Carolyne Pehora

Intraoperative low-dose ketamine does not prevent a remifentanil-induced increase in morphine requirement after pediatric scoliosis surgery.

BACKGROUND: Remifentanil-based anesthesia is commonly used to facilitate neurophysiologic monitoring during pediatric scoliosis surgery. Acute opioid tolerance and/or hyperalgesia resulting from remifentanil-based anesthesia may involve activation of N-methyl-d-aspartate systems. We hypothesized that low-dose intraoperative infusion of the N-methyl-d-aspartate antagonist ketamine would suppress the development of tolerance and thereby decrease postoperative morphine consumption in children receiving remifentanil-based anesthesia for scoliosis surgery. METHODS: Thirty-four adolescents aged 12–18 yr scheduled for scoliosis surgery were randomly assigned to receive intraoperative low-dose ketamine (bolus dose of 0.5 mg/kg followed by continuous infusion of 4 &mgr;g · kg−1 · min−1) or an equal volume of saline during propofol/remifentanil anesthesia. Cumulative morphine consumption was assessed using a patient-controlled analgesia device for 72 h after surgery. Postoperative morphine consumption, pain scores at rest and during cough, and sedation scores were recorded by a blinded investigator every hour for the first 4 h, every 4 hours for 20 h, and then every 12 hours for 72 h. RESULTS: Cumulative morphine consumption at 24, 48, and 72 h after surgery did not differ significantly between groups (ketamine group: 1.57 ± 0.56, 3.05 ± 1.14, and 4.46 ± 1.53 mg/kg; saline group: 1.60 ± 0.53, 2.87 ± 1.05, and 4.11 ± 1.71 mg/kg, respectively). No differences in pain or sedation scores were found. The duration of anesthesia was similar in the two groups. CONCLUSIONS: These data do not support the use of intraoperative low-dose ketamine to prevent the development of remifentanil-induced acute opioid tolerance and/or hyperalgesia during pediatric scoliosis surgery.

Pre-treatment with morphine does not prevent the development of remifentanil-induced hyperalgesia

Purpose: Remifentanil, an ultra short-acting opioid commonly used to supplement general anesthesia, is associated with the development of hyperalgesia that manifests clinically as an increase in postoperative analgesic requirement. This study involving adolescents undergoing scoliosis surgery evaluated whether pre-treatment with morphine prior to commencing remifentanil infusion would decrease the initial 24-hr morphine consumption and pain scores.Methods: Forty ASA 1–11 pediatric patients undergoing surgical correction of idiopathic scoliosis were recruited in a prospective, randomized, double-blind fashion to receive 150µg·kg−1 morphine or an equal volume saline prior to commencing remifentanil by infusion. The primary outcome was the initial 24-hr postoperative morphine consumption. Numeric rating scale (NRS) pain scores at rest and on coughing were recorded, as were scores for nausea, vomiting, and sedation and incidences of pruritus.Results: The groups were demographically similar. No differences were observed between groups vis-à-vis the initial 24-hr morphine consumption, NRS pain scores, sedation, nausea, or vomiting.Conclusion: Pre-treatment with 150µg·kg−1 morphine did not decrease the initial 24-hr morphine consumption in adolescents who received remifentanil by infusion for surgical correction of idiopathic scoliosis.RésuméObjectif: Le rémifentanil est un opioïde à action extra-courte couramment utilisé comme adjuvant à une anesthésie générate. II est associé à l’apparition d’hyperalgéesie, laquelle prend la forme clinique d’une augmentation des besoins analgésiques postopératoires. Cette étude portait sur des adolescents subissant une chirurgie de correction de scoliose. Son objectif était de déterminer si un prétraitement à la morphine avant la perfusion de rémifentanil diminuerait la consommation de morphine et l’intensite de la douleur dans les 24 premières heures suivant l’opération.Méthode: Quarante adolescents ASA 1–11 subissant une chirurgie corrective pour une scoliose idiopathique ont été recrutés de façon prospective, randomisée et à double insu, à recevoir de la morphine 150 µg·kg−1 ou un volume équivalent de sérum physiologique avant le début d’une perfusion de rémifentanil. La consommation de morphine durant les 24 premières heures postopératoires était l’objectif primaire. Les scores de douleur sur l’échelle d’évaluation numérique (EEN) au repos et en toussant ont été notes, de même que les scores concernant les nausées, les vomissements, la sédation et l’aptparition de prurit.Résultats: Les groupes étaient semblables d’un point de vue démographique. Aucune différence n’a été observée entre les groupes quant à la consommation de morphine des 24 premières heures, les scores de douleur EEN, la sédation, les nausées ou les vomissements.Conclusion: Le prétraitement avec 150µ·kg−1 de morphine n’a pas diminué la consommation de morphine durant les 24 premières heures postopératoires chez des adolescents recevant une perfusion de rémifentanil pour une chirurgie corrective d’une scoliose idiopathique.

Dose-dependent suppression of the electrically elicited stapedius reflex by general anesthetics in children undergoing cochlear implant surgery.

BACKGROUND: Cochlear implants stimulate the auditory nerve to enable hearing. Determining appropriate upper and lower limits of stimulation is essential for successful cochlear implantation. The intraoperative evoked stapedius reflex threshold (ESRT) and evoked compound action potential (ECAP) are commonly used to determine the limits of implant stimulation. In this study, we evaluated the dose-related effects of sevoflurane, desflurane, isoflurane, and propofol on the intraoperative ESRT and ECAP. METHODS: Forty-four children aged 6 mo to 17 yr undergoing cochlear implantation were recruited. Each child was randomly assigned to receive sevoflurane, desflurane, isoflurane, or propofol. Evoked responses were measured by a blinded investigator at end-tidal anesthetic concentrations corresponding to 0, 0.75, and 1.5 age-adjusted minimum alveolar concentration administered in random sequence and at targeted blood concentrations of propofol of 0, 1.5, and 3.0 &mgr;g/mL. Data were analyzed using one-way repeated-measures analysis of variance. P < 0.05 was considered statistically significant. RESULTS: The ESRT increased dose dependently with increasing volatile anesthetic concentration (P < 0.01). The stapedius reflex was completely abolished by volatile anesthesia in more than half of children. Propofol minimally affected the ESRT. In contrast, the ECAP was unaffected by anesthesia. CONCLUSIONS: Volatile anesthetics suppress the stapedius reflex in a dose-dependent manner, suggesting that ESRT measurements acquired during volatile anesthesia will overestimate the maximum comfort level, which may cause discomfort postoperatively and adversely affect the child’s adaptation to the implant. We advise against the use of volatile anesthetics for measurement of the stapedius reflex threshold during cochlear implant surgery.

Coadministration of Propofol and Remifentanil for Lumbar Puncture in Children Dose-Response and an Evaluation of Two Dose Combinations

Background:The combination of propofol and remifentanil may be particularly suitable for short-duration procedures such as lumbar puncture. The authors undertook a two-part study to evaluate coadministration of propofol and remifentanil as an anesthetic technique for lumbar puncture in children. Methods:The first part was a sequential allocation dose-finding study to determine the minimum effective dose of remifentanil when coadministered with 2.0 or 4.0 mg/kg propofol. The second was a randomized double-blind study to compare the intraoperative and recovery characteristics of 2.0 or 4.0 mg/kg propofol coadministered with the corresponding effective dose of remifentanil. Results:Effective doses of remifentanil in 98% of children were 1.50 ± 1.00 and 0.52 ± 1.06 &mgr;g/kg when coadministered with 2.0 and 4.0 mg/kg propofol, respectively. The duration of apnea was longer (median, 110 vs. 73 s; P < 0.05) and the time to awakening was shorter (median, 10 vs. 23 min; P < 0.05) after 2.0 mg/kg propofol plus 1.5 &mgr;g/kg remifentanil compared with 4.0 mg/kg propofol plus 0.5 &mgr;g/kg remifentanil. No child experienced hypotension or postprocedure nausea or vomiting after either dose combination. Conclusions:Both dose combinations (2.0 mg/kg propofol plus 1.5 &mgr;g/kg remifentanil and 4.0 mg/kg propofol plus 0.5 &mgr;g/kg remifentanil) provide effective anesthesia for lumbar puncture in children. However, the intraoperative and recovery characteristics of the two dose combinations differ in that the duration of apnea increases whereas recovery time decreases as the dose of remifentanil is increased and that of propofol is decreased.

Effect of low-dose ketamine on voltage requirement for transcranial electrical motor evoked potentials in children.

Study Design. Randomized controlled trial. Objective. To determine the effect of low-dose ketamine on the voltage needed to elicit maximal amplitude of the motor-evoked response to transcranial electrical stimulation during propofol/remifentanil anesthesia in children undergoing scoliosis surgery. Summary of Background Data. Motor-evoked potentials (MEPs) are increasingly used to assess the integrity of motor pathways during surgery. Whereas most general anesthetics depress MEP amplitude, the effect of ketamine has been variable, ranging from little or no reduction to an increase in amplitude, suggesting that ketamine may be useful as an agent to facilitate MEP monitoring. We tested the hypothesis that low-dose ketamine would reduce the voltage required to elicit maximal amplitude of the motor-evoked response to transcranial electrical stimulation during propofol/remifentanil anesthesia. Methods. Thirty-four patients 12 to 16 years of age undergoing posterior instrumentation for correction of idiopathic scoliosis were randomly assigned to receive low-dose ketamine (0.5 mg/kg bolus, followed by 4 &mgr;g/kg/min infusion) or an equal volume of saline. Anesthesia was maintained using a mixture of 30% oxygen in air, continuous infusion of propofol at a rate of 100 to 150 &mgr;g/kg per min, and continuous infusion of remifentanil. Myogenic motor-evoked responses to transcranial electrical stimulation of the motor cortex were recorded. The minimum voltage required to elicit maximal amplitude of the MEP response was determined. Voltage requirements were compared using the Mann-Whitney U rank sum test. P < 0.05 was considered statistically significant. Results. No significant difference was found in the minimal voltage needed to elicit maximum amplitude of the MEP response. Median (range) voltage requirements in the ketamine and control groups were 227 V (range, 160–350 V) and 215 V (range, 150–300 V), respectively. Conclusion. Addition of low-dose ketamine to propofol/remifentanil anesthesia does not significantly reduce the voltage needed to elicit maximum amplitude of the motor-evoked response to transcranial electrical stimulation.

The use of NSAIDs in pediatric scoliosis surgery – a survey of physicians’ prescribing practice

Background:  Pediatric scoliosis surgery is associated with considerable postoperative pain requiring opioids for analgesia. Nonsteroidal antiinflammatory drugs (NSAIDs) can be used as adjuvants for analgesia; however, the potential of these agents to affect bone healing raises concerns. No large‐scale prospective studies have been performed to evaluate the benefit‐to‐risk ratio of NSAID use after pediatric scoliosis surgery. Given the lack of evidence in the literature, a survey of practice patterns of anesthesiologists from around the world was conducted with respect to the use of NSAIDs after pediatric spinal fusion surgery for scoliosis.

Drug-Induced Acute Pancreatitis in Children Receiving Chemotherapy for Acute Leukemia: Does Propofol Increase the Risk?

BACKGROUND: The use of propofol is controversial in patients with a history of acute pancreatitis or those taking drugs, including certain chemotherapeutic drugs, that are associated with pancreatitis. METHODS: To investigate this issue, we reviewed the medical records of all children who were diagnosed with pancreatitis while receiving chemotherapy for acute leukemia during a 5-year period. RESULTS: A temporal relationship between propofol use and development of acute pancreatitis could not be established. CONCLUSION: Propofol can be considered for general anesthesia in children who are receiving chemotherapeutic drugs that are themselves associated with acute pancreatitis or those who have a history of chemotherapy-induced pancreatitis.

Cardiac arrest upon induction of anesthesia in children with cardiomyopathy: an analysis of incidence and risk factors

Introduction:  It is thought that patients with cardiomyopathy have an increased risk of cardiac arrest on induction of anesthesia, but there is little available data. The purpose of this study was to identify the incidence and potential risk factors for cardiac arrest upon induction of anesthesia in children with cardiomyopathy in our institution.

The construction and implementation of a novel postburn pruritus scale for infants and children aged five years or less: introducing the Toronto Pediatric Itch Scale.

The authors’ objectives were to design, refine, validate and implement a behavior-anchored postburn pruritus scale for children aged 5 years or less. We engaged a range of professionals involved in the care of children with burns. We used Q-methodology in interprofessional team exercises to identify and stratify itch behaviors into categories of increasing severity, and then iteratively refined these into a draft scale. We used a range of quantitative and qualitative techniques to assess the utility, feasibility, and validity of the scale and refined it accordingly. During the implementation phase we collected some preliminary reliability data. We generated a 4-point scale of itch severity with simple descriptors of each score. We also designed a separate guidance note and example behaviors that could be used to orientate new users without the need for rater training. End-user interviews revealed high levels of feasibility and content validity. The reliability data showed moderate inter-observer agreement, with a Cohen’s kappa of 0.52 (P < .001). We have developed and implemented a behavioral post-burn pruritus scale for use in children aged less than 5 years and have demonstrated its utility, feasibility, validity, and reliability. The development of a validated symptom scoring scales will allow for the conduct of high-quality quantitative clinical trials and the subsequent implementation of evidence-based management protocols.

A retrospective review of pediatric difficult airways: once easy, not always easy

To the Editor, Retrospective series tend to report a lower incidence of difficult intubation in pediatric patients than in adults. It is also believed that the incidence of unanticipated difficult intubation in children is exceedingly low. We conducted a retrospective review in a pediatric tertiary care facility to identify the incidence and clinical characteristics of patients with difficult airways undergoing surgery. With research ethics board approval (December 2011), we analyzed the anesthesia records of all patients \ 18 yr presenting for surgery at The Hospital for Sick Children over a two-year period (January 1, 2010 to December 31, 2011). Patients with a difficult airway were defined as (1) those having a Cormack-Lehane grade 3 or worse view on direct laryngoscopy (which was routinely documented in the anesthesia record) or (2) those who were identified preoperatively as potentially having a difficult airway or who had been previously demonstrated to have one and were subsequently managed by pre-planned videolaryngoscopic or flexible bronchoscopic intubation. All cases were assessed and managed by an attending pediatric anesthesiologist. The patients’ charts were reviewed for demographics, preoperative airway history/characteristics, and airway management details. Descriptive statistics were used to analyze the data. Of the 22,766 cases of anesthetics delivered during the study period, 125 (0.5%) were deemed to have a difficult intubation. Among them, 21 (16%) were emergency procedures, 13 of which were primary airway emergencies. Also, 73 (58%) of the patients were diagnosed to have a syndrome known to be associated with difficult intubation. In descending order of prevalence, the following accounted for 48 (66%) of these cases: Goldenhar, Pierre-Robin, arthrogryposis, Apert, Treacher-Collins, and various mucopolysaccharidoses. Of the 125 difficult airway patients, 70 (56%) had undergone general anesthesia prior to the study period. Only 32 (46%) of the 70 patients had a history of prior difficult airway. In all, 100 (80%) of the 125 cases had an anticipated difficult airway based on their history and airway physical examination. Airway management in the remaining 25 (20%) patients in whom a difficult airway had been unanticipated is shown in the Figure. The vast majority (91.2%) of the difficult airway cases were managed with endotracheal intubation. Another 5.6% were managed with a supraglottic airway and the remaining 3.2% with nasal prongs or face mask. There were no deaths attributable to airway management in this series. A particularly interesting finding in this study was that one in five difficult airways was unanticipated despite the fact that an attending anesthesiologist was involved in each case and the study took place in a pediatric tertiary care center. This is in contrast to the popular belief that the vast majority of pediatric difficult airway cases are predictable. We also found that, among the difficult airway patients in our study who had had a previous anesthetic, more than half did not have a history of airway difficulty. This finding speaks against a commonly held adage that tracheal intubation usually becomes less difficult as the child develops. Indeed, in conditions such as Goldenhar syndrome, arthrogryposis, and the mucopolysaccharidoses, C. Karsli, MD (&) C. Pehora, MN A. Al-Izzi, MD P. Mathew, MD Department of Anesthesiology and Pain Medicine, The Hospital for Sick Children, Toronto, ON, Canada e-mail: Cengiz.karsli@sickkids.ca