Pharmacokinetics of bupivacaine following caudal anesthesia in infants

Comparative Methods to Predict Redosing of Bupivacaine and Ropivacaine in Truncal Catheters

BACKGROUND

Despite the frequent use of ropivacaine and bupivacaine, there is limited guidance on redosing of these medications after an initial bolus. Intermittent redosing is a clinical practice in the setting of nerve catheters, often utilizing large doses. Comparatively, theoretical elimination rates are available from pharmacokinetic studies, providing estimates on total body content of these drugs. The authors hypothesized that published redosing of bupivacaine and ropivacaine in clinical literature comported with safe elimination of the drugs based on pharmacokinetic studies.

METHODS

Clinical redosing of bupivacaine and ropivacaine were identified from previously published articles that used intermittent bolus dosing into the transversus abdominis plane and paravertebral space. The dosing data were fit to an exponential curve using least squares regression and 1/Y 2 weighting with the equation: Y = Y M - (Y M - Y 0 ) * e -k * x , where YM is the maximal dose (175 mg for bupivacaine, 210 mg for ropivacaine), Y0 is the dose at time zero, k is the elimination constant, and x is time. Both minimal ( i.e. , slowest) and average pharmacokinetic elimination constants for ropivacaine and bupivacaine were identified in the published literature. Clinical redosing was compared with pharmacokinetic elimination.

RESULTS

The maximal pharmacokinetic half-lives of bupivacaine and ropivacaine were 603 min (range, 154 to 2,970 min; N = 49) and 528 min (range, 204 to 3,276 min; N = 39), respectively. Clinically reported redosing of bupivacaine fit to an exponential curve with k bupi(clinical) = 0.077 h -1 , representing the 53.5th percentile of extracted pharmacokinetic minimal elimination constants. Clinically reported redosing of ropivacaine fit to a curve with k ropi(clinical) = 0.083 h -1 consistent with the 52nd percentile of minimal pharmacokinetic elimination constants.

CONCLUSIONS

Clinically reported redosing of bupivacaine and ropivacaine in the published literature reflect the slowest pharmacokinetic elimination based on human studies. The combined data without evidence of toxicity permit the authors to make practical recommendations about safe redosing of these agents.

Intravenous Lipid Emulsion for Managing Local Anesthetic Toxicity in a Three-Month-Old Patient

Local anesthetic systemic toxicity (LAST) is a well-known life-threatening local anesthetics complication, especially if given in inappropriate doses or routes. Therefore, physicians should be aware of LAST symptoms, such as neurological and cardiac symptoms. In addition, they should always consider it in the differential diagnosis when they encounter similar symptoms. The early recognition of LAST and initiation of intravenous lipid emulsion (ILE) can decrease mortality and morbidity rates. Multiple organizations and guidelines use ILE as standard LAST management. We present a three-month-old infant who received a caudal block that was complicated by an inadvertent intravascular injection that led to LAST cardiac symptoms. ILE successfully managed these symptoms, and the patient returned to normal vital signs without any complications.

Lipid emulsion treatment for local anesthetic systemic toxicity in pediatric patients: A systematic review

BACKGROUND

Local anesthetic systemic toxicity (LAST) is rare, but fatal; the current widely used treatment is lipid emulsion (LE). The goal of this study was to analyze and review case reports on LE treatment for LAST in pediatric patients.

METHODS

We performed a systematic review using case reports on LE treatment for LAST in pediatric patients, searching PubMed and Scopus databases to March 2023 using the following keywords: ("local anesthetic toxicity" OR "local anesthetic systemic toxicity" OR LAST") AND ("newborn" OR "infant" OR "child" OR "children" OR "adolescent" OR "pediatric") AND ("lipid emulsion" OR "Intralipid").

RESULTS

Our search yielded 21 cases, revealing that nearly 43% patients with LAST were less than 1 year old, and most cases were caused by bupivacaine (approximately 67% cases). "Inadvertent intravascular injection" by anesthesiologists and "overdose of local anesthetics" mainly by surgeons were responsible for 52% and 24% cases of LAST, respectively. LAST occurred in the awake state (52%) and under general anesthesia (48%), mainly causing seizures and arrhythmia, respectively. Approximately 55% of patients received LE treatment in <10 minutes after LAST, mainly improving cardiovascular symptoms. A 20% LE (1.5 mL/kg) dose followed by 0.25 mL/kg/minutes dose was frequently used. LE and anticonvulsants were mainly used in the awake state, whereas LE with or without vasopressors was mainly used under general anesthesia. LE treatment led to full recovery from LAST in 20 cases; however, 1 patient died due to underlying disease.

CONCLUSION

Consequently, our findings reveal that LE is effective in treating pediatric LAST.

Paediatric pain management: from regional to virtual

PURPOSE OF REVIEW

Due to increased interest in opioid-sparing multimodal analgesic strategies both inside and outside of the operating room, anaesthesiologists have started to look towards regional anaesthesia as well as nonpharmacological pain-reducing techniques. The purpose of this article is to discuss current trends and recent developments in regional anaesthesia and virtual reality for paediatric pain management.

RECENT FINDINGS

The development of novel fascial plane blocks has expanded regional options for anaesthesiologists, especially when neuraxial anaesthesia is not a viable or straightforward option. Other regional techniques, such as spinal anaesthesia and continuous epidural analgesia for infants and neonates, are becoming more popular, as more paediatric anaesthesiologists become familiar with these techniques. Virtual reality for paediatric pain management is a relatively new area of study that has shown promise, but more research needs to be done before widespread adoption of this practice becomes a reality. Various preexisting pain-reducing strategies such as distraction and biofeedback are being integrated with virtual reality to help optimize its effect on pain and anxiety for paediatric patients.

SUMMARY

Regional anaesthesia and virtual reality are valuable tools that serve to alleviate pain in paediatric patients. Advances are being made within both fields in various healthcare settings for different types of pain. Over the next few years, they will likely both play an increasing role in paediatric pain management.

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.

A multicenter study to evaluate the pharmacokinetics and safety of liposomal bupivacaine for postsurgical analgesia in pediatric patients aged 6 to less than 17 years (PLAY)

STUDY OBJECTIVE

To evaluate the pharmacokinetics and safety of liposomal bupivacaine in pediatric patients undergoing spine or cardiac surgery.

DESIGN

Multicenter, open-label, phase 3, randomized trial (PLAY; NCT03682302).

SETTING

Operating room.

PATIENTS

Two separate age groups were evaluated (age group 1: patients 12 to <17 years undergoing spine surgery; age group 2: patients 6 to <12 years undergoing spine or cardiac surgery).

INTERVENTION

Randomized allocation of liposomal bupivacaine 4 mg/kg or bupivacaine hydrochloride (HCl) 2 mg/kg via local infiltration at the end of spine surgery (age group 1); liposomal bupivacaine 4 mg/kg via local infiltration at the end of spine or cardiac surgery (age group 2).

MEASUREMENTS

The primary and secondary objectives were to evaluate the pharmacokinetics (eg, maximum plasma bupivacaine concentrations [C_max], time to C_max) and safety of liposomal bupivacaine, respectively.

MAIN RESULTS

Baseline characteristics were comparable across groups. Mean C_max after liposomal bupivacaine administration was lower versus bupivacaine HCl in age group 1 (357 vs 564 ng/mL); mean C_max in age group 2 was 320 and 447 ng/mL for spine and cardiac surgery, respectively. Median time to C_max of liposomal bupivacaine occurred later with cardiac surgery versus spine surgery (22.7 vs 7.4 h). In age group 1, the incidence of adverse events (AEs) was comparable between liposomal bupivacaine (61% [19/31]) and bupivacaine HCl (73% [22/30]). In age group 2, 100% (5/5) and 31% (9/29) of patients undergoing spine and cardiac surgery experienced AEs, respectively. AEs were generally mild or moderate, with no discontinuations due to AEs or deaths.

CONCLUSIONS

Plasma bupivacaine levels following local infiltration with liposomal bupivacaine remained below the toxic threshold in adults (~2000-4000 ng/mL) across age groups and procedures. AEs were mild to moderate, supporting the safety of liposomal bupivacaine in pediatric patients undergoing spine or cardiac surgery. Clinical trial number and registry URL: ClinicalTrials.gov identifier: NCT03682302.

Update on Local Anesthetic Toxicity, Prevention and Treatment During Regional Anesthesia in Infants and Children

Local anesthetic agents play a key role in the treatment and prevention of pain in children. Although generally safe and effective, as with any pharmacologic agent, adverse effects may occur with the administration of these medications. Systemic absorption or inadvertent systemic injection during bolus dosing or continuous infusion can result in local anesthetic systemic toxicity with life-threatening neurological and cardiac complications. The following article reviews the pharmacology of local anesthetic agents, outlines previous reports of systemic toxicity during regional anesthesia, and discusses prevention and treatment algorithms.

Prediction of levobupivacaine concentrations in neonates and infants following neuraxial rescue blocks

AIM

Pharmacokinetic simulation was used to characterize levobupivacaine disposition after regional anesthetic rescue for failed spinal anesthesia in neonates and infants.

METHODS

Population pharmacokinetics of levobupivacaine were estimated after spinal blockade in a cohort of neonates and infants (n = 25, postnatal age 5-18 weeks, gestation 21-41 weeks, weight 2.4-6 kg). Total levobupivacaine concentrations were assayed 3-4 times in the first hour after spinal levobupivacaine 1 mg kg^-1 administration. Parameters were estimated using nonlinear mixed-effects models and supported by priors. Covariates included postnatal age and total body weight. Parameter estimates were used to simulate total levobupivacaine concentrations after a primary spinal levobupivacaine 1 mg kg^-1 with rescue caudal levobupivacaine 1.5-2.5 mg kg^-1 .

RESULTS

A one-compartment model with a mature clearance 21.5 L h^-1  70 kg^-1 (CV 47.3%) and central volume 189 L 70 kg^-1 (CV 37%) adequately described time-concentration profiles. Clearance maturation was described using a maturation half-time of 11.5 weeks postnatal age. The absorption half-time for spinal levobupivacaine was 2.6 min (CV 56.8%). The upper (97.5% prediction) for peak concentrations after rescue caudal levobupivacaine were 1.5 mg kg^-1 , 2 mg kg^-1 , and 2.5 mg kg^-1 was 2.05 mg L^-1 , 2.5 mg L^-1 , and 2.9 mg L^-1 respectively.

CONCLUSION

Total bupivacaine concentrations greater than 2.5 mg L^-1 are associated with neurotoxicity in adults. Predicted concentrations after either a repeat spinal or a caudal rescue dose of levobupivacaine 1.5 mg kg^-1 1 h after spinal levobupivacaine administration are below the neurotoxic concentration threshold.

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).

Fundamentals and innovations in regional anaesthesia for infants and children

Regional anaesthesia in children has evolved rapidly in the last decade. Although it previously consisted of primarily neuraxial techniques, the practice now incorporates advanced peripheral nerve blocks, which were only recently described in adults. These novel blocks provide new avenues for providing opioid-sparing analgesia while minimising invasiveness, and perhaps risk, associated with older techniques. At the same time, established methods, such as infant spinal anaesthesia, under-utilised in the last 20 years, are experiencing a revival. The impetus has been the concern regarding the potential long-term neurocognitive effects of general anaesthesia in the young child. These techniques have expanded from single shot spinal anaesthesia to combined spinal/epidural techniques, which can now effectively provide surgical anaesthesia for procedures below the umbilicus for a prolonged period of time, thereby avoiding the need for general anaesthesia. Continuous 2-chloroprocaine infusions, previously only described for intra-operative regional anaesthesia, have gained popularity as a means of providing prolonged postoperative analgesia in epidural and continuous nerve block techniques. The rapid, liver-independent metabolism of 2-chloroprocaine makes it ideal for prolonged local anaesthetic infusions in neonates and small infants, obviating the increased risk of local anaesthetic systemic toxicity that occurs with amide local anaesthetics. Debate continues over certain practices in paediatric regional anaesthesia. While the rarity of complications makes comparative analyses difficult, data from large prospective registries indicate that providing regional anaesthesia to children while under general anaesthesia appears to be at least as safe as in the sedated or awake patient. In addition, the estimated frequency of serious adverse events demonstrates that regional blocks in children under general anaesthesia are no less safe than in awake adults. In infants, the techniques of direct thoracic epidural placement or caudal placement with cephalad threading each have distinct advantages and disadvantages. As the data cannot support the safety of one technique over the other, the site of epidural insertion remains largely a matter of anaesthetist discretion.

Treatment of Postoperative Pain in Pediatric Operations: Comparing the Efficiency of Bupivacaine, Bupivacaine-Dexmedetomidine and Bupivacaine-Fentanyl for Caudal Block

BACKGROUND

Caudal analgesia is a common method for postoperative pain management in pediatric patients. Additive agents such as opioids and α₂ agonists have been used to enhance the analgesic effects of local anesthetics for caudal block.

OBJECTIVES

The aim of this study was to compare the additive effects of dexmedetomidine and fentanyl on bupivacaine-induced caudal analgesia in pediatric patients who had undergone elective inguinal hernia repair.

METHODS

This randomized, double-blind clinical trial included children aged 1 - 5 years who were divided into three groups: the bupivacaine group (Group B) received 0.25% bupivacaine (1 ml/kg), the bupivacaine-dexmedetomidine group (Group BD) received 0.25% bupivacaine (1 mL/kg) plus 2 µg/kg dexmedetomidine, and the bupivacaine-fentanyl group (Group BF) received 0.25% bupivacaine (1 mL/kg) plus 2 µg/kg fentanyl. The hemodynamic variables (heart rate, systolic blood pressure, respiratory rate, and peripheral arterial oxygen saturation) were measured perioperatively. Pain, sedation and motor block scores and adverse events (nausea and vomiting, pruritis, hypotension, bradycardia, urinary retention and respiratory depression) were documented at 30 and 60 minutes, and the 1st, 2nd, 4th, 6th, 12th and 24th hours after the operation. The other recordings include the duration of surgery and analgesic requirement.

RESULTS

A total of 61 patients were analyzed. The lowest pain scores were found in the BD group at all time points (P < 0.001). The sedation scores were higher in the BD group than in the other two groups at all time points (P < 0.001). No motor block was observed after the operation. Only three patients required analgesic administration 2 to 6 hours after the operation in group B. No side effects were observed in any of the groups, and there was no significant difference in the duration of surgery among the three groups.

CONCLUSIONS

The results show that the analgesic and sedative effects were better when dexmedetomidine was added to bupivacaine than when fentanyl was added or bupivacaine alone was administered in the pediatric population studied here that underwent elective inguinal hernia repair.

Continuous Lidocaine Infusions to Manage Opioid-Refractory Pain in a Series of Cancer Patients in a Pediatric Hospital

BACKGROUND

Research on the safety and efficacy of continuous lidocaine infusions (CLIs) for the treatment of pain in the pediatric setting is limited. This article describes a series of pediatric oncology patients who received lidocaine infusions for refractory, longstanding, cancer-related pain.

PROCEDURE

This is a retrospective review of patients who underwent lidocaine infusions to manage severe, opioid-refractory, cancer-related pain. Four patients ranging in age from 8 to 18 years were admitted to a pediatric hospital for their medical conditions and/or pain management. Structured chart review established demographic and diagnosis information, infusion rates, side effects, and efficacy of infusions in providing pain relief. Lidocaine bolus doses, infusion rates, serum concentrations, and subjective pain scores were analyzed.

RESULTS

Median pain scores prior to lidocaine infusions were 8/10, falling to 2/10 at the infusion termination (P < 0.003), and rising to 3/10 in the first 24 hr after lidocaine (P < 0.029 compared to preinfusion pain). The infusions were generally well tolerated, with few side effects noted. In most cases, the improvement in pain scores persisted beyond termination of the infusion.

CONCLUSIONS

CLIs were a helpful adjuvant in the four cases presented and may be an effective therapy for a more diverse array of refractory cancer pain. The majority of patients experienced pain relief well beyond the metabolic elimination of the lidocaine, corroborating a modulation effect on pain windup. Additional research regarding infusion rates, serum concentrations, side effects, and outpatient follow-up in a larger group of patients will provide additional insight into the role and safety of this therapy in children.

Pharmacokinetics of levobupivacaine following infant spinal anesthesia

BACKGROUND

Infant spinal anesthesia with levobupivacaine has been promoted as a technique to reduce both the risk of postoperative apnea and exposure to volatile anesthesia. There is, however, no pharmacokinetic data to support the currently recommended doses.

AIMS

Our aim was to determine whether infant levobupivacaine spinal anesthesia is associated with plasma concentrations consistent with a low risk of local anesthetic systemic toxicity.

METHODS

This was an open-label pharmacokinetic safety and tolerability study of levobupivacaine spinal anesthesia in infants <55 weeks Post Menstrual Age undergoing lower abdominal surgery. Infants received a spinal anesthetic with levobupivacaine 1 mg·kg(-1) in the left lateral position.

RESULTS

Spinal anesthesia was successful in 25 (86.2%) of 29 infants (postmenstrual age 36-52 weeks; weight 2.2-4.7 kg). The median (IQR) total venous levobupivacaine plasma concentrations was 0.33 (0.25-0.42) μg·ml(-1) and unbound venous levobupivacaine was 19.5 (14.5-38) ng·ml(-1) . Median protein binding was 93.5 (91.4-96%). Alpha-1 acid glycoprotein concentrations were 0.25 (0.17-0.37) g·l(-1) and albumin concentrations were 29 (24-32) g·l(-1) .

CONCLUSION

Total plasma concentrations and unbound (free) concentration of levobupivacaine were consistently lower than concentrations reported in cases of pediatric local anesthetic toxicity. In a small number of infants requiring a repeat spinal of 1 mg·kg(-1) was also associated with acceptable total and free concentrations. We conclude that levobupivacaine at 1 mg·kg(-1) is associated with no systemic side effects in infants receiving awake spinal anesthesia.

Ontogeny of plasma proteins, albumin and binding of diazepam, cyclosporine, and deltamethrin

BACKGROUND

To characterize the ontogeny of plasma albumin and total proteins, due to the lack of a comprehensive pediatric database. Secondly, to establish the magnitude and duration of maturational changes in binding of highly-bound drugs/chemicals.

METHODS

Anonymized plasma samples from 296 donors were pooled in 6 age brackets from birth to adolescence. Total protein and albumin levels were measured in each age group, as was the age-dependency of plasma binding of diazepam (DZP), cyclosporine (CYC), and deltamethrin (DLM), a pyrethroid insecticide.

RESULTS

Plasma levels of albumin and total proteins steadily increased for the first 1-3 y of life. Unbound DZP and CYC fractions were elevated three- to fourfold in neonates, but decreased to adult levels after 1 and 3 y, respectively. Unbound DLM levels exceeded those in adults for just 1 mo.

CONCLUSION

Neonates and infants under 1-3 y may be at risk from increased amounts of free drug, when given standard doses of some highly-bound drugs. Pyrethroid insecticides might be anticipated to pose increased risk for 1 mo.

Regional anaesthesia in neonates, infants and children: an educational review

Prophylactic analgesia with local anaesthesia is widely used in children and has a good safety record. Performing regional blocks in anaesthetised children is a safe and generally accepted practice. When compared with adults, lower concentrations of local anaesthetics are sufficient in children; the onset of a block occurs more rapidly but the duration is usually shorter. Local anaesthetics have a greater volume of distribution, a lower clearance and a higher free (non-protein-bound) fraction. The recommended maximum dose has to be calculated for every individual. Peripheral blocks provide analgesia restricted to the site of surgery, and some of them have a very long duration of action. Abdominal wall blocks, such as transverse abdominis plane or ilio-inguinal nerve block, should be performed with the aid of ultrasound. Caudal anaesthesia is the single most important technique. Ropivacaine 0.2% or levobupivacaine 0.125 to 0.175% at roughly 1 ml  kg⁻¹ is adequate for most indications. Clonidine and morphine can be used to prolong the duration of analgesia. Ultrasound is not essential for performing caudal blocks, but it may be helpful in case of anomalies suspected at palpation and for teaching purposes. The use of paediatric epidural catheters will probably decline in the future because of the potential complications.

Continuous chloroprocaine infusion for thoracic and caudal epidurals as a postoperative analgesia modality in neonates, infants, and children

BACKGROUND

Neonates and infants have decreased metabolic capacity for amide local anesthetics and increased risk of local anesthetic toxicity compared to the general population. Chloroprocaine is an ester local anesthetic that has an extremely short plasma half-life in infants as well as adults. Existing reports support the safety and efficacy of continuous chloroprocaine epidural infusions in neonates and young infants during the intraoperative period. Despite this, continuous chloroprocaine epidural infusion may be an under-utilized method of postoperative analgesia for this patient population. In particular, it may improve pain control in neonates and infants with incisions stretching many dermatomes or those with hepatic impairment.

METHODS

We retrospectively reviewed our experience over 4 years with continuous chloroprocaine epidural infusions in neonates, infants, and children with a focus on the postoperative management of pain.

RESULTS

Twenty-one pediatric patients received continuous 2-chloroprocaine epidural infusions for postoperative pain management from January 2010 to April 2014 for thoracic, abdominal, and limb procedures. The epidural infusion consisted of 1.5% chloroprocaine or 1.5% chloroprocaine with fentanyl. Tabulating the morphine and hydromorphone used for rescue analgesia, the median (interquartile range) opioid consumption (mg·kg(-1) ·day(-1) of intravenous morphine equivalents) for the first, second, and third 24-h postoperative periods were 0.02 (0-0.48), 0.30 (0-0.44), and 0.14 (0-0.29), respectively. Examining the total fentanyl usage, the median (interquartile range) fentanyl consumption (μg·kg(-1) ·day(-1)) for first, second, and third 24-h postoperative periods were 3.89 (0.41-7.24), 0 (0.00-4.06), and 0 (0.00-0.51), respectively. The median N-PASS score assessed every 6 h from 0 to 72 h postoperatively was 0, 1, 2, 0, 0, 1, 0, 0, 0, 0, 1, 0, and 0, respectively. The median FLACC score assessed every 6 h from 0 to 72 h postoperatively was 0, 0, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, and 0, respectively.

CONCLUSION

The results suggest that chloroprocaine offers an efficacious alternative to the amide local anesthetics for postoperative epidural analgesia in the pediatric population.

Neonatal pain management

The past 2-3 decades have seen dramatic changes in the approach to pain management in the neonate. These practices started with refuting previously held misconceptions regarding nociception in preterm infants. Although neonates were initially thought to have limited response to painful stimuli, it was demonstrated that the developmental immaturity of the central nervous system makes the neonate more likely to feel pain. It was further demonstrated that untreated pain can have long-lasting physiologic and neurodevelopmental consequences. These concerns have resulted in a significant emphasis on improving and optimizing the techniques of analgesia for neonates and infants. The following article will review techniques for pain assessment, prevention, and treatment in this population with a specific focus on acute pain related to medical and surgical conditions.

Combined use of neuraxial and general anesthesia during major abdominal procedures in neonates and infants

With the advent of ultrasound and improvements in equipment, the applications of regional anesthesia in the pediatric population have continued to expand. Although frequently used for postoperative analgesia or as a means of avoiding general anesthesia in patients with comorbid conditions, the adjunctive use of regional anesthesia during general anesthesia may effectively decrease the intraoperative requirements for intravenous and volatile agents, thereby providing a more rapid awakening and earlier tracheal extubation. More recently, the limitation of the requirements for volatile and other anesthetic agents may be desirable, given concerns regarding the potential impact of these agents on neurocognitive outcome in neonates and infants. Several authors have demonstrated the potential utility of combining a neuraxial technique (spinal or epidural anesthesia) with general anesthesia in neonates and infants undergoing intraabdominal procedures. We review the literature regarding the combined use of neuraxial and general anesthesia in neonates and infants during major abdominal surgery, discuss its potential applications in this population, and review the techniques of such practice.

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.

Acute pain management in children

The greatest advance in pediatric pain medicine is the recognition that untreated pain is a significant cause of morbidity and even mortality after surgical trauma. Accurate assessment of pain in different age groups and the effective treatment of postoperative pain is constantly being refined; with newer drugs being used alone or in combination with other drugs continues to be explored. Several advances in developmental neurobiology and pharmacology, knowledge of new analgesics and newer applications of old analgesics in the last two decades have helped the pediatric anesthesiologist in managing pain in children more efficiently. The latter include administering opioids via the skin and nasal mucosa and their addition into the neuraxial local anesthetics. Systemic opioids, nonsteroidal anti-inflammatory agents and regional analgesics alone or combined with additives are currently used to provide effective postoperative analgesia. These modalities are best utilized when combined as a multimodal approach to treat acute pain in the perioperative setting. The development of receptor specific drugs that can produce pain relief without the untoward side effects of respiratory depression will hasten the recovery and discharge of children after surgery. This review focuses on the overview of acute pain management in children, with an emphasis on pharmacological and regional anesthesia in achieving this goal.

Combined regional and general anesthesia for ambulatory peripheral orthopedic surgery in children

Pediatric orthopedic surgery is rarely done in an outpatient setting because of the postoperative pain. The purpose of this study was to evaluate the children's comfort and parents' satisfaction after ambulatory peripheral pediatric orthopedic surgery performed under general anesthesia combined with regional anesthesia (RA). Sixty consecutive children were enrolled in this prospective study. All children fulfilled inclusion criteria for outpatient and for RA and parents received proper information regarding their child postoperative care. Postoperative pain control was sustained for 48 h using routine paracetamol, ibuprofen, and oral tramadol if needed. A telephone survey was conducted on day 1 and day 2 to evaluate pain scores, limb motor function, occurrence of postoperative nausea and vomiting, and feeding, sleep or play disturbance. The parents were also asked about their overall satisfaction rate and the choice of ambulatory mode versus inpatient admission in case of future orthopedic procedure. A total of 34 soft tissue procedures and 26 bony procedures were performed. 63.3% recovered motor function before discharge from the postanesthesia care unit. Low pain scores and good postoperative comfort were observed. Parents' satisfaction was greater than eight out of 10 in 88.3% of the cases, and 85% of the parents would choose ambulatory surgery in case of a second procedure. RA used with level I or II analgesics is compatible with ambulatory peripheral pediatric orthopedic surgery. Resulting good analgesia and postoperative comfort render the ambulatory mode to be favored by the parents.

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.

Anesthesia and analgesia during and after surgery in neonates

BACKGROUND

Historically, the use of anesthetics and analgesics in neonates and infants has been based on extrapolations from studies performed in adults and older children. Over the past 20 years, there has been a growing body of research on the clinical pharmacology and clinical outcomes of these agents in neonates and infants.

OBJECTIVE

This article summarizes clinical pharmacology and clinical outcomes studies of opioids, opioid antagonists, sedative-hypnotics, nonsteroidal anti-inflammatory drugs and acetaminophen, and local anesthetics in neonates and infants to highlight gaps in the available knowledge, review some concerns about study design, and identify drugs that should receive high priority for future study.

METHODS

Relevant studies were identified through a search of MEDLINE and a review of textbooks, conference proceedings, and abstracts. The available literature was subjected to expert committee-based review.

CONCLUSIONS

There is a growing body of information on analgesic and anesthetic pharmacokinetics, pharmacodynamics, and clinical outcomes in neonates and infants, permitting safe and effective use in some clinical settings. Major gaps in knowledge persist, however. Future research may involve a combination of clinical trials and preclinical studies in suitable infant animal surrogate models.

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.

Caudal Regional Anesthesia, Ropivacaine Concentration, Postoperative Analgesia, and Infants

In this randomized, double-blind trial we evaluated the quality and duration of analgesia and motor effects after caudal block using 1 mL/kg of ropivacaine 0.1% (Group 1), 0.15% (Group 2), 0.175% (Group 3) compared to 0.2% (Group 4) in infants 1-12 mo old. Postoperatively, the number of infants who received pain medication differed among the groups (P < 0.0005). There were more infants in Groups 1 and 2 compared with Group 4 and there was no difference between Groups 3 and 4. In the postanesthesia care unit, infants in Groups 1 and 2 received more pain medication than did those in Group 4 (P = 0.0098). In the day surgery unit, there was a significant difference among the groups (P = 0.0326); infants in Groups 3 and 4 required no pain medication. The analgesia duration differed among the groups (P = 0.034). Infants in Groups 1 and 2 had a shorter duration, and there was no difference between Groups 3 and 4. Infants in Group 4 took longer to regain their motor power compared with those in Group 3 (P = 0.0347). We conclude that in infants, ropivacaine 0.175% provided postoperative analgesia and duration similar to that of ropivacaine 0.2%, whereas ropivacaine 0.1% and 0.15% did not, and it was associated with fewer motor effects.

Liquid chromatography–electrospray mass spectrometry determination of free and total concentrations of ropivacaine in human plasma

A specific and sensitive liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS) method was developed for the determination of free and total ropivacaine in human plasma. The work-up procedure involved a simple precipitation of plasma proteins with methanol. Etidocaine served as the internal standard. After microscale equilibrium-dialysis, measurement of free ropivacaine levels was performed after direct injection of the dialysate into the chromatograph. The system used a Zorbax eclipse XD8 C8 analytical column packed with 5 microm diameter particles as the stationary phase. The mobile phase consisted of a 15-min gradient (mobile phase A: 0.05% (v/v) trimethylamine in acetonitrile, mobile phase B: 2mM ammonium formate buffer (pH 3)). Mass spectrometric data were acquired in single ion monitoring mode at m/z 275 for ropivacaine and m/z 277 for etidocaine. The drug/internal standard peak area ratios (plasma) or peak areas (dialysate) were linked via a quadratic relationship to concentrations. Precision ranged from 1 to 7.6% accuracy was between 92.6 and 109%. The lower limits of quantitation were 1 microg/l in plasma and 2 microg/l in the dialysate. This method was found suitable for the analysis of plasma samples collected during a clinical trial performed in 30 infants undergoing epidural anaesthesia or continuous psoas compartment block.

Postoperative pain management in children

There is increased awareness of the need for effective postoperative analgesia in infants and young children. A multi-modal approach to preventing and treating pain usually is used. Mild analgesics, local and regional analgesia, and opioids when indicated, frequently are combined to minimize adverse effects of individual drugs or techniques.

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.

Pharmacokinetics of levobupivacaine 0.25% following caudal administration in children under 2 years of age † †Declaration of interest. This work was funded by Chiroscience Limited, Cambridge, UK

BACKGROUND

Levobupivacaine, the S(-)enantiomer of racemic bupivacaine is less cardiotoxic than racemic bupivacaine and the R(+)enantiomer dexbupivacaine, while retaining similar local anaesthetic properties and potency to racemic bupivacaine. The pharmacokinetic profiles of the two bupivacaine enantiomers differs and that of racemic bupivacaine may be age dependent. We examined the pharmacokinetics of levobupivacaine after its single shot caudal epidural administration in children.

METHODS

An open-label phase 2 study was undertaken to examine the pharmacokinetics of levobupivacaine 0.25% 2 mg kg(-1) in 49 children aged less than 2 yr, after single shot caudal epidural administration. Plasma concentrations were determined at intervals up to 60 min after caudal injection.

RESULTS

Time to peak plasma concentration (T(max)) ranged between 5 and 60 min (median 30 min) and was reached later in children aged less than 3 months (P<0.005). Peak plasma concentration (C(max)) ranged between 0.41 and 2.12 micro g ml(-1) (median 0.80, mean (SD) 0.91 (0.40) micro g ml(-1)).

CONCLUSION

After the caudal epidural administration of levobupivacaine 2 mg kg(-1) in children less than 2 yr of age, C(max) was within the accepted safe range for racemic bupivacaine. T(max) varied and occurred later in some children, particularly those aged less than 3 months. Sampling in future pharmacokinetic studies in this age group should extend beyond 60 min.

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.

Awake spinal or caudal anaesthesia in preterms for herniotomies: what is the evidence based benefit compared with general anaesthesia?

PURPOSE OF REVIEW

Postoperative apnoea is known to threaten preterm and ex-preterm infants undergoing surgery for inguinal hernia. Awake regional anaesthesia, initially spinal and later caudal anaesthesia have been suggested as effective techniques to avoid these complications. However, most herniotomies in this group of patients are still performed under general anaesthesia without deleterious consequences. Whereas some experts continue to claim advantages for awake regional over general anaesthesia for preterm infants, others consider awake regional anaesthesia to be an exclusive, technically difficult and unreliable technique of unconfirmed benefit.

RECENT FINDINGS

It is appropriate to weigh the scarce available evidence that has been accumulated since 1984, and put it into perspective with new developments in paediatric general anaesthesia. The actual clinical significance of postoperative apnoea and improvements in neonatal and perioperative care and monitoring must also be reconsidered.

SUMMARY

The available evidence does not allow unequivocal conclusions to be drawn or recommendations to be made. Awake regional anaesthesia for herniotomies in preterm infants has been found to be superior in most studies; however, it requires technical expertise and dedication on the part of the anaesthetist and surgeon. When light general anaesthesia with modern anaesthetic agents such as sevoflurane or desflurane is combined with a caudal block, postoperative apnoea is very rare, and can easily be recognized and managed with good postoperative monitoring and therapy.

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.

Efficacy and safety of caudal injection of levobupivacaine, 0.25%, in children under 2 years of age undergoing inguinal hernia repair, circumcision or orchidopexy

BACKGROUND

Levobupivacaine is the S(-)-enantiomer of racemic bupivacaine. Evidence suggests that it is less cardiotoxic than racemic bupivacaine and the R(+)-enantiomer, dexbupivacaine, while retaining similar local anaesthetic properties and potency to racemic bupivacaine.

METHODS

This was an open study designed to assess the efficacy and safety of 0.25% levobupivacaine administered as a caudal injection at a dose of 2 mg.kg(-1) to 49 paediatric patients aged less than 2 years old undergoing circumcision (group 1), or hernia repair or orchidopexy (group 2).

RESULTS

Adequate analgesia (an increase of <20% in pulse or respiratory rate compared with baseline and an absence of gross movement on application of surgical stimulus) was achieved in 43/48 patients evaluable for efficacy (89.6%). All 22 patients in the circumcision group had adequate analgesia, and two of these patients did not require additional analgesia. The mean time to the use of additional analgesia was 7.3 h. Only one event (a mild rash) was considered possibly related to study medication.

CONCLUSIONS

Levobupivacaine is a promising new local anaesthetic agent for pain management in paediatric patients and appears to offer similar anaesthetic efficacy to racemic bupivacaine with a potentially improved tolerability profile.

Caudal block with 4 mg x kg-1 (1.6 ml x kg-1) of bupivacaine 0.25% in children undergoing surgical correction of congenital pyloric stenosis

BACKGROUND

Since 1970, bupivacaine 0.25% in a dose of 4 mg x kg-1 (1.6 ml x kg-1) has been used at the Hospital Infantil de México for caudal block in children undergoing surgical correction of congenital pyloric stenosis (CPS). Although this dose is considered unsafe, in our experience, it has been associated with a high success rate and a low incidence of adverse events. This experience has not been previously documented.

METHODS

A retrospective cohort of patients undergoing surgical correction of CPS was studied. Nineteen patients received general anaesthesia while 223 received caudal block. The latter were then grouped according to the sedation technique. The rate of successful caudal blocks and complications were considered the major outcomes of the study, whereas the postsurgical fasting period and hospital stay were considered secondary outcomes.

RESULTS

The rate of success of caudal block was 96%. Anaesthetic complications related to bupivacaine were present in 1.3%. Mortality occurred in the postoperatory period in one septic patient who also was suffering from gastroschisis that required general anaesthesia. Postoperatory fasting period and hospital stay tended to be higher with general anaesthesia than caudal block. However, of the 19 patients receiving general anaesthesia, five suffered serious comorbidity and nine were failed caudal blocks.

CONCLUSIONS

Caudal block with bupivacaine 0.25% (4 mg x kg-1) was associated with a low rate of anaesthetic complications. Further prospective studies to clarify the risks and benefits are required.

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.