Ropivacaine: an update of its use in regional anaesthesia

Ropivacaine is a long-acting, enantiomerically pure (S-enantiomer) amide local anaesthetic with a high pKa and low lipid solubility which blocks nerve fibres involved in pain transmission (Adelta and C fibres) to a greater degree than those controlling motor function (Abeta fibres). The drug was less cardiotoxic than equal concentrations of racemic bupivacaine but more so than lidocaine (lignocaine) in vitro and had a significantly higher threshold for CNS toxicity than racemic bupivacaine in healthy volunteers (mean maximum tolerated unbound arterial plasma concentrations were 0.56 and 0.3 mg/L, respectively). Extensive clinical data have shown that epidural ropivacaine 0.2% is effective for the initiation and maintenance of labour analgesia, and provides pain relief after abdominal or orthopaedic surgery especially when given in conjunction with opioids (coadministration with opioids may also allow for lower concentrations of ropivacaine to be used). The drug had efficacy generally similar to that of the same dose of bupivacaine with regard to pain relief but caused less motor blockade at low concentrations. Lumbar epidural administration of 20 to 30ml ropivacaine 0.5% provided anaesthesia of a similar quality to that achieved with bupivacaine 0.5% in women undergoing caesarean section, but the duration of motor blockade was shorter with ropivacaine. For lumbar epidural anaesthesia for lower limb or genitourinary surgery, comparative data suggest that higher concentrations of ropivacaine (0.75 or 1.0%) may be needed to provide the same sensory and motor blockade as bupivacaine 0.5 and 0.75%. In patients about to undergo upper limb surgery, 30 to 40ml ropivacaine 0.5% produced brachial plexus anaesthesia broadly similar to that achieved with equivalent volumes of bupivacaine 0.5%, although the time to onset of sensory block tended to be faster and the duration of motor block shorter with ropivacaine. Ropivacaine had an adverse event profile similar to that of bupivacaine in clinical trials. Several cases of CNS toxicity have been reported after inadvertent intravascular administration of ropivacaine, but only 1 case of cardiovascular toxicity has been reported to date. The outcome of these inadvertent intravascular administrations was favourable. CONCLUSION: Ropivacaine is a well tolerated regional anaesthetic with an efficacy broadly similar to that of bupivacaine. However, it may be a preferred option because of its reduced CNS and cardiotoxic potential and its lower propensity for motor block.     

Benefit-risk assessment of ropivacaine in the management of postoperative pain.

Ropivacaine is a long-acting amide-type local anaesthetic, released for clinical use in 1996. In comparison with bupivacaine, ropivacaine is equally effective for subcutaneous infiltration, epidural and peripheral nerve block for surgery, obstetric procedures and postoperative analgesia. Nevertheless, ropivacaine differs from bupivacaine in several aspects: firstly, it is marketed as a pure S(-)-enantiomer and not as a racemate, and secondly, its lipid solubility is markedly lower. These features have been suggested to significantly improve the safety profile of ropivacaine, and indeed, numerous studies have shown that ropivacaine has less cardiovascular and CNS toxicity than racemic bupivacaine in healthy volunteers.Extensive clinical data have demonstrated that epidural 0.2% ropivacaine is nearly identical to 0.2% bupivacaine with regard to onset, quality and duration of sensory blockade for initiation and maintenance of labour analgesia. Ropivacaine also provides effective pain relief after abdominal or orthopaedic surgery, especially when given in conjunction with opioids or other adjuvants. Nevertheless, epidurally administered ropivacaine causes significantly less motor blockade at low concentrations. Whether the greater degree of blockade of nerve fibres involved in pain transmission (Adelta- and C-fibres) than of those controlling motor function (Aalpha- and Abeta-fibres) is due to a lower relative potency compared with bupivacaine or whether other physicochemical properties or stereoselectivity are involved, is still a matter of intense debate.Recommended epidural doses for postoperative or labour pain are 20-40 mg as bolus with 20-30 mg as top-up dose, with an interval of >or=30 minutes. Alternatively, 0.2% ropivacaine can be given as continuous epidural infusion at a rate of 6-14 mL/h (lumbar route) or 4-10 mL/h (thoracic route).Preoperative or postoperative subcutaneous wound infiltration, during cholecystectomy or inguinal hernia repair, with ropivacaine 100-175 mg has been shown to be more effective than placebo and as effective as bupivacaine in reducing wound pain, whereby the vasoconstrictive potency of ropivacaine may be involved. Similar results were found in peripheral blockades on upper and lower limbs. Ropivacaine shows an identical efficacy and potency to that of bupivacaine, with similar analgesic duration over hours using single shot or continuous catheter techniques.In summary, ropivacaine, a newer long-acting local anaesthetic, has an efficacy generally similar to that of the same dose of bupivacaine with regard to postoperative pain relief, but causes less motor blockade and stronger vasoconstriction at low concentrations. Despite a significantly better safety profile of the pure S(-)-isomer of ropivacaine, the increased cost of ropivacaine may presently limit its clinical utility in postoperative pain therapy.     

Clinical application of ropivacaine for the lower extremity

Ropivacaine is a new amide local anaesthetic, which is the first commercially available in its category as a pure S-(-) enantiomer. In most recent studies, ropivacaine exhibited a very close pharmacodynamic profile to equipotent doses of bupivacaine. Concentrations of 0.5%, 0.75% and 1% (5, 7.5 and 10 mg/mL, respectively) ropivacaine are used for intraoperative anaesthesia, while the concentration of 0.2% (2 mg/mL) is preferred for postoperative analgesia, either alone or in combination with opioids and/or clonidine. Ropivacaine is responsible for excellent postoperative analgesia following epidural and peripheral perineural injections, using single-shot injections and continuous infusions. Differential sensory/motor block is only apparent at low concentrations (0.2% and less). A significant amount of recent literature focuses on its use for peripheral blocks of the lower limbs, i.e. sciatic and femoral nerve blocks. The primary benefit of ropivacaine is its lower toxicity, mainly lower cardiotoxicity, following accidental intravascular injection. This higher therapeutic index leads to an improved safety profile as compared with potent local anaesthetics such as racemic bupivacaine. For that reason, ropivacaine is a good choice for both intraoperative and postoperative regional anaesthesia and analgesia.     

Update on ropivacaine

Long-acting local anaesthetics are primarily used in the practice of anaesthesia, particularly in regional anaesthesia and analgesia. Ropivacaine is a new long-acting local anaesthetic that has been the focus of interest because of its increased cardiovascular safety compared with bupivacaine. Other advantages of ropivacaine over bupivacaine include a greater sensorimotor differential block and shorter elimination half-life (t(1/2)), with a lower potential for accumulation. The most important attribute of ropivacaine, however, is its increased margin of safety compared with bupivacaine when given in equal doses. Many post-marketing studies have focused on the comparisons of efficacy in blocks and toxicity profiles of bupivacaine versus ropivacaine. Recent animal toxicity studies confirm the results of original studies showing that ropivacaine has less cardiovascular toxicity than bupivacaine with respect to direct myocardial depression, success of resuscitation and arrhythmogenic potential when given in equal doses. Reduced cardiotoxicity may be a distinct characteristic of ropivacaine. A review of current literature suggests that, at clinically relevant doses, ropivacaine provides the lowest potential risk of cardiotoxicity for inadvertent intravascular injection. Studies are currently under way comparing ropivacaine with levobupivacaine, the latest addition to the group of long-acting local anaesthetics.     

Update on ropivacaine

Long-acting local anaesthetics are primarily used in the practice of anaesthesia, particularly in regional anaesthesia and analgesia. Ropivacaine is a new longacting local anaesthetic that has been the focus of interest because of its increased cardiovascular safety compared with bupivacaine. Other advantages of ropivacaine over bupivacaine include a greater sensorimotor differential block and shorter elimination half-life (t_1/2), with a lower potential for accumulation. The most important attribute of ropivacaine, however, is its increased margin of safety compared with bupivacaine when given in equal doses. Many post-marketing studies have focused on the comparisons of efficacy in blocks and toxicity profiles of bupivacaine versus ropivacaine. Recent animal toxicity studies confirm the results of original studies showing that ropivacaine has less cardiovascular toxicity than bupivacaine with respect to direct myocardial depression, success of resuscitation and arrhythmogenic potential when given in equal doses. Reduced cardiotoxicity may be a distinct characteristic of ropivacaine. A review of current literature suggests that, at clinically relevant doses, ropivacaine provides the lowest potential risk of cardiotoxicity for inadvertent intravascular injection. Studies are currently under way comparing ropivacaine with levobupivacaine, the latest addition to the group of long-acting local anaesthetics.     

Ropivacaine

Ropivacaine (Naropin, AstraZeneca) is a long-acting amide local anaesthetic released for clinical use in 1996. Similar to bupivacaine, ropivacaine is equally effective for s.c. infiltration, epidural and peripheral nerve block for surgery, obstetric and post-operative analgesia. Ropivacaine differs from most other amide-type local anaesthetics in that it is marketed as a pure S-enantiomer, instead of as a racemate. This feature improves the safety of ropivacaine, and, indeed, studies have shown ropivacaine to have less cardiovascular and CNS toxicity than bupivacaine. Ropivacaine is nearly identical to bupivacaine in onset, quality and duration of sensory block, but it produces less motor block. Whether or not the motor sparing effect of ropivacaine is due to a lower relative potency compared to bupivacaine is a matter of intense debate. Despite a better safety profile, the increased cost of ropivacaine may limit its clinical utility.     

Clinical application of ropivacaine in obstetrics

Ropivacaine is a new long-acting local anesthetic which is a pure (S)-(-)-enantiomer, with an efficacy profile similar to that of bupivacaine. Compared in equal doses, ropivacaine shows more separation between sensory and motor blockade than bupivacaine. Moreover, ropivacaine has a lower systemic toxicity than bupivacaine. In obstetrics, ropivacaine and bupivacaine have been compared for Cesarean section and for epidural pain relief during labor and delivery. For Cesarean section, both drugs provide similar analgesia when given in equal doses, but motor block is less pronounced with ropivacaine. Neonatal outcome as determined by Apgar scores and Neurological Adaptive Capacity Scores (NACS) is also similar. For epidural pain relief during labor and delivery, both drugs are equally effective, either when given alone or in combination with opioids; a meta-analysis of six studies showed that compared to bupivacaine, the use of ropivacaine is associated with significantly less motor block and instrumental deliveries.     

Levobupivacaine: a review of its pharmacology and use as a local anaesthetic

Based on findings that the cardiotoxicity infrequently observed with racemic bupivacaine shows enantioselectivity, i.e. it is more pronounced with the R(+)-enantiomer, the S(-)-enantiomer (levobupivacaine) has been developed for clinical use as a long acting local anaesthetic. The majority of in vitro, in vivo and human pharmacodynamic studies of nerve block indicate that levobupivacaine has similar potency to bupivacaine. However, levobupivacaine had a lower risk of cardiovascular and CNS toxicity than bupivacaine in animal studies. In human volunteers, levobupivacaine had less of a negative inotropic effect and, at intravenous doses >75 mg, produced less prolongation of the QTc interval than bupivacaine. Fewer changes indicative of CNS depression on EEG were evident with levobupivacaine. Levobupivacaine is long acting with a dose-dependent duration of anaesthesia. The onset of action is < or = 15 minutes with various anaesthetic techniques. In studies of surgical anaesthesia in adults, levobupivacaine provided sensory block for up to 9 hours after epidural administration of < or = 202.5 mg, 6.5 hours after intrathecal 15 mg, and 17 hours after brachial plexus block with 2 mg/kg. Randomised, double-blind clinical studies established that the anaesthetic and/or analgesic effects of levobupivacaine were largely similar to those of bupivacaine at the same dose. Sensory block tended to be longer with levobupivacaine than bupivacaine, amounting to a difference of 23 to 45 minutes with epidural administration and approximately 2 hours with peripheral nerve block. With epidural administration, levobupivacaine produced less prolonged motor block than sensory block. This differential was not seen with peripheral nerve block. Conditions satisfactory for surgery and good pain management were achieved by use of local infiltration or peribulbar administration of levobupivacaine. Levobupivacaine was generally as effective as bupivacaine for pain management during labour, and was effective for the management of postoperative pain, especially when combined with clonidine, morphine or fentanyl. The tolerability profiles of levobupivacaine and bupivacaine were very similar in clinical trials. No clinically significant ECG abnormalities or serious CNS events occurred with the doses used. The most common adverse event associated with levobupivacaine treatment was hypotension (31%). Conclusions: Levobupivacaine is a long acting local anaesthetic with a clinical profile closely resembling that of bupivacaine. However, current preclinical safety and toxicity data show an advantage for levobupivacaine over bupivacaine. Clinical data comparing levobupivacaine with ropivacaine are needed before the role of the drug can be fully established. Excluding pharmacoeconomic considerations, levobupivacaine is an appropriate choice for use in place of bupivacaine.     

罗哌卡因与布比卡因用于腰-硬联合阻滞的临床比较

目的探讨罗哌卡因与布比卡因用于腰麻-硬膜外联合麻醉的临床效果。方法选择40例ASAI-Ⅱ级,下腹部手术采用腰-硬联合麻醉患者的临床资料进行分析,随机分为罗哌卡因组（A组）和布比卡因组（B组）各20例,分别注入0.89％罗哌卡因14.3mg、0.75％布比卡因9.0mg,术中酌情于硬膜外给予2％利多卡因维持麻醉。观察并记录2组患者麻醉效果（2种药物对感觉、运动神经的阻滞情况）以及麻醉不良反应。结果两药均能达到满意的镇痛和肌松效果,但A组运动神经阻滞维持时间短于B组,最大运动阻滞程度〈B组,A组感觉神经阻滞起效快于B组,感觉神经最大阻滞时间〉B组,差异均有统计学意义（P〈0.05）;且A组患者的不良反应（低血压、恶心、呕吐等）发生率较低,循环功能更稳定。结论罗哌卡因可安全有效地用于下腹部手术的腰-硬联合麻醉,与布比卡因相比,具有感觉阻滞起效快,运动阻滞维持时间短,有利于患者术后早期恢复。     

罗哌卡因复合咪唑安定在小儿骶管阻滞麻醉中的临床研究

目的：观察罗哌卡因复合咪唑安定在小儿骶管阻滞麻醉中的有效性和安全性。方法：40例1～6岁行下腹部、会阴部及下肢手术患儿，随机双盲分成布比卡因（2．5mg／kg）对照组，罗哌卡因低、中、高（2．5、3．5、5．0mg／kg）剂量组。采用七氟醚诱导吸入麻醉加骶管阻滞罗哌卡因，复合咪唑安定（0．2mg／kg）。结果：在一定剂量范围内，罗哌卡因复合咪唑安定对舒张压、平均动脉压的影响小；术中心率、动脉血氧饱和度有轻度下降，但均在生理范围内；高、中剂量组术后镇痛持续时间类似布比卡因，低剂量短于布比卡因。除个别患儿在术中有牵拉反应和术后呕吐外，其余均未见明显不良反应。结论：罗哌卡因骶管阻滞复合咪唑安定在小儿麻醉中对患儿血液动力学影响小、可延长镇痛时间，且无明显不良反应。     

Clinical application of ropivacaine for the upper extremity

Ropivacaine, the S-(-)-enantiomer of N-(2,6-dimethylphenyl)-1-propyl-2-piperidinecarboxamide is a new long-acting local anesthetic. This review demonstrates that it is effective in brachial plexus anesthesia. It is at least as efficient as bupivacaine in terms of quality, duration of analgesia, anesthesia, and motor block. It could have some advantages over bupivacaine in terms of onset time of sensory and motor block, but this remains controversial. In single-shot brachial plexus block, it is equipotent to bupivacaine and has a similar pharmacokinetic profile. Its minimal effective concentration is 0.5%, and the benefit of increasing its concentration to 0.75 or 1% remains debatable. Its use during continuous brachial plexus block has been much less studied, and conflicting results involving efficacy during continuous interscalene block and inefficacy during continuous axillary block have been obtained. Further investigations are required to assess its efficacy during such block. Because of lower CNS and cardiac toxicity, ropivacaine is safer than bupivacaine. It would be thus the preferred local anesthetic for brachial plexus blockade when long-lasting anesthesia and analgesia is required.     

甲磺酸罗哌卡因与盐酸罗哌卡因用于分娩镇痛的比较

目的比较甲磺酸罗哌卡因与盐酸罗哌卡因用于分娩镇痛的有效性和安全性。方法选在南通大学附属泰州人民医院2009年1月至2010年1月间主动要求行分娩镇痛、健康、单胎、足月临产初产妇100例随机分成甲磺酸罗哌卡因组与盐酸罗哌卡因组。采用视觉模拟疼痛评分(VAS),记录两组疼痛程度、产程时间、分娩方式、新生儿Apgar评分、运动神经阻滞评分(MBS)及不良反应情况。结果在疼痛程度、产程时间、分娩方式、新生儿Apgar评分、运动神经阻滞评分(MBS)以及不良反应方面,甲磺酸罗哌卡因与盐酸罗哌卡因未见明显的差异(P>0.05)。结论甲磺酸罗哌卡因与盐酸罗哌卡因应用于分娩镇痛,具有相似的有效性和安全性。     

The local anaesthetic activity of levobupivacaine does not differ from racemic bupivacaine (Marcain): first clinical evidence

The local anaesthetic efficacy of levobupivacaine was compared with racemic bupivacaine (Marcain) in healthy male volunteers who were undergoing ulnar nerve blockade. Levobupivacaine, like racemic bupivacaine, produced blockade of nerve function with evidence of a dose response relationship for levobupivacaine. There were no statistically significant differences with respect to duration of sensory pain, sensory touch or motor block when the adjusted mean for the levobupivacaine groups (0.125, 0.25 and 0.5%) were compared with the 0.25% racemic bupivacaine control group. It is concluded that levobupivacaine is an effective local anaesthetic in humans with a dose-related duration of effect. Its local anaesthetic effect did not differ from that of racemic bupivacaine.     

Actions of three local anaesthetics: lidocaine, bupivacaine and ropivacaine on guinea pig papillary muscle sodium channels (Vmax)

The new local anaesthetic ropivacaine (LEA 103) like lidocaine and bupivacaine used as references, blocked cardiac sodium channels in a use-dependent fashion. At equimolar concentrations lidocaine had the lowest efficacy and bupivacaine the highest. The action potential was shortened and the plateau was depressed at high concentrations of each drug. Pacing a papillary muscle at 3.3 Hz in the presence of all three drugs resulted in a marked use-dependent accumulation of block (P less than 0.01). The accumulated block slowly dissipated after rest. At -90 mV holding (= resting) potential, and at a concentration of 10 microM, the time constant for recovery from block was 186 msec. in lidocaine (n = 4), 1.4 sec. in ropivacaine (n = 7), and 2.1 sec. in bupivacaine (n = 7). Lidocaine decreased Vmax progressively at high rates of stimulation, but not significantly at rates below 2 Hz. Ropivacaine progressively decreased Vmax significantly at rates above 1 Hz, but to a lesser degree than bupivacaine. The use-dependent action of the drugs was increased at more depolarized (less negative) holding potentials, whereas at more hyperpolarized potentials the block was diminished. Lidocaine and ropivacaine could be readily dissociated from the receptors at more hyperpolarized membrane potentials (-100 to -120 mV), whereas bupivacaine bound much harder. All three drugs blocked sodium channels more effectively after a long single conditioning pulse. Bupivacaine had the most prominent effect, and lidocaine was least effective. Bupivacaine and ropivacaine seem to interact with the inactivated state of the sodium channels, whereas lidocaine acted on both the open and on the inactivated state of the channels.(ABSTRACT TRUNCATED AT 250 WORDS)     

罗哌卡因与左旋布比卡因用于腹部手术腰硬联合麻醉效果比较

目的:比较罗哌卡因与左旋布比卡因在腹部手术腰硬联合麻醉中的效果安全性。方法:腰硬联合麻醉的腹部手术患者86例随机分为A、B两组各43例。A组采用罗哌卡因麻醉、B组采用左旋布比卡因麻醉,比较两组患者麻醉效果、各时间点患者血流动力学变化,及药品不良反应发生情况。结果:两组患者感觉阻滞时间比较,差异无统计学意义(P>0.05),而A组术后运动神经恢复时间显著短于B组(P<0.05),Bromege评分也显著低于B组(P<0.05)。两组患者麻醉阻滞起效后SBP、DBP、HR等指标均较麻醉前显著降低(P<0.05),而麻醉结束后两组收缩压(SBP)、舒张压(DBP)、心率(HR)与麻醉前比较,差异无统计学意义(P>0.05)。术中各时间点两组SBP、DBP、HR等指标比较,差异也无统计学意义(P>0.05)。两组药品不良反应发生率比较,差异无统计学意义(P>0.05)。结论:罗哌卡因与左旋布比卡因对患者感觉神经的阻滞作用相当,对患者血流动力学的影响及药品不良反应发生率也基本相同。而罗哌卡因对于运动神经的阻滞作用较弱,更有利于患者术后早期运动。     

Epidural block with ropivacaine and bupivacaine for elective caesarean section: maternal cardiovascular parameters, comfort and neonatal well-being

OBJECTIVE: To determine cardiovascular effects and neonatal outcome of ropivacaine 0.75% and bupivacaine 0.5% for elective epidural caesarean section. RESEARCH DESIGN AND METHODS: Healthy pregnant women, scheduled for elective caesarean section, were enrolled in this randomised, double-blind study. Epidural block was obtained with 20-30 ml of ropivacaine 0.75% (Group R) or bupivacaine 0.5% (Group B) and surgery did not commence until anaesthesia was achieved bilaterally to T6. MAIN OUTCOME MEASURES: Maternal heart rate and blood pressure were assessed before the main dose of local anaesthetic and at 5-min intervals until 35 min. Neonatal umbilical pH and Apgar scores were determined after delivery. Ten, twenty and thirty minutes after the main dose, sensory and motor block characteristics were determined. Quality of analgesia was assessed by the anaesthetist, surgeon and the patient. Adverse events were recorded. RESULTS: Sixty-two patients were enrolled and the data of 60 of them were eligible for analysis: 31 in Group R and 29 in Group B. The area under the curve (AUC) for maternal heart rate decreased significantly less in Group B than in Group R (p = 0.038). Twenty-five and thirty minutes after administration of the main local anaesthetic dose, heart rate decreased significantly less in Group B than in Group R (p = 0.006 and p = 0.007). There was no difference in AUC for maternal blood pressure (p = 0.32). Repeated measurement analysis showed no difference between groups in motor block (p = 0.78) and in spread of the sensory block (lower level: p = 0.83, upper level: p = 0.88). There was no statistical difference in neonatal umbilical pH (p = 0.22) and Apgar score (p = 0.59). Multiple linear regression analysis showed a significant influence of maternal body mass index on neonatal pH (p = 0.004), but not of maternal blood pressure (p = 0.323), nor of maternal heart rate (p = 0.12). The quality of analgesia and incidence of adverse events were similar in both groups. CONCLUSIONS: Both drugs produced equally satisfactory epidural block. Although ropivacaine 0.75% resulted in a greater decrease of maternal heart rate, this effect did not influence neonatal well-being. Both ropivacaine 0.75% and bupivacaine 0.5% can therefore be recommended for epidural anaesthesia in elective caesarean section.     

甲磺酸罗哌卡因和盐酸罗哌卡因用于腰丛一坐骨神经联合阻滞的比较

目的比较甲磺酸罗哌卡因和盐酸罗哌卡因用于腰丛-坐骨神经联合阻滞行单侧下肢手术的麻醉效果和安全性。方法选择ASAⅠ～Ⅱ级行单侧下肢手术患者45例,随机分为两组,均在周围神经刺激器（PNS）引导下行腰丛和坐骨神经联合阻滞,Ⅰ组（23例）注入0．596％甲磺酸罗哌卡因45ml,Ⅱ组（22例）注入0．5％盐酸罗哌卡因45ml。注药完毕后,观察平均动脉压及心率的变化情况,测定并记录下肢感觉及运动阻滞起效、维持时间,观察术后麻醉相关并发症及不良反应,对麻醉满意度进行综合评价。结果两组间下肢感觉及运动阻滞起效和维持时间差异无统计学意义（P〉0．05）;平均动脉压、心率及麻醉满意度综合评价组间差异无统计学意义（P〉0．05）;两组未见严重的不良反应或并发症。结论0.596％甲磺酸罗哌卡因在腰丛-坐骨神经联合阻滞中与盐酸罗哌卡因具有相似的麻醉效应及安全性,为临床麻醉工作提供了更多一种选择。     

超声引导股神经联合坐骨神经阻滞在下肢手术中的应用

目的探讨超声引导下股神经联合坐骨神经阻滞在下肢手术中镇痛及阻滞效果。方法选择择期单侧下肢手术患者60例,ASAII或Ⅲ级,随机均分为超声引导股神经联合坐骨神经阻滞组（A组）和腰硬联合麻醉组（B组）。A组在超声引导下进行坐骨神经联合股神经阻滞,分别在坐骨神经及股神经周围注射25ml、20ml0．5％罗哌卡因。记录两组感觉、运动神经阻滞起效、完善及持续时间,术后镇痛持续时间,运动阻滞持续时间,视觉模拟疼痛评分（VAS）。结果A组在超声引导下顺利完成股神经联合坐骨神经阻滞;与B组比较,A组术后各时点VAS评分均在3分以下,且术后24h明显低于B组（P〈0．05）;A组感觉阻滞持续时间明显长于B组（P〈0．05）,运动阻滞持续时间明显长于B组（P〈0．05）。结论超声引导下行股神经联合坐骨神经阻滞用于下肢手术准确及成功率高,明显增加术后镇痛效果。     

Dose-response of ropivacaine administered caudally to children undergoing surgical procedures under sedation with midazolam

1. In a double-blind randomized controlled design, 50 children were allocated to receive bupivacaine 0.25% or ropivacaine 0.25%, 0.32%, 0.40% or 0.50% by caudal block. 2. Caudal block was performed after induction of anaesthesia with 2-5% sevoflurane, atropine 10 microg/kg and midazolam 100-300 microg/kg. During the surgical procedure, patients were maintained under spontaneous ventilation and no intravenous or inhalatory anaesthetic agent was administered. For transoperative sedation, midazolam 100-300 microg/kg was administered every 0.5-1.0 h. Transoperative cardiovascular response, postoperative analgesia and local and systemic complications were evaluated. 3. Groups were similar (P > 0.05) in sex, age, weight and in the time elapsed from caudal block to the beginning of the surgical procedure. The surgical time was significantly lower in the ropivacaine 0.25% group. The duration of analgesia was 24 h with ropivacaine 0.25% and approximately 10 h in the other four groups (P < 0.001). Linear regression analysis revealed a significant relationship between the postoperative analgesic period produced by ropivacaine and the surgical time (r = -0.48, two-sided P = 0.002). Systolic and diastolic blood pressures remained in the physiologically normal range for the duration of the transoperative period. Vomiting was present in only one patient receiving ropivacaine 0.50%. 4. In children, the duration of analgesia produced by caudal block with ropivacaine may be affected by surgical time. At surgical times of 0.5-1 h, ropivacaine 0.25% produced at least 24 h postoperative analgesia. At similar surgical times, ropivacaine 0.32%, 0.40% and 0.50% produced similar analgesic times to bupivacaine 0.25%.