During recent years there has been renewed interest in noninvasive methods of assessing respiratory function in infants, since the use of face masks and pneumotachographs (PNT) have both been shown to affect breathing pattern [1]. Respiratory inductive plethysmography (RIP) is a means of measuring breathing movements without any connections at the airway opening, and therefore has numerous potential applications in infants, including prolonged respiratory monitoring in the intensive care unit or postoperatively. RIP uses inductance coils within elasticated bands to measure the respiratory excursion of the ribcage (rc) and abdomen (abd). The respiratory system is assumed to move with two "degrees of freedom", so that changes in inductance are proportional to changes in ribcage and abdominal volume. The weighted sum of the rc and abd is therefore proportional to the tidal volume (VT). Studies using RIP have increased our understanding of respiratory control and mechanics [2,3], including the fact that infancy is characterized by abdominal breathing [4], and that halothane anaesthesia is associated with a loss of ribcage recruitment [5].Whereas uncalibrated RIP is a valuable means of assessing both respiratory timing and various qualitative aspects of rc and abd asynchrony [6][7][8], calibration is essential if quantitative changes in ventilation are to be assessed. Such calibration, which involves a two-stage process of determining the relative contributions of rc and abd to each breath and then ascertaining a proportionality coefficient in order to scale the weighted sum to actual tidal volume, has, however, proved to be a major challenge when using RIP in infants. Three main methods of calibration have been proposed, as outlined below.1) The rc and abd signals are compared with simultaneous recordings of VT from a PNT, according to the equation:where Vrc is the inductance (voltage) of the rc signal and Vabd is that of the abd signal. Providing VT is measured over a large enough number of breaths, a proportionality coefficient K can then be derived using a least squares or graphical solution to the equation. However, since this always requires the simultaneous use of a PNT, the advantages of RIP are at least partially lost.2) In 1987, KONNO and MEAD [9] described the isovolume manoeuvre, as a means of determining the relative contribution of rc and abd without a PNT. This requires the subject to shift gas gently between the rc and abd during a breath hold or airway occlusion, thereby producing paradoxical movements of the two compartments. Since VT does not change, equation (1) Measurements were made during spontaneous (SV) and intermittent positive pressure (IPPV) ventilation, sighs and airway occlusions. The VT,DIF was the difference between VT,QDC and VT,PNT (%VT). The contribution of the ribcage (rc) to VT,QDC (%rc) and the thoracoabdominal phase lag were also derived. Twenty-eight infants, mean (SD) age 14.0 (6.2) months were studied.VT,QDC represented VT,PNT most closely when Š20 breaths were analysed. The...

This is the largest study of the incidence of VAE in children undergoing neurosurgery. Our results suggest that the sitting position can be used safely for neurosurgery in children.

Sevoflurane has a lower blood-gas solubility and a less pungent odour than halothane; this may allow more rapid induction of anaesthesia. In a randomized, blinded study, we compared the induction characteristics of maximum initial inspired concentration of 8% sevoflurane and 5% halothane using conventional vaporizers in children aged 3 months to 3 years. There was no statistically significant difference in induction times between the two groups: mean times to loss of consciousness were 1 min 12 s (SD 18 s, range 40 s-1 min 44 s) for sevoflurane and 1 min 16 s (SD 17 s, range 50 s-1 min 52 s) for halothane, although these times were shorter than in previous studies using a gradual increase in vapour concentration. A small number of complications were noted in both groups, although none interfered with induction of anaesthesia. Struggling scores were lower in the sevoflurane group than in the halothane group (chi-square for trends = 6.34, P < 0.02). A significant number (11 of 15) of parents of children in the sevoflurane group who had previous experience of halothane induction preferred sevoflurane (chi-square for trends = 4.03, P < 0.05). We conclude that with this technique, induction was rapid with both sevoflurane and halothane. Our assessment of patient struggling and parents' perceptions suggests that induction with sevoflurane was more pleasant than with halothane.

SummaryThe

SummaryThe induction characteristics qf'set'oflurane and halothane were Key wordsAnaesthetics, rolatile; sevoflurane, halothane. Anaesthesia; induction.Sevoflurane has the potential to be the ideal inhalational induction agent for children [l]. It is pleasant smelling, non-irritant and, by virtue of its insolubility, rapidly acting. Although it was licenced in Japan in 1992 it did not receive Food and Drug Administraion (FDA) and Committee of Safety of Medicines (CSM) approval until 1995. Halothane is currently the preferred inhalational agent because it is relatively non-irritant and produces a rapid and smooth induction, even in children with difficult airways. Its disadvantages, however, include a strong odour, cardiovascular depression at high concentrations and, rarely, it causes hepatic necrosis. This study, part of a multicentre international Phase 3 trial, compared the induction characteristics of sevoflurane and halothane in children. MethodsEighty-one children were randomly allocated to receive anaesthesia by inhalational induction with either sevoflurane or halothane. Children were aged between 6 months and 6 years, ASA 1 or 2, and were having general surgical, urological, plastic or orthopaedic procedures. Patients with epilepsy were specifically not studied. Of the 8 1 children, 40 had day case surgical procedures. The study was approved by the hospital ethics committee and informed and written consent was obtained from parents.Children were anaesthetised by one of four consultants and the induction technique was standardised. The study was not blind. Oral sedative and atropine premedication was administered when clinically indicated. The inhalational agent was administered with 66% nitrous oxide in oxygen via a Mapleson F breathing system, the anaesthetist holding the patient end of the system as close to the child's face as could be tolerated. Inspired concentrations were steadily increased in increments of 0.5-1%0 for halothane or 1.5-2% for sevoflurane every three breaths up to the maximum of 5% for halothane and 7 % for sevoflurane. As soon as consciousness was lost a face mask was applied and an intravenous cannula sited.Adequate depth of anaesthesia was maintained with inspired concentrations between 1 and 2% for halothane and 2 and 4% for sevoflurane. After, or towards the end of the induction period, either a laryngeal mask airway or a tracheal tube was inserted as appropriate for the surgical procedure. Tracheal intubation was accomplished after muscle relaxation with atracurium. No other drugs were administered during the induction period.The time taken to achieve unconsciousness (loss of eyelash reflex) was recorded for all children. The time taken to complete induction (to achieve steady spontaneous ventilation and small pupils with central gaze) was recorded except in children whose tracheas were