Investigation of TL and OSL detectors in ultra-high dose rate electron beams.

Objective.This work aims at investigating the response of various thermally stimulated luminescence detectors (TLDs) and optically stimulated luminescence detectors (OSLDs) for dosimetry of ultra-high dose rate electron beams. The study was driven by the challenges of dosimetry at ultra-high dose rates and the importance of dosimetry for FLASH radiotherapy and radiobiology experiments.Approach.Three types of TLDs (LiF:Mg,Ti; LiF:Mg,Cu,P; CaF2:Tm) and one type of OSLD (Al2O3:C) were irradiated in a 15 MeV electron beam with instantaneous dose rates in the (1-324) kGy s-1range. Reference dosimetry was carried out with an integrating current transformer, which was calibrated in absorbed dose to water against a reference ionization chamber. Additionally, dose rate independent BeO OSLDs were employed as a reference. Beam non-uniformity was addressed using a matrix of TLDs/OSLDs.Main results.The investigated TLDs were shown to be dose rate independent within the experimental uncertainties, which take into account the uncertainty of the dosimetry protocol and the irradiation uncertainty. The relative deviation between the TLDs and the reference dose was lower than 4 % for all dose rates. A decreasing response with the dose rate was observed for Al2O3:C OSLDs, but still within 10 % from the reference dose.Significance.The precision of the investigated luminescence detectors make them suitable for dosimetry of ultra-high dose rate electron beams. Specifically, the dose rate independence of the TLDs can support the investigation of the beam uniformity as a function of the dose rate, which is one of the challenges of the employed beam. Al2O3:C OSLDs provided high precision measurements, but the decreasing response with the dose rate needs to be confirmed by additional experiments.

The effect of intravenous lidocaine on laryngeal and respiratory reflex responses in anaesthetised children*.

We studied the effect of intravenous lidocaine on laryngeal and respiratory reflex responses in children anaesthetised with sevoflurane. We tested the hypothesis that the incidence of laryngospasm evoked by laryngeal stimulation is temporarily diminished after the administration of lidocaine. Forty children, aged between 25 and 84months, were anaesthetised with sevoflurane and breathed spontaneously through a laryngeal mask airway. Respiratory reflex responses were elicited by spraying distilled water onto the laryngeal mucosa at three time intervals: (i) before lidocaine was administered (baseline); (ii) at 2min and (iii) at 10min following the intravenous administration of a bolus of lidocaine 2mg.kg(-1) . A blinded reviewer assessed the evoked responses. The incidence of laryngospasm was reduced from 38% at baseline to 15% 2min after lidocaine administration (p<0.02) and 18% 10min after lidocaine administration (p=0.10). We conclude that intravenous lidocaine significantly reduced the incidence of laryngospasm but that the effect was short-lived.

[Uncooperative children during induction of anesthesia : theory and practice]. / Unkooperatives Kind bei Narkoseeinleitung : Theorie und Praxis.

Perioperative anxiety and the resulting lack of cooperation during induction of anesthesia is a common problem in pediatric anesthesia. The extent of anxiety depends on a variety of factors concerning the child, the parents, the anesthesia team and the hospital's friendly atmosphere and infrastructure. Apart from premedication there are a number of non-pharmacological means to improve the child's cooperation and thereby facilitate the induction of anesthesia. If the child is still uncooperative despite an optimal preparation, the anesthetist has to decide whether to postpone the operation or to perform induction of anesthesia under physical restraint in consideration of various criteria.

Avaliação do potencial alelopático, atividade antimicrobiana e antioxidante dos extratos orgânicos das folhas de Pyrostegia venusta (Ker Gawl. ) Miers (Bignoniaceae) / Evaluation of allelopathic potential, antimicrobial and antioxidant activities of Pyrostegia venusta (Ker Gawl. ) Miers (Bignoniaceae) leaf organic extracts

Este trabalho apresenta os resultados de atividade alelopática, antimicrobiana e antioxidante dos extratos orgânicos (hexano, acetato de etila e metanol) das folhas de Pyrostegia venusta (Ker Gawl.) Miers (Bignoniaceae). Para alelopatia, foi estudado o desenvolvimento de Cucumis sativus (pepino), sendo avaliados o comprimento da raiz principal, o número de raízes secundárias e o comprimento do hipocótilo. Os dois primeiros parâmetros foram afetados por todos os três extratos testados enquanto o comprimento do hipocótilo só não foi afetado pelo extrato acetato de etila. Quanto à atividade antimicrobiana, avaliada pelo ensaio de CIM, o extrato hexânico apresentou inibição moderada frente ao Staphylococcus aureus (0,9 mg mL-1) e forte ao Enterococcus hirae (0,5 mg mL-1). O extrato acetato de etila apresentou forte atividade frente Candida albicans (0,3 mg mL-1) enquanto o extrato metanólico não mostrou-se ativo para os microrganismos testados. Por outro lado, o extrato metanólico apresentou a maior capacidade de seqüestrar radicais livres (Concentração Efetiva 50 por cento-CE50 =102,0 ± 56,9 mg mL-1, com TCE50 = 30 min) no ensaio com DPPH (2,2-difenil-1-picril-hidrazila) e o maior teor de compostos fenólicos (116,2 ± 83,0 mg ácido gálico g amostra-1), avaliado pelo ensaio de Folin-Ciocalteau.

This paper presents the results of allelopathic, antimicrobial and antioxidant activities of organic extracts (hexane, ethyl acetate and methanol) from the leaves of Pyrostegia venusta (Ker Gawl.) Miers (Bignoniaceae). Allelopathic activity was assessed based on Cucumis sativus (cucumber) development for the parameters main root length, number of secondary roots and hypocotyl length. All tested extracts affected the first two parameters, while the hypocotyl length was not affected only by the ethyl acetate extract. For antimicrobial activity, assessed by MIC assay, hexane extract showed moderate inhibition for Staphylococcus aureus (0.9 mg mL-1) and strong inhibition for Enterococcus hirae (0.5 mg mL-1). Ethyl acetate extract showed strong activity against Candida albicans (0.3 mg mL-1), whereas methanolic extract was not active against the tested microorganisms. On the other hand, methanol extract showed the most promising radical scavenging capacity (Effective Concentration 50 percent - EC50 = 102.0 ± 56.9 mg mL-1, with TEC50 = 30 min) in DPPH assay (2,2-diphenyl-1-picryl-hidrazil) and the highest level of phenolic compounds (116.2 ± 83.0 mg acid garlic g sample-1), as indicated by Folin-Ciocalteau assay.

Ovarian histology and follicular score in female rats treated with nandrolone decanoate and submitted to physical effort.

The study was conducted to analyze the histology of the ovaries of adults rats treated with steroids, and submitted or not to physical effort. The control group consisted of females submitted to physical effort and sedentary females, both of which received a physiological solution of 0.9% saline. Treated females, sedentary or not, received 6 mg/kg of body weight of nandrolone decanoate. The steroid and physiological solution were administered intraperitoneally, with a single injection per week for 4 consecutive weeks. The applied physical effort was swimming (20 minutes daily, 5 days/week, for the 4 weeks of treatment). Serial sections (5 mum) of ovaries were prepared for histological evaluation and follicular score. The weight of ovaries and hypophysis, the number of antral and atretic follicles, and the area of corpus luteum were all affected by the steroids. In the ovaries of the control groups, well-developed corpus luteum was observed. In the treated groups, the cortical stroma was occupied by ovarian interstitial tissue. The females treated with steroids presented estral acyclicity. The use of nandrolone decanoate, whether associated with physical effort or not, affected the morphological pattern of the ovaries.

Space-time coupling in femtosecond pulse shaping and its effects on coherent control.

We present a Fourier optical analysis of a typical femtosecond pulse shaping apparatus and derive analytic expressions for the space-time dependence of the emerging waveform after the pulse shaper and in the focal volume of an additional focusing element. For both geometries the results are verified experimentally. Hereafter, we analyze the influence of space-time coupling on nonlinear processes, specifically second harmonic generation, resonant interaction with an atomic three-level system, and resonant excitation of a diatomic molecule.

The impact of head position on the cuff and tube tip position of preformed oral tracheal tubes in young children.

Head and neck movements affect both the length of the trachea and the position of tracheal tubes. This is of relevance when using cuffed tubes because changes in the position of the tube tip may not be equal to changes in the position of the cuff. The aim of the study was to assess the impact of head and neck movement on the position of the tube tip and the cuff of newly designed, oral preformed tracheal tubes in children. The tracheas of 128 children aged 1-8 years were intubated with preformed oral tubes. The distances 'carina-to-tracheal tube tip' and 'vocal cords-to-tube tip' were measured endoscopically. These measurements were performed with the head and neck in a functional neutral position (110 degrees ), during neck flexion (80 degrees ) and neck extension (130 degrees ). Tracheal length was dependent on head and neck position: neck extension elongated the trachea (p < 0.0001), and neck flexion shortened the trachea (p < 0.0001). Neck flexion moved the tube inward and resulted in endobronchial displacement in two patients. Neck extension moved the tube outwards. While no cuff was positioned between the vocal cords, cuff movement to the cricoid area occurred frequently. Complex interactions during head and neck movement along with the fixed insertion depth of preformed tubes often cause inadvertent malpositioning of the tube tip and cuff. Further changes to tube and cuff lengths might improve the safety of oral preformed tubes in children.

Impact of depth of propofol anaesthesia on functional residual capacity and ventilation distribution in healthy preschool children.

BACKGROUND: Propofol is commonly used in children undergoing diagnostic interventions under anaesthesia or deep sedation. Because hypoxaemia is the most common cause of critical deterioration during anaesthesia and sedation, improved understanding of the effects of anaesthetics on pulmonary function is essential. The aim of this study was to determine the effect of different levels of propofol anaesthesia on functional residual capacity (FRC) and ventilation distribution. METHODS: In 20 children without cardiopulmonary disease mean age (SD) 49.75 (13.3) months and mean weight (SD) 17.5 (3.9) kg, anaesthesia was induced by a bolus of i.v. propofol 2 mg kg(-1) followed by an infusion of propofol 120 microg kg(-1) min(-1) (level I). Then, a bolus of propofol 1 mg kg(-1) was given followed by a propofol infusion at 240 microg kg(-1) min(-1) (level II). FRC and lung clearance index (LCI) were calculated at each level of anaesthesia using multibreath analysis. RESULTS: The FRC mean (SD) decreased from 20.7 (3.3) ml kg(-1) at anaesthesia level I to 17.7 (3.9) ml kg(-1) at level II (P < 0.0001). At the same time, mean (SD) LCI increased from 10.4 (1.1) to 11.9 (2.2) (P = 0.0038), whereas bispectral index score values decreased from mean (SD) 57.5 (7.2) to 35.5 (5.9) (P < 0.0001). CONCLUSIONS: Propofol elicited a deeper level of anaesthesia that led to a significant decrease of the FRC whereas at the same time the LCI, an index for ventilation distribution, increased indicating an increased vulnerability to hypoxaemia.

The effect of caudal block on functional residual capacity and ventilation homogeneity in healthy children.

Caudal block results in a motor blockade that can reduce abdominal wall tension. This could interact with the balance between chest wall and lung recoil pressure and tension of the diaphragm, which determines the static resting volume of the lung. On this rationale, we hypothesised that caudal block causes an increase in functional residual capacity and ventilation distribution in anaesthetised children. Fifty-two healthy children (15-30 kg, 3-8 years of age) undergoing elective surgery with general anaesthesia and caudal block were studied and randomly allocated to two groups: caudal block or control. Following induction of anaesthesia, the first measurement was obtained in the supine position (baseline). All children were then turned to the left lateral position and patients in the caudal block group received a caudal block with bupivacaine. No intervention took place in the control group. After 15 min in the supine position, the second assessment was performed. Functional residual capacity and parameters of ventilation distribution were calculated by a blinded reviewer. Functional residual capacity was similar at baseline in both groups. In the caudal block group, the capacity increased significantly (p < 0.0001) following caudal block, while in the control group, it remained unchanged. In both groups, parameters of ventilation distribution were consistent with the changes in functional residual capacity. Caudal block resulted in a significant increase in functional residual capacity and improvement in ventilation homogeneity in comparison with the control group. This indicates that caudal block might have a beneficial effect on gas exchange in anaesthetised, spontaneously breathing preschool-aged children with healthy lungs.

[Management of the upper airway in spontaneously breathing children. A challenge for the anaesthetist]. / Management der oberen Atemwege beim spontan atmenden Kind. Eine Herausforderung für den Anästhesisten.

In unconscious, spontaneously breathing and anaesthetised children, a high incidence of partial or complete airway obstruction jeopardizes sufficient oxygenation. In this situation, the most important and efficient manoeuvre is to open up the upper airway. Chin lift, jaw thrust and continuous positive airway pressure (CPAP) are proven and effective methods for opening an obstructed upper airway. In addition to these simple airway manoeuvres, different techniques of body positioning (e.g., lateral positioning or supine position in combination with the "sniffing position") are effective to improve and maintain upper airway patency.

Use of continuous positive airway pressure during flexible bronchoscopy in young children.

Young children are at increased risk for hypoxaemia and hypercapnia during flexible bronchoscopy due to the small size and increased collapsibility of their airways. Various strategies are used to prevent hypoventilation and to provide oxygen during the procedure. The aim of this study was to assess the impact of continuous positive airway pressure (CPAP) on ventilation during flexible bronchoscopy in infants and young children. Tidal breathing was measured in 16 spontaneously breathing and deeply sedated children, aged 3-25 months, by ultrasound spirometry via an airway endoscopy mask. Measurements were made with the tip of the bronchoscope positioned in the pharynx with no CPAP, and in mid-trachea with 0, 5 and 10 cmH2O of CPAP. Transition of the bronchoscope through the vocal cords was associated with significant decreases of tidal volumes (5.0+/-0.5 versus 3.4+/-0.5 mL.kg(-1)), peak tidal expiratory flows (78+/-12 versus 52+/-10 mL.s(-1)) and peak tidal inspiratory flows (98+/-15 versus 66+/-12 mL.kg(-1)). CPAP (5-10 cmH2O) induced almost complete reversal of these changes. In conclusion, it is shown here that flexible bronchoscopy in spontaneously breathing young children is associated with significant decreases in tidal volume and respiratory flow. These changes are largely reversible with continuous positive airway pressure.

Jaw thrust can deteriorate upper airway patency.

Upper airway obstruction is a frequent problem in spontaneously breathing children undergoing anesthesia or sedation procedures. Failure to maintain a patent airway can rapidly result in severe hypoxemia, bradycardia, or asystole, as the oxygen demand of children is high and oxygen reserve is low. We present two children with cervical masses in whom upper airway obstruction exaggerated while the jaw thrust maneuver was applied during induction of anesthesia. This deterioration in airway patency was probably caused by medial displacement of the lateral tumorous tissues which narrowed the pharyngeal airway.

[Vascular access in emergency paediatric anaesthesia]. / Vaskulärer Zugang in der Kindernotfallanästhesie.

There is very little literature to guide the young practitioner in caring for a child that needs emergency surgery and has difficult venous access. Questionnaires were sent to 89 members of the Swiss Paediatric Anaesthesia Society and to the heads of Anaesthesia Departments of Swiss teaching hospitals. Two typical case records were presented, both of which were characterised by the fact that 2-3 peripheral venous cannulation attempts were unsuccessful. Case A: a young child with a fracture of the radius and case B an infant with upper gastrointestinal ileus. The anaesthetists were then questioned regarding their preferences for optimal treatment. The majority would proceed with further attempts and, if these still failed, intramuscular or inhalational induction of anaesthesia was suggested as a reasonable choice for case A. However, for case B, a femoral venous or intraosseous access to the venous system was judged to be the safest method. On the basis of our inquiry and a literature search, a priority list was developed to suggest the best possible techniques for vascular access and alternative anaesthesia induction techniques for emergency paediatric procedures.