Minimum local analgesic concentration of ropivacaine for intra‐operative caudal analgesia in pre‐school and school age children

Abstract

SummaryWe compared the minimum local analgesia concentration of ropivacaine for intra-operative caudal analgesia in pre-school and school age children. Fifty-one boys, undergoing hypospadius repair surgery, were stratified into pre-school or school age groups. After induction of anaesthesia, caudal block was performed with ropivacaine 1 ml.kg )1 of the desired concentration. The first child in each group received ropivacaine 0.125%, and subsequent concentrations were determined by the analgesic response of the previous patient using Dixon's up-and-down method. Under general anaesthesia with 0.7 minimum alveolar concentration of sevoflurane, the minimum local analgesia concentration of ropivacaine for intra-operative caudal block was 34% greater in school age than in pre-school age boys (0.143% (95% CI 0.132-0.157%) vs 0.107% (95% CI 0.089-0.122%), respectively; p < 0.001). This study indicates that a higher concentration of ropivacaine is needed for school age than pre-school age children to provide intra-operative caudal analgesia when combined with general anaesthesia. Caudal block is usually performed under general anaesthesia for intra-operative and postoperative pain relief in paediatric, urological or lower abdominal procedures [1][2][3]. Ropivacaine is less cardiotoxic and has a greater separation of sensory and motor effects than bupivacaine [4][5][6]. It is increasingly used for paediatric caudal block. The concentrations of ropivacaine used in caudal analgesia range from 0.1% to 0.5% [3,[7][8][9][10]. Young animals are more sensitive to local anaesthetic toxicity than older ones [11,12], and nerves of young animals are also more sensitive to local anaesthetic-induced blockade [13]. So it may be possible to provide a safe and adequate surgical block with a lower concentration of local anaesthetics in younger children. The concept of minimum local analgesic concentration (MLAC) of local anaesthetics has been developed to serve as a benchmark for epidural dosing in labour [14]. The relations of age and the MLAC of ropivacaine for intra-operative caudal supplementation of general anaesthesia are not clear. We performed a prospective, double-blind study to determine the MLAC of ropivacaine to establish caudal analgesia combined with general anaesthesia in pre-school and school age children undergoing hypospadius repair. MethodsAfter approval by the Hospital Ethics Committee and informed, written consent from parents, 51 healthy (ASA physical status 1) boys, aged between 1 and 12 years old were enrolled. All children were scheduled for elective hypospadius repair under sevoflurane anaesthesia combined with caudal blockade. Children were stratified into pre-school (age 1-5 years) and school (age 6-12 years) age groups. Children were excluded in cases of local skin infections of the caudal area; neurological or neuromuscular disorders; delayed development; history of Anaesthesia, 2010, 65, pages 991-995

The European Society of Regional Anaesthesia and Pain Therapy/American Society of Regional Anesthesia and Pain Medicine Recommendations on Local Anesthetics and Adjuvants Dosage in Pediatric Regional Anesthesia

“…27 Some authors used more volume of diluted ropivacaine (0.15%): if the total dose is fixed, caudal analgesia with a larger volume of diluted ropivacaine provides better quality and longer duration after discharge than a smaller volume of more concentrated ropivacaine (0.125%). [28][29][30][31] In addition, ropivacaine undergoes slower systemic absorption from the caudal epidural space than bupivacaine; ropivacaine produces lower incidence of motor blockade in the early postoperative period than bupivacaine.…”

Infant spinal anesthesia: Do girls need a larger dose of local anesthetic?

“…15,16 Deng has demonstrated a 34% higher ropivacaine ED50 in preschool-aged children compared to school age children (0.143% vs 0,107%) but did not report a sex difference. 17 There have been no other pediatric studies specifically addressing sex as a covariate in epidural or spinal anesthetic response.…”

Effect of caudal ketamine on minimum local anesthetic concentration of ropivacaine in children: a prospective randomized trial

“…Ingelmo et al [7] investigated the MLAC of a single dose of caudal ropivacaine with 1 MAC of sevoflurane in children aged 1-6 years old, and the MLAC of caudal ropivacaine was 0.066%. Deng et al [5,11] reported that the MLAC of caudal ropivacaine with 0.5 MAC enflurane was 0.11% in children aged 1-5 years old, and it was 0.107% in preschool age children with 0.7 MAC sevoflurane. The MLAC values of ropivacaine were 0.128% in the present study, and the value reported in our study was consistent with the value reported elsewhere, but it was different from certain other studies.…”

“…Adjuvants were usually used to decrease the dose of local anesthetic and prolong the duration of analgesia. The minimum local anesthetic concentration (MLAC) has been conventionally used for evaluating the relative efficacy of generally used local anesthetics [5][6][7]. Many additives have been administrated in order to decrease the concentration of local anesthetics for caudal analgesia, while the effect of some additives on the MLAC values of local anesthetics have been explored in some previous studies [8,9].…”