Nitric Oxide and Transfusion Therapy for Sickle Cell Patients With Pulmonary Hypertension

Overview

This study will test whether inhaling nitric oxide (NO) gas mixed with room air can improve pulmonary hypertension (high blood pressure in the lungs) in patients with sickle cell anemia. Patients with sickle cell disease 18 years of age or older may be eligible to participate in one or more parts of this three-stage study, as follows: Stage 1 Patients undergo the following tests to determine the cause of their pulmonary hypertension: blood tests; echocardiogram (heart ultrasound); asthma test; oxygen breathing study with measurement of arterial blood oxygen levels; chest X-ray; lung scans; MRI of the heart; 6-minute walk test; night-time oxygen measurement while sleeping; and exercise studies. Stage 2 Patients have a detailed MRI evaluation of the heart and are admitted to the NIH Clinical Center intensive care unit (ICU) for the following test: A plastic tube is placed in a vein in the patient's arm and another tube is placed in a deeper neck or leg vein. A third tube is inserted through the vein into the heart and the lung artery to measure blood pressures in the heart and lungs directly. Following baseline measurements, three medications (inhaled oxygen, infused prostaglandin, and inhaled NO) are delivered for 2 hours each, separated by a 30-minute washout period. A small blood sample is drawn during the NO administration. Patients who cannot be treated with nitric oxide or for whom the treatment does not work may receive monthly exchange transfusions for 3 months. For this procedure, 3 to 5 five units of the patient's blood is removed and replaced with 3 to 5 units that do not have sickle hemoglobin. Some patients who do not respond to NO or exchange transfusions may receive an alternative therapy, such as oxygen, prostacyclin, L-arginine, bosentan or sidenafil. Stage 3 Patients remain in the ICU with catheters in place for another 24 hours. During this time they breathe NO. Lung pressures are measured every 4 hours and blood is drawn every 8 hours. They then stay in the hospital 1 more day for observation. Patients then breathe nitric oxide continuously for 2 months using a tank of gas that delivers the NO through tubes placed in the nose. They may do this at home on an outpatient basis or may remain in the hospital for the 2 months. Patients have an echocardiogram and blood tests every week and do a 6-minute walk test every 2 weeks....

Sickle cell anemia is an autosomal recessive disorder and the most common genetic disease affecting African-Americans. Approximately 0.15% of African-Americans are homozygous for sickle cell disease, and 8% have sickle cell trait. Acute pain crisis, acute chest syndrome (ACS), and secondary pulmonary hypertension are common complications of sickle cell anemia. Pulmonary hypertension has now been identified as a major cause of death in adults with sickle cell disease. Inhaled nitric oxide (NO) has been proposed as a possible therapy for both primary and secondary pulmonary hypertension. Furthermore, a number of recent studies have suggested that NO may have a favorable impact on sickle red cells at the molecular level and could improve the abnormal microvascular perfusion that is characteristic of sickle cell anemia. In addition, chronic exchange transfusion therapy may reduce the progression and/or severity of pulmonary hypertension in these patients. This clinical trial is designed (1) to determine the pathophysiologic processes that are associated with and potentially contribute to secondary pulmonary hypertension in adult patients with sickle cell anemia, by comparing the cardio-pulmonary status of patients with sickle cell disease with and without pulmonary hypertension (2) to determine the relative acute vasodilatory effects of oxygen, intravenous prostacyclin, and inhaled nitric oxide on pulmonary artery pressures and other hemodynamic parameters in patients with secondary pulmonary hypertension and sickle cell anemia, (3) to determine the effects of two months of inhaled nitric oxide on pulmonary artery pressures, other hemodynamic parameters, exercise tolerance, and symptoms in this patient population, and (4) to determine the effects of three months of exchange transfusion on pulmonary artery pressures, other hemodynamic parameters, exercise tolerance, and symptoms in patients who do not receive or fail to respond to NO therapy.