emDocs - June 4, 2016 - Authors: Shah S and Endrizzi J - Edited by: Robertson J and Koyfman A
"Diffuse alveolar hemorrhage (DAH) is a life-threatening medical emergency that is associated with pulmonary disease, bronchial disease and/or trauma. DAH is characterized by bleeding of the pulmonary microvasculature into the alveoli. It is imperative to understand this pathophysiology as many clinical findings are nonspecific and thus, the diagnosis may be difficult to ascertain.
DAH is characterized by 3 distinct histological types: Pulmonary Capillaritis, Bland Damage, and Diffuse Alveolar Damage. The most common, Pulmonary Capillaritis, is defined as neutrophilic predominant infiltration of the alveolar septa leading to fibrinoid necrosis of the alveolar and capillary walls. This occurs because the neutrophils undergo cell damage, which causes accumulation of debris, and toxic radicals that undermine the integrity of the cell wall. Drugs such as hydralazine, propylthiouracil (PTU), and carbimazole can trigger this process, but it can also occur due to a number of vasculitides.
The second histologic type of damage is known as Bland Damage. In this subtype, the RBCs leak into the alveoli without histologic findings of inflammation or destruction. This is associated with many of the same diseases that cause capillaritis, such as thrombocytopenia and Anti-GBM (Goodpasture’s) disease, but is also associated with mitral valve pathology.
The final subtype of DAH is Diffuse Alveolar Damage. This subtype is defined as edema of the alveolar septa and by formation of hyaline membranes that line the alveolar spaces. (6) This subtype tends to be the most familiar as it encompasses Acute Respiratory Distress Syndrome (ARDS). ARDS has a variety of causes that range from infection to crack cocaine use.
Summary
- DAH is a medical emergency characterized by bleeding of pulmonary microvasculature into the alveoli.
- The clinical presentation is nonspecific – most commonly the patient will present with cough, dyspnea, fever, and hemoptysis. Though 33% will present without hemoptysis.
- Cough, dyspnea, hemoptysis, and bronchoalveolar lavage (BAL) positive for RBCs is enough for a diagnosis
- Consider the patient’s timeline of symptoms – acute hemorrhagic events are more likely to be caused by toxins than vasculitides.
- Protecting the airway is the most important part of management. Then identify and stop the offending agent if possible and administer immunosuppressive
- Mainstay for moderate to severe DAH is methylprednisone (500-2000mg x 5 days IV followed by prednisone 1mg/kg PO) and cyclophosphamide (2mg/kg/day adjusted for renal function)"