Apheresis

The term Apheresis is Greek in origin and it means 'to take away'. This is a medical technology wherein the blood of a donor/patient is passed through an apparatus that separates one particular required component. The separated portion is withdrawn and the remaining components are retransfused into the patient/donor. The components thus separated from the patient/donor includes, plasma, platelets or leukocytes. This procedure is adhered to as an extracorporeal therapy.

In the process of apheresis, whole blood is removed from the patient/donor. The components of whole blood are separated by a centrifuge or an instrument specially designed for this purpose. The apheresis procedure is often employed to obtain stem cells from peripheral blood of patients suffering leukemia, a blood disease. Stem cells are infused into the patient's blood stream in order to produce cells that eventually will mature into red blood cells, white blood cells and platelets.

In transplants such as bone marrow procedures, the sick person happens to be his/her own donor. Blood is drawn and at a later time reinfused into that patient's blood stream in a procedure known as autologous bone marrow transplant. When stem cells are obtained from a healthy person, the procedure is allogeneic bone marrow transplant. Here, another person, may or may not be related, is the donor. Apheresis has become essential in providing blood components for several types of therapies. The process of apheresis takes a couple of hours and the volunteer donor/patient undergoes apheresis to supply specific components.

Leukapheresis is the removal of PMNS (Polymorphonuclear leukocytes), basophils and eosinophils for transfusion into patients whose PMNs are ineffective or in whom the traditional line of therapy has failed. LDL apheresis is the removal of low density lipoprotein in patients suffering from hypercholesterolemia. Erythrocytapheresis is the collection of red blood cells (RBCs) either two standard units of RBCs or one unit plus either plasma or platelets. This process is commonly known as 'double reds' or 'double red cell apheresis'.

Apheresis is used in stem cell harvesting for circulating bone marrow cells during transplantations. To collect sufficient stem cells, apheresis process is performed for at least two consecutive days, although at times five or even more procedures become necessary.

It is pertinent to understand that when apheresis system is adopted for therapy, the system is removing relatively small amounts of fluid, not more than 10.5 mL/kg body weight. That fluid which is removed must be replaced in order to maintain the intravascular volume.
The apheresis process is painless. Some patients/donors may experience lightheadedness, numbness or tingling of the nose, lips or fingers. These symptoms are short lived and treatable. Possible complications include bleeding in needle sites, thrombosis or clotting in blood vessels, or rarely surgical complications if a temporary apheresis catheter is inserted. Infection is always a risk as this procedure involves penetrating the skin and open access to blood vessels.

Hyperlipidemia

Hyperlipidemia is an excess of fatty substances called lipids, which largely consists of cholesterol and triglycerides in the blood. Also known as hyperlipoproteinernia, due to the fatty substances that travel in the blood, this is perhaps the only way fatty substances can remain dissolved while in circulation. Secondary causes of hypercholesterolemia include hypothyroidism, pregnancy, and kidney failure. Hyperlipidemia, along with diabetes is a major risk factor for coronary heart disease. Medications most commonly used to treat high LDL cholesterol levels are statins or simyastatin. These work by reducing the production of cholesterol within the body.

Atherosclerosis

Atherosclerosis is characteristic inflammatory disease of the arteries. It is triggered by a process called atherogenesis in which there is an accumulation of low density lipoproteins causing the formation of plaque. The plaque thus formed gets accumulated in the arteries causing blockage in the blood flow. The most prominent arteries prone to these plaque accumulations are the elastic and muscular arteries.

Pathology of atherosclerosis

Atherosclerosis in the initial stages appears as a fatty streak and over time it develops into a more prominent condition causing hardening of the arteries. It results in the reduction of the arterial pathway of carotid, abdominal, cardiac and other arteries of the lower and upper extremities. The etiology associated with this condition is the deposition of cholesterol and lipids in the internal lumen of the artery. These depositions are focal in origin. The disruption caused in the endothelial lining because of cholesterol accumulation leads to the emergence of inflammatory disease and arterial injuries.

Atherosclerosis triggers many conditions such as atherosclerotic heart disease, peripheral vascular disorder, coronary artery disease, and carotid artery disease. In atherosclerotic condition, some diagnostic investigations may be non-specific to the patho-physiology associated with the disease. One such test is analysis of C reactive protein which is a non-specific marker of inflammatory disease. However, the fatty streaks and associated lesions caused are identified by the characteristic smooth muscles containing lipids in it.

A fibrous plaque is formed initiating the changes in the arterial wall. The cholesterol translocation in the arterial intima (inner region) is facilitated by the lipoproteins. The fibrous streak contains collagen which is grayish white or yellow in appearance resulting in the narrowing of the blood vessel. The emergence of a complicated lesion like this can induce the formation of ulcers leading to rupture and dissemination of the accumulated plaque to various regions. This leads to the occurrence of three types of strokes. The Thrombolytic stroke which is a result of a clot or thrombus formation, hemorrhagic stroke because of blood vessel damage and embolic stroke in which the clot does not pass through the narrow artery. This eventually results in the occurrence of ischemic stroke in which there is a lack of blood supply to the brain.

Factors associated with atherosclerosis

Hypercholesterolemia is one of the main causes as it causes the low density lipo-proteins to occupy the inner layer of the artery. Elevated homocysteine levels also play an important role in the occurrence of atherosclerosis. Homocyteine levels are generally high in patients who have a history of high red meat consumption rate. Increased homocysteine levels facilitate the hardening of the arterial wall causing atherosclerotic lesions. Increased angiotensin-II concentration is also an important factor in the initiation of atherosclerotic condition as it causes vasoconstriction and associated hypertension. Other factors include infections caused by Chlamydia and Herpes viruses.

In all these factors causing atherosclerosis, the nature of inflammatory response is associated with interactions related to the monocytes, endothelial cells and T cells. In most cases, plaques or associated clots occur in the region of branching, bifurcation or curvature of the arteries. This is because of the alternating blood flow path occurring in the respective region.

The risk factors associated with atherosclerosis are mainly because of lifestyle and preexisting medical conditions. Smoking, alcoholism, obesity and hereditary factors are the predominant reasons. Other factors include diabetes, hypertension and family history of which is associated with a specific altered gene.

Patients with atherosclerosis are advised to incorporate lifestyle changes with constant watch on their eating habits. Physicians and cardiologists recommend cardiovascular exercises on a regular basis apart from medication. Surgical interventions are required in case of increased coronary artery blockage and dispersed thrombus in the blood circulation.

The plaques formed in the arterial walls of one who suffers from atherosclerosis contain significant levels of cholesterol. The risk factor of Coronary Heart Disease (CHD) rises in direct proportion to the level of LDL - Low density Lipoprotein and comes down with an increase in the HDL cholesterol. The LDL is estimated by the following formula:

LDL Cholesterol = Total Cholesterol (mg/dL) - HDL Cholesterol (mg/dL) - (Triglycerides (mg/dL)/5)

Atherosclerotic Peripheral Vascular Disease occurs owing to Atherosclerosis in Aorta and Iliac Arteries which results in Claudication (pain on exertion) or in some cases lesions in the vessels of legs ( Occlusive Atherosclerotic Lesions). The severity of the symptom can vary from time to time and usually subsides after some rest. For men, bilateral common iliac disease can often start with Erectile Dysfunction (ED).