A nurse is caring for an adolescent who has sickle-cell anemia. Which of the following manifestations indicates acute chest syndrome and should be immediately reported to the provider?

Rationale: A. Temperature 37.9° C (100.2° F): A mild temperature elevation is common in sickle cell crises due to inflammation or infection, but it does not independently indicate acute chest syndrome. It should be monitored but does not require immediate reporting unless it progresses or is accompanied by respiratory distress. B. Sneezing: Sneezing is a nonspecific symptom often related to upper respiratory irritation or allergies. It does not signify acute chest syndrome or lower airway involvement and is not an immediate concern in this context. C. Hematuria: Blood in the urine can occur from sickling in the renal vasculature but is not related to acute chest syndrome. While it requires evaluation, it does not pose an immediate respiratory threat. D. Substernal retractions: Substernal retractions indicate increased work of breathing and respiratory distress, which are hallmark signs of acute chest syndrome. This complication involves pulmonary infarction or infection leading to hypoxia, and prompt provider notification is essential to prevent respiratory failure.