Experimental magnesium depletion in adult rabbits caused by blast overpressure

The complex pressure wave (blast) generated by some explosions causes pulmonary pathological changes which resemble the histological findings of the adult respiratory distress syndrome (ARDS). The development of indirect neurotrauma following experimental pulmonary blast injury has been shown previously. The purpose of this study was to evaluate lung and brainstem total tissue magnesium concentrations in adult rabbits following pulmonary blast injury. In order to assess the interrelationship between magnesium and other secondary injury factors, total calcium and high energy phosphate (phosphocreatine, PCr; adenosine triphosphate, ATP) contents were simultaneously measured. Twenty adult male rabbits were divided into two groups. Group C (n = 10) served as control, while group B (n = 10) was subjected to a focused blast wave, generated in laboratory conditions using an air-driven shock tube. Moderate pulmonary blast injury was verified by histological examination in group B. Total tissue magnesium and calcium contents were measured by atomic absorption spectrophotometry in the lungs and brainstem of adult rabbits 30 min following blast overpressure and in their uninjured controls. Simultaneously, PCr and ATP contents were measured by fluorimetric enzymatic analyses in same structures. Lung and brainstem water contents were determined by wet weight to dry weight ratio. Blast overpressure to the lungs induced significant magnesium depletion, increased calcium and decreased the Mg/Ca ratio in lung tissue of injured animals. Increases in water content and PCr/ATP ratio were also observed. Significant correlations between these Mg/Ca and PCr/ATP and between Mg and ATP parameters confirmed the functional relationship between magnesium depletion and impaired bioenergetic state in indirect neurotrauma in adult rabbits through blast overpressure.