Abstract
The effects of acid aspiration on lung mechanics, gas exchange, haemodynamics and lung water, and their modification by nebulized dexamethasone were studied in 10 dogs. Each dog received 0.1 N HC1 pH of 1.0(15 ml/1 vital capacity), instilled down the tracheal tube. PEEP 0.98 kPa (10cm H2O) was introduced 20 minutes after aspiration and was continued until the completion of experiment. Treated animals (N = 5) received dexamethasone 5 mg.kg-1 by continuous nebulization over a two hour period starting 20 minutes after aspiration. Untreated (N = 5) animals received nebulized saline. Measurements were taken before aspiration and at 20 minutes 2.5 and 5.0 hours after aspiration. Red blood cells labelled with5lCr were injected before sacrifice. After sacrifice multiple lung samples were taken for measurement of pulmonary extravascular water (PEW) by the gravimetric technique. Acid aspiration caused significant changes in lung volumes, Pao2, and intrapulmonary shunt. Pulmonary extravas cular water was 6.16 ± 0.93 ml/g dry tissue in treated and 6.47 ± 0.60 ml/g dry tissue in untreated animals. These results indicate the presence of severe pulmonary oedema. There were no significant differences in any measured parameter between treated and untreated animals We conclude that nebulized dexamethasone is of no value in treatment of the acute changes induced by acid aspiration.
RéSUMé
Les effets d’une aspiration de liquide acide ainsi que les modifications de ses effets par un traitement à la dexaméthazone, en nébulisation, ont fait l’objet d’une étude chez le chien. Les modifications étudiées étaient celles de la mécanique et de l’hémodynamique pulmonaire, ainsi que celles des échanges gazeux et de l’eau pulmonaire extra-vasculaire. A cet effet, on instillait dans le tube trachéal de chacun des animaux 15 ml/1 de capacité vitale d’une solution 0.1 N d’acide chlorhydrique. Une PEEP de 10 cm H2O était initiée vingt minutes après l’aspiration. Chez cinq des animaux on commencait également la nébulisation de dexaméthazone (5 mg-kg-1) vingt minutes après l’aspiration. Cette nébulisation s’étendait sur une période de deux heures. Cinq autres animaux (groupe témoin) recevaient du soluté physiologique en nébulisation. Les mesures étaient effectuées avant l’aspiration, puis vingt minutes, deux heures et demie et, enfin, cinq heures après l’aspiration. On injectait des globules rouges marqués au Cr51 avant de sacrifier les animaux. Des échantillons pulmonaires multiples étaient prélevés après le sacrifice pour la mesure de l’eau pulmonaire extravasculaire (technique gravimétrique).
L’aspiration de liquide acide causait des modifications significatives des volumes pulmonaires, de la Pao2, et du shunt. L’eau pulmonaire extravasculaire était de 6.16 ± 0.93 ml/g de tissu sec chez les animaux traités et de 6.47 ± 0.6 ml/g chez les animaux non traités. Ces résultats témoignent d’un oedème pulmonaire important. On n’a pas trouvé de différence significative dans les paramètres mesurés entre les animaux traités et non traités. Nous concluons que le dézaméthazone en nébulisation est sans valeur dans le traitement des modifications aigues causées par une aspiration de liquide acide.
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Supported by a Research Fellowship of the British Columbia Lung Association
Supported in part by Medical Research Council of Canada Grant MT-4219
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Warriner, C.B., Brooks, L. & Pare, P.D. The effect of inhalation of nebulized steroid on the acid aspiration syndrome. Canad. Anaesth. Soc. J. 28, 436–441 (1981). https://doi.org/10.1007/BF03010352
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DOI: https://doi.org/10.1007/BF03010352