Plastic bronchitis is a rare condition characterized by the formation of large, branching fibrinous or mucoid casts that occlude the tracheobronchial tree, causing acute respiratory distress and potentially fatal airway obstruction. The casts are composed of fibrin and inflammatory cells (type 1, associated with pulmonary inflammation from asthma, infections, or allergic bronchopulmonary aspergillosis) or acellular mucin and chyle (type 2, associated with congenital heart disease, particularly after Fontan palliation where elevated central venous pressure disrupts pulmonary lymphatic drainage). In post-Fontan patients, elevated systemic venous pressure impairs lymphatic drainage from the lungs, causing lymphatic fluid to leak into the airways and polymerize into rubbery, tree-shaped casts that conform to the bronchial anatomy. Clinical presentation includes acute dyspnea, cough (sometimes expectorating intact casts), wheezing, and respiratory failure. The nurse monitors respiratory status closely, recognizes acute deterioration from airway obstruction, assists with emergent bronchoscopy for cast removal, administers mucolytics (inhaled tissue plasminogen activator, dornase alfa), monitors oxygen saturation continuously, provides airway management support, and educates patients about recognizing symptoms of recurrence.