***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: The position of lumbar epidural catheters was confirmed by radiography in 71 patients .  Catheters were advanced by 5 cm cephalad in the lumbar epidural space by paramedian approach ( Group P : n = 28 ) or median one ( Group M : n = 43 ) and contrast media was injected through the catheters . If the contrast media was present in the paravertebral regions , the catheter was considered to be in the abnormal position . The incidence of the abnormal position of the catheters was higher in group M than in group P significantly . To advance an epidural catheter longer into the lumbar epidural space , paramedian approach may be superior to median one Epidural catheter insertion may be associated with blood vessel trauma or nerve root irritation . The purpose of this study was to assess whether the injection of small amounts of fluid through the Tuohy needle prior to catheter insertion reduced the incidence of these and other minor complications . Two hundred patients in labour , requesting epidural analgesia , were r and omly assigned to one of three groups : Group I —the catheter was inserted without previous injection of fluid ; Group II —3 ml , 1.5 per cent lidocaine hydrochloride was injected through the needle prior to catheter insertion ; Group III —3 ml , saline was injected prior to catheter insertion . There were no differences among the groups in the incidence of blood vessel trauma or paraesthesiae . We conclude that there is no advantage in injecting of fluid routinely into the epidural space prior to catheter insertion . RésuméUn cathéter qui pénètre dans l’espace épidural peut irriter une racine nerveuse ou transpercer un vaisseau . Nous avons essayé de diminuer l’incidence de ces complications en injectant du liquide dans l’aiguille de Tuohy avant d’y introduire le cathéter . Nous avons r and omisé en trois groupes , 200 c and i date s à l’analgésie épidurale pendant le travail . Dans le groupe I , nous insérions le cathéter sans injection préalable alors que dans les groupes II et III , nous injections respectivement 3 ml de lidocaïne à 1,5 pour cent et 3 ml de soluté physiologique avant de passer le cathéter . Nous n’avons pu démontrer quelque différence que ce soit entre les groupes quant à l’incidence de traumatisme vasculaire ou de paresthésie . Il ne semble donc pas y avoir d’avantage à injecter de liquide dans l’espace épidural avant d’y introduire un cathéter The extent of epidural anaesthesia and pattern of spread of contrast medium , using different injection techniques , has not been well documented . Therefore , in this prospect i ve , r and omized , double-blind study , the extent of anaesthesia and pattern of spread of contrast medium following an epidural bolus injection , via either a Tuohy needle or an epidural catheter , were compared . The study had two parts . In the first , 59 of 79 patients scheduled for a lower extremity operation under epidural anaesthesia  were r and omly allocated to one of the two groups . Anaesthesia was achieved with an epidural injection of 10 to 15 ml ( including a 3 ml test dose ) of 0.75 % ropivacaine and fentanyl 25 μg via either a Tuohy needle ( Group N , n=31 ) or a catheter ( Group C , n=28 ) . The level of sensory anaesthesia was recorded . In the second part , the remaining 20 patients were r and omized to initially receive 5 ml of contrast medium via either a Tuohy needle ( Group NE , n=10 ) or a catheter ( Group CE , n=10 ) . The extent of spread was recorded radiologically . Unilateral or missed blocks and additional dose requirement were absent in Groups N and C. No differences were found in the extent of sensory anaesthesia or the spread of contrast medium . Twenty per cent of catheter tips lay outside the lateral margins of the vertebral bodies . We found that an epidural bolus injection , via either a Tuohy needle or a catheter , made no difference in regard to spread of local anaesthetic or contrast medium in the epidural space The effects of injecting normal saline 4 ml through the epidural needle before catheter passage on ease of catheterisation and incidence of certain complications were investigated in 189 non-obstetric patients . The use of saline had no effect on ease of catheterisation , with 84.2 % of Group S patients ( saline , n = 95 ) and 88.3 % of Group C patients ( control , n = 94 ) having the difficulty of passing the catheter rated as " easy " ( P = 0.31 ) . The incidence of complications was not affected by the use of saline .  Paraesthesia occurred in 27.4 % of Group S patients compared with 16.0 % of Group C patients ( P = 0.08 ) . Epidural venous cannulation occurred in 6.3 % of Group S patients versus 11.7 % of Group C patients ( P = 0.30 ) . We conclude that the use of 5 ml of normal saline prior to catheter threading provides no significant benefit in improving the ease of catheterisation or decreasing the incidence of catheter complications A system has been constructed to evaluate the design , implementation , and analysis of  r and omized control trials ( RCT ) . The degree of quadruple blinding ( the r and omization process , the physicians and patients as to therapy , and the physicians as to ongoing results ) is considered to be the most important aspect of any trial . The analytic techniques are scored with the same emphasis as is placed on the control of bias in the planning and implementation of the studies . Description of the patient and treatment material s and the measurement of various controls of quality have less weight . An index of quality of a RCT is proposed with its pros and cons . If published papers were to approximate these principles , there would be a marked improvement in the quality of r and omized control trials . Finally , a reasonable st and ard design and conduct of trials will facilitate the interpretation of those with conflicting results and help in making valid combinations of undersized trials Although epidural anaesthesia and analgesia are widely used in obstetrics , there are no large contemporary prospect i ve series detailing associated complications . Prospect i ve data was collected on all obstetric epidural blocks performed for labour and delivery in a single institution between July 1989 and August 1994 . A data entry sheet was compiled and entered onto a computer data base . Confidence intervals for proportions were calculated using st and ard methods . Information from 10 995 epidural blocks was analysed .  Epidural analgesia in labour was the primary indication in 7648 , and anaesthesia for caesarean section in 3311 . Minor complications included failed or ab and oned insertion ( incidence 0.5 % ) , reinsertion of the epidural catheter ( 5 % ) , and inadequate anaesthesia ( 1.7 % ) or analgesia ( 0.9 % ) . Three percent were associated with venous puncture and 0.6 % with accidental dural puncture . Maternal mortality was zero . Unexpectedly high blocks occurred on eight occasions ( 0.07 % ) , two requiring intubation and ventilation . Three women ( 0.06 % ) experienced mild respiratory depression after postoperative epidural opioid . There was no major local anaesthetic toxicity or neurological deficit . The incidence of potentially life-threatening morbidity was thus 0.02 % although in both cases outcome was good . The only persisting complication was neurological , an apparent epidural catheter-induced traumatic mononeuropathy BACKGROUND The technique of epidural volume extension ( EVE ) involves the injection of saline into the extradural space immediately following the intrathecal injection , as part of a combined spinal-epidural ( CSE ) anaesthetic . One of the suggested benefits of EVE is a reduction in local anaesthetic required . The aim of this study was to test this hypothesis by comparing the median effective doses ( ED50 ) of hyperbaric bupivacaine with fentanyl 25 microg with and without EVE for Caesarean section .  METHODS Sixty women were r and omized to receive either CSE anaesthesia with EVE ( EVE group ) or no EVE ( NEVE group ) . Using a double-blinded , up-down sequential technique , varying doses of bupivacaine with fentanyl 25 microg were administered . ED50 was estimated from up-down reversals and probit regression . RESULTS The ED50 for bupivacaine  was similar and not significantly different in the two groups ( 5.1 mg in the EVE and 6.1 mg in the NEVE group ; difference 1.0 mg , 95 % CI -0.12 to 2.2 , P=0.08 ) . CONCLUSIONS This study illustrates that whilst low doses of intrathecal bupivacaine can be effectively used for Caesarean section , at such doses EVE does not appear to offer reliable or clinical ly relevant reductions in dosing with intrathecal bupivacaine Background This study prospect ively evaluated the ability of aspiration to detect intravascular placement of multiple‐orifice epidural catheters . Methods Multiple‐orifice , 20‐gauge epidural catheters were inserted in 1,029 laboring women . Catheters were observed and aspirated for blood or cerebrospinal fluid before they were tested with 2 ml local anesthetic . If the results of this test were negative ( no spinal anesthesia ) , the authors induced and maintained labor analgesia with a dilute local anesthetic and opioid solution .  Patients with bilateral sensory change and effective labor analgesia had a “ positive ” epidural catheter . Women with unilateral block , inadequate analgesia despite some sensory change or those who delivered before being adequately assessed had “ equivocal ” catheters . Patients with neither analgesia nor sensory change had “ negative ” catheters . Results Aspiration and observation identified 60 intravenously placed catheters . Six catheters , which were placed initially in a blood vessel , were withdrawn until aspiration was negative , and then the anesthetic was infused . Four of these catheters were positive and two were still positioned intravascularly . Two other catheters may have been intravenously placed despite negative results of aspiration . The incidence of false‐negative results of aspiration was 0 to 2 of 1,085 ( upper limit of 95 % CI , 0.2 % to 0.4 % ) . No patient showed any signs or symptoms of local anesthetic toxicity . Conclusions Under the conditions of this study , which include using multiple‐orifice catheters and dilute solutions of local anesthetic and opioid , aspiration and incremental drug injection alone safeguard against the risks of intravenously positioned local anesthetics . These results should not be extrapolated to other clinical setting s without further study STUDY OBJECTIVE To compare a multiport , firm-tipped , close-ended , epidural catheter ( Portex catheter ) with a uniport , open-ended , soft-tipped , wire-reinforced catheter ( Arrow catheter ) in obstetric patients . STUDY DESIGN Prospect i ve data collection for intradepartmental quality assurance . SETTING Obstetric unit in a tertiary care maternity hospital . PATIENTS 2612 patients requesting labor analgesia . INTERVENTIONS The Arrow catheter was used in 1,352 women and the Portex catheter in 1,260 women . MEASUREMENTS AND MAIN RESULTS The incidence of unsatisfactory block were 3.3 % and 4.4 % with the Arrow and Portex catheters , respectively ( p = 0.2 ) . The catheter perforated the dura matter in 0.4 % of cases with both catheters . The incidence of epidural venipuncture was 1.1 % with the Arrow catheter and 5.7 % with the Portex catheter ( p = 0.0001 ) . Paresthesias occurred in 6 % of cases with the Arrow catheter and 11 . 2 % of cases with the Portex catheter ( p = 0.0001 ) . Epidural catheter reinsertion was required in fewer patients in the Arrow group than in the Portex group ( 4.8 % vs. 7.1 % ; p = 0.01 ) . CONCLUSIONS In obstetric patients , the softer uniport Arrow catheter produces paresthesias and venipunctures less frequently than the firm multiport Portex catheter Purpose To examine the effects of the volume of saline and the concentration of local anesthetic on the quality of anesthetic level . Methods One hundred and fifty two patients received thoracic epidural anesthesia  were allocated into two groups ; mepivacaine 1 % ( 75 patients ) and 1.5 % ( 77 patients ) . Each group was r and omly divided into three sub-groups depending on epidural saline volumes of 1 ml , 5 ml , or 10 ml . Fifteen minutes after the injection of 10 ml mepivacaine , the dermatome levels of hypesthesia to cold and pinprick were determined by an individual blinded to the saline volume . Results The number of spinal segments with hypesthesia to cold in the three subgroups in the mepivacaine 1 % group were 12.5 [ 6–20 ] , 13 [ 8.5–20.5 ] and 12.5 [ 6.5–22 ] , respectively ( median [ range ] ) . The segments in the mepivacaine 1.5 % group were 12 [ 7– 
    Output:
    
The paramedian as opposed to midline needle approach and smaller epidural needle or catheter gauges do not reduce the risk of epidural vein cannulation .
CONCLUSION : The risk of intravascular placement of a lumbar epidural catheter in pregnancy may be reduced with the lateral patient position , fluid predistension , a single orifice catheter , a wire-embedded polyurethane epidural catheter and limiting the depth of catheter insertion to 6 cm or less .