
    poor enrollment.
  
['acute chest syndrome', 'sickle cell disease']
['unfractionated heparin']

        Inclusion Criteria:

          -  Diagnosis of ACS defined as a new pulmonary infiltrate involving at least one segment
             of the lung on a chest x-ray or chest CT scan with 2 or more of the following: chest
             pain, tachypnea, dyspnea, cough, hypoxemia, or body temperature greater than or equal
             to 38.0 degrees Celsius

          -  Hemoglobin electrophoresis confirming HbSS, SC, or B0 (historical records sufficient)

          -  Age greater than or equal to 18

        Exclusion Criteria:

          -  Any absolute contraindication to heparin

          -  Platelet count less than 50 per microliter (current admission)

          -  Historical diagnosis of moyamoya disease as documented in medical records

          -  Historical diagnosis of proliferative retinopathy as documented in medical records

          -  Current participation in a chronic exchange transfusion program

          -  Underlying hypercoagulable disorder other than sickle cell disease

          -  Currently receiving therappeutic anticoagulation

          -  Currently receiving antiplatelet agents

          -  Currently receiving estrogen containing oral contraceptives

          -  Chest CT scan documented PE performed as standard of care prior to study enrollment
             (current admission)
      