Effect of position on transdiaphragmatic pressure and hemodynamic variables in anesthetized horses.

Recumbency affects respiratory mechanics and oxygenation in anesthetized horses. Changes in pleural and abdominal pressures that can impair ventilation have not been described in all recumbencies. The objective of this study was to determine the effects of patient positioning on transdiaphragmatic pressure and selected hemodynamic variables. Horses were maintained under total intravenous general anesthesia with nasal oxygen supplementation. Transnasal balloon catheters in the stomach and thoracic esophagus were used to measure intrathoracic and gastric pressures in standing horses and in anesthetized horses positioned in right and left lateral recumbency, dorsal recumbency, reverse Trendelenburg position, and Trendelenburg position. Transdiaphragmatic pressure was calculated as the difference between gastric and intrathoracic pressures. Measurements of oxygen saturation (SpO2), heart rate, systolic, diastolic and mean arterial pressures, and respiratory rate were obtained every 5 minutes. When compared to dorsal recumbency, gastric expiratory pressure is decreased in the standing position. Thoracic expiratory pressure is decreased in standing and reverse Trendelenburg. Transdiaphragmatic expiratory pressure and SpO2 are decreased in Trendelenburg. Heart rate is increased in reverse Trendelenburg. Systolic, diastolic, and mean arterial pressures are decreased in reverse Trendelenburg and increased in left lateral and right lateral recumbency. We found that there is wide variation in respiratory pressures between horses and positions and they are not predictive of associated changes in hemodynamic variables.

Le décubitus affecte la mécanique respiratoire et l'oxygénation chez les chevaux anesthésiés. Les changements dans les pressions pleurales et abdominales qui peuvent affecter la ventilation n'ont pas été décrites dans tous les décubitus. L'objectif de la présente étude était de déterminer les effets du positionnement du patient sur la pression trans-diaphragmatique et une sélection de variables hémodynamiques. Des chevaux furent maintenus sous anesthésie intraveineuse générale totale avec supplémentation en oxygène par voie nasale. Des cathéters à ballon intra-nasal placés dans l'estomac et l'oesophage thoracique furent utilisés pour mesurer les pressions intrathoracique et gastrique chez des chevaux en position debout et des chevaux anesthésiés positionnés en décubitus latéral droit et gauche, en décubitus dorsal, en position renversée de Trendelenburg et en position de Trendelenburg. La pression trans-diaphragmatique fut calculée comme étant la différence entre les pressions gastrique et intrathoracique. Les mesures de saturation en oxygène (SpO2), du rythme cardiaque, des pressions artérielles systolique, diastolique et moyenne, ainsi que le rythme respiratoire furent obtenues à toutes les 5 minutes. Lors de la comparaison avec le décubitus dorsal, la pression expiratoire gastrique est diminuée dans la position debout. La pression thoracique expiratoire est diminuée en position debout et en position renversée de Trendelenburg. La pression expiratoire trans-diaphragmatique et la SpO2 sont diminuées en position Trendelenburg. Le rythme cardiaque est augmenté en position renversée de Trendelenburg. Les pressions artérielles systolique, diastolique et moyenne sont diminuées en position renversée de Trendelenburg et augmentées en décubitus latéral gauche et droit. Nous avons trouvé qu'il y avait de grandes variations dans les pressions respiratoires entre les chevaux et les positions et qu'elles ne sont pas prédictives de changements associés dans les variables hémodynamiques.(Traduit par Docteur Serge Messier).

Using microwave thermal ablation to develop a subtotal, cortical-sparing approach to the management of primary aldosteronism.

Objective: To investigate the feasibility and efficacy of localized, subtotal, cortical-sparing microwave thermal ablation (MTA) as a potential curative management for primary aldosteronism. The study investigated with equal importance the selected ablation of small volumes of adrenal cortex while sparing adjacent cortex. Method: An in-vivo study was carried out in swine (n = 8) where MTA was applied under direct visualization, to the adrenal glands at 45 W or 70 W for 60 s, using a lateral, side-firing probe and a non-penetrative approach. Animals were survived for 48 h post-procedurally. Animals were investigated for markers of histological, immunohistochemical and biochemical evidence of adrenal function and adrenal damage by assessing samples drawn intra-operatively and at the time of euthanasia. Results: Selected MTA (70 W for 60 s) successfully ablated small adrenocortical volumes (∼0.8 cm3) characterized by coagulative necrosis and abnormal expression of functional markers (CYP11B1 and CYP17). Non-ablated, adjacent cortex was not affected and preserved normal expression of functional markers, without increased expression of markers of heat damage (HSP-70 and HMGB-1). Limited adrenal medullary damage was demonstrated histologically, clinically and biochemically. Conclusion: MTA offers potential as an efficient methodology for delivering targeted subtotal cortical-sparing adrenal ablation. Image-guided targeted MTA may also represent a safe future modality for curative management of PA, in the setting of both unilateral and bilateral disease.