body mass index > 30 kg/m2 were prospect ively examined . Patients were r and omised to two groups as l and mark group ( n = 49 ) and ultrasound group ( n = 48 ) . The needle insertion point was determined at L4–L5 level before the procedure through palpation in the l and mark group and with the examination in the ultrasound . The numbers of skin punctures and needle passes , total procedure time ( TPT ) and spinal block occurrence time ( SBOT ) were recorded . TPT was significantly longer in the ultrasound than in the l and mark group ( p < 0.001 ) ( 8 ± 2 and 5 ± 1 ; respectively ) . Whereas SBOT values were similar ( p = 0.063 ) . The numbers of skin punctures and needle passes were significantly fewer in the ultrasound than in the l and mark group ( p < 0.001 ) . We believe that , accurate determination of the needle introducing site before the procedure by viewing the vertebral structures through ultrasound examination in obese pregnants could increase the success rate Ultrasound assistance for neuraxial techniques may improve technical performance ; however , it is unclear which population s benefit most . Our study aim ed to investigate the efficacy of neuraxial ultrasound in women having caesarean section with combined spinal‐epidural anaesthesia , and to identify factors associated with improved technical performance . Two‐hundred and eighteen women were r and omly allocated to ultrasound‐assisted or control groups . All the women had a pre‐procedure ultrasound , but only women in the  ultrasound group had this information conveyed to the anaesthetist . Primary outcomes were first‐pass success ( a single needle insertion with no redirections ) and procedure difficulty . Secondary outcomes were block quality , patient experience and complications . Exploratory sub‐group analysis and regression analysis were used to identify factors associated with success . Data from 215 women were analysed .  First‐pass success was achieved in 67 ( 63.8 % ) and 42 ( 38.2 % ) women in the ultrasound and control groups , respectively ( adjusted p = 0.001 ) . Combined spinal‐epidural anaesthesia was ‘ difficult ’ in 19 ( 18.1 % ) and 33 ( 30.0 % ) women in the ultrasound and control groups , respectively ( adjusted p = 0.09 ) . Secondary outcomes did not differ significantly . Anaesthetists misidentified the intervertebral level by two or more spaces in 23 ( 10.7 % ) women . Sub‐group analysis demonstrated a benefit for ultrasound in women with easily palpable spinous processes ( adjusted p = 0.027 ) . Regression analysis identified use of ultrasound and easily palpable spinous processes to be associated with first‐pass success BACKGROUND Ultrasound imaging of the spine is thought to reduce failed and traumatic neuraxial procedures . Most of the evidence supporting this assumption has been produced in the context of an expert sonographer performing the ultrasound assessment , and it remains unknown whether this technique is useful when used by multiple individual operators . OBJECTIVE To invesstigate the impact of preprocedural spinal ultrasound on the ease of insertion of labour epidurals by a group of trainees . We hypothesised that the ultrasound-assisted technique would improve the ease of insertion when compared with the conventional palpation technique . DESIGN A r and omised controlled trial . SETTING Academic hospital in Toronto , Canada . PARTICIPANTS AND INTERVENTION A group of 17 second-year anaesthesia residents and five anaesthesia fellows underwent a training programme in ultrasound assessment of the spine . Parturients with easily palpable lumbar spines were r and omised to either ultrasound or palpation group . Residents and fellows performed both the assessment ( ultrasound or palpation ) and the epidural procedure . MAIN OUTCOME MEASURES Primary outcome : ease of insertion of epidural catheter composed of the time taken to insert the epidural catheter , number of interspace levels attempted and number of needle passes . Secondary outcomes : total procedural time ( assessment and insertion ) ; first pass success rate ; number of attempts required to thread the epidural catheter ; failure of epidural analgesia ; and patient satisfaction . RESULTS We analysed 128 epidural catheter insertions ( residents 84 , fellows 44 ) . There was no difference in median ( interquartile range , IQR ) epidural insertion time between the ultrasound and palpation groups [ 174 ( 120 to 241 ) versus 180 ( 130 to 322.5 ) s , respectively ; P = 0.14 ] . The number of interspace levels attempted and needle passes were also similar in both groups . The total procedural time was longer in the ultrasound group . CONCLUSION The use of preprocedural spinal ultrasound by a cohort of anaesthesia trainees did not improve the ease of insertion of labour epidural catheters in patients with easily palpable lumbar spines , as compared with the traditional palpation technique based on anatomical l and marks . TRIAL REGISTRATION Clinical Trials.gov identifier : NCT00996905 STUDY OBJECTIVE To assess the clinical use of ultrasonographic localization of the epidural space , and to evaluate the clinical efficacy of ultrasound diagnostics in obstetric anesthesia . DESIGN R and omized prospect i ve study . SETTING University Clinic of Obstetrics and Gynecology . PATIENTS 300 parturients , 85 of whom had conventional delivery and 65 who underwent cesarean section . INTERVENTIONS Patients underwent ultrasonography for the identification of the intervertebral structures . Puncture depth and angle were measured to improve the placement of the Tuohy needle . MEASUREMENTS In the ultrasound group , additional puncture data , optimized puncture point , expected puncture depth , and angle were used to optimize the puncture technique . To control for side effects , we compiled data on the number of puncture attempts and the number of necessary puncture levels , visual analog scale ( VAS ) scores , the rate of side effects , and the patient acceptance of the technique . MAIN RESULTS The two groups were similar regarding demographic data . Using ultrasound for structure detection , the rate of puncture attempts were significantly ( p < 0.013 ) reduced from 2.18 + /- 1.07 to 1.35 + /- 0.61 . The mean rate of necessary puncture levels was 1.30 + /- 0.55 and with ultrasound detection 1.136 + /- 0.36 ( p < 0.029 ) . Complete analgesia was achieved in 147 patients with ultrasound detection versus 138 patients in the Control group ( p < 0,03 ) . The maximum VAS pain score in the control group was 1.3 + /- 2.1 versus 0.8 + /- 1.5 in the Ultrasound group ( p < 0.006 ) . The rate of side effects were reduced significantly : 99 patients in the Control group had no side effects compared with 120 patients from the Ultrasound group who were free of side effects . Patient acceptance of the technique in the Ultrasound group was significantly higher than in the Control group . CONCLUSION The clinical use of ultrasound for epidural catheter placement may improve regional anesthesia . The use of ultrasound result ed in superior quality in all measured endpoints Palpation method is widely used in clinical practice to identify the puncture site during combined spinal-epidural ( CSE ) blocks . Tuffier ’s line , is an anatomical l and mark between two iliac crests ( inter-cristal ) , which is widely used to identify the puncture site during CSE blocks is not always an indicator for specific vertebral level or inter-vertebral space . One hundred and Ten ( 110 ) women were scheduled for normal vaginal delivery and were r and omized into two equal groups ; palpation group and an ultrasound guided group to detect the efficacy of puncture ultrasound before CSE blocks to increase chances of successful CSE procedure on the first attempt and to reduce the number of attempts or punctures during insertion of CSE catheter . There were no significant differences between two studied groups regarding ; maternal age , weight and height , while , there was a significant difference between two studied groups regarding ; parity . Percentage of successful CSE procedure on the first attempt was significantly higher ( 67.27 % ) in ultrasound compared to palpation group ( 40 % ) . Number of punctures ( attempts ) were significantly less in ultrasound ( 1.2 ± 0.6 ) compared to palpation group ( 2.3 ± 0.8 ) and the number of redirections was also significantly less in ultrasound ( 1.4 ± 0.5 ) compared to palpation group ( 2.8 ± 1.6 ) . Although , time to identify puncture site was significantly longer in ultrasound compared to palpation group and total procedure time was longer in ultrasound ( 9.1 ± 1.5 min ) compared to palpation group ( 6.2 ± 1.2 min ) , there was no significant difference between two studied groups regarding ; time to identify puncture site and total procedure time . Two cases of dural puncture in palpation versus no cases in ultrasound group and two cases of intravascular catheter placement ( one in each group ) , with no significant difference between two groups . Pre- puncture ultrasound guided epidural insertion before vaginal delivery , increases the chance of a successful CSE procedure on the first attempt and reduces the number of attempts during insertion of CSE catheter BACKGROUND Data are scarce on the advantage of ultrasound-guided spinal anaesthesia in patients with easily identifiable bony l and marks . In this study , we compared the use of ultrasound to the l and mark method in patients with no anticipated technical difficulty , presenting for caesarean delivery under spinal anaesthesia . METHODS A total of 150 pregnant women were recruited in this r and omized , controlled study . Ultrasound examination and spinal anaesthesia were performed by three anaesthetists with experience in ultrasound-guided neuraxial block . Patients were r and omized to either the Ultrasound Group ( n=75 ) or the L and mark Group ( n=75 ) . In both groups the level of L3 - 4 or L4 - 5 was identified by ultrasound ( transverse and longitudinal approach ) or palpation . The primary outcome was the procedure time , measured from the time of skin puncture by the introducer to the time of viewing cerebrospinal fluid at the hub of the spinal needle . Secondary outcomes were the number of skin punctures , number of passes , and incidence of successful spinal blockade . RESULTS The average procedure time , number of skin punctures and needle passes , were similar in both groups . The number of patients with successful spinal anaesthesia after one puncture was not statistically different between the groups . CONCLUSION The present results indicate that when performed by anaesthetists experienced in both ultrasound and l and mark techniques , the use of ultrasound does not appear to increase the success rate of spinal anaesthesia , or reduce the procedure time or number of attempts in obstetric patients with easily palpable spines Background and Aims : Identification of subarachnoid space in pregnant patients can pose a great challenge to anaesthesiologists . This study was design ed to compare conventional l and mark technique with pre-procedural ultrasonography-assisted midline approach for identification of the subarachnoid space in elective caesarean section . Methods : After institute ethics committee approval and written informed consent , 100 parturients scheduled for elective caesarean section under spinal anaesthesia were included in this prospect i ve r and omised control trial and divided into Group L ( n = 50 ) ( l and mark technique ) and Group U ( n = 50 ) ( ultrasound-guided technique ) . Parameters such as time taken for the identification of the interspace , distance between skin and dura mater , number of insertion attempts ( the primary outcome ) , number of passes and time taken were recorded in both the groups . Statistical analysis was done using SPSS software 16 . Results : Demographic profiles of both groups were comparable . The number of attempts for needle insertion ( 1.04 ± 0.19 vs. 1.97 ± 0.77 ) , number of passes in the same interspinous space ( 1.26 ± 0.44 vs. 1.90 ± 0.51 ) and the total time for successful lumbar puncture ( 31.90 ± 6.30 vs. 51.80 ± 12.28 s ) were significantly less in Group U as compared to Group L , but the time of identification of interspinous space was significantly more in Group U ( 56.70 ± 13.08 s ) as compared to Group L ( 47.10 ± 10.45 s ) . Conclusion : Pre-procedural ultrasound is a useful tool for successful lumbar puncture in parturients as it reduces the number of attempts with fewer side effects as compared to conventional l and mark technique STUDY OBJECTIVE This r and omized controlled trial was design ed to evaluate the efficacy of additional information from preprocedure ultrasound examination to aid anesthesiology trainees performing spinal anesthesia for obstetric patients . DESIGN Trainee residents were r and omly allocated to 
    Output:
    
The primary results showed that preprocedural ultrasound increased the FPS rate in patients with predicted puncture difficulty but not in patients who were easily punctured .
Preprocedural ultrasound reduced the number of redirections and punctures and decreased the incidence of vascular puncture and backache .
There was no evidence of a reduction in failed punctures .
We also noted that preprocedural ultrasound prolonged the identification time but not the procedure time .
Thus , this systematic review provides evidence that preprocedural ultrasound does not improve the FPS rate of  neuraxial anesthesia in patients who are easily palpated , although it increases the FPS rate in patients who are difficult to palpate