LYMPHATIC AIR-EMBOLISM - A NEW HYPOTHESIS REGARDING THE PATHOGENESIS OF NEONATAL SYSTEMIC AIR-EMBOLISM

Objective. Neonatal systemic air embolism (NSAE) has been thought to r esult from introduction of air into the pulmonary veins through hypoth esized alveolar-capillary fistula. The objective of this paper is to r eassess the distribution of intravascular air visualized radiographica lly in this entity. Based on these data, an alternative theory for the pathogenesis of NSAE is proposed. Materials and methods. Four cases f rom our institutions and 21 additional reviewable published radiograph s of NSAE were evaluated for the presence and location of intravascula r air. Nonparametric statistical analysis was performed to determine i f the predominance of intravascular air was venous or arterial in loca tion, and to determine the presence or absence of pulmonary interstiti al emphysema (PIE), pneumothorax, pneumomediastinum, and pneumopericar dium. Results. Isolated systemic venous air was present significantly more often than isolated systemic arterial air (p < 0.0005). In additi on, the presence of isolated right-sided cardiac air was found signifi cantly more often than air within left heart chambers alone (p < 0.000 5). PIE in patients with NSAE was found to be statistically more preva lent than pneumomediastinum or pneumopericardium, though similar in pr evalence to pneumothorax. Conclusion. Our data support the hypothesis that intravascular air in NSAE is predominantly venous in location. PI E was found to be a very common associated finding in NSAE. Based on o ur current knowledge of pulmonary lymphatics, radiographic anatomy, an d the lymphatic location of PIE, we propose that air within the pulmon ary lymphatic system (PIE) gains access to the systemic venous system via lymphatic ducts, which results in the clinical entity NSAE. This r eadily explains the venous predominance of air in NSAE.