Summary The purpose of this study was to assess whether ultrasonography is useful for determining uncuffed tracheal tube sizes for paediatric patients. The equation for selecting the correctly sized tracheal tube was developed using data on the subglottic diameter measured by ultrasonography and air leak test. The efficacy of the new equation was evaluated by comparing it with the conventional age‐based formula (4 + age/4) in another 100 patients. Tracheal tube sizes were selected using two methods, and air leakage pressure was measured after each intubation. The ultrasonographic method allowed the correct tube size to be selected in 60% of cases, whereas the age‐based method enabled this in 31% of cases (p < 0.001). Ultrasound can offer a useful means of selecting correct tracheal tube size compared with the age‐based formula in paediatric patients. However, even using ultrasound, the success rate of correct tube size selection is still not very high. You can respond to this article at http://www.anaesthesiacorrespondence.com

SummaryThis study was aimed to determine whether pre-operatively measured linear and nonlinear analysis of heart rate variability might predict the occurrence of the oculocardiac re¯ex (OCR) or other arrhythmia during strabismus surgery in children (n 185, mean (SD) age 8.09 (3.31) years). We compared time-and frequency-domain, and nonlinear dynamic indices of pre-operatively measured RR interval data between the OCR-positive group (maximum heart rate decrement 20 beat.min À1 during the traction of extraocular muscle, n 54), OCR-negative group (< 20 beat.min À1 , n 78) and arrhythmia-positive group (all other arrhythmias; n 53). pNN50, rMSSD, high-frequency power and nonlinear prediction error were signi®cantly lower in the OCR-positive and arrhythmia-positive groups than in the OCR-negative group. Discriminant analysis using these indices could correctly identify 39/54 (72.2%) OCR-positive patients. Some pre-operatively measured indices of linear and nonlinear heart rate variability, especially when used in combination, are valuable for predicting signi®cant bradycardia during strabismus surgery in children.

SummarySevoflurane prolongs the QT interval (QTI). Patients with congenital sensorineural hearing loss (SNHL) often have a prolonged QTI. This study was to investigate the effects of sevoflurane on the QTI in SNHL and control children. Thirty patients with SNHL and 30 controls were studied. The corrected QT interval (QTc), interval from peak to end of T wave (Tp-e) and QT variability index (QTVI) were analysed. QTc and Tp-e were estimated by the average QTc and Tp-e measured beat-by-beat for 15 min. Heart rate power spectral analysis was performed. In both groups, QTc and QTVI increased during anaesthesia, but Tp-e did not change. There were no differences in QTc, QTVI, Tp-e, low-and high-frequency power between the two groups. In both groups, sevoflurane lengthened the QTc and QTVI intervals but not Tp-e. Sevoflurane is a popular inhalational agent for general anaesthesia. It blocks the slowly activating delayed rectifier K current (I Ks ) and prolongs the QT interval in both children [1,2] and adults [3,4]. Such changes may be of clinical significance in patients presenting with long QT syndrome, hypokalaemia or in the presence of other agents or factors that lengthen the QT interval.The Jervell and Lange-Nielson syndrome [5] is a long-QT syndrome found among patients with congenital sensorineural hearing loss (SNHL). The deafness is attributed to mutations on the KCNQ1 or KCNE1 genes encoding the rapidly activating delayed rectifier K + channel (I Kr ) in the inner ear. Similar mutations, present in the cardiomyocyte, cause the long QT syndrome. However, it was reported that even patients with congenital SNHL who do not meet the criteria for Jervell and Lange-Nielsen syndrome have increased QTc [6,7]. Thus such children may be at increased risk of corrected QT (QTc) prolongation during sevoflurane anaesthesia.The aim of this study was to investigate how sevoflurane changes the QT parameters in children with congenital SNHL, and whether this differs from the changes in normal children produced by sevoflurane.The QT parameters we analysed were QTc, interval from peak to end of T wave (Tp-e) and QT variability index (QTVI) which reflect the action potential duration of the ventricle, transmural repolarisation dispersion in the action potential duration [8,9] and temporal repolarisation lability [10], respectively. The clinical importance of increases in QT parameter values lies in their association with malignant ventricular arrhythmias [11][12][13]. To improve the accuracy of the average of QTc and Tp-e, we averaged all beat-by-beat QTc and Tp-e values measured automatically over the 15 min period, as well as four manually measured values of QTc and Tp-e. Methods Study populationAfter obtaining approval from the institutional ethics committee of the hospital and written informed consent from parents or guardians, the study was performed on 30 children with congenital SNHL (SNHL group) and 30 patients with chronic otitis media (control group), both of whom required ear surgery and were aged between 2 and 15 year...