The pharmacokinetics of caudal ropivacaine 0.2% in children. A study of infants aged less than 1 year and toddlers aged 1-5 years undergoing inguinal hernia repair

Ropivacaine as the drug of choice for regional anesthesia: why so?

While writing the article, we analyzed all the studies related to ropivacaine for the first half of 2021, which were published in PubMed. Previous review articles on ropivacaine were also analyzed. Purpose: collection and analysis of the latest research results on ropivacaine. Assessment of the place of ropivacaine in modern regional anesthesia.

Regional anesthesia in neonates and infants outside the immediate perioperative period: A systematic review of studies with efficacy and safety considerations

This review examines the quality and quantity of literature regarding methods that measure efficacy in the context of reported safety of regional anesthesia techniques in preterm and term infants <1 year of age. Because the role of anesthesiologists continues to expand outside the operating room, we focused on all relevant settings with assessments that extend beyond 24 hours from the intraoperative period. All study designs were included from a search of MEDLINE, EMBASE, CINAHL, Scopus, and Cochrane databases from 1946 to the end of 2019. A total of 31 studies were included (n = 1038 participants), consisting of five randomized controlled trials and 26 observational studies. Twenty-three studies examined neuraxial procedures, seven studies examined peripheral procedures, and one study examined both. Efficacy measures included pain assessment tools, analgesic use, and factors pertaining to the recovery of patients. Safety was assessed in multiple systems (neurological, cardiovascular, respiratory, pathological) and with vital signs and/or measures of systemic toxicity. Evidence in this review establishes that neuraxial and peripheral anesthesia treatments may be applied to neonates and infants with a high degree of safety. However, large gaps in the consistency of methods used to assess pain in these studies underline the need for rigorous prospective efficacy studies of these techniques in this population. This systematic review was registered on PROSPERO (CRD42018114466).

Neuraxial analgesia in neonates and infants: a review of clinical and preclinical strategies for the development of safety and efficacy data

Neuraxial drugs provide robust pain control, have the potential to improve outcomes, and are an important component of the perioperative care of children. Opioids or clonidine improves analgesia when added to perioperative epidural infusions; analgesia is significantly prolonged by the addition of clonidine, ketamine, neostigmine, or tramadol to single-shot caudal injections of local anesthetic; and neonatal intrathecal anesthesia/analgesia is increasing in some centers. However, it is difficult to determine the relative risk-benefit of different techniques and drugs without detailed and sensitive data related to analgesia requirements, side effects, and follow-up. Current data related to benefits and complications in neonates and infants are summarized, but variability in current neuraxial drug use reflects the relative lack of high-quality evidence. Recent preclinical reports of adverse effects of general anesthetics on the developing brain have increased awareness of the potential benefit of neuraxial anesthesia/analgesia to avoid or reduce general anesthetic dose requirements. However, the developing spinal cord is also vulnerable to drug-related toxicity, and although there are well-established preclinical models and criteria for assessing spinal cord toxicity in adult animals, until recently there had been no systematic evaluation during early life. Therefore, in the second half of this review, we present preclinical data evaluating age-dependent changes in the pharmacodynamic response to different spinal analgesics, and recent studies evaluating spinal toxicity in specific developmental models. Finally, we advocate use of neuraxial drugs with the widest demonstrable safety margin and suggest minimum standards for preclinical evaluation before adoption of new analgesics or preparations into routine clinical practice.

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.

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.

Regional anaesthetic techniques for neonatal surgery: indications and selection of techniques

The goal of neonatal care is to optimise the outcome of term and preterm infants with minimal suffering. Neonates are rare patients for the anaesthetist, therefore personal and even global experiences are limited. This chapter focuses on strategies for dealing with common clinical situations, e.g. heel lancing, obtaining vascular access, circumcision, hernia repair and pyloric stenosis, as well as major neonatal surgery. With the exception of heel lancing, regional techniques are useful in all cases. However, a careful risk-benefit analysis is mandatory, especially when considering more invasive techniques such as epidural catheters.

Postoperative pain control in children: a guide to drug choice

Postoperative pain in children can usually be well controlled with a combination of analgesics, including acetaminophen (paracetamol), NSAIDs, opioids, and local/regional anesthesia. Recent research has shown that the dosage of acetaminophen required to provide analgesia is higher than the traditional dosages used for the regulation of elevated body temperature. Rectal administration of acetaminophen gives a lower and more variable bioavailability compared with oral administration. There is growing experience with the use of NSAIDs in children and several studies have demonstrated the relatively strong analgesic potential of these drugs. Titration of opioids to analgesic effect, and the use of nurse- and patient-controlled continuous opioid infusions in children have gained widespread use and, with proper education and supervision, are considered excellent methods of pain control. Local peripheral and central blocks decrease the need for anesthetics during surgery and provide effective postoperative pain relief.

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.

[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.

The caudal catheter in neonates: where are the restrictions?

PURPOSE OF REVIEW

In neonates, epidural catheters inserted at the sacral hiatus can easily be advanced to a lumbar or thoracic level. These 'caudal catheters' are popular because they allow the neonate to benefit from epidural analgesia without the concerns of spinal cord injury potentially associated with primary thoracic placement in an asleep neonate. This review looks at use and benefits, and risks and complications of caudal epidural catheters in neonates.

RECENT FINDINGS

Restrictions of neonatal caudal catheters are related to risks associated with placement and advancement of the catheters, infectious risks of caudal catheters, and toxicity risks related to the higher free fraction and lower clearance of bupivacaine in neonates. Caudal catheters in neonates are popular, but evidence that they improve outcome is lacking.

SUMMARY

Epidural anesthesia and analgesia for neonates should be performed and managed by pediatric anesthesiologists. Potential risks and complications must be appreciated and all steps to maximize safety of the technique must be taken. In particular, close postoperative observation and pain service management are indispensable. Future research should investigate the risks of caudal and segmentally placed catheters in neonates, study the role of epidural analgesia in outcome improvement for neonates, and guide us to safer use of local anesthetics suitable for neonates with their pharmacologic immaturity.

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.

The pharmacokinetics of epidural ropivacaine in infants and young children

The pharmacokinetic variables of ropivacaine were characterized after epidural bolus injection in pediatric patients. The subjects, 7 infants (aged 3-11 mo) and 11 young children (aged 12-48 mo), received 1.7 mg/kg of ropivacaine via a lumbar epidural catheter. Total plasma concentrations of ropivacaine measured over 24 h were assayed by high-pressure liquid chromatography, and pharmacokinetic modeling was performed by Nonlinear Mixed Effects Modeling analysis. The median peak venous plasma concentrations (C(max)) in infants and young children were 610 microg/L (interquartile range [IQR], 550-725 microg/L) and 640 microg/L (IQR, 540-750 microg/L), respectively. The median times to maximum plasma ropivacaine concentration (T(max)) were 60 min (IQR, 60-120 min) in infants and 60 min (IQR, 30-90 min) in young children. There were no statistical differences between median values of C(max) and T(max) between infants and young children. The calculated clearance (CL) in infants was 4.26 mL x min(-1) x kg(-1) (9% coefficient of variation), and in young children it was 6.15 mL x min(-1) x kg(-1) (11% coefficient of variation). The CL for infants was significantly less than the CL for young children (P < 0.01). The volume of distribution was estimated to be 2370 mL/kg (9% coefficient of variation) for both young children and infants. No systemic toxicity was observed in either group.

IMPLICATIONS

This study revealed that the pharmacokinetic variables of lumbar epidural bolus ropivacaine in pediatric patients aged 3 to 48 mo are similar to those of adults, except that drug clearance was less in infants compared with older children.

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.