***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: Background The minimum local analgesic concentration ( MLAC ) has been defined as the median effective local analgesic concentration ( EC50 ) in a 20-ml volume for epidural analgesia in the first stage of labor . The aim of this study was to determine the relative local anesthetic sparing efficacies of intravenous and epidural fentanyl by comparison of their effects on the MLAC of bupivacaine . Methods In this double-blind , r and omized , prospect i ve study , 84 parturients at ≤ 7-cm cervical dilation who requested epidural analgesia were allocated to one of two groups . After lumbar epidural catheter placement , 20 ml bupivacaine ( n = 44 ) or bupivacaine with 3 & mgr;g/ml ( 60 & mgr;g ) fentanyl ( n = 40 ) was administered . The plain bupivacaine group then received 60 & mgr;g intravenous fentanyl . The bupivacaine – fentanyl group received intravenous saline . The concentration of bupivacaine was determined by the response of the previous patient in that group to a higher or lower concentration using up – down sequential allocation . Analgesic efficacy was assessed using 100-mm visual analog pain scores , with ≤ 10 mm within 30 min defined as effective . Results The MLAC  of bupivacaine – intravenous fentanyl was 0.064 % wt/vol ( 95 % confidence interval , 0.049–0.080 ) , and the MLAC of bupivacaine – epidural fentanyl was 0.034 % wt/vol ( 95 % confidence interval , 0.017–0.050 ) . Epidural fentanyl significantly increased the analgesic potency of bupivacaine  by a factor of 1.88 ( 95 % confidence interval , 1.09–3.67 ) compared with intravenous fentanyl . The epidural fentanyl group demonstrated significantly higher dermatomal spread ( P = 0.0064 ) and increased pruritus ( P = 0.01 ) . Conclusions Epidural fentanyl significantly reduced the MLAC of bupivacaine when compared with intravenous fentanyl for the parturients in this study . The significantly enhanced local anesthetic sparing , dermatomal level , and pruritus with epidural fentanyl suggest a primarily spinal site of action Purpose Epidural analgesia is associated with hyperthermia  during labor and presumably causes it , although no convincing mechanism has been postulated . It seems likely that fever associated with pyrogenic factors related to labor is suppressed by opioids , whereas it is expressed normally in patients given epidural analgesia . We examined this hypothesis and the possible etiology of temperature elevation in labor . Methods In this prospect i ve , r and omized , controlled study , we assessed 201 parturients during spontaneous labor . Analgesia was r and omly provided with one of four treatment groups : ( 1 ) epidural ropivacaine alone , ( 2 ) IV remifentanil alone , ( 3 ) epidural ropivacaine plus IV remifentanil , and ( 4 ) epidural ropivacaine plus IV acetaminophen . At r and omization , patients were normothermic . Intrapartum hyperthermia ( ≥38 ° C ) was correlated to the analgesic technique . Results The maximum increase in oral temperature was greatest in the ropivacaine group ( 0.7 ± 0.6 ° C ) and least in the remifentanil group ( 0.3 ± 0.4 ° C ; P = 0.013 ) . The percentage of patients who became hyperthermic ( ≥38 ° C ) during the first 6 h of labor was greatest in the ropivacaine group ( 14 % ) and least in the remifentanil-alone group ( 2 % ) , but the difference was not statistically significant . The maximum forearm-finger gradients were lower ( less vasoconstriction ) in the remifentanil group when compared to the gradients in patients with epidural analgesia ( 1.4 ± 1.8 vs 3.0 ± 1.7 , respectively ; P < 0.001 ) . Conclusion Our results are consistent with the theory that low-dose opioids inhibit fever in patients not given epidural analgesia . However , in view of the negative results , the hypothesis of epidural-induced hyperthermia may be question able BACKGROUND The pharmacokinetics of remifentanil suggests that it may be suitable for analgesia during labour . METHODS In an open pilot study , 36 women requesting meperidine for analgesia were recruited early in labour and r and omized to receive either meperidine i.m . or remifentanil given as patient-controlled analgesia ( PCA ) .  Pain severity , sedation and anxiety were assessed with visual analogue scales and overall effective analgesia was assessed by the woman and midwife . RESULTS The pain scores were lower in the remifentanil group : median pain score at 60 min was 72 mm for meperidine and 48 mm for remifentanil ( P=0.004 ) and median maximum pain score during the first 2 h was 82.5 mm for the meperidine group and 66.5 mm for the remifentanil group ( P=0.009 ) . Both the midwives ' and the women 's assessment s of overall effective analgesia were higher in the remifentanil group [ Likert scale ( 5 = excellent to 1 = poor ) : chi2=12.10 , P=0.002 for mothers ' assessment ; chi2=12.80 , P=0.002 for midwives ' assessment ] . CONCLUSION In this pilot study , remifentanil by PCA gave better pain relief to mothers in labour than intramuscular meperidine . However , remifentanil is a potent respiratory depressant and adequate continuous monitoring is necessary Meptazinol and pethidine were compared in a double-blind r and omized trial with regard to  analgesia during the first stage of labour . It was concluded that neither drug is effective for sustained pain relief , and that there is no advantage of one over the other . However , neither drug affected maternal condition as reflected by respiratory rate , pulse rate and blood pressure , nor was any detrimental effect noted on the condition of the newborn infant . The critical re assessment of traditional drugs for analgesia in labour is suggested Background Pain relief during labour is a topic of major interest in the Netherl and s. Epidural analgesia is considered to be the most effective method of pain relief and recommended as first choice . However its uptake by pregnant women is limited compared to other western countries , partly as a result of non-availability due to logistic problems . Remifentanil , a synthetic opioid , is very suitable for patient controlled analgesia . Recent studies show that epidural analgesia is superior to remifentanil patient controlled analgesia in terms of pain intensity score ; however there was no difference in satisfaction with pain relief between both treatments . Methods / design The proposed study is a multicentre r and omized controlled study that assesses the cost-effectiveness of remifentanil patient controlled analgesia compared to epidural analgesia . We hypothesize that remifentanil patient controlled analgesia is as effective in improving pain appreciation scores as epidural analgesia , with lower costs and easier achievement of 24 hours availability of pain relief for women in labour and efficient pain relief for those with a contraindication for epidural analgesia . Eligible women will be informed about the study and r and omized before active labour has started . Women will be r and omly allocated to a strategy based on epidural analgesia or on remifentanil patient controlled analgesia when they request pain relief during labour . Primary outcome is the pain appreciation score , i.e. satisfaction with pain relief . Secondary outcome parameters are costs , patient satisfaction , pain scores ( pain-intensity ) , mode of delivery and maternal and neonatal side effects . The economic analysis will be performed from a short-term healthcare perspective . For both strategies the cost of perinatal care for mother and child , starting at the onset of labour and ending ten days after delivery , will be registered and compared . Discussion This study , considering cost effectiveness of remifentanil as first choice analgesia versus epidural analgesia , could strongly improve the care for 180.000 women , giving birth in the Netherl and s yearly by giving them access to pain relief during labour , 24 hours a day . Trial registration numberDutch Trial Register NTR2551 , Background Whether epidural analgesia for labor prolongs the active-first and second labor stages and increases the risk of vacuum-assisted delivery is a controversial topic . Our study was conducted to answer the question : does lumbar epidural analgesia with lidocaine affect the progress of labor in our obstetric population ? Method 395 healthy , nulliparous women , at term , presented in spontaneous labor with a singleton vertex presentation . These patients were r and omized to receive analgesia either , epidural with bolus doses of 1 % lidocaine or intravenous , with meperidine 25 to 50 mg when their cervix was dilated to 4 centimeters . The duration of the active-first and second stages of labor and the neonatal apgar scores were recorded , in each patient . The total number of vacuum-assisted and cesarean deliveries were also measured . Results 197 women were r and omized to the epidural group . 198 women were r and omized to the single-dose intravenous meperidine group . There was no statistical difference in rates of vacuum-assisted delivery rate . Cesarean deliveries , as a consequence of fetal bradycardia or dystocia , did not differ significantly between the groups . Differences in the duration of the active-first and the second stages of labor were not statistically significant . The number of newborns with 1-min and 5-min Apgar scores less than 7 , did not differ significantly between both analgesia groups . Conclusion Epidural analgesia with 1 % lidocaine does not prolong the active-first and second stages of labor and does not increase vacuum-assisted or cesarean delivery rate A double-blind between-patient study was carried out comparing pentazocine with pethidine in 94 women in labour . Similar analgesic and sedative effects were obtained with the two drugs , and Apgar scores were similar for babies of both drug groups . Fewer emetic sequelae were reported after pentazocine injections , though there was no statistically significant difference between the two drug groups in incidence of other side-effects The perfect analgesic regimen is constantly sought , no matter how labor is conducted . The quest for an effective drug that will afford maximum relaxation and pain relief with minimum interruption of any natural homeostatic mechanism is a foremost subject in present obstetric analgesics research . Synthetic alternatives are being offered , promising perfect compatibility with the clinician 's dem and s. Nalbuphine , a semisynthetic narcotic agonist-antagonist analgesic of the penanthren series , is supposed not to be liable to cause respiratory depression and is expected to have fewer side effects . A double-blind , r and omised prospect i ve study of 137 patients who received 10 mg nalbuphine or 50 mg pethidine i.v . during the active phase of labor in term was carried out .  Maternal cardiovascular variables , pain intensity , progress of labor and fetal heart rate during labor were related to side effect and neonatal outcome ( 1- and 5-min Apgar scores and umbilical venous pH ) . Neither regimen showed an advantage over the other . Data analysis points to a possible transient depressive effect induced by nalbuphine on the fetal or neonatal central nervous system Objective . To characterize different methods of monitoring neonatal effects associated with  maternal opioid analgesia .  Special focus was on the static-charge-sensitive bed ( SCSB ) , which could potentially serve as a non-invasive neonatal monitor . Methods . 12 healthy , term newborns from normal pregnancies were included in this prospect i ve , r and omized , controlled study . Maternal labor analgesia was either intravenous fentanyl ( n= 5 ) or paracervical bupivacaine blockade ( n= 7 ) . Neonatal recording from delivery to the age of 12 hours included continuous SCSB monitoring with ECG and oximeter  for sleep states , respiration , oxygenation , heart rate , and body movements . In addition , umbilical blood pH , Apgar , Amiel-Tison 's Neurologic and Adaptive Capacity Scoring ( NACS ) , skin cyanosis scoring , blood pressure , rectal and skin temperatures , and skin blood flow measurements were performed . Results . The study was interrupted , because one baby in the fentanyl group had a significant decrease in oxyhemoglobin saturation ( SpO2 ) to 59 % . This was considered to be residual effect of fentanyl and was treated with naloxone . SpO2 was generally lower in the fentanyl group . Epochs with SpO2 < 90 % were more frequent in the fentanyl group , especially during active sleep ( mean ± SD11.9 ± 10.7 % vs. 2.0 ± 1.7 % of epochs , p= 0.034 ) . Mean heart rate values were lower in the fentanyl group ( 121.1 ± 6.4 vs. 132.6 ± 6.8 beats per minute , p= 0.02 ) , and this difference was seen during wake and all sleep states . Maximum heart rate values were lower in the fentanyl group , too . The opiate group had less quiet sleep than controls ( 9.6 ±2.8 % vs. 18.3 ± 8.3 % , p = 0.0 
    Output:
    
Pain scores ( reduction in visual analogue scale ( VAS ) score of at least 40 mm : 50 women ; 1 trial ; RR 25 , 95 % CI 1.56 to 400 , low- quality evidence ) and pain measured in labour ( women reporting pain relief to be " good " or " fair " within one hour of administration : 116 women ; 1 trial ; RR 1.75 , 95 % CI 1.24 to 2.47 , low- quality evidence ) were both reduced in the pethidine group , and fewer women requested any additional analgesia ( 50 women ; 1 trial ; RR 0.71 , 95 % CI 0.54 to 0.94 , low- quality evidence ) .There was limited information on adverse effects and harm to women and babies .
There were few results that clearly showed that one opioid was more effective than another .
Overall , findings indicated that parenteral opioids provided some pain relief and moderate satisfaction with analgesia in labour .
Opioid drugs were associated with maternal nausea , vomiting and drowsiness , although different opioid drugs were associated with different adverse effects .
There was no clear evidence of adverse effects of opioids on the newborn .
We did not have sufficient evidence to assess which opioid drug provided the best pain relief with the least adverse effects .
AUTHORS ' CONCLUSIONS Though most evidence is of low- or very-low quality , for healthy women with an uncomplicated pregnancy who are giving birth at 37 to 42 weeks , parenteral opioids appear to provide some relief from pain in labour but are associated with drowsiness , nausea , and vomiting in the woman .
Effects on the newborn are unclear .
Maternal satisfaction with opioid analgesia was largely unreported .