What is Sickle Cell Disease?
Sickle Cell Disease is a genetic disorder of the red blood cells. It is autosomal recessive (you need to get one defective gene copy from each of your parents). Patients with sickle cell disease have abnormal hemoglobin in their red cells. Under periods of stress the red cells become deformed and plug up the blood vessels of the lungs and other organs leading to painful episodes, strokes, and in some cases pulmonary hypertension.
Sickle Cell Associated with Pulmonary Hypertension
Sickle Cell Disease associated Pulmonary Hypertension is very complicated. It may be due to loss of lung tissue from repeated episodes of red cells plugging up the vessels. However, it may also be due to problems on the left side of the heart such as stiffening or diastolic dysfunction. Patients with sickle cell disease may also develop larger blood clots. There has been one large study of children with sickle cell disease who have Pulmonary Hypertension using sildenafil. Unfortunately, the trial was stopped in the middle due to worse outcomes in the patients receiving sildenafil (an increase in the number of painful episodes). As a result, sildenafil and tadalafil (Adcirca) are not used in this disease.
So How Do We Treat Patients with Sickle Cell Disease Who Have Pulmonary Hypertension?
First and most importantly, you need to be seen by an expert in Pulmonary Hypertension who works together with an expert in Sickle Cell Disease. As there are no good studies that show effective treatment options we rely on expert opinion and years of experience. In my practice, we start by ensuring that the Sickle Cell Disease is under good control. This usually means the use of hydoxyurea to raise the amount of good hemoglobin. In children, exchange transfusions are used in many cases.
Next, we work hard to understand why the pulmonary pressures are elevated. Right heart catheterization is essential. If the problem is stiffness of the left side of the heart then medications that lower pulmonary artery pressures (PAH meds) are generally not helpful. If blood clots are present we use blood thinners. Oxygen is used to improve the oxygen saturation in patients with low oxygen levels. After all of that is done, if we still think that there is Pulmonary Hypertension due to problems in the pulmonary arteries (PAH-type disease) then we cautiously use endothelin receptor antagonists. In our sickest patients we use prostanoids (Remodulin/Flolan…). Diuretics are used carefully to remove excess water but care is taken to avoid “dehydration”.
We are hopeful that we will have better quality data to guide our treatment decisions in the future.