Effets de l’halothane sur la ventilation et les gaz du sang artériel chez le rat avec ou sans paralysie diaphragmatique

Certains patients atteints de paralysie diaphragmatique ou de dysfonctionnement diaphragmatique maintiennent leur ventilation par la mise en jeu d’autres muscles que le diaphragme. L’anesthésie, modifiant le fonctionnement de ces muscles, représente un risque potentiel chez ces patients. Afin d’évaluer ce risque, nous avons étudié les effets de l’halothane sur la ventilation et sur les gaz du sang artériel sur un modèle de paralysie diaphragmatique bilatérale, le rat phrénicectomisé. L’étude a été réalisée sur 43 rats. L’efficacité de la phrénicectomie a été contrôlée par l’observation directe, après laparotomie. La laparotomie n’entraine pas de modification des gaz du sang. Chez 23 rats, une laparotomie a été effectuée et une artère carotide a été cathétérisée. Chez 11 rats témoins, les nerfs phréniques ont été abordés, sans être sectionnés. Chez 12 rats, les phréniques ont été sectionnés. La ventilation a été mesurée par une technique pléthysmographique, chez les rats éveillés, avant et après l’opération, puis chez les mêmes rats anesthésiés avec 1,1%, d’halothane inspiré. Les gaz du sang ont été mesurés après l’opération chez les rats éveillés, puis anesthésiés. Chez les 23 rats opérés on observe, après l’opération, une diminution du poids et de la température centrale, plus importante chez les phrénicectomisés que chez les témoins. Chez les 11 rats témoins, après l’opération, la ventilation augmente, sans modification des gaz du sang. Chez ces rats, l’halothane provoque une diminution de la ventilation minute et de la PaO₂ et une augmentation de la PaCO₂. La phrénicectomie entraine chez les 12 rats, éveillés, une augmentation de la ventilation minute, une hypoxémie et une hypercapnie. Chez ces rats, l’halothane entraine le décès dans trois cas, une diminution de la ventilation minute et une hypercapnie et une hypoxémie importantes chez les neuf autres rats. Les modifications des gaz du sang sont plus importantes que chez les témoins anesthésiés. Chez le rat intact, l’halothane provoque des modifications des gaz du sang comparables à celles observées chez d’autres espèces et chez l’homme. La présente étude confirme les effets de l’halothane sur les muscles respiratoires autres que le diaphragme. Elle met en évidence le risque respiratoire majeur que l’anesthésie peut fair courir aux patients dont la ventilation est maintenue par d’autres muscles que le diaphragme.     

Vers une approche métabolique du centre locomoteur autonome chez l’animal : le modèle d’hémisection médullaire chez le rat

It has been shown that the onset of a central nervous system lesion in the rat results in morphological modifications of the peripheral nerves and the underlying neuromuscular junctions, without suggesting a functional correlation between recuperation of motor functions and sublesional metabolic activity. Using double lesion localization (T2 and T6) in a spinal rat model has nevertheless pointed out the functional importance of the T2–T6 metameric interval in the reinnervation phenomena observed, raising the problem of spinal generation in locomotor movements. Motivated by electrophysiological data that have given support to the concept of an anatomic substrate for these intramedullary rhythm generators, we attempted to establish a relation between the functional recuperation possible after a central nervous system lesion and modifications within the metabolism of the underlying neuromuscular system. We notably focused on Na/K-ATPase, whose crucial role in neuromuscular transmission has been evidenced. This paper proposes to demonstrate the involvement in the mechanisms of metabolic regulation after trans-synaptic denervation, i.e., a central nervous system lesion. Our study includes the Na/K-ATPase activity analysis on the sublesional peripheral nerve and the combined analysis of the expression of different RNA messengers within the corresponding muscle groups. We have also investigated the spatiotemporal organization of the compensating processes of the nerves underlying the lesion using magnetic resonance spectroscopy.     

Effets hémodynamiques comparatifs du sévoflurane et de l'halothane à la concentration télé-expiratoire d'intubation chez le nourrisson

ObjectiveTo compare the cardiovascular changes at the end-tidal concentrations of sevoflurane versus halothane required for tracheal intubation in infants (intubation MAC).Study designProspective randomized study.PatientsThirty-two infants, ASA physical status 1 or 2, scheduled for elective surgery, randomized to receive either halothane or sevoflurane for anaesthetic induction by inhalation.MethodsCardiovascular and echocardiographic data were recorded in both groups at baseline, and at the endtidal concentrations needed for intubation.ResultsIntubation MAC was significantly less with sevoflurane than with halothane in infants. Sevoflurane did not change heart rate (HR) and cardiac index (CI) compared to values when awake. Sevoflurane significantly decreased blood pressure, systemic vascular resistance (SVR) and shortening fraction (SF). Myocardial contractility assessed by stressvelocity index (SVI) and stress-shortening index (SSI) decreased significantly at the intubation MAC, but did not fall into the abnormal range. Halothane caused a greater decrease in HR, SF, SSI, and CI than sevoflurane.ConclusionsSevoflurane decreases cardiac output less than halothane in infants at the intubation MAC, due to a lower end-tidal concentration at intubation MAC and to less effects on haemodynamic variables.     

Estimation du volume de distribution de l’urée chez le patient hémodialysé

BackgroundOn-line urea clearance estimation, currently available on some dialysis monitors, makes it possible to calculate the dialysis dose Kt and thus allows to estimate Kt/V for each session, providing an estimation of urea distribution volume (V) at equilibrium assumed equal to total body water.MethodsThree methods suitable for routinely estimating V, using the anthropometric Watson formula (V_Wat), the body composition monitor (BCM) device (Fresenius Medical Care) based on bio-impedance analysis (V_imp) and the indirect estimation (V_Daug) obtained from measurement of Kt/(Kt/V)_sp ratio respectively are compared during 25 dialysis sessions in 15 patients to a direct estimation (V_DDQ) obtained by direct quantification of dialysis (DDQ) considered as the gold standard in hemodialysis patient..ResultsV_Watson overestimates V_DDQ by about 20%. The values of V_imp (29.1 ± 5.6 L) and V_Daug (29.5 ± 4.6 L) are in agreement with V_DDQ (29.9 ± 5.2 L). Correlation coefficient with V_DDQ is better for V_imp (r = 0.94) than for V_Daug (r = 0.85).ConclusionBio-impedancemetry using BCM and indirect method using the second generation Daugirdas equation are two methods of clinical interest for estimating V. Bio-impedancemetry does not require blood sample, but it needs to have a specific device at disposal.     

Effets ventilatoires d’une hypothermic modérée (36° C–28° C) chez le chien anesthésie à l’halothane

Changes in systemic haemodynamic variables (mean arterial pressure, MAP; heart rate, HR; cardiac output, Qc), in oxygen consumption, VO2, and in ventilation (minute ventilation, V; respiratory frequency, f; tidal volume, VT; and arterial blood gases) with particular attention to respiratory times (duration of inspiration, TI; duration of expiration, TE; duration of the breathing cycle, TTOT), to respiratory timing (TI/TTOT) and respiratory drive (VT/TI) were studied during moderate progressive hypothermia (36 degrees C to 28 degrees C) during stable halothane anaesthesia (MAC = 1.5) in six dogs. MAP, HR and Qc decreased; V and f decreased, the decrease in f being correlated with that in temperature (r = 0.66; P < 0.01). Tidal volume did not change. The PaO2 and pHa decreased while PaCO2 increased slightly. The decrease in ventilation was related to changes in respiratory times (TI and TE) which increased (TE more than TI) and in respiratory drive (VT/TI which decreased due to the increase in TI). The relation between VT/TI and TI/TTOT changes was not constant during cooling. Changes in respiratory times and drive could be due to the effect of cold on medullar respiratory control.     

Repenser le handicap : leçons du passé, questions pour l’avenir. Apports et limites du modèle social,de la sociologie des sciences et des techniques,de l’éthique du care

In this article, I analyze one evolution in disability research over the past 30 years: the shift from an individual to a social approach to disability. While most disability research has currently “socialized” disability or at the least situates disabled people within a social context, not all do so in the same way nor based on the same assumptions. They lead to different concepts of the person and society and different concepts of disability and normalcy. I analyze this evolution by looking at three approaches to disability: the social model, the approach taken in the sociology of science and technology, and the ethics of care. I show how each, by renewing the analysis of disability, has brought about changes for disabled people and transformed ways of “living together” and “making society”. I also show the limits of these approaches and propose lines of thought for the continuation of our research, notably around the question of autonomy. I propose that we rethink autonomy from the standpoint of the notion of “recalcitrance”.     

Considérations sur le syndrome du canal tarsien postéromédial et les formes apparentées (lésions du nerf tibial et de ses branches)

Tarsal tunnel syndrome is relatively unheard of due to there being numerous unrecognized atypical morphologies. Analysis of functional signs is important in obtaining a diagnosis. A careful and thorough physical examination can confirm the probability of the diagnosis. However, ENMG is necessary to confirm this diagnosis, even if the reliability of this examination technique is sometimes called into question. Imaging data is used to complete the etiologic investigation, if required. X-rays and ultrasounds are often prescribed. An MRI scan may also be necessary. Simple medical treatment can improve the symptoms in many cases, but in certain situations, surgery may be indicated. The patient must be informed that many contributory factors affecting the results are not always complete.