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Summary Objectives: To describe the challenges associated with providing safe anesthesia and perioperative care for children in a remote intraoperative magnetic resonance (iMR) operating room (OR) and to identify perioperative anesthesia outcomes, including adverse events related to the iMR environment. Background: Increasingly, children undergo neurosurgical procedures in a high-field iMR OR. We describe a 10-year experience of providing anesthesia for children in this environment with a mobile 1.5-Tesla magnet. Methods: A 10-year retrospective analysis was conducted of children who underwent neurosurgical procedures in a high-field mobile iMR OR. Primary outcomes related to perioperative adverse events and recovery profiles. Results were expressed as mean ± sd or median (range), as appropriate. Results: One hundred and five procedures were performed on 98 children, aged 4 months–18 years, weighing 6–112 kg. The commonest two diagnostic categories were tumor (n = 52) and seizures (n = 27). Median anesthetic time was 439 (185–710) mins. There were no significant adverse events related to the iMR environment. The mean postanesthetic care unit admission temperature was 37 ± 0.9°C and the mean modified Aldrete Score at 30 mins was 7.2 ± 0.9. Two patients experienced seizures in the immediate postoperative period, readily controlled with propofol. There was one breach of MR safety protocol, and no adverse events related to patient transport. Conclusions: Anesthesia and perioperative care of children in an iMR setting were associated with a very low incidence of complications, despite the duration of the procedures involved. Such success depends upon a cohesive team-based approach.

The purpose of this evidence-based clinical update is to identify the best evidence when selecting a long-acting local anesthetic agent for single-shot pediatric caudal anesthesia in children. A structured literature search was conducted using PubMed and Medline (OVID) using the terms “caudal” and combinations of at least two of “bupivacaine”, “ropivacaine”, and “levobupivacaine”. The search limits included “randomized controlled trials” (RCTs), “meta-analysis”, “evidence-based reviews” or “reviews”, “human”, and “all child: 0-18 yr”. Seventeen RCTs were identified that concerned single-shot pediatric caudal anesthesia with at least two of the three drugs in question. Data were extracted for the areas of clinical efficacy and side effects. Study findings were assigned levels of evidence, and grades of recommendation were made according to Centre for Evidence-Based Medicine criteria. The three drugs investigated were found to be equivalent in terms of efficacy. Evidence showed bupivacaine with the highest incidence of motor block and ropivacaine with the lowest. Adverse effects were rare and unrelated to the choice of drug. There were no serious adverse events. None of the three agents was shown to be superior in terms of efficacy. Bupivacaine is preferred if motor block is desired, ropivacaine is preferred if motor block is to be minimized. Adverse effects in human studies are rare, mild, and unrelated to the choice of drug. Despite encountering the absence of serious adverse events in each of the studies reviewed, it is noted that animal studies suggest a safer profile with ropivacaine or levobupivacaine than with bupivacaine.

To determine whether a functional difference exists between the size 2 laryngeal mask airway (LMA)-Classic (CLMA) and LMA-Proseal (PLMA) in anesthetized children who have received neuromuscular blockade. Airway leak during intermittent positive pressure ventilation (IPPV) and adequacy of fibreoptic laryngeal view were the primary study outcomes.A randomized, controlled, single-blinded study of 51 ASA I or II children weighing 10-20 kg was undertaken. The anesthetic technique was standardized. Following insertion of the LMA and cuff inflation to 60 cm H(2)O, we measured oropharyngeal leak pressure and gastric insufflation and leak fraction during IPPV, and evaluated the adequacy of fibreoptic view.Oropharyngeal leak pressure measured by neck auscultation was higher for the PLMA compared to the CLMA (23.7 vs 16.5 cm H(2)O, P = 0.009) but, when measured by the inspiratory hold maneuver was not significantly different (24.8 vs 20.3 cm H(2)O, respectively, P = 0.217). Leak fraction values were similar for the CLMA and the PLMA (21.2%. vs 13.3%, respectively, P = 0.473). A satisfactory view of the larynx was obtained more frequently in the PLMA group (21/25 vs 10/25, P = 0.003). Gastric insufflation during leak determination was more common with the CLMA (12/26 vs 2/25 CLMA vs PLMA, respectively, P = 0.006).In children undergoing IPPV with neuromuscular blockade, the size 2 PLMA is associated with a higher leak pressure by auscultation and less gastric insufflation compared to the CLMA. Leak pressures assessed by manometric stability are similar with these two devices. The improved fibreoptic view of the larynx through the PLMA may be advantageous for bronchoscopy.

Bilateral flexion-induced ankle clonus has been proposed as a test of spinal cord integrity during anesthesia for scoliosis surgery. The purpose of this study was to establish the reliability of this test in normal children emerging from volatile anesthesia. A secondary objective was to determine if there was a difference in the validity of this test with either sevoflurane or isoflurane anesthesia. In a randomized, prospective blinded clinical trial, 32 healthy children aged three to 13 yr, were randomized to receive either isoflurane (Group I,n = 15) or sevoflurane (Group S,n = 17) for maintenance of anesthesia during dental restorative surgery. During emergence, an observer, blinded to group allocation, recorded ankle clonus scores (number of beats to a maximum of 5 on each side) at 60-sec intervals until tracheal extubation. End-tidal anesthetic concentration was measured contemporaneously. Non-sustained ankle clonus was elicited in a majority of children during emergence: 13 (87%) patients in Group I and 15 (88%) in Group S demonstrated at least non-sustained or unilateral clonus. However, bilateral sustained (> 5 beats·min-1) ankle clonus occurred in only four (27%) patients in Group I and four (24%) patients in Group S (P = 0.83). We conclude that the specificity of the ankle clonus test is too low to be clinically useful as a measure of spinal cord integrity in children, both when isoflurane and sevoflurane are used as the primary anesthetic agent.

This study was conducted to determine whether hyperalgesic effects of subanaesthetic concentrations of thiopentone could be attributed to GABAA receptor effects.All studies were performed on 50 rats in a prospective, randomized, blinded fashion using saline-injected animals as controls. Using a modified Randall-Selitto technique, the motor behavior stimulated by noxious stimulation was quantified by determining the lowest tail pressure required to provoke a withdrawal response (somatic motor response threshold, SMRT). In the first protocol (21 rats), we studied the effects of 0.5, 1.5 and 5 mg.kg-1 i.v. of the GABAA agonist, muscimol, on SMRT. In the second protocol (20 rats), the effects of administration of saline, muscimol 0.5 mg.kg-1, or the competitive GABAA antagonist, bicuculline 0.25 mg.kg-1, upon the SMRT-reducing effects of a standardized thiopentone infusion were observed.No dose of muscimol produced hyperalgesia. The highest dose of muscimol used (5 mg.kg-1) produced pronounced analgesic effects, raising the SMRT above 750 g. No change in SMRT was detected with the smaller doses of muscimol. Given in combination with muscimol (0.5 mg.kg-1), thiopentone produced analgesia, as shown by an increase in SMRT (P = 0.009). In the bicuculline treated animals, SMRT decreased linearly with increasing plasma thiopentone concentrations (P0.001). The slope of the relationship in the bicuculine group was not significantly different from that observed in the saline-treated group, indicating that bicuculline did not block the hyperalgesic effects of thiopentone.The results of these studies suggest that hyperalgesia associated with thiopentone is not mediated primarily by GABAA receptors.

Dexamethasone reduces postoperative morbidity after adenotonsillectomy, strabismus surgery, and third molar extraction. Our hypothesis was that dexamethasone would reduce pain and other morbidity in children undergoing dental surgery for up to 24 hr postoperatively.A triple-blinded, randomized, controlled trial was carried out on 200 children undergoing prolonged dental rehabilitation under general anesthesia. Subjects were randomized into two groups: group D, given dexamethasone 0.3 mg·kg(-1); group S, given normal saline. The primary outcome measure was pain over 24 hr as evaluated by a parental 0-10 numerical rating scale (NRS). Key secondary outcomes included oral intake on a four-point scale at 24 hr and the overall incidence of postoperative vomiting (POV). Analysis for the primary outcome consisted of comparison of means in the NRS with the Wilcoxon rank sum test and for occurrence of POV with Fisher's test.After eliminating 22 subjects for protocol violations and withdrawals, 178 subjects were analyzed. There was no significant difference in pain scores (NRS) at 24 hr or the worst NRS experienced over the preceding 24 hr. There was no difference in the quality of oral intake between the groups. There was a significant difference in the percentage of patients who vomited during the first 24 hr: eight of 91 in group S and one of 87 in group D. Therefore, 7.74% more vomited in group S (P = 0.045), with a 95% confidence interval of 0.32 to15.16 for the difference in percentages.Dexamethasone, 0.3 mg·kg(-1), did not reduce pain over 24 hr in healthy children undergoing dental rehabilitation under general anesthesia. The quality of oral intake was also unaffected by dexamethasone at 24 hr. Dexamethasone did produce a significant reduction in postdischarge vomiting, beyond the incidence found with ondansetron alone.

To describe the challenges associated with providing safe anesthesia and perioperative care for children in a remote intraoperative magnetic resonance (iMR) operating room (OR) and to identify perioperative anesthesia outcomes, including adverse events related to the iMR environment.Increasingly, children undergo neurosurgical procedures in a high-field iMR OR. We describe a 10-year experience of providing anesthesia for children in this environment with a mobile 1.5-Tesla magnet.A 10-year retrospective analysis was conducted of children who underwent neurosurgical procedures in a high-field mobile iMR OR. Primary outcomes related to perioperative adverse events and recovery profiles. Results were expressed as mean ± sd or median (range), as appropriate.One hundred and five procedures were performed on 98 children, aged 4 months-18 years, weighing 6-112 kg. The commonest two diagnostic categories were tumor (n = 52) and seizures (n = 27). Median anesthetic time was 439 (185-710) mins. There were no significant adverse events related to the iMR environment. The mean postanesthetic care unit admission temperature was 37 ± 0.9°C and the mean modified Aldrete Score at 30 mins was 7.2 ± 0.9. Two patients experienced seizures in the immediate postoperative period, readily controlled with propofol. There was one breach of MR safety protocol, and no adverse events related to patient transport.Anesthesia and perioperative care of children in an iMR setting were associated with a very low incidence of complications, despite the duration of the procedures involved. Such success depends upon a cohesive team-based approach.

This study was undertaken to quantify the exposure of operating room staff to nitrous oxide during routine paediatric otolaryngeal surgery and to determine the influence of the method of induction of anaesthesia on this exposure. The nitrous oxide exposure of the anaesthetist, the surgeon and the circulating nurse were measured, using body-worn passive atmospheric samplers, during twelve routine paediatric otolaryngeal surgical lists. During six of the lists an inhalational technique, with nitrous oxide, oxygen and halothane, was used for the induction of anaesthesia. During the other six lists anaesthesia was induced using intravenous thiopentone. In all cases, anaesthesia was maintained using nitrous oxide, oxygen and halothane. Regardless of the induction technique used, the mean nitrous oxide exposures of the anaesthetist, the surgeon and the nurse all exceeded the maximum level of 25 ppm · hr−1 recommended by the United States National Institute for Occupational Safety and Health (NIOSH). The use of an intravenous technique for the induction of anaesthesia reduced the nitrous oxide exposure of the anaesthetist and the circulating nurse. This suggests that, although the use of an intravenous induction may reduce exposure to nitrous oxide, the NIOSH recommendations for maximum exposure of operating room personnel to nitrous oxide are currently unattainable in practice.

The purpose of this evidence-based clinical update was to identify the best evidence to determine if behavioural outcomes are improved in children after oral midazolam premedication.A literature search was conducted using both PubMed and OVID programs, utilizing the terms "midazolam", and either "premedication" or "preoperative treatment". Search limits that were employed included randomized controlled trials (RCTs), English language, human studies, children aged 0-18 yr, and publication dates 1990 - present (January 2006). A review of the 171 abstracts obtained was undertaken and, of these, 30 papers were identified that concerned oral midazolam in children prior to general anesthesia, and that involved a RCT with a placebo or control arm. These studies were assigned levels of evidence, and grades of recommendation were made according to Centre for Evidence-Based Medicine criteria.Oral midazolam premedication in children was found to reduce the anxiety associated with separation from parents/guardians, and with induction of anesthesia. Recovery times are not significantly delayed. There is no consistent evidence to suggest a reduction in the phenomenon of emergence agitation. Evidence suggesting an improvement in behavioural outcomes at home is also inconsistent.Premedication with midazolam 0.5 mg x kg(-1) po administered 20-30 min preoperatively, is effective in reducing both separation and induction anxiety in children (grade A recommendation), with minimal effect on recovery times. However improved postoperative behavioural outcomes in the postanesthesia care unit, or at home cannot be predicted on a consistent basis.

Ten healthy (ASA I or II) anaesthetized infants undergoing clubfoot surgery were studied. General anaesthesia included rocuronium, nitrous oxide and isoflurane. Volume controlled ventilation (12 ml.kg-1) was delivered via a coaxial Mapleson-D (Bain) system and a Datex AS/3 ventilator. Pulmonary mechanics were measured sequentially in the supine and prone positions using a Bicore CP-100 pulmonary function monitor. Subjects had a mean age of 6 (+/- 2) months and a mean weight of 8.3 (+/- 1.4) kg. Dynamic compliance (CDYN) and static compliance (CSTAT) were both significantly lower in the prone position than in the supine position (P < 0.0005). Mean CDYN decreased from 14.9 +/- 4.9 ml.cmH2O-1 (supine) to 11.6 +/- 3.5 ml.cmH2O-1 (prone). Mean CSTAT decreased from 10.2 +/- 2.8 ml.cmH2O-1 (supine) to 8.9 +/- 2.3 ml.cmH2O-1 (prone). No clinically significant differences in gas exchange were noted, however, on repositioning.

Subhypnotic doses of thiopentone are considered to possess antianalgesic or hyperalgesic properties. In this study, we have tested the hypothesis that the coincidence of sedation and hyperalgesia is a property of both barbiturate and non- barbiturate anaesthetic agents. In a randomized, prospective, blinded study, the effects of slow (20 min) iv infusions of thiopentone, pentobarbitone, methohexitone or propofol on nociceptive threshold were measured in rats by tail pressure analgesimetry and compared with saline- infused control animals. Nociceptive thresholds were correlated with measurements of plasma drug concentrations and behavioural assessments. Comparison of pre- infusion nociceptive threshold with the lowest threshold obtained during drug infusion revealed decreases in all four treatment groups. As a percentage of the pre- infusion values, the decreases were: thiopentone: 42.5% (P < 0.001), pentobarbitone : 27.8% (P = 0.014), methohexitone: 24.9% (P = 0.013), propofol: 21.6% (P = 0.006). There were no changes in nociceptive threshold in the control groups. The relationship between nociceptive threshold and plasma drug concentration was usually characterized by an initial decline followed by a rise in nociceptive threshold as the plasma concentration and degree of sedation increased. The results support the hypothesis that hyperalgesia is a property of different anaesthetic agents when administered at sub- hynotic concentrations.

BACKGROUND Although low doses of barbiturates are widely believed to increase sensitivity to pain, studies of the electrophysiologic effects of these drugs on the neurons involved in nociception in the spinal cord have detected only depressant effects. The goal of the studies reported here was to quantify the hyperalgesia resulting from low-dose thiopental infusions and to measure the associated concentrations of thiopental in the plasma, brain, and spinal cord. METHODS Nociception was measured using the threshold for motor response to pressure stimulation of the tail (nociceptive threshold) and tail flick latency in the rat. Thiopental was administered by intravenous infusions designed to produce plasma concentrations that either slowly increased or remained at a steady state. Plasma and tissue thiopental concentrations were measured by high-performance liquid chromatography. RESULTS We observed a reduction in nociceptive threshold that was correlated with the plasma thiopental concentration over the range 2-20 micrograms.ml-1 (7.6-76 microM). The relationship was nonlinear. Nociceptive threshold reached a nadir (36% less than control values) at a mean plasma thiopental concentration of 13.7 micrograms.ml-1 (51.9 microM). The steady-state study showed a similar reduction in nociceptive threshold, with an equilibrium plasma thiopental concentration of 7.6 +/- 1.3 micrograms.ml-1 (28.8 +/- 4.9 microM). Concentrations of thiopental in brain and spinal cord samples were 1.7 +/- 0.03 and 3.5 +/- 1.7 micrograms.g-1, respectively. CONCLUSIONS These studies confirm previous reports of hyperalgesia in association with small doses of thiopental. Reductions in nociceptive threshold and tail flick latency were observed in association with spinal cord concentrations of thiopental in a range reported by others to depress the electrophysiologic activity of neurons involved in nociception.

One hundred and twenty healthy, elective surgical inpatients were randomly assigned to one of four groups. Between two and three hours before the scheduled time of surgery all patients ingested a marker dye, phenol red, 50 mg in 10 ml water, with placebo tablet alone (Groups 1 and 2), placebo tablet with 150 ml oral fluid (Group 3), or oral ranitidine 150 mg with oral fluid 150 ml (Group 4). Patients in Group 1 received oral diazepam or no premedication, while those in Groups 2, 3, and 4 received IM narcotic and atropine one hour preoperatively. Following induction of anaesthesia the residual gastric fluid was aspirated through a Salem sump tube and its volume, pH, and phenol red content measured. Mean volumes were Group 1: 24 ml; Group 2: 13 ml; Group 3: 17 ml; Group 4: 14 ml. Mean pH values were Group 1: 2.99; Group 2: 3.03; Group 3: 3.44; Group 4: 5.28. The amount of phenol red in the samples indicated at least 90 per cent gastric emptying had occurred in 90 per cent of patients. We conclude that, in healthy patients, 150 ml oral fluid is almost completely emptied from the stomach within two hours of ingestion, even when followed one hour later by narcotic-atropine premedication.