Simon D. Whyte

The effects of propofol and sevoflurane on the QT interval and transmural dispersion of repolarization in children.

Prolongation of the QT interval is associated with torsades de pointes (TdP), especially in children or young adults with long QT syndromes. Susceptibility to TdP arises from increased transmural dispersion of repolarization (TDR) across the myocardial wall. Several anesthetic drugs prolong the QT interval, but their effect on TDR is unknown. TDR can be measured on the electrocardiograph (ECG) as the time interval between the peak and end of the T wave (Tp-e). We investigated the effects of propofol and sevoflurane on the corrected QT (QTc) and Tp-e intervals in 50 unpremedicated ASA physical status I–II children, aged 1–16 yr, who were randomized to receive propofol (group P) or sevoflurane (group S). Twelve-lead ECGs were recorded preoperatively and intraoperatively. Sevoflurane significantly prolonged the preoperative QTc; propofol did not. Neither anesthetic had any significant effect on the preoperative Tp-e. Sevoflurane increases the duration of myocardial repolarization in children to a larger extent than does propofol, but as the dispersion of repolarization appears unaffected, the risk of TdP is likely to be minimal with either anesthetic.

A Comparison of the Effect on Dispersion of Repolarization of Age-Adjusted MAC Values of Sevoflurane in Children

BACKGROUND: QT interval prolongation is associated with torsades des pointes (TdP), but is a poor predictor of drug torsadogenicity. Susceptibility to TdP arises from increased transmural dispersion of repolarization (TDR) across the myocardial wall, rather than QT interval prolongation per se. TDR can be measured on the electrocardiogram as the time interval between the peak and end of the T-wave (Tp-e). Thus Tp-e is a readily measured assay of drug torsadogenicity. Several anesthetic drugs prolong the QT interval, but their effect on TDR is largely unknown. METHODS: We investigated the effects of sevoflurane on corrected QT (QTc) and Tp-e intervals in 54 unpremedicated ASA I-II children, aged 3–10 yr, who were randomized to receive sevoflurane 1, 1.25, or 1.5 MAC, age-adjusted. Twelve-lead electrocardiograms were recorded before and after sevoflurane exposure. QTc and Tp-e were compared within and among groups using 2-way analysis of variance. Change in Tp-e after sevoflurane exposure was the primary outcome measure. RESULTS: Sevoflurane significantly prolonged preoperative QTc at all doses (P < 0.005), with no dose-response relationship, but had no effect on preoperative Tp-e. CONCLUSION: Sevoflurane markedly prolongs the QTc in healthy children, but does not increase dispersion of repolarization as measured by the Tp-e interval, indicating low or no torsadogenicity, and making it unlikely to increase predisposition to TdP.

Total intravenous anesthesia and spontaneous respiration for airway endoscopy in children – a prospective evaluation

Introduction:  Inhalational anesthesia with spontaneous respiration is traditionally used to facilitate airway endoscopy in children. The potential difficulties in maintaining adequate depth of anesthesia using inhalational anesthesia and the anesthetic pollution of the surgical environment are significant disadvantages of this technique. We report our institutional experience using total intravenous anesthesia (TIVA) and spontaneous respiration.

The Effect of Propofol Concentration on Dispersion of Myocardial Repolarization in Children

BACKGROUND:QT interval prolongation on the electrocardiogram (ECG) may be drug-induced and is traditionally associated with torsades des pointes. A better predictor of torsades des pointes is the time interval between the peak and the end of the T-wave (Tp-e). Older studies of propofol’s effect on the corrected interval (QTc) are conflicting and confounded by polypharmacy. It was recently shown that target-controlled infusion of propofol at 3 &mgr;g/mL has no effect on QTc or Tp-e. This plasma concentration of propofol is at the extreme lower end of the range for surgical anesthesia. In this randomized, double-blind, clinical study, we investigated the dose–response relationship between propofol, QTc, and Tp-e in a range of doses clinically relevant for surgical anesthesia. METHODS:Sixty healthy unpremedicated children, aged 3–10 yr, were recruited. Subjects were randomized to receive target-controlled infusions of propofol, to achieve 1 of 3 plasma concentrations: 3, 4.5, and 6 &mgr;g/mL. A preoperative 12 lead ECG was performed and repeated 5 min after induction. Two investigators, blinded to group allocation and to the timing of the ECG traces, independently measured QTc and Tp-e within and between each group. Paired t-tests were used to compare QTc and Tp-e within groups. One-way analysis of variance was used for intergroup analysis. The primary outcome measure was a change of >25 ms in Tp-e both within and between groups. RESULTS:ECG recordings were obtained in 51 children. There were no demographic or ECG differences at baseline, at which time QTc and Tp-e values were within normal limits. There were no differences in QTc or Tp-e after induction within or between the three different groups. DISCUSSION:Propofol has no effect on myocardial repolarization in healthy children at clinically relevant doses. This suggests that propofol would be a rational choice for children with a preexisting repolarization abnormality.

The effects of droperidol and ondansetron on dispersion of myocardial repolarization in children

Objectives:  To compare the effects of droperidol and ondansetron on electrocardiographic indices of myocardial repolarization in children.

The safety of modern anesthesia for children with long QT syndrome.

BACKGROUND:Patients with long QT syndrome (LQTS) may experience a clinical spectrum of symptoms, ranging from asymptomatic, through presyncope, syncope, and aborted cardiac arrest, to sudden cardiac death. Arrhythmias in LQTS are often precipitated by autonomic changes. This patient population is believed to be at high risk for perioperative arrhythmia, specifically torsades de pointes (TdP), although this perception is largely based on limited literature that predates current anesthetic drugs and standards of perioperative monitoring. We present the largest multicenter review to date of anesthetic management in children with LQTS. METHODS:We conducted a multicentered retrospective chart review of perioperative management of children with clinically diagnosed LQTS, aged 18 years or younger, who received general anesthesia (GA) between January 2005 and January 2010. Data from 8 institutions were collated in an anonymized database. RESULTS:One hundred three patients with LQTS underwent a total of 158 episodes of GA. The median (interquartile range) age and weight of the patients at the time of GA was 9 (3–15) years and 30.3 (15.4–54) kg, respectively. Surgery was LQTS-related in 81 (51%) GA episodes (including pacemaker, implantable cardioverter-defibrillator, and loop recorder insertions and revisions and lead extractions) and incidental in 77 (49%). &bgr;-blocker therapy was administered to 76% of patients on the day of surgery and 47% received sedative premedication. Nineteen percent of patients received total IV anesthesia, 30% received total inhaled anesthesia, and the remaining 51% received a combination. No patient received droperidol. There were 5 perioperative episodes of TdP, all in neonates or infants, all in surgery that was LQTS-related, and none of which was overtly attributable to anesthetic regimen. Thus the incidence (95% confidence interval) of perioperative TdP in incidental versus LQTS-related surgery was 0/77 (0%; 0%–5%) vs 5/81 (6.2%; 2%–14%). CONCLUSIONS:With optimized perioperative management, modern anesthesia for incidental surgery in patients with LQTS is safer than anecdotal case report literature might suggest. Our series suggests that the risk of perioperative TdP is concentrated in neonates and infants requiring urgent interventions after failed first-line management of LQTS.

A retrospective audit to examine the effectiveness of preoperative warming on hypothermia in spine deformity surgery patients.

Hypothermia (core body temperature <36°C) during surgery has been associated with surgical site infection, a major risk in all spine deformity surgeries. Forced air warming is an important method of intraoperative temperature maintenance in children. In mid‐2010, we empirically introduced preoperative warming as a strategy to reduce intraoperative hypothermia.

Usability and performance characteristics of the pediatric air-Q® intubating laryngeal airway

PurposeThe air-Q® intubating laryngeal airway (ILA) is a supraglottic device (SGD) designed specifically to function as both a primary airway and a bridging device and conduit for fibreoptic intubation in difficult airway scenarios. This observational study evaluated the usability and performance characteristics of pediatric air-Q ILA sizes 1.0, 1.5, 2.0, and 2.5 when used as a primary airway.MethodsOne hundred ten children, American Society of Anesthesiologists physical status I-III and undergoing elective surgery, received a weight-appropriate air-Q ILA following induction of anesthesia. The evaluation criteria included ease of insertion, quality of ventilation, presence of gastric insufflation, oropharyngeal leak pressures (OLPs) and maximum tidal volumes (VT max) in five different head positions, and fibreoptic view of the glottis.ResultsFor sizes 1.0, 1.5, 2.0, and 2.5, the median [P25,P75] neutral OLPs (cm H2O) were 23.0 [20.0,30.0], 16.5 [15.0,20.8], 14.0 [10.0,17.8], and 14.0 [11.3,16.8], respectively. The median [P25,P75] neutral VT max values (mL·kg−1) were 17.4 [14.3,19.7], 20.3 [16.8,25.5], 17.8 [14.5,22.1], and 14.0 [11.6,16.0], respectively. Median [P25,P75] ease of insertion scores (0-10; 0 = easiest ever, 10 = most difficult ever) were 1 [1,2], 2 [2,3], 2 [1,2.8], and 2 [2,3] respectively. Ventilation was adequate in 108/110 cases, and a fibreoptic view of the vocal cords was obtained in 102/110 cases.ConclusionsThe air-Q ILA functions acceptably as a primary SGD in infants and children. The OLPs are lower than published values for the ProSeal laryngeal mask airway (LMA ProSeal™), the current pediatric SGD of choice, but adequate tidal volumes are readily achievable. The fibreoptic views of the glottis portend well for fibreoptic intubation through the device. (This trial was registered at clinicaltrials.gov number, NCT00885911).RésuméObjectifLe masque laryngé d’intubation air-Q® est un dispositif supraglottique (DSG) conçu spécialement pour fonctionner aussi bien seul comme instrument de gestion des voies aériennes que comme pont et guide d’intubation fibroscopique en cas de voies aériennes difficiles. Cette étude observationnelle a évalué les caractéristiques de convivialité et de performance du masque laryngé air-Q de tailles 1,0, 1,5, 2,0 et 2,5 utilisé seul.MéthodeAprès l’induction de l’anesthésie, on a inséré un masque laryngé d’intubation air-Q adapté au poids chez 110 enfants de statut physique I-III selon la classification de l’American Society of Anesthesiologists devant subir une chirurgie non urgente. Les critères d’évaluation comprenaient la facilité d’insertion, la qualité de la ventilation, la présence d’insufflation gastrique, les pressions de fuite oropharyngée (OLP) et les volumes courants maximaux (VT max) dans cinq positions différentes de la tête, ainsi que la vue fibroscopique de la glotte.RésultatsPour les tailles 1,0, 1,5, 2,0, et 2,5, les OLP neutres médianes [P25,P75] (cm H2O) étaient de 23,0 [20,0,30,0], 16,5 [15,0,20,8], 14,0 [10,0,17,8], et 14,0 [11,3,16,8], respectivement. Les valeurs VT maximales neutres médianes [P25,P75] (mL·kg−1) étaient de 17,4 [14,3,19,7], 20,3 [16,8,25,7], 17,8 [14,5,22,1], et 14,0 [11,6,16,0], respectivement. Les scores médians [P25,P75] de facilité d’insertion (0-10; 0 = le plus facile, 10 = le plus difficile) étaient de 1 [1,2], 2 [2,3], 2 [1,2.8], et 2 [2,3] respectivement. La ventilation était adéquate dans 108/110 cas, et une vue fibroscopique des cordes vocales a été obtenue dans 102/110 cas.ConclusionLe fonctionnement du masque laryngé d’intubation air-Q est acceptable utilisé seul chez les nourrissons et les enfants. Les OLP sont plus basses que les valeurs publiées pour le masque laryngé ProSeal (LMA ProSeal™), le DSG actuellement privilégié en pédiatrie, mais on peut facilement atteindre des volumes courants adéquats. Les vues fibroscopiques de la glotte laissent présager une bonne intubation fibroscopique via le dispositif. (Cette étude a été enregistrée au numéro ClinicalTrials.gov NCT00885911).

Anesthetic considerations in the management of Wilms’ tumor

Max Wilms, a German anatomist and surgeon, described a series of seven cases of nephroblastoma in 1899 (1). Although not the first to do so, his name has become eponymous with the malignancy. Just over a century later, the management of patients with Wilms’ tumor has developed into a multidisciplinary undertaking by surgeons, oncologists and pathologists, guided by the results of a series of national clinical trials in the US [National Wilms’ Tumor Study Group (NWTSG)], France [Société Internationale d’Oncologie Pédiatrique (SIOP)], the UK [UK Children’s Cancer Study Group (UKCCSG)], Germany, and Brazil. Anesthetists become involved in the care of these patients during imaging studies, primary or delayed surgical resection, and management of central venous access for chemotherapy administration. This review aims to provide an overview of current management of nephroblastoma and to address anesthesia implications of the disease and its treatment.

Preoperative warming and undesired surgical and anesthesia outcomes in pediatric spinal surgery—a retrospective cohort study

Underbody forced air warming is a method commonly used for intraoperative temperature maintenance in children. We previously reported that preoperative forced air warming of children undergoing spinal surgery substantially reduces the incidence and duration of intraoperative hypothermia (<36°C).