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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)

AIM: While the proportion of pediatric anesthetics with regional anesthesia in pediatric patients has steadily increased, there are only a few series that describe the use of lower limb peripheral nerve blocks in children. Our aim was to describe the indications, anesthetic approach, and complications associated with lower limb blocks in children undergoing orthopedic surgery in a center with a large caseload of complex patients. METHODS: In a retrospective analysis of prospectively collected data, we reviewed children who had a peripheral nerve block for orthopedic surgery placed between January 2016 and January 2021 at the Royal Children's Hospital Melbourne. Block data were sourced from the electronic medical record and departmental regional anesthesia database. Data collected included demographics, the site of catheter placement and technique of nerve block, presence of sensory/motor blockade, the use of perioperative opioids, and any complications related to peripheral nerve block. RESULTS: A total of 1438 blocks were performed in 1058 patients. Four patients had clinical features of perioperative neurological injury giving an incidence of 3 per 1000 blocks (95% CI 1.1-8:1000). Only one patient had a sensory deficit persisting longer than 6 months for an incidence of 0.8 per 1000 blocks (95% CI 0.1-5:1000). All four peripheral nerve injury followed tibial osteotomy for lengthening procedures or correction of tibial torsion. The etiology of the injury could not be determined despite imaging and surgical exploration and the contribution of popliteal sciatic nerve block to the subsequent PNI could not be confirmed. There were no cases of local anesthetic systemic toxicity. CONCLUSION: An increased risk of perioperative peripheral nerve injury is associated with pediatric tibial osteotomy for congenital deformity. While popliteal sciatic nerve block was not directly implicated in the nerve injury the presence of a prolonged sensory block can delay early recognition

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.

AIMS: The aim of this study was to report the incidence of perioperative adverse events occurring in infants undergoing diode laser photocoagulation of retinopathy of prematurity and to identify clinical risk factors that may affect the incidence. METHODS: This was a retrospective study of anesthetic and medical records of premature infants who were treated in the neonatal intensive care unit or an operating theater with laser photocoagulation in our institution between January 2014 and December 2019. Infants less than 38 weeks post-menstrual age or less than 2000 grams were considered high risk for complications. Electronic medical records were evaluated for clinical and demographic characteristics, comorbidities, and perioperative complications of anesthesia. RESULTS: Sixty-one infants (39 males, 22 females) underwent 72 laser treatments. The mean gestational age was 25.3 weeks (SD 1.6), and mean birth weight was 730 grams (SD 202). At treatment, the mean postmenstrual age was 37.5 weeks (SD 2.7) and weight was 2320 g (SD 610). Laser therapy was performed in an operating theater in 66 procedures (91.7%) and in the neonatal unit in 6 cases (8.3%). Twenty-nine (40.3%) laser surgeries occurred outside normal week-day daytime operating hours. Intraoperative hypotension occurred in 12 procedures (16.7%) but was not significantly different in high-risk infants (16.1% vs 16.7% OR 0.94 P = .94) or in procedures performed in-hours (16.3% vs 17.2% OR 0.93 P = .91). Post-extubation apnea occurred in 21 procedures (29%) but was not significantly different in high-risk infants (29.0% vs 27.3% OR 0.98 P = .34) or in procedures performed in-hours (27.9% vs 31.1% OR 0.86 P = .77). Infants remained intubated at the end of the procedure in 58 (80.5%) cases and 29 (40.3%) remained ventilated more than 24 hours after the procedure. CONCLUSION: The incidence of perioperative adverse events was not associated with patient's age, current weight, timing, or location of the procedure. Ext

Background: In laboratory animals, exposure to most general anaesthetics leads to neurotoxicity manifested by neuronal cell death and abnormal behaviour and cognition. Some large human cohort studies have shown an association between general anaesthesia at a young age and subsequent neurodevelopmental deficits, but these studies are prone to bias. Others have found no evidence for an association. We aimed to establish whether general anaesthesia in early infancy affects neurodevelopmental outcomes. Methods: In this international, assessor-masked, equivalence, randomised, controlled trial conducted at 28 hospitals in Australia, Italy, the USA, the UK, Canada, the Netherlands, and New Zealand, we recruited infants of less than 60 weeks' postmenstrual age who were born at more than 26 weeks'

BACKGROUND: The General Anesthesia compared to Spinal anesthesia (GAS) study is a prospective randomized, controlled, multisite, trial designed to assess the influence of general anesthesia (GA) on neurodevelopment at 5 years of age. A secondary aim obtained from the blood pressure data of the GAS trial is to compare rates of intraoperative hypotension after anesthesia and to identify risk factors for intraoperative hypotension. METHOD(S): A total of 722 infants <=60 weeks postmenstrual age undergoing inguinal herniorrhaphy were randomized to either bupivacaine regional anesthesia (RA) or sevoflurane GA. Exclusion criteria included risk factors for adverse neurodevelopmental outcome and infants born at <26 weeks of gestation. Moderate hypotension was defined as mean arterial pressure measurement of <35 mm Hg. Any hypotension was defined as mean arterial pressure of <45 mm Hg. Epochs were defined as 5-minute measurement periods. The primary outcome was any measured hypotension <35 mm Hg from start of anesthesia to leaving the operating room. This analysis is reported primarily as intention to treat (ITT) and secondarily as per protocol. RESULT(S): The relative risk of GA compared with RA predicting any measured hypotension of <35 mm Hg from the start of anesthesia to leaving the operating room was 2.8 (confidence interval [CI], 2.0-4.1; P <.001) by ITT analysis and 4.5 (CI, 2.7-7.4, P <.001) as per protocol analysis. In the GA group, 87% and 49%, and in the RA group, 41% and 16%, exhibited any or moderate hypotension by ITT, respectively. In multivariable modeling, group assignment (GA versus RA), weight at the time of surgery, and minimal intraoperative temperature were risk factors for hypotension. Interventions for hypotension occurred more commonly in the GA group compared with the RA group (relative risk, 2.8, 95% CI, 1.7-4.4 by ITT). CONCLUSION(S): RA reduces the incidence of hypotension and the chance of intervention to treat it compared with sevoflurane anest

BACKGROUND: Gender differences in absorption, distribution, and metabolism of a number of anesthetic agents have been identified in adults. Clinically, adult studies suggest women demonstrate slower onset of opioid analgesic effects, lower spinal and epidural dose requirements, and greater sensitivity to neuromuscular blocking agents. Sex-related differences in the pharmacokinetics and pharmacodynamics of local anesthetics in neonates and infants, however, have not been well documented. As a result, it is not known whether modification of the dose of local anesthetic for awake spinal anesthesia in infants is required. AIMS: Our aim was to determine whether the ED50 and ED95 of local anesthetics used for infant spinal anesthesia are different between sexes. METHODS: This was a retrospective analysis of data previously collected during dose-response studies of levobupivacaine and ropivacaine spinal anesthetics. The doses were reanalyzed using generalized linear regression analysis to determine whether there is a discernible difference in dose requirements between male and female infants. RESULTS: One hundred and twenty infant spinal anesthetics were reviewed. For levobupivacaine, the ED50 (95% CI) was 0.69 (0.49-0.88) mg vs 0.49 (0.33-0.65), whereas the ED95(95% CI) was 1.07 (0.73-1.41) vs 0.93 (0.64-1.22) for girls and boys, respectively. For ropivacaine spinal anesthesia, the ED50 (95% CI) was 0.64 (0.35-0.92) mg vs 0.30 (-0.32-0.92), whereas the ED95 (95% CI) was 1.30 (0.73-1.87) vs 1.66 (0.55-2.76) for girls and boys, respectively. CONCLUSION: There is no evidence that sex differences occur at the ED50 dose range or at the clinically relevant ED95 dose. Modification of spinal anesthetic dose is not required for infant girls.

The General Anesthesia compared to Spinal anesthesia (GAS) study is a prospective randomized, controlled, multisite, trial designed to assess the influence of general anesthesia (GA) on neurodevelopment at 5 years of age. A secondary aim obtained from the blood pressure data of the GAS trial is to compare rates of intraoperative hypotension after anesthesia and to identify risk factors for intraoperative hypotension. A total of 722 infants ≤60 weeks postmenstrual age undergoing inguinal herniorrhaphy were randomized to either bupivacaine regional anesthesia (RA) or sevoflurane GA. Exclusion criteria included risk factors for adverse neurodevelopmental outcome and infants born at <26 weeks of gestation. Moderate hypotension was defined as mean arterial pressure measurement of <35 mm Hg. Any hypotension was defined as mean arterial pressure of <45 mm Hg. Epochs were defined as 5-minute measurement periods. The primary outcome was any measured hypotension <35 mm Hg from start of anesthesia to leaving the operating room. This analysis is reported primarily as intention to treat (ITT) and secondarily as per protocol. The relative risk of GA compared with RA predicting any measured hypotension of <35 mm Hg from the start of anesthesia to leaving the operating room was 2.8 (confidence interval [CI], 2.0-4.1; P < .001) by ITT analysis and 4.5 (CI, 2.7-7.4, P < .001) as per protocol analysis. In the GA group, 87% and 49%, and in the RA group, 41% and 16%, exhibited any or moderate hypotension by ITT, respectively. In multivariable modeling, group assignment (GA versus RA), weight at the time of surgery, and minimal intraoperative temperature were risk factors for hypotension. Interventions for hypotension occurred more commonly in the GA group compared with the RA group (relative risk, 2.8, 95% CI, 1.7-4.4 by ITT). RA reduces the incidence of hypotension and the chance of intervention to treat it compared with sevoflurane anesthesia in young infants undergoing inguinal herni

BACKGROUND: Pectus excavatum (PE) is the most common congenital chest wall deformity, occurring in 1 : 1000 children with a male to female ratio of 4 : 1. Several procedures have been described to manage this deformity, including cartilage resection with sternal osteotomy (the Ravitch procedure) and a minimally invasive repair technique (the Nuss procedure). While initially described as a nonthoracoscopic technique, the current surgical approach of the Royal Childrens Hospital involves thoracoscopic assistance. Postoperative pain is significant in patients undergoing the pectus repair and multiple analgesic regimens have been advocated with continuous thoracic epidural infusions and opioid infusions the most common. Some authors have advocated patient-controlled analgesia (PCA), paravertebral nerve blocks (PVNB), and wound infusion catheters as alternatives. AIMS: The primary aim of this study was to assess our experience with postoperative pain and analgesia requirements associated with the minimally invasive repair of pectus excavatum in children. METHODS: This is a retrospective cohort study with a contemporaneous comparison group examining patients treated between January 2005 and December 2015 for minimally invasive repair of pectus excavatum by the Nuss procedure. RESULTS: Two hundred and seventeen patients [mean age 14.9 (sd 1.9) years] with pectus excavatum treated at the Royal Childrens Hospital between 2005 and 2015 were identified. All patients were managed with thoracic epidural analgesia and intravenous morphine infusions. The epidural was effective in the postanesthesia care unit in 97.3% (failure to place an epidural rate was 4 (1.9%); no block on awakening 0.9%). A further 4 (1.8%) were removed within 24 h. The mean morphine equivalent dose in the first 24 h was 0.8 mg·kg-1 ·day-1 . PCA was continued for a mean of 3.8 days and the total mean morphine equivalent dose was 2.2 mg·kg-1 ·day-1 . Minor complications occurred in 67 (30.9%) with postoperativ

Background: Postoperative apnea is a complication in young infants. Awake regional anesthesia (RA) may reduce the risk; however, the evidence is weak. The General Anesthesia compared to Spinal anesthesia study is a randomized, controlled trial designed to assess the influence of general anesthesia (GA) on neurodevelopment. A secondary aim is to compare rates of apnea after anesthesia. Method(s): Infants aged 60 weeks or younger, postmenstrual age scheduled for inguinal herniorrhaphy, were randomized to RA or GA. Exclusion criteria included risk factors for adverse neurodevelopmental outcome and infants born less than 26 weeks gestation. The primary outcome of this analysis was any observed apnea up to 12 h postoperatively. Apnea assessment was unblinded. Result(s): Three hundred sixty-three patients were assigned to RA and 359 to GA. Overall, the incidence of apnea (0 to 12 h) was similar between arms (3% in RA and 4% in GA arms; odds ratio [OR], 0.63; 95% CI, 0.31 to 1.30, P = 0.2133); however, the incidence of early apnea (0 to 30 min) was lower in the RA arm (1 vs. 3%; OR, 0.20; 95% CI, 0.05 to 0.91; P = 0.0367). The incidence of late apnea (30 min to 12 h) was 2% in both RA and GA arms (OR, 1.17; 95% CI, 0.41 to 3.33; P = 0.7688). The strongest predictor of apnea was prematurity (OR, 21.87; 95% CI, 4.38 to 109.24), and 96% of infants with apnea were premature. Conclusion(s): RA in infants undergoing inguinal herniorrhaphy reduces apnea in the early postoperative period. Cardiorespiratory monitoring should be used for all ex-premature infants.Copyright © 2015, the American Society of Anesthesiologists, Inc. Wolters Kluwer Health, Inc. All Rights Reserved.

Background: Awake regional anesthesia (RA) is a viable alternative to general anesthesia (GA) for infants undergoing lower abdominal surgery. Benefits include lower incidence of postoperative apnea and avoidance of anesthetic agents that may increase neuroapoptosis and worsen neurocognitive outcomes. The General Anesthesia compared to Spinal anesthesia study compares neurodevelopmental outcomes after awake RA or GA in otherwise healthy infants. The aim of the study is to describe success and failure rates of RA and report factors associated with failure. Method(s): This was a nested cohort study within a prospective, randomized, controlled, observer-blind, equivalence trial. Seven hundred twenty-two infants 60 weeks or less postmenstrual age scheduled for herniorrhaphy under anesthesia were randomly assigned to receive RA (spinal, caudal epidural, or combined spinal caudal anesthetic) or GA with sevoflurane. The data of 339 infants, where spinal or combined spinal caudal anesthetic was attempted, were analyzed. Possible predictors of failure were assessed including patient factors, technique, experience of site and anesthetist, and type of local anesthetic. Result(s): RA was sufficient for the completion of surgery in 83.2% of patients. Spinal anesthesia was successful in 86.9% of cases and combined spinal caudal anesthetic in 76.1%. Thirty-four patients required conversion to GA, and an additional 23 patients (6.8%) required brief sedation. Bloody tap on the first attempt at lumbar puncture was the only risk factor significantly associated with block failure (odds ratio = 2.46). Conclusion(s): The failure rate of spinal anesthesia was low. Variability in application of combined spinal caudal anesthetic limited attempts to compare the success of this technique to spinal alone.Copyright © 2015, the American Society of Anesthesiologists, Inc. Wolters Kluwer Health, Inc. All Rights Reserved.

Postoperative apnea is a complication in young infants. Awake regional anesthesia (RA) may reduce the risk; however, the evidence is weak. The General Anesthesia compared to Spinal anesthesia study is a randomized, controlled trial designed to assess the influence of general anesthesia (GA) on neurodevelopment. A secondary aim is to compare rates of apnea after anesthesia. Infants aged 60 weeks or younger, postmenstrual age scheduled for inguinal herniorrhaphy, were randomized to RA or GA. Exclusion criteria included risk factors for adverse neurodevelopmental outcome and infants born less than 26 weeks gestation. The primary outcome of this analysis was any observed apnea up to 12 h postoperatively. Apnea assessment was unblinded. Three hundred sixty-three patients were assigned to RA and 359 to GA. Overall, the incidence of apnea (0 to 12 h) was similar between arms (3% in RA and 4% in GA arms; odds ratio [OR], 0.63; 95% CI, 0.31 to 1.30, P = 0.2133); however, the incidence of early apnea (0 to 30 min) was lower in the RA arm (1 vs. 3%; OR, 0.20; 95% CI, 0.05 to 0.91; P = 0.0367). The incidence of late apnea (30 min to 12 h) was 2% in both RA and GA arms (OR, 1.17; 95% CI, 0.41 to 3.33; P = 0.7688). The strongest predictor of apnea was prematurity (OR, 21.87; 95% CI, 4.38 to 109.24), and 96% of infants with apnea were premature. RA in infants undergoing inguinal herniorrhaphy reduces apnea in the early postoperative period. Cardiorespiratory monitoring should be used for all ex-premature infants.

Awake regional anesthesia (RA) is a viable alternative to general anesthesia (GA) for infants undergoing lower abdominal surgery. Benefits include lower incidence of postoperative apnea and avoidance of anesthetic agents that may increase neuroapoptosis and worsen neurocognitive outcomes. The General Anesthesia compared to Spinal anesthesia study compares neurodevelopmental outcomes after awake RA or GA in otherwise healthy infants. The aim of the study is to describe success and failure rates of RA and report factors associated with failure. This was a nested cohort study within a prospective, randomized, controlled, observer-blind, equivalence trial. Seven hundred twenty-two infants 60 weeks or less postmenstrual age scheduled for herniorrhaphy under anesthesia were randomly assigned to receive RA (spinal, caudal epidural, or combined spinal caudal anesthetic) or GA with sevoflurane. The data of 339 infants, where spinal or combined spinal caudal anesthetic was attempted, were analyzed. Possible predictors of failure were assessed including patient factors, technique, experience of site and anesthetist, and type of local anesthetic. RA was sufficient for the completion of surgery in 83.2% of patients. Spinal anesthesia was successful in 86.9% of cases and combined spinal caudal anesthetic in 76.1%. Thirty-four patients required conversion to GA, and an additional 23 patients (6.8%) required brief sedation. Bloody tap on the first attempt at lumbar puncture was the only risk factor significantly associated with block failure (odds ratio = 2.46). The failure rate of spinal anesthesia was low. Variability in application of combined spinal caudal anesthetic limited attempts to compare the success of this technique to spinal alone.

BACKGROUND: Comparing relative potency of new local anesthetics, such as levobupivacaine and ropivacaine, by the minimum local analgesic concentration model has not been described for caudal anesthesia. Therefore, we performed a prospective, randomized, double-blind study to determine the minimum local analgesic concentrations of a caudal single shot of ropivacaine and levobupivacaine in children and to describe the upper dose-response curve. METHODS: We performed a two-stage prospective, randomized, double-blind study comparing the dose-response curves of caudal ropivacaine and levobupivacaine in children. In phase 1, 80 boys were randomized to receive either ropivacaine or levobupivacaine. In the second phase a further 32 patients were randomly allocated to receive caudal anesthesia with doses designed to delineate the upper dose-response range (the 50% effective dose [ED(50)]-ED(95) range). RESULTS: There were no significant differences in ED(50) values for caudal ropivacaine and levobupivacaine. The ED(50) for levobupivacaine estimated from the Dixon Massey method was 0.069% (95% CI 0.056%-0.082%) and for ropivacaine was 0.075% (95% CI 0.058%-0.092%). Estimated by isotonic regression the ED(50) and ED(95) respectively of levobupivacaine were 0.068 (0.04-0.09) and 0.20% (95% CI 0.16%-0.24%). For ropivacaine ED 50 and ED95 were 0.066 (0.033-0.098) and 0.225% (95% CI 0.21%-0.24%). CONCLUSIONS: In children receiving one minimum alveolar anesthetic concentration of sevoflurane, there were no significant differences in the ED(50) for caudal levobupivacaine and ropivacaine. The potency ratio at ED(50) was 0.92 and 0.89 at ED(95), indicating that caudal levobupivacaine and ropivacaine have a similar potency.

BACKGROUND: There is no consensus on the concentration or type of local anesthetic used for initiation of epidural anesthesia. The aim of this randomized, double-blind, controlled trial was to compare the clinical effectiveness of epidural administration of both levobupivacaine and bupivacaine in 0.2% and 0.25% concentrations in pediatric patients undergoing abdominal and urological surgery. METHODS: One hundred and forty-one children scheduled for lower abdominal and urological surgery were randomized to receive 0.4-0.6 ml.kg(-1) epidural, 0.25% bupivacaine, 0.2% bupivacaine, 0.25% levobupivacaine or 0.2% levobupivacaine. Initial epidural volumes, onset times; hemodynamic consequences, postoperative pain scores and degree of residual postoperative motor block were all recorded. RESULTS: There were no significant differences in the proportion of children with effective analgesia after incision [0.20% bupivacaine 97%, 0.25% bupivacaine 94%, 0.20% levobupivacaine 91%, 0.25% levobupivacaine 92% (P=0.73)] when a median volume of 0.55 ml.kg(-1) was used. There was no association between the volume used for thoracic, lumbar, or sacral epidural anesthesia and the effectiveness of the agents used. There was a significantly greater incidence of pain on awakening with the 0.2% solutions compared with the 0.25% solutions, but no differences in the incidence of residual motor block between groups. CONCLUSIONS: While there is no difference in the proportion of effective surgical anesthesia, the lower incidence of pain and distress with the 0.25% solutions suggests that this concentration has clinical advantages over the 0.2% solutions for pediatric epidural anesthesia.

Background: The primary objective of this prospective, randomized trial was to compare the effect of propofol and sevoflurane on effectiveness of regional anesthesia. As a secondary objective, we aimed at evaluating the influence of age on neuraxial block profile. Methods: One hundred and thirteen healthy children aged < 10 years, scheduled for general or urological surgical procedures were randomly allocated to receive either propofol or sevoflurane induction and maintenance. Children received caudal or lumbar epidural block depending on their weight and expected surgery. Time to onset of surgical anesthesia, intraoperative analgesic effectiveness, residual motor blockade, postoperative pain, and adverse effects were evaluated. To assess the influence of age on these measures children were further divided into three age groups: 0-24, 25-60 and > 60 months. Results: The mean time to onset of surgical anesthesia was significantly shorter in the sevoflurane group than the propofol group (3.1 vs 4.7 min, P < 0.01), independent of the type of regional technique employed. Distress on arousal in recovery was increased in children receiving sevoflurane (P = 0.03). There was no significant difference in residual motor blockade between the groups but children between 0 and 24 months receiving sevoflurane had a higher incidence of residual motor blockade 3 h after local anesthetic injection (P = 0.01). Conclusions: This study has demonstrated that general anesthesia with sevoflurane decreases the time to onset of surgical anesthesia relative to propofol anesthesia. This effect was most marked when sevoflurane anesthesia preceded caudal epidural blockade. The basis for this effect is most likely to be related to differential binding of the two anesthetic agents to receptors in the spinal cord that mediate immobility in response to surgical stimuli.