Low pressure gynecological laparoscopy (7mmHg) with AirSeal® System versus a standard insufflation (15mmHg): A pilot study in 60 patients.

OBJECTIVES: To evaluate feasibility of performing benign gynecologic pathology low pressure (7mmHg) laparoscopy (LPL) with AirSeal® system and to study benefits in terms of postoperative pain, when compared to a standard insufflation group (15mmHg). MATERIALS AND METHODS: In this prospective randomized pilot study, 60 patients had laparoscopy for gynecologic benign pathology: 30 with 7mmHg and AirSeal system, and 30 with 15mmHg standard insufflator. The primary endpoint was incidence of shoulder pain. A postoperative questionnaire was completed by each patient to assess shoulder pain (Numeric Rating Scale [NRS], from 0 to 10) at H4, H8, H24, and consumption of morphinics was notified. During each procedure, anesthesia parameters were collected (peak airway pressure, systolic blood pressure, end tidal CO2). RESULTS: Laparoscopy was performed on 30 patients in AirSeal®-LP group without need to increase pressure above 7mmHg, and no complication was reported. Incidence of shoulder pain was significantly lower in the AirSeal®-LP group (23.3% vs. 73.3%, P<0.001). NRS shoulder pain was significantly lower in AirSeal® LP group at hour 4, 8 and 24. Maximal values of ETCO2, systolic blood pressure, and peak airway pressure were significantly lower in AirSeal®-LP group. CONCLUSION: LP (7mmHg) laparoscopy with AirSeal® platform allows laparoscopic surgery with less postoperative shoulder pain. These results could facilitate the development of ambulatory laparoscopy.

Vibration-induced compaction of granular suspensions.

We investigate the compaction dynamics of vibrated granular suspensions using both digital imaging technique and MRI measurements. Starting from initialy loose packings, our experimental data suggest the existence of two stages in the compaction dynamics: a fast stage at short times where a rising compaction front propagates through the granular suspension and a slow stage at large times where the packing compacts slowly and homogeneously. The compaction dynamics in each stage can be well fitted to usual stretched exponential laws with stretching exponents equal to 2 and 0.45, respectively. The transition time between these two stages, τ c , depends on the fluid viscosity, vibration intensity and grain diameter. We show that τ c (-1) and the velocity of the front decrease roughly linearly with the lubrication Peclet number, Pe lub related to the competition between the lubrication stress induced by vibrations and the granular pressure.

Foam clogging.

To what extent are aqueous foams prone to clogging? Foam permeability is measured as a function of particulate loading (trapped hydrophilic particles) under conditions where the particle to bubble size ratio is allowed to increase when the number of particles per bubble is fixed. In addition to experiments performed on the foam scale, we investigated experimentally and numerically the hydrodynamic resistance of a single foam node loaded with one particle. It is shown that, with respect to solid porous media, aqueous foams clog more efficiently due to two reasons: (i) the deformation of interfaces allows for larger particles to be incorporated within the interstitial network and (ii) the interfacial mobility contributes to lowering of the reduced permeability.

Pregnancy is associated with a decrease in pharyngeal but not tracheal or laryngeal cross-sectional area: a pilot study using the acoustic reflection method.

BACKGROUND: The risk of difficult upper airway access is increased during pregnancy, especially in labor. Changes in upper airway calibre have been poorly studied during pregnancy. The acoustic reflection method is a non-invasive technique that allows a longitudinal assessment of the cross-sectional area of the upper airway from the mouth to carina. We used this technique to evaluate upper airway calibre during normal pregnancy. METHODS: We conducted a prospective, single centre, observational study with a clinical and upper airway acoustic reflection method evaluation of healthy women during the first, second and third trimesters of pregnancy, and up to two days and one month after delivery. RESULTS: Fifty women participated to the study. The mean pharyngeal cross-sectional area decreased between the first and third trimesters (P < 0.001) with no significant change of the minimal and mean tracheal cross-sectional areas. The Mallampati score increased during pregnancy between the first and third trimesters (P< 0.001). CONCLUSION: Using measurements with the acoustic reflection method, normal pregnancy is associated with a significant reduction in the cross-sectional area of the pharynx and a concomitant increase in the Mallampati score. No change was observed in the minimal and mean tracheal cross-sectional areas.

[Video-assisted surgery in children: current progress and future perspectives]. / Vidéochirurgie chez l'enfant : progrès actuels et perspectives.

This review presents the evidence of video-assisted surgery in the pediatric population and discusses future progress in this field. Videosurgery minimizes the cosmetic impact and the pain induced by open procedures and has been in constant development in adults and children. Earlier training of surgeons and residents combined with advances in anesthetics and technology have expanded the use of videosurgery for more complex interventions. Although most feasible surgical procedures have been performed by laparoscopy, the literature has not yet defined it as the gold standard for most interventions, especially because of the lack of evidence for many of them. However, laparoscopy for cholecystectomy is now the preferred approach with excellent postoperative outcomes and few complications. Although no evidence has been demonstrated in children, laparoscopy has been shown to be superior in adults for gastroesophageal reflux disease and splenectomy. Laparoscopic appendectomy remains controversial. Nevertheless, meta-analyses have concluded in moderate but significant advantages in terms of pain, cosmetic considerations, and recovery for the laparoscopic approach. Laparoscopy is now adopted for undescended testes and allows both localization and surgical treatment if necessary. For benign conditions, videosurgery can be an excellent tool for nephrectomy and adrenalectomy. However, laparoscopy remains controversial in pediatric surgical oncology.

[Gestational diabetes insipidus during a twin pregnancy]. / Diabète insipide gestationnel au cours d'une grossesse gémellaire.

Gestational diabetes insipidus is an uncommon clinical disease whose prevalence is approximately two to three pregnancies per 100,000. It may be isolated or associated with preeclampsia. We report a case of gestational diabetes insipidus in a twin pregnancy, originally isolated during two months, and secondarily complicated by HELLP-syndrome. We recall the specific pathophysiology of polyuric-polydipsic syndrome during pregnancy and summarize its various causes. Finally, we discuss the indications, in case of isolated gestational diabetes insipidus, of treatment by dDAVP.

[Informed consent for standard procedures and for clinical research in paediatric anaesthesia]. / Consentement éclairé en anesthésie pédiatrique pour les soins courants et pour la recherche.

This short review is aimed at describing the particularities of consent in paediatric patients. For routine procedures, the consent of one of the parents is required whereas both parents should sign the consent for research protocols. In case of difficulties such as Jehovah witnesses or parental opposite opinions, doctors should ask the question to the judge in charge of protection of children. Consent or at least assent of minors enrolled in research protocols should be obtained provided their maturity is sufficient to understand correctly the purpose of clinical research.

[Update on propofol TCI in children]. / Nouvelles avancées en AIVOC pédiatrique au propofol.

For several years, total intravenous anaesthesia (TIVA) has demonstrated many advantages that allow considering propofol anaesthesia as an interesting alternative in pediatric anaesthesia. TCI in children requires calculation and validation of pharmacokinetic (PK) models specifically adapted to the paediatric population. Several PK models based on a 3-compartement approach have been proposed in children: all these models, which integrate only weight as covariable, show increased distribution volumes with a wide interindividual variability. The particular importance to include physiological covariables, as age and lean body mass, to describe metabolic processes during growth and maturation in pediatric PKPD models is in agreement with recent allometric scaling works in children. However, as pharmacodynamic (PD) parameters are still debated in children, there is up to now, no PKPD model currently available for paediatric anaesthesia. Schnider et al.'s model, a model described in adults that includes numerous covariables, may be adapted and more efficient than the classical paediatric models to describe propofol-PKPD relationship in children over 5years. Whatever the model, a pharmacodynamic feedback such as the bispectral index may be useful to counteract interindividual variability in the paediatric population.

[General anaesthesia in children: a French survey of practices]. / Anesthésie générale chez l'enfant : quid des pratiques en 2010 ?

INTRODUCTION: The practice of pediatric anesthesia requires a regular update of scientific knowledge and technical skills. To provide the most adequate Continuing Medical Education programs, it is necessary to assess the practices of pediatric anesthesiologists. Thus, the objective of this survey was to draw a picture of the current clinical practices of general anesthesia in children, in France. MATERIAL AND METHODS: One thousand one hundred and fifty questionnaires were given to anesthesiologists involved in pediatric cases. These questionnaires collected information on various aspects of clinical practice relative to induction, maintenance, recovery from general anaesthesia and also classical debated points such as children with Upper Respiratory Infection (URI), emergence agitation, epileptoid signs or anaesthetic management of adenoidectomy. Differences in practices between CHG (general hospital), CHU (teaching hospital), LIBERAL (private) and PSPH (semi-private) hospitals were investigated. RESULTS: There were 1025 questionnaires completed. Fifty-five percent of responders worked in public hospitals (CHG and CHU); 77% had a practice that was 25% or less of pediatric cases. In children from 3 to 10 years: 72% of respondents used always premedication and two thirds performed inhalation induction in more than 50% of cases. For induction, 53% used sevoflurane (SEVO) at 7 or 8%. Respondents from LIBERAL used higher SEVO concentrations. Tracheal intubation was performed with SEVO alone (37%), SEVO and propofol (55%) and SEVO with myorelaxant (8%), 93% of respondents used a bolus of opioid. For maintenance, the majority of respondents used SEVO associated with sufentanil; desflurane and remifentanil were more frequently used in CHU. Two thirds of respondents used N(2)O. Depth of anesthesia was commonly assessed by hemodynamic changes (52%), end tidal concentration of halogenated (38%) or automated devices based on EEG (7%). In children with URI, 98% of respondents used SEVO for anesthesia. To control the airway 42% used a tracheal tube, 30% a laryngeal mask and 20% a facial mask. Emergence agitation was an important concern for two thirds of respondents, while epileptoid signs were considered as important by only 20%. Eighty-nine percent of respondents practiced anesthesia for adenoidectomy. Anesthesia was induced by inhalation of SEVO 7-8% (41%), 6% (39%) or 4% (12%), 66% put an intravenous line (less frequently in LIBERAL). 67% of the responders managed adenoidectomy without any device to control the airway (more frequently in LIBERAL), 32% administrated a bolus of opioid (less frequently in LIBERAL). DISCUSSION: This survey demonstrated that the practices regarding general anesthesia in children are relatively homogenous. Most of the differences appeared between LIBERAL and the others structures; the anaesthetic management for adenoidectomy illustrates these findings.

Minimal alveolar concentration of sevoflurane inhibiting the reflex pupillary dilatation after noxious stimulation in children and young adults.

BACKGROUND: In children, sevoflurane is the most commonly used anaesthetic. Its excellent haemodynamic tolerance gives it a wide therapeutic index. This halogenated agent can abolish movement [minimal alveolar concentration (MAC)] or haemodynamic responses (MACBAR) to noxious stimulus in children as in adults. Reflex pupillary dilatation (RPD) has been demonstrated as a very sensitive measure of noxious stimulation. In order to investigate the effect of sevoflurane on the RPD, a subcortical reflex, we determined the MAC of sevoflurane inhibiting the RPD in 50% of the subjects in response to skin incision (MACpup) in pre- and post-pubertal subjects. METHODS: We included 30 pre-pubertal children and 19 post-pubertal subjects. Patients received sevoflurane at preselected concentrations according to an 'up and down' design, and after a steady-state period, skin incision was performed. The RPD was considered as significant when the pupillary diameter increased by more than 100%. Heart rate (HR) and bispectral index (BIS) changes were analysed according to the pupillary response. RESULTS: The MACpup of sevoflurane was 4.8% (95% confidence interval, 4.6-5.1%) in pre-pubertal children vs 3.4% (3.5-3.3%) in post-pubertal subjects (P<0.001). Inhibition of RPD was always associated with lack of significant HR response. In pre-pubertal children receiving high concentrations of sevoflurane, RPD in response to noxious stimulation was frequently associated with lack of HR response and low BIS values. CONCLUSIONS: MACpup was higher than MAC and close to the MACBAR. Inhibition of RPD in pre-pubertal children required higher sevoflurane concentrations compared with post-pubertal subjects, suggesting that the relationship between the brain structure sensitivities may differ with brain maturation.

Capture of particles in soft porous media.

We investigate the capture of particles in soft porous media. Liquid foam constitutes a model system for such a study, allowing the radii of passage in the pore space to be tuned over several orders of magnitude by adjusting the liquid volume fraction. We show how particle capture is determined by the coupling of interstitial liquid flow and network deformation, and present a simple model of the capture process that shows good agreement with our experimental data.

Recirculation model for liquid flow in foam channels.

Although extensively studied in the past, drainage of aqueous foams still offers major unaddressed issues. Among them, the behaviour of foam films during drainage has great significance as the thickness of the films is known to control the Ostwald ripening in foams, which in turn impacts liquid drainage. We propose a model relating the films' behavior to the liquid flow in foam channels. It is assumed that Marangoni-driven recirculation counterflows take place in the transitional region between the foam channel and the adjoining films, and the Gibbs elasticity is therefore introduced as a relevant parameter. The velocity of these counterflows is found to be proportional to the liquid velocity in the channel. The resulting channel permeability is determined and it is shown that Marangoni stresses do not contribute to rigidify the channel's surfaces, in strong contrast with the drainage of horizontal thin liquid films. New experimental data are provided and support the proposed model.

Ripening of a draining foam bubble.

A forced Ostwald ripening experiment is performed on a single foam bubble. The bubble size is followed as the system is wetted with a constant liquid flow rate delivered from one of the bubble Plateau borders. Obtained ripening velocities cannot be described with a model based on a constant film thickness assumption. Within these well-controlled experimental conditions, the film thickness is measured and found to depend on the imposed liquid flow rate. It is shown that the bubble growth rate is well predicted as the films thickness evolution is explicitly introduced in the ripening model. Finally, it is suggested that existing results for the coarsening of draining foams could be understood following the approach validated on the bubble scale.

Permeability of aqueous foams.

We perform forced-drainage experiments in aqueous foams and compare the results with data available in the literature. We show that all the data can be accurately compared together if the dimensionless permeability of the foam is plotted as a function of liquid fraction. Using this set of coordinates highlights the fact that a large part of the published experimental results corresponds to relatively wet foams (epsilon approximately 0.1). Yet, most of the foam drainage models are based on geometrical considerations only valid for dry foams. We therefore discuss the range of validity of the different models in the literature and their comparison to experimental data. We propose extensions of these models considering the geometry of foam in the relatively wet-foam limit. We eventually show that if the foam geometry is correctly described, forced drainage experiments can be understood using a unique parameter --the Boussinesq number.

Specific surface area model for foam permeability.

Liquid foams were recognized early to be porous materials, as liquid flowed between the gas bubbles. Drainage theories have been established, and foam permeability has been modeled from the microscopic description of the equivalent pores geometry, emphasizing similarities with their solid counterparts. But to what extent can the theoretical work devoted to the permeability of solid porous materials be useful to liquid foams? In this article, the applicability of the Carman-Kozeny model on foam is investigated. We performed measurements of the permeability of foams with nonmobile surfactants, and we show that, in introducing an equivalent specific surface area for the foam, the model accurately describes the experimental data over two orders of magnitude for the foam liquid fraction, without any additional parameters. Finally, it is shown that this model includes the previous permeability models derived for foams in the dry foams limit.

Node contribution to the permeability of liquid foams.

This paper deals with the drainage of liquid foams. The liquid velocity is known to be related to viscous dissipation occurring within the elements of the liquid network, i.e. the channels and the nodes. When compared together, available values for the hydrodynamic resistance of a foam node appear to span over more than one order of magnitude. To clarify this point, we propose an alternative experimental method to estimate the value of this parameter. In contrast to previous experimental work performed on the foam scale, the node resistance is not treated as a fitting parameter, but instead it is measured directly on the microscopic scale. The results allow a consistent range of values to emerge for this parameter.