Pharmacokinetics and clinical efficacy of long-term epidural ropivacaine infusion in children

Efficacy of preemptive analgesia on acute postoperative pain in children undergoing major orthopedic surgery of the lower extremities

Background

Children undergoing major orthopedic surgery of the lower extremities can experience severe postoperative pain; yet, the ideal postoperative pain management strategy is unknown. Thus, in this patient population, we investigated the effect of intraoperative epidural infusion of local anesthetic on acute postoperative pain and analgesic consumption.

Patients and methods

Patients (N=50, 3-12 years) randomly received either ropivacaine 0.15% (preemptive group) or normal saline (control group) as an initial bolus of 0.2 mL/kg, followed by continuous infusion of 0.15 mL/kg/h throughout surgery. Following surgery, patient-controlled epidural analgesia with ropivacaine 0.1% was provided. The main study outcomes were the revised Face, Legs, Activity, Cry, and Consolability pain scores, epidural ropivacaine consumption, and additional analgesic requirements during the first 48 hours postoperatively.

Results

Forty-seven patients completed the study, 23 in the preemptive group and 24 in the control group, respectively. The revised Face, Legs, Activity, Cry, and Consolability pain scores were significantly lower in the preemptive group only at 30 minutes after postanesthesia care unit arrival and 6 hours after surgery (median difference -1.0, 95% CI -2.0 to -1.0, P=0.001 and median difference -2.0, 95% CI -3.0 to -1.0, P=0.005, respectively). However, they were not significantly different between the groups at 12, 24, and 48 hours postoperatively. Epidural ropivacaine consumption and additional analgesic requirements throughout 48 hours postoperatively were not significantly different between the groups.

Conclusion

Intraoperative epidural infusion of ropivacaine did not demonstrate preemptive analgesic efficacy within 48 hours postoperatively in children undergoing extensive lower limb orthopedic surgery.

Flip-Flop Phenomenon in Epidural Sufentanil Pharmacokinetics: A Population Study in Children and Infants

The aims of this study were to develop a population pharmacokinetic model of sufentanil coadministered with 0.2% ropivacaine as an epidural infusion in infants and describe the sufentanil absorption profile from epidural space. Data from 2 previously published studies were merged for analysis-20 infants aged 3-36 months receiving sufentanil as an epidural infusion and 41 children 0-17 years old receiving sufentanil as a long-term intravenous infusion. A population nonlinear mixed-effects model was built in NONMEM. Sufentanil pharmacokinetics were described by a 2-compartment model with first-order absorption. The effect of body size on all volume and clearance parameters was included in the model according to allometric scaling with theoretical exponents. The maturation process of metabolic clearance was described by the Hill model. During the model-building process the population was divided into 2 fractions with different typical values of metabolic clearance (CL1 and CL2). The typical values of systemic clearance scaled to a 70-kg patient for the 2 subpopulations were CL1 = 52.6 L/h and CL2 = 158 L/h. The parameters of the Hill function were 54.9 weeks for the postmenstrual age of 50% clearance maturation and 0.802 for the Hill coefficient. The typical values of distribution clearance and volumes of the central and peripheral compartments for a patient with a weight of 70 kg were Q = 40.5 L/h, VC = 7.63 L, and VT = 473 L, respectively. The value of the absorption rate constant from the epidural space was 0.0459/h, which suggests flip-flop pharmacokinetics of sufentanil after epidural administration.

Autologous blood transfusion after local infiltration analgesia with ropivacaine in total knee and hip arthroplasty

Aims. To study the safety of autotransfusion following local infiltration analgesia (LIA) with ropivacaine. Background. Knowledge of blood concentrations of ropivacaine after LIA and autotransfusion is crucial. However, very limited data are available for toxicological risk assessment. Methods. Autotransfusion was studied in patients after total knee arthroplasty (TKA: n = 25) and total hip arthroplasty (THA: n = 27) with LIA using 200 mg ropivacaine, supplemented with two postoperative bolus injections (150 mg ropivacaine). Drainage blood was reinfused within 6 h postoperatively. Results. Reinfusion caused a significant increase in the serum concentration of total ropivacaine for TKA from 0.54 ± 0.17 (mean ± SD) to 0.79 ± 0.20 μg/mL (P < 0.001) and a nonsignificant increase for THA from 0.62 ± 0.17 to 0.63 ± 0.18 μg/mL. The maximum free (unbound) concentration after reinfusion was 0.038 μg/mL. Peak total and free venous ropivacaine concentrations after 8 h and 16 h postoperative bolus injections were 2.6 μg/mL and 0.11 μg/mL, respectively. All concentrations observed were below the threshold for toxicity and no side effects were observed. Conclusion. Autotransfusion of patients undergoing knee or hip arthroplasty after local infiltration analgesia with 200 mg ropivacaine can be performed safely, even supplemented with 8 h and 16 h postoperative bolus injections.

Pharmacokinetic profiles of epidural bupivacaine and ropivacaine following single-shot and continuous epidural use in young infants

AIMS

The primary aim of this study was to describe the pharmacokinetics of total and unbound bupivacaine and ropivacaine following epidural bolus and infusion in neonates and young infants. Secondary aims were to investigate the influence of alpha-1-acid glycoprotein (AAG) on the concentration-time profiles and to determine the efficacy and adverse event profile of the epidural regimen.

METHODS/MATERIALS

Thirty-one infants aged 40-63 weeks of postmenstrual age (PMA) undergoing hernia repair or abdominal surgery received an epidural injection of 1.5 mg · kg(-1) bupivacaine (0.25%) or ropivacaine (0.2%) followed 2 h later by an infusion of 0.2 mg · kg(-1) · h(-1) in those undergoing abdominal surgery. Total and unbound concentrations of bupivacaine and ropivacaine were analyzed using nonmem. Hourly pain scores and adverse effects were recorded.

RESULTS

Bupivacaine data were available from 11 infants (five had infusions) and ropivacaine from 13 infants (four had infusions). Alpha-1-acid glycoprotein and total bupivacaine and ropivacaine concentrations accumulated during infusions, but unbound concentrations did not. Maximum unbound concentrations for bupivacaine and ropivacaine were 0.12 mg · l(-1) (bupivacaine) and 0.13 mg · l(-1) (ropivacaine). Typical clearance/bioavailability estimates of total (unbound) bupivacaine were 0.215 (4.65) l · h(-1) · kg(-1) and of total (unbound) ropivacaine were 0.288 (3.31) l · h(-1) · kg(-1). Pain scores requiring pain team referral occurred once with bupivacaine and four times with ropivacaine. No toxicity was observed.

CONCLUSIONS

Epidural infusions of 0.2 mg(-1) · kg(-1) · h(-1) bupivacaine or ropivacaine appeared to be well tolerated and efficacious in this population. No accumulation of unbound drug concentrations occurred.

Epidural and opioid analgesia following the Nuss procedure

Background

Parents have the right to decide on behalf of their children and deny consent to regional anaesthesia. The investigators decided to investigate quality of postoperative analgesia in adolescents undergoing epidural and opioid analgesia following the Nuss procedure.

Material/Methods

The study subjects were 61 adolescents aged 11–18 years who underwent pectus excavatum repair with the Nuss procedure. Patients were divided into epidural (n=41) and opioid (n=20) groups, depending on their parents’ consent to epidural catheter insertion. Intraoperatively, 0.5% epidural ropivacaine with fentanyl or intermittent intravenous injections of fentanyl were used. Postoperative analgesia was achieved with either epidural infusion of 0.1% ropivacaine with fentanyl, or subcutaneous morphine via an intraoperatively inserted “butterfly” cannula. Additionally, both groups received metamizol and paracetamol. Primary outcome variables were postoperative pain scores (Numeric Rating Scale and Prince Henry Hospital Pain Score). Secondary outcome variables included hemodynamic parameters, additional analgesia and side effects.

Results

Heart rate and blood pressure values in the postoperative period were significantly higher in the opioid group. Pain scores requiring intervention were noted almost exclusively in the opioid group.

Conclusions

Denial of parental consent to epidural analgesia following the Nuss procedure results in significantly worse control of postoperative pain. Our data may be useful when discussing with parents the available anaesthetic techniques for exceptionally painful procedures.

Caudal ropivacaine-clonidine: A better post-operative analgesic approach

The aim was to determine qualitative and quantitative aspects of caudal block, haemodynamic effects, and post-operative pain relief of ropivacaine 0.25% versus ropivacaine 0.25% with clonidine for lower abdominal surgeries in paediatric patients. A double-blind study was conducted among 44 paediatric patients in the Department of Anaesthesiology and Intensive Care of our institute. A total of 44 ASA-I paediatric patients between the ages of 1 and 9 years, scheduled for elective hernia surgery, were enrolled in this randomised double-blind study. The caudal block was administered with ropivacaine 0.25% (Group I) and ropivacaine 0.25% and clonidine 2 µg/kg (Group II) after induction with general anaesthesia. Haemodynamic parameters were observed before, during and after the surgical procedure. Post-operative analgesic duration, total dose of rescue analgesia, pain scores and any side effects were looked for and recorded. All the results were tabulated and analysed statistically. The variables in the two groups were compared using the non-parametric tests. For all statistical analyses, the level of significance was P < 0.05. Forty-four patients were enrolled in this study and their data were subjected to statistical analysis: 22 patients in both the groups were comparable with regard to demographic data, haemodynamic parameters and other vitals and were statistically non-significant (P>0.05). The duration of analgesia was significantly prolonged in Group II (P<0.05). The dose requirement for post-operative pain relief was also significantly lesser in Group II. The incidences of side effects were almost comparable and non-significant. A caudal block with 0.25% of isobaric ropivacaine combined with 2 µg/kg of clonidine provides efficient analgesia intra-operatively and prolonged duration of analgesia post-operatively.

Persistent hiccups associated with epidural ropivacaine in a newborn

OBJECTIVE

To report a case of persistent hiccups associated with epidural ropivacaine in a newborn infant.

CASE SUMMARY

A term female infant (3.05 kg) received epidural ropivacaine for pain control during and after an operative procedure to correct a tracheoesophageal fistula. Three intermittent doses of ropivacaine were administered during the operative period (total dose 2.29 mg/kg) followed by a continuous epidural (caudal) infusion (0.1% ropivacaine; initial dose 0.23 mg/kg/h plus fentanyl 0.46 μg/kg/h). The infant was extubated in the recovery area and transferred to the intensive care unit. Within hours of transfer, she developed persistent hiccups. The epidural infusion was titrated for pain control, up to 0.32 mg/kg/h (ropivacaine). The hiccup frequency increased to every 10-30 seconds, with the patient appearing hypotonic with lip trembling and intermittent tongue fasciculation. An electroencephalogram did not show any epileptiform activity or focal features consistent with seizure activity. The epidural infusion was reduced to 0.26 mg/kg/h (ropivacaine), with dramatic improvement in hiccups and tone. The infusion was discontinued and complete resolution of hiccups was observed.

DISCUSSION

Ropivacaine is commonly used for infiltration anesthesia and peripheral and epidural block anesthesia. Use of the Naranjo probability scale determined that our patient's hiccups were probably caused by ropivacaine. To our knowledge, this is the first report of persistent hiccups associated with epidural ropivacaine.

CONCLUSIONS

Clinicians should consider the potential of neurotoxicity, manifested as persistent hiccups, when epidural ropivacaine is administered to young infants.

Regional anesthesia for postoperative pain control in children: focus on continuous central and perineural infusions

Regional anesthesia is widely employed for postoperative pain control in both adults and children. Central or perineural approaches can be performed as a bolus injection or as a continuous infusion of local anesthetics. However, bolus injections, even with the addition of adjuvants, are inadequate for prolonged surgery and long-term pain control. Continuous infusion remains the technique of choice when there is a prolonged operation or intense postoperative pain. This article reviews the safety and efficacy of central and perineural continuous infusions for postoperative pain control in children. The literature confirms the very low rate of complications and adverse effects of regional anesthesia in children. However, clinicians need to be aware of the key points for performing a block and placing a catheter in children: good knowledge of anatomic and physiologic differences between adults and children is necessary; the use of newer local anesthetics, such as ropivacaine and levobupivacaine, increases the therapeutic window; and that it is mandatory to work with dedicated pediatric equipment. Through the use of new techniques such as nerve mapping and/or ultrasound the success of blocks can be improved and the risks reduced.

Safety of multiple, simultaneous continuous peripheral nerve block catheters in a patient receiving therapeutic low-molecular-weight heparin

OBJECTIVE

The application of continuous peripheral nerve block (CPNB) has been an important anesthetic tool in the management of combat soldiers wounded from current conflicts. Placing and maintaining CPNBs becomes a challenge in this patient population due to concomitant prophylactic and therapeutic anticoagulation.

CASE REPORT

A 32-year-old male sustained multiple traumatic injuries from an improvised explosive device, including a right tibial fracture, a left tibial fracture, and a left ulnar fracture. His pain was originally well controlled with a left infraclavicular CPNB (0.2% ropivacaine at 10 mL/h with 3 mL bolus every 20 minutes) and an epidural (0.2% ropivacaine at 10 mL/h with 5 mL bolus every 30 minutes). He subsequently developed a common femoral vein thrombus and was treated with low-molecular-weight heparin. His epidural catheter was discontinued; however, his pain was not well controlled with intravenous and oral pain medication. We elected to place bilateral, tunneled sciatic CPNBs and a left, tunneled femoral CPNB. We started infusions of 0.2% ropivacaine at 10 mL/h in each catheter, in addition to 5 mL every 30 minutes demand dose in each sciatic catheter. The patient's serum ropivacaine levels were analyzed 24 hours after the start of the infusions and were found to be 5.8 mg/L and <0.1 mg/L for total and free concentrations, respectively.

CONCLUSIONS

This case highlights the application of simultaneous CPNB techniques in a patient with multiple extremity injuries receiving anticoagulant therapy.

[Perioperative analgesia with continuous peripheral nerve blocks in children]

Recently, regional anaesthesia in children has generated increasing interest. But single injection techniques have a limited duration of postoperative analgesia. Then, continuous peripheral nerve blocks have taken an important position in the anaesthetic arsenal, allowing an effective, safe and prolonged postoperative pain management. As adults, indications for continuous peripheral nerve blocks depend on the analysis of individual benefits/risks ratio. Main indications are intense postoperative pain surgical procedures, with or without postoperative rehabilitation, and complex regional pain syndrome. Contraindications to these procedures are rather similar to those in adults, plus parental and/or children refusal. Continuous peripheral nerve blocks are usually performed under general anaesthesia or sedation in children, and require appropriate equipment in order to decrease the risk of nerve injury. New techniques, such as transcutaneous nerve stimulation or ultrasound guidance, appeared to facilitate nerve and plexus approach identification in paediatric patients. Nevertheless, continuous peripheral nerve block may theoretically mask a compartment syndrome after trauma surgical procedures. Finally, ropivacaine appears to be the most appropriate drug for continuous peripheral nerve blocks in children, requiring low flow rates and concentrations of local anaesthetic. These techniques may facilitate early ambulation by an improved pain management or even postoperative analgesia at home with disposable pumps. One might infer from the current review that excellent pain relief coupled with a reduction of side effects would contribute to improve the quality of life and to decrease the frequency of disabling behavioural modifications in children, sometimes psychologically injured by hospital stay and postoperative pain.

[Thoracic epidural analgesia for a thrombocytopenic child]

Per- and postoperative analgesia of patients with chronic pain is a challenging issue for anaesthetists and can be achieved with locoregional anaesthesia, unless it is contraindicated. We report the case of a thrombocytopenic child presenting for thoracotomy and in whom intravenous analgesia failed after previous surgeries. Due to the central origin of the thrombocytopenia, thoracic epidural analgesia could be achieved, after platelet transfusions. When clinical advantage of thoracic epidural is unquestionable, central thrombocytopenia is a relative contraindication.

Ropivacaine: a pharmacological review

Ropivacaine (Naropin, AstraZeneca) a new long-acting amide local anaesthetic agent, is a pure S-enantiomer, with a high pKa and relatively low-lipid solubility. Since its clinical introduction in 1996, it has been the focus of intense interest because of its increased CNS and cardiovascular safety compared with bupivacaine. This article reviews the pharmacology of ropivacaine with particular emphasis placed on toxicological issues. Compared with bupivacaine (the drug of choice for many years), ropivacaine is equally effective for subcutaneous infiltration, epidural, intrathecal and peripheral nerve block surgery, and obstetrics and postoperative analgesia. Ropivacaine is virtually identical to bupivacaine in terms of onset, quality and duration of sensory block, but seems to produce less motor block. The lesser toxicity of ropivacaine compared with bupivacaine has been confirmed in numerous animal experiments as well as human studies, including studies considering the presumed lower potency of ropivacaine. In fact, the reduced cardiovascular toxicity compared with bupivacaine may be a distinct feature of ropivacaine. So far, the increased cost of ropivacaine compared with bupivacaine has limited its wider clinical use -- in spite of the improved safety profile. During the last few years, cost differences between bupivacaine and ropivacaine have been minimized, thus making pharmacoeconomical speculations a much lesser concern when choosing a local anaesthetic drug. In conclusion, ropivacaine appears to be a safer local anaesthetic agent than bupivacaine. It seems particularly indicated for major peripheral nerve blocks and obstetrics. Ropivacaine should be considered when regional blocks are used in neonates and young infants. With the current trend in the cost development, ropivacaine will most likely be used increasingly in the future.

Ropivacaine: a review of its use in regional anaesthesia and acute pain management

Ropivacaine (Naropin) is the pure S(-)-enantiomer of propivacaine, and is a long-acting amide local anaesthetic agent, eliciting nerve block via reversible inhibition of sodium ion influx in nerve fibres. Ropivacaine is a well tolerated regional anaesthetic effective for surgical anaesthesia as well as the relief of postoperative and labour pain. The efficacy of ropivacaine is similar to that of bupivacaine and levobupivacaine for peripheral nerve blocks and, although it may be slightly less potent than bupivacaine when administered epidurally or intrathecally, equi-effective doses have been established. Clinically adequate doses of ropivacaine appear to be associated with a lower incidence or grade of motor block than bupivacaine. Thus ropivacaine, with its efficacy, lower propensity for motor block and reduced potential for CNS toxicity and cardiotoxicity, appears to be an important option for regional anaesthesia and for the management of postoperative and labour pain.

Continuous Epidural Block Versus Continuous Popliteal Nerve Block for Postoperative Pain Relief After Major Podiatric Surgery in Children: A Prospective, Comparative Randomized Study

Foot and ankle surgery in children is very painful postoperatively. Adverse effects from opioids and continuous epidural block (CEB) limit their use in children. Continuous popliteal nerve blocks (CPNB) have not been studied for this indication in children. In this prospective, randomized study we evaluated the effectiveness and adverse events of CPNB or CEB in children after podiatric surgery. Fifty-two children scheduled for foot surgery were separated into four groups by age and analgesia technique. After general anesthesia, 0.5 to 1 mL/kg of an equal-volume mixture of 0.25% bupivacaine and 1% lidocaine with 1:200000 epinephrine was injected via epidural or popliteal catheters. In the postoperative period, 0.1 mL x kg(-1) x h(-1) (group CPNB) or 0.2 mL x kg(-1) x h(-1) (group CEB) of 0.2% ropivacaine was administered for 48 h. Niflumic acid was routinely used. Adverse events were noted in each treatment group. Postoperative pain during motion was evaluated at 1, 6, 12, 18, 24, 36, and 48 h. Requirement for rescue analgesia (first-line propacetamol 30 mg/kg 4 times daily or second-line 0.2 mg/kg IV nalbuphine), and motor blockade were recorded. Parental satisfaction was noted at 48 h. Twenty-seven patients were included in the CEB groups and 25 in CPNB groups. There were 32 children 1 to 6 yr of age (CPNB = 15; CEB = 17) and 20 children 7 to 12 yr of age (CPNB = 10; CEB = 10). The demographic data were comparable among groups. Postoperative analgesia was excellent for the two continuous block techniques and in the two age groups. Motor block intensity was equal between techniques. Adverse events (postoperative nausea or vomiting, urinary retention, and premature discontinuation of local anesthetic infusion in the 1- to 6-yr-old group) were significantly more frequent in the CEB group (P < 0.05). Eighty-six percent of the parents in the CEB groups and 100% in the CPNB groups were satisfied. We conclude that although both CEB and CPNB resulted in excellent postoperative analgesia in this study, CPNB was associated with less urinary retention and nausea and vomiting. Therefore, we recommend CPNB as the ideal form of postoperative analgesia after major podiatric surgery in 1- to 12-yr-old children.

Pharmacokinetics and efficacy of ropivacaine for continuous epidural infusion in neonates and infants

INTRODUCTION

The primary objective of this noncomparative study was to evaluate the pharmacokinetics of ropivacaine during a 48-72-h continuous epidural infusion of ropivacaine in children under 1 year. The secondary objectives were to assess efficacy and safety.

METHODS

Neonates and infants (ASA I-III, gestational age > or =37 weeks, > or =2.5 kg, scheduled for major abdominal or thoracic surgery) were included and separated into age groups: 0-30 (neonate), 31-90, 91-180, and 181-365 days. Ethics committee approval and informed parental consent were obtained before inclusion. An epidural catheter was introduced under general anesthesia at the appropriate dermatomal level. An initial bolus dose (0.9-2.0 mg.kg(-1) of ropivacaine 0.2%) was followed by an epidural infusion (0.2 mg.kg(-1).h(-1) for infants <180 days or 0.4 mg.kg(-1).h(-1) for infants >180 days). Plasma samples were collected every 12 h from 24 h, and on termination of the epidural infusion. Postoperative pain was evaluated using both the Objective Pain Scale and a four-graded descriptive scale.

RESULTS

Forty-five infants, median age 116 (0-362) days, were included. Forty-three and 19 patients received an infusion for at least 48 and 72 h, respectively. Satisfactory analgesia was provided in the majority, only 20 patients were given supplementary medication during the infusion. In all age groups, plasma concentrations of unbound ropivacaine leveled at 24 h, without any further increase at 48 and 72 h. Because of lower clearance of unbound ropivacaine in neonates (mean 33 ml.min(-1).kg(-1)) than in infants above the age of 30 days (80, 124, and 163 ml.min(-1).kg(-1), respectively, in the age groups 31-90, 91-180, and 180-365 days), unbound ropivacaine concentrations at the end of infusion were higher in neonates [median 0.10 mg.l(-1) (0.04-0.21 mg.l(-1))] than in infants >30 days [median 0.03 mg.l(-1) (0.003-0.10 mg.l(-1))].

CONCLUSION

Epidural infusions (0.2-0.4 mg.kg(-1).h(-1) ropivacaine) provided satisfactory pain relief in neonates and infants under 1 year. As plasma concentrations of unbound ropivacaine were not influenced by the duration of the infusion, ropivacaine can be safely used for postoperative epidural infusion for 48-72 h. Levels of unbound ropivacaine were higher in the neonates than in the infants, but were below threshold concentrations for CNS toxicity in adults (> or =0.35 mg.l(-1)). This should not preclude the use of ropivacaine infusions in neonates but suggests a need for caution during the first weeks of life.

Continuous peripheral nerve blocks in children

In recent years, regional anaesthesia in children has generated increasing interest. Continuous peripheral nerve blocks have an important role in the anaesthetic arsenal, allowing effective, safe and prolonged postoperative pain management. Indications for continuous peripheral nerve blocks depend on benefits/risks analysis of each technique for each patient. The indications include surgery associated with intense postoperative pain, surgery requiring painful physical therapy, and complex regional pain syndrome. Continuous peripheral nerve blocks are usually performed under general anaesthesia or sedation, and require appropriate equipment in order to decrease the risk of nerve injury. New techniques, such as transcutaneous stimulation or ultrasound guidance, appear to facilitate nerve and plexus identification in paediatric patients. Nevertheless, continuous peripheral nerve block may mask compartment syndrome in certain surgical procedure or trauma. Finally, ropivacaine appears to be the best local anaesthetic for continuous peripheral nerve blocks in children, requiring low flow rate with low concentration of the local anaesthetic.

Ropivacaine in neonates and infants: a population pharmacokinetic evaluation following single caudal block

BACKGROUND

The aims of this study were to evaluate pharmacokinetics, efficacy and safety of ropivacaine in infants aged 0-12 months following a single caudal injection.

METHODS

Term ASA I-III patients, scheduled for surgery, with a body weight of > or = 2500 g received a caudal block with ropivacaine 2 mg x ml(-1), 1.0 ml x kg(-1). Plasma samples were collected at different time intervals up to 30 h, for analysis of total and unbound ropivacaine and alpha-1-acid glycoprotein (AAG). Pharmacokinetic data were characterized by population analysis. Unbound and total concentrations from 35 patients, median (min-max) postnatal age of 66 (4-351) days, were included in the nonlinear mixed effects modeling to provide estimates of pharmacokinetic parameters and the exploration of covariate relationships. Simulations were made to test the predictive performance of the final model and to describe the effect of significant covariates on systemic exposure.

RESULTS

The mean (min-max) peak plasma concentration of total ropivacaine was 0.83 (0.05-1.57) mg x l(-1) at 0.5-5.7 h (median: 1.0 h) and the plasma concentration of unbound ropivacaine was 0.042 (0.012-0.081) mg x l(-1) within 0.5-1 h. The observed unbound fraction in plasma was 6% (1%-14%). A one-compartment open model with first-order absorption and elimination, incorporating a linear-binding model of ropivacaine to AAG best described the data. The only significant covariate relationship was that of age on Clu/F according to the following relationship Clu/F = 3.01 x e0.00474 x Age. This predicts a Clu/F of 3.5 l x h(-1) x kg(-1) at 30 days and 10.8 l x h(-1) x kg(-1) at 270 days with corresponding terminal half-lives of 6.7 and 2.2 h. The interindividual variability (coefficient of variation, CV) in Clu/F was 39%. The population estimate (CV) of ka was 1.65 h(-1) (30%), Vu/F was 33.6 (l x kg(-1)) (45%) and Ka was 1.78 l x mg(-1) (14%). Thirty-five infants received supplementary analgesics (mostly paracetamol). The median time to first supplementary analgesic (based on all 37 patients) was 3.9 h. No safety concerns or signs of systemic toxicity were observed.

CONCLUSIONS

Following a caudal block with ropivacaine 2 mg x kg(-1) plasma concentrations of unbound ropivacaine were well below threshold levels for toxicity in adults. Apparent volume of distribution is unchanged, apparent unbound clearance increases and the terminal half-life decreases with age in 0-12-month-old neonates and infants. The postoperative pain management provided adequate analgesia and was well tolerated.

Pharmacokinetics of Local Anaesthetics in Infants and Children

Amide local anaesthetics used for regional anaesthesia in paediatric patients are potent sodium channel blockers with marked stereospecificity, which consistently influences their action, especially their toxic action on the heart. At toxic concentrations, they induce severe arrhythmias with the potential for cardiac arrest. These agents are all bound to serum proteins, mainly to alpha(1)-acid glycoprotein (AAG), but also to human serum albumin. Protein binding ranges from 65% (lidocaine) to more than 95% (bupivacaine, ropivacaine). Because AAG is a major acute phase protein, its concentration rapidly increases when inflammatory processes develop, particularly during the postoperative period. Neonates and infants have a lower AAG concentration in serum as compared with adults; therefore, their free fraction of local anaesthetics is increased accordingly. This has important clinical implications since, at least at steady state, the toxic effects of local anaesthetics are directly related to the free (unbound) drug concentration. After injection into the epidural space, absorption into the bloodstream follows a biphasic process. The buffering properties of the epidural space are important and prevent a rapid rise in concentration. In infants and children, the epidural space seems to protect patients in a similar manner. Moreover, it has been observed that the peak plasma concentration (C(max)) of ropivacaine is delayed in infants and children when compared with adults. The time to C(max) decreases from 90-120 minutes in infants aged less than 6 months to 30 minutes in children aged more than 8 years. This delay in C(max) may also be related to the lower clearance observed in younger patients. Local anaesthetics are metabolised by cytochrome P450 (CYP). The main CYP isoforms involved are CYP3A4 for lidocaine and bupivacaine and CYP1A2 for ropivacaine. CYP3A4 is not mature at birth but is partly replaced by CYP3A7. The intrinsic clearance of bupivacaine is only one-third of that in adults at 1 month of age, and two-thirds at 6 months. CYP1A2 is not fully mature before the age of 3 years. Indeed, the clearance of ropivacaine does not reach its maximum before the age of 5 years. However, at birth this clearance is not as low as expected, and ropivacaine may be used even in younger patients.

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.

Patient-Controlled Epidural Analgesia Versus Continuous Epidural Infusion with Ropivacaine for Postoperative Analgesia in Children

Epidural ropivacaine infusion has been used in children; however, patient-controlled epidural analgesia (PCEA) has not been evaluated in the pediatric population. In this study, we compared the clinical efficiency of PCEA and of continuous epidural infusion analgesia (CEA) in children. Forty-eight children undergoing orthopedic surgery were randomized to receive PCEA or CEA with ropivacaine 0.2%. All patients underwent a standard general anesthetic. Children also received ketoprofen and propacetamol. Pain scores and side effects were recorded for 48 h. If the visual analog score scale score was >4 of 10, analgesia was considered inadequate, and rescue treatment was administered. Both groups obtained effective pain relief. Children in the PCEA group received significantly less local anesthetic than those in the CEA group (0.20 +/- 0.08 mg x kg(-1) x h(-1) versus 0.40 +/- 0.08 mg x kg(-1) x h(-1); P < 0.001). Motor effects, supplemental analgesic requirements, and side effects did not differ. We concluded that PCEA with ropivacaine 0.2% can provide adequate postoperative analgesia for pediatric orthopedic procedures with smaller dose requirements than CEA.

IMPLICATIONS

We studied patient-controlled epidural analgesia (PCEA) and continuous epidural infusion analgesia (CEA) with 0.2% ropivacaine during the postoperative period in children. We found that either PCEA or CEA with plain ropivacaine 0.2% provided adequate pain relief in children during the first 48-h postoperative course. However, adequate analgesia was obtained with 50% less volume infused with PCEA compared with CEA.

Benefit and risks of local anesthetics in infants and children

Regional anesthesia has become a routine part of the practice of anesthesiology in infants and children. Local anesthetic toxicity is extremely rare in infants and children; however, seizures, dysrhythmias, cardiovascular collapse, and transient neuropathic symptoms have been reported. Infants and children may be at increased risk from local anesthetics compared with adults. Larger volumes of local anesthetics are used for epidural anesthesia in infants and children than in adults. Metabolism and elimination of local anesthetics can be delayed in neonates, who also have decreased plasma concentrations of alpha(1)-acid glycoprotein, leading to increased concentrations of unbound bupivacaine. Most regional anesthetic procedures in infants and children are performed with the patient heavily sedated or anesthetized; because of this, and because a test dose is not a particularly sensitive marker of intravenous injection in the anesthetized patient, detection of intravascular local anesthetic injection is extremely difficult. The same local anesthetics used in adult anesthetic practice are also used in infants and children. Because of its extremely short duration of action, chloroprocaine has been used primarily for continuous epidural techniques in infants and children. The use of tetracaine has generally been limited to spinal and topical anesthesia. Lidocaine (lignocaine) has been used extensively in infants and children for topical, regional, plexus, epidural and spinal anesthesia. The association between prilocaine and methemoglobinemia has generally restricted prilocaine use in infants and children to the eutectic mixture of local anesthetics (EMLA). Because of its greater degree of motor block compared with other long-acting local anesthetics, etidocaine has generally been limited to plexus blocks in infants and children. Mepivacaine has been used for both plexus and epidural anesthesia in infants and children. Because postoperative analgesia is often the primary justification for regional anesthesia in infants and children, bupivacaine, a long-acting local anesthetic, is the most commonly reported local anesthetic for pediatric regional anesthesia. Given the lower toxic threshold of bupivacaine compared with other local anesthetics, the risk-benefit ratio of bupivacaine may be greater than that of other local anesthetics. Two new enantiomerically pure local anesthetics, ropivacaine and levobupivacaine, offer clinical profiles comparable to that of bupivacaine but without its lower toxic threshold. The extreme rarity of major toxicity from local anesthetics suggests that widespread replacement of bupivacaine with ropivacaine or levobupivacaine is probably not necessary. However, there are clinical situations, including prolonged local anesthetic infusions, use in neonates, impaired hepatic metabolic function, and anesthetic techniques requiring a large mass of local anesthetic, where replacement of bupivacaine with ropivacaine, levobupivacaine or (for continuous techniques) chloroprocaine appears prudent.

[Use of ropivacaine for peridural postoperative analgesia]

OBJECTIVES

To describe pharmacology and toxicology of ropivacaine. To assess the clinical efficacy of ropivacaine when used for postoperative epidural analgesia and to provide recommendations for clinical practice.

DATA SOURCES

Search in the Medline data base of original articles in French and English published since 1995, using the following key words: ropivacaine, postoperative analgesia, epidural, caudal block.

STUDY SELECTION

Prospective randomised studies in adults and children were selected. Letters to editors and editorials were excluded.

DATA EXTRACTION

Articles have been analyzed: to determine the dose of ropivacaine required for postoperative epidural analgesia, to assess the benefits of combination of epidural ropivacaine and additives (opioids or other), to compare epidural ropivacaine and bupivacaine and to assess the use of ropivacaine via caudal route for paediatric postoperative analgesia.

DATA SYNTHESIS

20 mg h-1 of ropivacaine is required to provide effective analgesia. This dose produces a motor block in a significant number of patients. Combination with an opioid allows for a reduction in ropivacaine requirement and subsequently in the incidence of motor blockade. In adults, equipotency ratio of ropivacaine and bupivacaine varies between 1.5/1 and 1/1 depending upon the concentration used. At equipotent doses, early postoperative mobilisation is facilitated with ropivacaine. In case of paediatric caudal analgesia, this ratio is close to 1.

CONCLUSIONS

Epidural ropivacaine combined with opioid provide good postoperative pain relief. Reduction in the incidence of motor blockade and safe toxicological profile make this local anaesthetic a suitable alternative of bupivacaine for postoperative epidural analgesia.

New concepts in acute and extended postoperative pain management in children

Increased knowledge of the pathophysiology of pain in children and an improved understanding of the pharmacology and pharmacodynamics of multiple agents have provided the clinician with a wide variety of tools to treat postoperative pain in children. The interest in a multimodal approach is kindled by the realization that the combination of a number of therapies can enhance analgesia with fewer untoward side effects. The expertise of other health care professionals should be tapped to open new avenues of treatment. Many therapies still require critical evidence-based evaluations to assess how well they work in larger patient populations. Dedication to research, compassionate patient care, and a willingness to teach the next generation of clinicians will bring us closer to the goal of safe and pain-free surgery.

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.

The dose-response relationship for clonidine added to a postoperative continuous epidural infusion of ropivacaine in children

Epidurally administered clonidine enhances the quality and duration of postoperative analgesia when it is used as an adjunct to local anesthetics in children. We investigated the dose-response relationship for epidural clonidine when added to a continuous postoperative epidural infusion of ropivacaine. By use of an observer-blinded design, 55 pediatric patients (1-4 yr old) were randomly given a postoperative epidural infusion of plain ropivacaine 0.1% 0.2 mg. kg(-1). h(-1) (Group R), ropivacaine 0.08% 0.16 mg. kg(-1). h(-1) plus clonidine 0.04 microg. kg(-1). h(-1) (Group RC1), ropivacaine 0.08% 0.16 mg. kg(-1). h(-1) plus clonidine 0.08 microg. kg(-1). h(-1) (Group RC2), or ropivacaine 0.08% 0.16 mg. kg(-1). h(-1) plus clonidine 0.12 microg. kg(-1). h(-1) (Group RC3). A clear dose-response relationship could be identified for a continuous infusion of epidural clonidine, with clonidine dosages in the 0.08-0.12 microg. kg(-1). h(-1) range providing improved postoperative analgesia (reduced Children's Hospital of Eastern Ontario pain score, increased time to first supplemental analgesic demand, and a reduced total number of doses of supplemental analgesics during the first 48 h after surgery). Analgesia was improved without any signs of increased sedation or other side effects. The adjunct use of epidural clonidine in the dosage range of 0.08-0.12 microg. kg(-1). h(-1) appears effective and safe for use in children.

IMPLICATIONS

The addition of clonidine (0.08-0.12 microg.kg(-1).h(-1))to a continuous epidural infusion of ropivacaine was found to improve postoperative pain relief in children. No clinically significant signs of sedation or other side effects were observed.

New insights into paediatric regional anaesthesia: new drugs

Over the years paediatric regional anaesthesia has gained a worldwide consensus, and it can now be considered a significant part of perioperative pain control in children. As in many fields, with the use of drugs administered epidurally there is a fundamental need for safety and efficacy. Two new local anaesthetic agents have recently entered the market, ropivacaine and levobupivacaine, which seem to offer a wider safety margin in comparison with the old drugs as well as valid pain control. To prolong their analgesic duration, many adjuvants can be used, and clonidine and ketamine are probably the best solution. This review summarizes the most recent data on these drugs and their use in children.

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.