Ropivacaine pharmacokinetics after caudal block in 1-8 year old children

Methods of prolonging the effect of caudal block in children

Caudal epidural blockade is one of the most frequently administered regional anesthesia techniques in children. It is a supplement during general anesthesia and for providing postoperative analgesia in pediatrics for sub-umbilical surgeries, especially for genitourinary surgeries. However, the duration of the analgesic effect is occasionally unsatisfactory. In this review, we discuss the main advantages and disadvantages of different techniques to prolong postoperative analgesia for single-injection caudal blockade in children. A literature search of the keywords "caudal", "analgesia", "pediatric", and "children" was performed using PubMed and Web of Science databases. We highlight that analgesic quality correlates substantially with the local anesthetic's type, dose, the timing relationship between caudal block and surgery, caudal catheterization, and administration of epidural opioids or other adjuvant drugs.

The median effective concentration of ropivacaine for ultrasound-guided caudal block in children: a dose-finding study

PURPOSE

To determine the 50% minimum effective concentration (MEC50) and the 95% effective concentration (MEC95) of ropivacaine for ultrasound-guided caudal block during hypospadias repair surgery of pediatric patients.

METHODS

Children were enrolled with the American Society of Anesthesiologists (ASA) physical status I-II undergoing elective hypospadias repair surgery. Children were grouped into two age groups: toddlerhood (1-3 years old) and preschool (3-6 years old). We measured The MEC50 using Dixon's up-and-down method. The first children received the caudal block with 1.0 mL/kg of 0.15% ropivacaine. We determined each subsequent patient's concentration based on the previous patient's response and adjusted the concentration in intervals of 0.015%. Meanwhile, the probit regression analysis obtains 95% effective concentration (MEC95). In addition, we recorded the general condition, adverse events, and postoperative pain of each child.

RESULTS

46 children undergoing elective hypospadias repair surgery were included in this study, 22 in the toddlerhood group and 24 in the preschool group. Of the total number of patients, the caudal block was successful in 25 (54%) and failed in 21 (46%). The MEC50 of 1 ml/kg ropivacaine was 0.102% (95% CI 0.099%, 0.138%) in the toddlerhood group and 0.129% (95% CI 0.124%, 0.138%) in the preschool group. The MEC95 of 1 ml/kg ropivacaine was 0.148% (95% CI 0.131%, 0.149%) in the toddlerhood group and 0.162% (95% CI 0.134%, 0.164%) in the preschool group. Our results showed that ropivacaine concentration was statistically different between preschool children and toddlers (P < 0.001). None of the adverse events occurred.

CONCLUSIONS

This study showed that children in the preschool group required higher concentrations of ropivacaine than children in the toddler group during ultrasound-guided sacral block combined with non-intubated general anesthesia. At the same time, this method of anesthesia is safe and effective for children undergoing surgery for hypospadias.

Levobupivacaine plasma concentrations following repeat caudal anesthetics

AIM

A single caudal anesthetic at the start of lower abdominal surgery is unlikely to provide prolonged analgesia. A second caudal at the end of the procedure extends the analgesia duration but total plasma concentrations may be associated with toxicity. Our aim was to measure total plasma levobupivacaine concentrations after repeat caudal anesthesia in infants and to generate a pharmacokinetic model for prediction of plasma concentrations after repeat caudal anesthesia in neonates, infants and children.

METHODS

Infants undergoing definitive repair of anorectal malformations or Hirschsprung's disease received a second caudal anesthesia at the end of the procedure. Total levobupivacaine concentrations were assayed 3-4 times in the first 6 h after the initial caudal. These data were pooled with data from four studies describing plasma concentrations after levobupivacaine caudal or spinal anesthesia. Population pharmacokinetic parameters were estimated using nonlinear mixed-effects models. Covariates included postmenstrual age and body weight. Parameter estimates were used to simulate concentrations after a repeat levobupivacaine 2.5 mg kg^-1 caudal at 3 or 4 h following an initial levobupivacaine 2.5 mg kg^-1 caudal.

RESULTS

Twenty-one infants (postnatal age 11-32 weeks, gestation 37-39 weeks, weight 5.2-8.6 kg) were included. The measured peak plasma concentration after repeat caudal levobupivacaine 2.5 mg kg^-1 4 h after initial caudal was 1.38 mg L^-1 (95% prediction interval 0.60-2.6 mg L^-1 ) and 3 h after initial caudal was 1.46 mg L^-1 (0.60-2.80) mg L^-1 . Simulation of total plasma concentrations in neonates (7 kg, 57 weeks postmenstrual age) given caudal levobupivacaine 4 h after the initial caudal were 1.76 mg L^-1 (0.68-3.50) mg L^-1 if 2.5 mg kg^-1 levobupivacaine was used and 0.88 mg L^-1 (0.34-1.73) mg L^-1 if 1.25 mg kg^-1 of 0.125% levobupivacaine was used. In simulated older children (20 kg, 6 years), the mean maximum concentration was 1.43 mg L^-1 (0.60-2.70) mg L^-1 if 2.5 mg kg^-1 levobupivacaine was repeated at 3 h.

CONCLUSION

Repeat caudal levobupivacaine 2.5 mg kg^-1 at 3 h after an initial 2.5 mg kg^-1 dose does not exceed the concentration associated with systemic local anesthetic toxicity. In 2.5% of simulated neonates (weight 3.8 kg, PMA 40 weeks), repeat caudal anesthesia demonstrates broaching of the lower concentration limit associated with toxicity at both 3 and 4 h after initial caudal.

Peribulbar block combined with general anesthesia in babies undergoing laser treatment for retinopathy of prematurity: a retrospective analysis

Background and objectives

Currently there is no agreement regarding which one is the most adequate anesthetic technique for the treatment of retinopathy of prematurity. Peribulbar block may reduce the incidence of oculocardiac reflex and postoperative apnea. The goal of this study was to report the outcomes of peribulbar block, when combined with general anesthesia, for the laser treatment for retinopathy of prematurity, in premature babies.

Methods

A retrospective analysis of anesthetic records of all babies who underwent laser treatment for retinopathy of prematurity from January 2008 through December 2015 in a tertiary hospital was performed.

Results

During that period a total of six babies was submitted to laser treatment for retinopathy of prematurity, all under peribulbar block combined with general anesthesia. A single infratemporal injection of 0.15 mL.kg⁻¹ per eye ropivacaine 1% or 0.75% was performed. At the end of the procedure, all babies resumed spontaneous ventilation. No perioperative complications were reported.

Conclusions

Peribulbar block was a safe anesthetic technique in our sample considered.

[Peribulbar block combined with general anesthesia in babies undergoing laser treatment for retinopathy of prematurity: a retrospective analysis]

BACKGROUND AND OBJECTIVES

Currently there is no agreement regarding which one is the most adequate anesthetic technique for the treatment of retinopathy of prematurity. Peribulbar block may reduce the incidence of oculocardiac reflex and postoperative apnea. The goal of this study was to report the outcomes of peribulbar block, when combined with general anesthesia, for the laser treatment for retinopathy of prematurity, in premature babies.

METHODS

A retrospective analysis of anesthetic records of all babies who underwent laser treatment for retinopathy of prematurity from January 2008 through December 2015 in a tertiary hospital was performed.

RESULTS

During that period a total of six babies was submitted to laser treatment for retinopathy of prematurity, all under peribulbar block combined with general anesthesia. A single infratemporal injection of 0.15mL.kg^-1 per eye ropivacaine 1% or 0.75% was performed. At the end of the procedure, all babies resumed spontaneous ventilation. No perioperative complications were reported.

CONCLUSIONS

Peribulbar block was a safe anesthetic technique in our sample considered.

Optimum Concentration of Caudal Ropivacaine & Clonidine - A Satisfactory Analgesic Solution for Paediatric Infraumbilical Surgery Pain

INTRODUCTION

Ropivacaine is amide local anaesthetic pure S(-)enantiomer of bupivacaine. Its duration of analgesia is similar to that of Bupivacaine (in equivalent doses) but the motor block is slower in onset, less intense, shorter in duration for a given level of sensory block with lesser cardiac side effects but addition of an adjuvant like clonidine which is an imidazoline derivative has been studied for its sedative, anxiolytic and analgesic properties.

AIM

This study was aimed to show the optimum concentrations of Ropivacaine and Clonidine to maximize analgesia without side effects by evaluating its safety and efficacy.

MATERIALS AND METHODS

Sixty children aged 2-10 years of ASA grade 1, scheduled to undergo infraumbilical surgeries were randomly allocated to Group A & Group B of 30 each. Group A received 0.2% Ropivacaine with normal saline and Group B received 0.2% Ropivacaine and preservative free Clonidine 1μg/kg, the total volume of solution being 1ml/kg haemodynamic changes were monitored intraoperatively and haemodynamic parameters along with motor blockade, pain score and sedation score were assessed postoperatively.

STATISTICAL ANALYSIS

Done with unpaired student t and Mann-Whitney test.

RESULTS

The groups were comparable regarding demographic characterstics. The mean duration of analgesia was prolonged in group B (12+2.22 hours) than in group A (6.53+1.16 hours) with p-value <0.001 leading to less rescue analgesia in former group. None of the children in the groups had a pain score of ≥ 4 at the end of 2 hours. A 6.6% and 60% of group A children had score of ≥ 4 at the end of 4(th) & 6(th) hour respectively. None in Group B had a score of ≥ 4. At the end of 8(th) hour, only 6.6% of the children in Group B had a pain score of ≥ 4 whereas it was 33.33% in Group A which is statistically significant. No bradycardia or hypotension and no significant sedation.

CONCLUSION

Combination of Ropivacaine and Clonidine in the concentration used (0.2% ropivacaine and 1μg/kg of clonidine) can be optimal for postoperative analgesia in paediatric population.

Perioperative effects of caudal and transversus abdominis plane (TAP) blocks for children undergoing urologic robot-assisted laparoscopic surgery

INTRODUCTION

Regional anesthesia is often used in combination with general anesthesia for pediatric surgery, however, it is unknown if adjunctive regional blocks are beneficial to children undergoing urologic laparoscopic or robot-assisted laparoscopic (RAL) procedures.

OBJECTIVE

To compare perioperative outcomes in children with adjunctive caudal blocks, transversus abdominis plane (TAP) blocks, or no regional anesthesia for common RAL surgical procedures in pediatric urology.

STUDY DESIGN

Inclusion in this retrospective study was limited to children who underwent RAL renal or ureteral/bladder procedures and received a standardized regimen of scheduled intravenous ketorolac and oral acetaminophen for acute postoperative pain control, with opioids as needed (PRN). Perioperative outcomes were compared between patients with an adjunctive caudal block (n = 25), bilateral TAP blocks (n = 44), or no regional anesthesia (n = 51).

RESULTS

Children with a preoperative caudal block received less intraoperative opioids than children with TAP blocks or no regional anesthesia (p < 0.001). This difference was observed both for renal procedures (p < 0.01) and ureteral/bladder procedures (p = 0.01). Patients with caudal blocks were also the least likely to require postoperative antiemetics (p = 0.03). There were no significant differences between groups in postoperative opioid use, maximum pain scores within 6 and 24 hours postoperatively, or length of hospital stay (LOS). No complications attributable to regional blocks were identified by chart review.

DISCUSSION

Use of adjunctive caudal blocks for pediatric RAL renal or ureteral/bladder surgical procedures may reduce need for alternate analgesic and/or anesthetic agents intraoperatively, as well as decrease postoperative nausea and vomiting. These findings may be related, since nausea and vomiting are common side effects of opioids and inhalational anesthetics. Consideration of the potential impact of caudal blocks on general anesthetic requirements is timely in light of concerns regarding the risk of anesthetic neurotoxicity in young patients. There was no evidence of improved postoperative pain control or shorter LOS for children who received regional anesthesia. It is unknown if regional blocks would have a greater impact in the absence of scheduled pain medications, which all patients in our study received. Limitations of this study include its retrospective nature and moderate sample size. Future randomized controlled trials are necessary to provide a more definitive understanding of regional anesthesia's role in minimizing pediatric surgical and anesthetic morbidity.

CONCLUSION

Administration of caudal blocks should be considered for children of suitable age undergoing RAL surgery involving either the upper or lower urinary tract.

Comparison of ropivacaine and bupivacaine with fentanyl for caudal epidural in pediatric surgery

CONTEXT

Ropivacaine, s-enantiomer of amide local anaesthetic produces differential neural blockade with less motor blockade, cardiovascular and neurological toxicity makes it suitable for day case surgery in children.

AIMS

To compare the effectiveness of Inj. Ropivacaine (0.2 or 0.25%) or Inj. Bupivacaine (0.25%) with fentanyl in caudal block for intra and postoperative analgesia.

SETTINGS AND DESIGN

Double blind retrospective randomized study.

MATERIALS AND METHODS

All the patients (n=112) varying from age group 3.02 ± 3.29 years belonging to ASA I-IV were randomly allocated to receive caudal analgesia Group BF inj. Bupivacaine (0.25%, 2 mg/kg) + Inj. Fentany1 μg/kg (n=70) and group RF: Inj. Ropivacaine (0.25% or 0.2%, 2 mg/kg) + inj. Fentanyl 1 μg/kg (n=42). We monitored vitals and requirement of inhalational gases inraoperatively and also observed pain by pain score (Visual Analogue Score in verbal group and Objective Pain Scale in nonverbal group) and vitals postoperatively. We used rescue analgesics (inj. Paracetamol 5 mg/kg iv) when VAS score ≥4.

STATISTICAL ANALYSIS

Student's t-test.

RESULTS

Duration of analgesia was prolonged in both group RF and BF. Time for first rescue analgesic for group RF (6.1 ± 1.1 hr) compared to group BF (5.6 ± 0.9 hr). Haemodynamic stability and less requirement of inhalation agent intraoperatively with group RF than others.

CONCLUSIONS

Ropivacaine with Fentanyl found to be better combination for pediatric surgeries for below umbilical surgeries as an adjuvant to general anaesthesia or sole technique with chances of less complication with high success rate.

Effect of caudal clonidine on emergence agitation and postoperative analgesia after sevoflurane anaesthesia in children: Randomised comparison of two doses

BACKGROUND AND AIMS

Sevoflurane, a popular inhalational anaesthetic for children, has been associated with significant emergence agitation in the recovery phase. This study was intended to compare two doses of caudal clonidine added to ropivacaine 0.2% in order to decide on the optimal dose for prevention of sevoflurane induced emergence agitation (EA) and to get a meaningful prolongation of postoperative analgesia with minimal side effects.

METHODS

Sixty-one children aged 1-7 years (American Society of Anaesthesiologists physical status I-II) received standardized general anaesthesia with inhaled sevoflurane and caudal epidural block with 0.2% ropivacaine 1 ml/kg for sub-umbilical surgeries. They were assigned randomly to two groups: (I) clonidine 1 μg/kg added to caudal ropivacaine; (II) clonidine 2 μg/kg added to caudal ropivacaine. EA and postoperative analgesia were assessed using pain/discomfort scale score and face, legs, activity, cry, consolability (FLACC) score respectively.

RESULTS

EA was observed in 8 children (26.6%) in group I when compared to only 2 children (6.4%) in group II after first 15 min postoperatively. Incidences of EA at 15 min, as well as total incidence of agitation, were both significantly lower in group II when compared to group I with P < 0.05. Duration of analgesia in group I (12 [8-20] h) and group II (16 [8-20] h) was statistically comparable (P > 0.05). There was no difference in the incidence of sedation or complications.

CONCLUSION

Caudal clonidine 2 μg/kg added to 0.2% ropivacaine 1 ml/kg is suggested to be the optimal dose, for prevention of EA and meaningful prolongation of postoperative analgesia with minimal side-effects.

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.

Local anesthetics and their adjuncts

Local anesthetics (LA) block propagation of impulses along nerve fibers by inactivation of voltage-gated sodium channels, which initiate action potentials (1). They act on the cytosolic side of phospholipid membranes. Two main chemical compounds are used, amino esters and amino amides. Amino esters are degraded by pseudocholinesterases in plasma. Amino amides are metabolized exclusively by the liver. Only amide LAs will be considered in this article.

A retrospective audit of three different regional anaesthetic techniques for circumcision in children

Postoperative analgesia for male circumcision surgery has been traditionally provided by a landmark-based dorsal penile nerve block (DPNB-LM) or by caudal epidural analgesia (CEA). In this study we report on a retrospective analysis of the effectiveness and safety of CEA, DPNB-LM and ultrasound-guided dorsal penile nerve block (DPNB-US) in our institution over a six-year period. Information was gathered from each patient's medical record. A total of 216 circumcisions were performed on patients aged from five months to 15 years. One hundred and fifteen patients received CEA, 46 DPNB-LM and 55 DPNB-US. Patients in the DPNB-LM group required rescue morphine administration in the recovery unit more frequently (30.4%) than either the DPNB-US (3.5%) or CEA groups (3.6%). Similarly, the DPNB-LM group required a larger total dose of morphine, and had longer recovery ward stays than CEA or DPNB-US groups. Time to first analgesia was greatest for the CEA group while there was no significant difference between time to first analgesia for DPNB-LM and DPNB-US. Sixty-three percent of patients in the DPNB-LM group, 1.7% of CEA and 5.5% of the DPNB-US required intraoperative opiates (P < 0.0001). There was no difference in time to hospital discharge.

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.

Pharmacokinetic/pharmacodynamic modeling of anesthetics in children: therapeutic implications

Modeling the pharmacokinetics and pharmacodynamics of anesthetics in children is performed as a response to the clinical need for safe and efficacious administration of drugs with a low therapeutic index. Rates and concentrations of these drugs, which are the primary parameters used by anesthesiologists, depend on physiologic parameters that are markedly affected by development. Volatile anesthetics have been used for >50 years in pediatric patients. The pharmacokinetics of inhalation agents are context sensitive, but little difference between age groups has been described. These agents are not only eliminated unchanged by the lung but they are also metabolized by the liver. Halothane has Michaelis-Menten kinetics, with up to 40% of the administered dose metabolized by the liver. For volatile anesthetics, the effect measured is the minimum alveolar concentration (MAC) that leads to movement of the limb in response to skin incision in 50% of the patients studied. The MAC is higher in infants than in children and adults. Infants aged 6 months have a MAC 1.5-1.8 times the MAC observed in adults aged 40 years. Children have a greater clearance and volume of distribution of propofol than adults. In order to achieve similar plasma concentrations, children require three times the initial dose used in adults. In adults, an increased sensitivity to propofol has been demonstrated with aging, but nothing is known about the effects in children. However, it is clear that equipotent doses of propofol induce marked deleterious hemodynamic effects in infants compared with children. Regional anesthesia is used in pediatrics, both in combination with general anesthesia during surgery or alone for postoperative analgesia. A marked decrease in protein binding has been described in infants. In the postoperative period, a rapid increase in binding because of inflammation decreases the free fraction, but the free drug concentration remains constant because of the resulting decrease in total clearance. A low clearance because of liver function immaturity has been observed during the first year(s) of life for bupivacaine and ropivacaine. Pharmacodynamic interactions between general anesthesia and regional anesthesia need to be modeled. This is one of the future tasks for pharmacokineticists. Methods such as the Dixon up-and-down allocation and the isobolographic technique are promising in this field.

[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.

Levobupivacaine caudal anesthesia in children: a randomized double-blind comparison with bupivacaine

BACKGROUND

Levobupivacaine is the pure S-enantiomer of bupivacaine. Despite obvious benefits in the event of accidental intravascular injection there has been no studies demonstrating a clinically significant benefit to levobupivacaine over racemic bupivacaine for pediatric regional anesthesia. Given the similar pharmacokinetic profiles of both drugs the studies to date have been underpowered to demonstrate what is likely to be a small difference in clinical effectiveness. Our aim was to determine if there are significant differences in the clinical effectiveness of levobupivacaine compared with racemic bupivacaine for caudal anesthesia in children having lower abdominal surgery. A secondary aim was to determine if there are differences in the incidence of postoperative motor blockade between these agents.

METHODS

Three hundred and ten children ranging in age from 1 month to 10.75 years in age having lower abdominal surgery were enrolled. Patients were randomized in a double blind manner to receive a caudal block with either 0.25% bupivacaine (n = 152) or 0.25% levobupivacaine (n = 155) to a total volume of 1 ml x kg(-1). Motor blockade (modified Bromage scale) and postoperative pain or distress (FLACC behavioral scale for postoperative pain) were measured at predetermined time points during the subsequent 120 min.

RESULTS

There were no significant adverse effects attributable to levobupivacaine. Success rates were defined as a lack of hemodynamic response to first surgical incision and low postoperative pain scores. At a mean duration of 5 min between block completion and first incision success for 1 ml x kg(-1) of 0.25% bupivacaine was 91% and 94% for 0.25% levobupivacaine. Satisfactory postoperative analgesia was present in 98% of patients after bupivacaine caudal anesthesia and 97.5% for levobupivacaine. At 30 min following caudal anesthesia the incidence of postoperative motor block with racemic bupivacaine was 84% and decreased to 7% at 120 min. For levobupivacaine motor block at 30 min postcaudal was present in 85% and decreased to 11% at 120 min.

CONCLUSIONS

Levobupivacaine is an effective agent for caudal anesthesia in children at a recommended dose of 2.5 mg x kg(-1). The rapidity of onset was suitable for establishment of surgical anesthesia and postoperative analgesia was achieved in greater than 97.5% of patients. It appears to be of equivalent potency to racemic bupivacaine in children requiring lower abdominal surgery.

Some current controversies in paediatric regional anaesthesia

PURPOSE OF REVIEW

Controversial topics in paediatric regional anaesthesia are discussed.

RECENT FINDINGS

The performance of blocks under general anaesthesia, new local anaesthetics, adjuvants, location techniques, and risks of masking compartment syndromes are contemplated.

SUMMARY

The performance of regional blocks in anaesthetized patients is generally contra-indicated in adults but accepted in children. Levobupivacaine displays the same pharmacokinetic profile as racemic bupivacaine with possibly less cardiac toxicity. Ropivacaine undergoes slower absorption and, in some studies, concomitant increase in peak plasma concentration in infants. Conversely, continuous infusion of ropivacaine offers the safest therapeutic index. Many adjuvants have been used but only epinephrine, clonidine, and preservative-free ketamine offer clear advantages. Midazolam and neostigmine are effective but have potential drawbacks and raise safety questions. Needle and catheter positioning is critical. Electrocardiogram guidance and electrical stimulation occasionally help identify the migration of epidural catheters. Stimulating catheters might be useful for continuous peripheral blockade. Ultrasonography will probably become the reference technique for peripheral catheter placement. Patients at risk of compartment syndrome must be monitored (measurement of compartmental pressures); adequate pain management does not 'hide' this complication but, on the contrary, can facilitate early diagnosis since the increase in requirement for pain medication precedes other clinical symptoms by an average of 7.3 h.

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.

Anesthésiques locaux : qu'apportent les formes lévogyres ?

The use of levobupivacaine and of ropivacaine may increase the safety of regional anaesthesia. These pure enantiomers have similar pharmacokinetic properties as those of the racemic mixtures. However, they are less cardiotoxic than the racemic mixtures, especially at the high heart rate usually encountered in infants. We may then recommend the use of these agents in the paediatric patients.

A Mechanistic Approach for the Scaling of Clearance in Children

BACKGROUND AND OBJECTIVE

Clearance is an important pharmacokinetic concept for scaling dosage, understanding the risks of drug-drug interactions and environmental risk assessment in children. Accurate clearance scaling to children requires prior knowledge of adult clearance mechanisms and the age-dependence of physiological and enzymatic development. The objective of this research was to develop and evaluate ontogeny models that would provide an assessment of the age-dependence of clearance.

METHODS

Using in vitro data and/or in vivo clearance values for children for eight compounds that are eliminated primarily by one process, models for the ontogeny of renal clearance, cytochrome P450 (CYP) 3A4, CYP2E1, CYP1A2, uridine diphosphate glucuronosyltransferase (UGT) 2B7, UGT1A6, sulfonation and biliary clearance were developed. Resulting ontogeny models were evaluated using six compounds that demonstrated elimination via multiple pathways. The proportion of total clearance attributed to each clearance pathway in adults was delineated. Each pathway was individually scaled to the desired age, inclusive of protein-binding prediction, and summed to generate a total plasma clearance for the child under investigation. The paediatric age range included in the study was premature neonates to sub-adults.

RESULTS

There was excellent correlation between observed and predicted clearances for the model development (R2 = 0.979) and test sets (Q2 = 0.927). Clearance in premature neonates could also be well predicted (development R2 = 0.951; test Q2 = 0.899).

CONCLUSION

Paediatric clinical trial development could greatly benefit from clearance scaling, particularly in guiding dosing regimens. Furthermore, since the proportion of clearance via different elimination pathways is age-dependent, information could be gained on the developmental extent of drug-drug interactions.

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.

Vertical infraclavicular brachial plexus block in children: a preliminary study

BACKGROUND

Brachial plexus blockade is a well-established technique in upper limb surgery. Among the infraclavicular approaches, the vertical infraclavicular brachial plexus (VIP) block is easy to perform and has a large spectrum of nerve blockade. The aim of this preliminary study was to determine the ease, effectiveness, safety, and duration of the VIP block in pediatric trauma surgery.

METHODS

Fifty-five patients (ASA physical status I and II, age range 5-17 years old) scheduled for upper limb trauma surgery received a VIP block under light general anesthesia, using 0.5 ml x kg(-1) of ropivacaine 0.5%. The number of attempts and time to perform the block, the occurrence of a surgical response, the visual analogue score (VAS) scores, the incidence of complications and the duration of the block were evaluated.

RESULTS

The brachial plexus was found easily at the first or second attempt in 85% (47 of 55) of the cases, in 15% (eight of 55) of the cases it was localized after three to four attempts. The mean time to perform the block was 3.35 +/- 3.37 min. Ninety-eight percentage (54 of 55) of the blockades were effective for surgery and in just one case was ineffective. The VAS scores at the end of the procedure in 100% (55 of 55) of the cases were <3. There were no cases with clinical signs of pneumothorax nor inadvertent puncture of major vessels. Two patients developed a Horner's syndrome and in one a mild superficial hematoma at the puncture site occurred. The mean sensory block duration was 8.45 +/- 1.71 h and the mean motor block duration was 6.52 +/- 2.50 h.

CONCLUSIONS

In this preliminary study, the VIP block was easy to perform, effective and free of major complications for pediatric trauma surgery. With the doses of ropivacaine we used it was useful for intra- and postoperative analgesia.

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.

Comparison of caudal ropivacaine, ropivacaine plus ketamine and ropivacaine plus tramadol administration for postoperative analgesia in children

BACKGROUND

The aim of this study was to compare the effect of single-dose caudal ropivacaine, ropivacaine plus ketamine and ropivacaine plus tramadol in children for postoperative pain management.

METHODS

Following ethics committee approval and informed parental consent, 99 ASA PS I or II children, between 1 and 10 years of age, scheduled for elective inguinal hernia repair with general anaesthesia, were recruited. After induction of anaesthesia and placement of a laryngeal mask airway (LMATM), the patients were randomly divided into three groups to receive either caudal ropivacaine alone (0.4%, 2 mg x kg(-1)) in group R (n = 32) or ropivacaine (0.2%, 1 mg x kg(-1)) plus ketamine (0.25 mg x kg(-1)) in group RK (n = 33) or ropivacaine (0.2%, 1 mg x kg(-1)) plus tramadol (1 mg x kg(-1)) in group RT (n = 34) with a total volume of 0.5 ml x kg(-1). Systemic blood pressure (SBP and DBP), heart rate (HR), peripheral O2 saturation (SpO2), respiratory rate (RR), sedation and pain scores were recorded at 5, 10, 15 and 30 min, 1, 3, 4 and 6 h following recovery from anaesthesia. Pain was evaluated by Children's Hospital of Eastern Ontario Pain Scale, and sedation with a five-point sedation test.

RESULTS

No difference was found regarding age, weight and duration of operation between the groups (P > 0.05). No patient experienced hypotension, bradycardia or respiratory depression. Duration of analgesia was longer in group RT (1377 +/- 204 min) than group R (1006 +/- 506 min) (P = 0.001). In the tramadol group, fewer patients required supplementary analgesics in the first 24 h (P = 0.005). Sedation scores were below 2 in all groups. Incidence of postoperative nausea and vomiting was higher in group RT (eight patients) and group RK (seven patients) than group R (one patient, P = 0.032).

CONCLUSIONS

Ropivacaine (0.4%), ropivacaine (0.2%) plus ketamine (0.25 mg x kg(-1)) and ropivacaine (0.2%) plus tramadol (0.5 mg x kg(-1)) provided sufficient analgesia in children, but the duration of analgesia was longer in the RT group.

High plasma ropivacaine concentrations after fascia iliaca compartment block in children

BACKGROUND

The pharmacokinetic profile of local anaesthetics is influenced by the mode of administration. We sought to compare the pharmacokinetics of two doses of ropivacaine after fascia iliaca compartment (FIC) block in children.

METHODS

In this prospective, double-blind study, children received an FIC block as a part of their anaesthetic management during elective orthopaedic surgery on the thigh. They were randomized to receive ropivacaine 0.7 ml x kg(-1) using either a 0.375% or 0.5% solution. Venous blood samples were drawn up to 6 h after injection. Plasma concentrations of ropivacaine were measured by gas-liquid chromatography.

RESULTS

Six children (10.2 (range 5-15) yr, 35.6 (sd 10) kg were included. FIC block provided satisfactory peroperative pain relief. No signs of toxicity were observed, but high maximal plasma concentrations (C(max) 4.33-5.6 microg ml(-1)), were observed for three of four patients in the ropivacaine 0.5% group. The two patients in the 0.375% group showed values within the safe range (C(max) 0.66 and 0.98 microg ml(-1) respectively). Even though no toxic effects were observed, these results led us to discontinue the study.

CONCLUSIONS

The administration of ropivacaine 3.5 mg x kg(-1) can be associated with sustained high plasma concentrations of ropivacaine, outside the tolerable range. In view of these results, we recommend the use of lower ropivacaine dosage during FIC block in children.

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.

A comparison of three different concentrations of levobupivacaine for caudal block in children

We investigated three different concentrations of levobupivacaine (0.125%, 0.20%, and 0.25%; n = 20 in each group) for caudal blockade in a prospective, randomized, observer-blinded fashion in children (1-7 yr) undergoing subumbilical surgery. The duration of postoperative analgesia was assessed as the time to first administration of supplemental analgesia (based on a Childrens and Infants Postoperative Pain Scale score of >or=4), and the degree of immediate postoperative motor blockade was determined by use of a 3-point scale. A dose-response relationship was observed both with regard to median duration of postoperative analgesia (0.125%, 60 min; 0.20%, 118 min; 0.25%, 158 min) and the number of patients with evidence of early postoperative motor blockade (0.125%, 0; 0.20%, 4; 0.25%, 8). The 0.125% concentration was associated with significantly less early motor blockade (P = 0.003) but was found to result in a significantly shorter duration of postoperative analgesia (P < 0.05). Based on these results, the use of 0.20% levobupivacaine might represent the best clinical option if a plain levobupivacaine solution is to be used for caudal blockade in children.

IMPLICATIONS

The use of 0.125% levobupivacaine for caudal blockade (1 mL/kg) in children (1-7 yr) was associated with less early postoperative motor blockade but a shorter duration of postoperative analgesia compared with 0.20% and 0.25% solutions.

Ropivacaine in infants and children

PURPOSE OF REVIEW

Ropivacaine is considered less toxic than bupivacaine. In addition, at the low concentrations used for providing postoperative analgesia, ropivacaine seems to produce less motor blockade than bupivacaine. These two properties are of particular interest in paediatric practice.

RECENT FINDINGS

In paediatric practice regional anaesthesia is usually performed under general anaesthesia, and postoperative analgesia was until recently the major concern for most practitioners. The question now is: what is the right concentration to provide adequate intraoperative anaesthesia when ropivacaine is used in combination with volatile anaesthetic agents? The low concentration of ropivacaine used for postoperative analgesia seems to provide adequate intraoperative anaesthesia when general anaesthesia with a 0.5 minimum concentration of volatile anaesthetic is used in combination. However, potential toxicity is still the subject of debate because ropivacaine clearance is low in infancy and early childhood. Ropivacaine has a longer absorption process than bupivacaine, which leads to a lower maximum peak concentration with ropivacaine than with bupivacaine either after central or peripheral blocks, thus increasing the safety of the drug. The addition of adjuvant drugs also permits lower concentrations of ropivacaine, while providing excellent analgesia. The addition of adrenaline at very low concentrations has recently been found to increase the quality of epidural analgesia.

SUMMARY

Ropivacaine is now the reference drug for regional anaesthesia in paediatric patients, mainly because it is considered less toxic than bupivacaine and provides excellent postoperative analgesia even when used at low concentrations.

In children, the addition of epinephrine modifies the pharmacokinetics of ropivacaine injected caudally

PURPOSE

To describe the modification of the ropivacaine (R) pharmacokinetics produced by the addition of epinephrine (E).

METHODS

After Institutional Review Board approval, 18 ASA I boys received a caudal block (1 mL x kg(-1)) with either plain 0.2% R (Group E-) or with 0.2% R containing E (5 microg x mL(-1); Group E+). Venous blood samples were taken at zero, 15, 30, 60, 90, 120, 180, 240, 420, 720, 1440 min after caudal injection. Total R concentration in plasma was determined by high pressure liquid chromatography. Maximal concentration (C(max)) and time to peak concentration (T(max)) were obtained from the data, terminal half-life (T(1/2z)), clearance (Cl) and volume of distribution (Vd) were estimated by a non-compartmental approach. Subsequently, in order to determine the absorption rate (Ka) and to reduce to number of blood samples, 25 other children, receiving plain R and another group of 25 receiving the E solution were studied using a population approach (NONMEM). A one compartment model with first order absorption was used. The effect of weight, age and E on Cl, Vd and Ka was estimated.

RESULTS

C(max) was significantly lower in Group E+ (0.93 mg x L(-1) +/- 0.29 vs 0.61 mg x L(-1) +/- 0.28, P = 0.05) and T(max) occurred later (124 min +/- 53 vs 47 min +/- 16, P = 0.003). Weight was a significant covariate for Cl and Vd while E significantly slowed R Ka [Group I Ka 0.025 min(-1) [coefficient of variation (CV) 21%] vs 0.078 min(-1) (CV 25%) in Group II].

CONCLUSION

The addition of E significantly modifies the pharmacokinetics of R injected caudally.

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.

Paediatric caudal and epidural analgesia

PURPOSE OF REVIEW

Epidural blocks (caudal, lumbar or thoracic) are of common use in paediatric patients for special procedures such as open fundoplication as well as for postoperative analgesia. However, because neonates and infants have lower metabolic capacities and specific anatomy as compared to adults, the dose of local anaesthetics and the way of their administration need careful attention.

RECENT FINDINGS

Recent pharmacokinetic studies have more precisely identified the differences in pharmacokinetics between age groups, and between local anaesthetic agents. In that respect, ropivacaine exhibits a unique pharmacokinetic profile. Among all adjuvant drugs proposed so far, S-ketamine is promising; however, complete safety in case of injection into the cerebrospinal fluid must be checked before routine use. Thoracic epidural anaesthesia is technically difficult, and carries a potential risk of spinal cord puncture. Numerous techniques have been proposed to avoid this risk. The advancement of a catheter into the epidural space after caudal insertion has long been proposed by German and Italian authors, but for anatomical reasons, this technique is only possible in young infants. Some improvement of the original technique using lumbar insertion at the L4-L5 interspace has recently been suggested; the possibility of catheter guidance by means of electric stimulation has also been proposed.

SUMMARY

Pharmacokinetic studies allowing safer dosing, especially with ropivacaine have recently been published. New techniques of thoracic epidural with puncture at the lumbar level are also proposed. However, all these new techniques need to pass the test of time.

Practical pediatric regional anesthesia

In children, regional anesthetic techniques are safe and effective adjuncts to general anesthesia and for postoperative pain relief. Application of the techniques described in this article will contribute to improved care for pediatric patients undergoing surgical procedures. The judicious choice of local anesthetics, along with the blockades of targeted nerves, decrease the need for supplemental analgesics in the recovery phase.

Ropivacaine undergoes slower systemic absorption from the caudal epidural space in children than bupivacaine

We compared the systemic absorption of ropivacaine and bupivacaine after caudal epidural administration in children. Twenty ASA physical status I or II children aged 1-7 yr undergoing elective hypospadias repair were randomized after the induction of general anesthesia to receive a single caudal epidural injection of 2 mg/kg of either ropivacaine 0.2% (R) or bupivacaine 0.2% (B) in a double-blinded fashion. Peripheral venous blood samples (1 mL) were obtained before and 1, 5, 10, 15, 20, 30, 40, 50, 60, 70, 80, 90, and 120 min after the caudal injection. The total R and B concentration was measured in plasma by using high-performance liquid chromatography. All blocks were successful, and there were no complications. The peak plasma concentration (mean +/- SD) (R = 0.67 +/- 0.16 and B = 0.73 +/- 0.23 microg/mL) and the area under the plasma concentration curve (R = 61.9 +/- 20.6 and B = 62.7 +/- 18.2 microg x mL(-1) x min(-1)) were comparable between the two study groups. The median (range) time to attain peak plasma concentration was significantly slower in children who received ropivacaine (R = 65 [10-120] min and B = 20 [15-50] min, P < 0.05). We conclude that ropivacaine undergoes slower systemic absorption from the caudal epidural space in children than does bupivacaine.

IMPLICATIONS

We compared the systemic absorption of ropivacaine (0.2%) and bupivacaine (0.2%) after caudal epidural injection of 2 mg/kg in children aged 1-7 yr. Our results show that ropivacaine undergoes slower systemic absorption from the caudal epidural space in children than does bupivacaine.

The efficacy of caudal ropivacaine 1, 2 and 3 mg x l(-1) for postoperative analgesia in children

BACKGROUND

The aim of this double blind, randomized, comparative study was to assess the analgesic efficacy and incidence of motor block after caudal block using three different concentrations of ropivacaine, 1, 2 and 3 mg x l(-1), in children 4-12-year-old.

METHODS

One hundred and ten children ASA I-II, scheduled for inguinal surgery, were included in the study. After induction of a standardized general anaesthetic technique, all patients received 1 ml x kg(-1) of the ropivacaine solution for a caudal block and were assessed for 8 h after the injection.

RESULTS

The ropivacaine was well tolerated in all patients. Median time to treatment with analgesics was 3.3, 4.5 and 4.2 h in the 1, 2 and 3 mg x ml(-1) groups, respectively. During the first 4 h, the pain scores for both a 6-graded faces scale and a 4-graded observer scale were higher in the 1 mg x ml(-1) group than the 3 mg x ml(-1) group. The median sensory block reached T12 in all groups 1 h after the caudal block. Thereafter, the speed of regression was correlated with the ropivacaine concentration. In the patients with a sensory block from T12 and above, the median time to treatment with analgesics was longer than in the children with a sensory block below T12. The incidence of motor block was 28% in the 3 mg x ml(-1) group in comparison with 0 and 13% in the 1 and 2 mg x ml(-1) groups.

CONCLUSIONS

It was concluded that 1 ml x kg(-1) of ropivacaine 2 mg x ml(-1) for caudal block provided satisfactory postoperative pain relief after inguinal surgery in 4-12-year-old children. Ropivacaine 1 mg x ml(-1) showed less efficacy while the use of ropivacaine 3 mg x ml(-1) was associated with a higher incidence of motor block with minimal improvement in postoperative pain relief.

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.