Arterial Degeneration and Other Blood Vessels Disorders
As a result of age or other degenerative changes, materials may be deposited within the arterial walls. These deposits cause an irregular thickening of the wall at the expense of the lumen (space inside the vessel), as well as a loss of elasticity. In some cases, calcium salts and scar tissue may cause this hardening of the arteries, technically called arteriosclerosis. The most common form of this disorder is atherosclerosis (Fig. 11-15), in which areas of yellow, fatlike material, called plaque, accumulate in the vessels and separate the muscle and elastic connective tissue. Sometimes, the arterial lining is also damaged, leading to possible blood clot (thrombus) formation. The thrombus may partially or completely obstruct the vessel, as it sometimes does in coronary thrombosis. A diet high in fats, particularly saturated fats, is known to contribute to atherosclerosis. Cigarette smoking also increases the extent and severity of this disorder. Arterial damage may be present for years without causing any noticeable symptoms. As the thickening of the wall continues and the lumen’s diameter decreases, limiting blood flow, a variety of symptoms can appear. The nature of these disturbances varies with the parts of the body affected and with the extent of the arterial changes. Some examples are as follows:
Aneurysm An aneurysm is a bulging sac in the wall of a blood vessel caused by a localized weakness in that part of the vessel (Fig. 11-16). The aorta and vessels in the brain are common aneurysm sites. The damage to the wall may be congenital or a result of hardening of the arteries. Whatever the cause, the aneurysm may continue to grow in size. As it swells, it may cause some derangement of other structures, in which case definite symptoms are present. If undiagnosed, the walls of the weakened area eventually yield to the pressure, and the aneurysm bursts like a balloon, usually causing death. Surgical replacement of the damaged segment with a synthetic graft may be lifesaving.
A profuse escape of blood from the vessels is known as hemorrhage, a word that means “a bursting forth of blood.” Such bleeding may be external or internal, from vessels of any size, and may involve any part of the body. Capillary oozing usually is stopped by the normal process of clot formation.
First Aid for Hemorrhage The loss of a small amount of blood will cause no problem for a healthy adult, but loss of one liter or more of blood is life-threatening. The first step to control bleeding is the application of direct pressure to the wound using a clean cloth. An assisting person should wear gloves to protect from bloodborne diseases. A bleeding extremity should be elevated above the level of the heart. In cases of severe, persistent bleeding, application of pressure where a local artery can be pressed against a bone slows the bleeding. The most important of these “pressure points” are the following:
* The facial artery, which may be pressed against the lower jaw for hemorrhage around the nose, mouth, and cheek. One can feel the pulse of the facial artery in the depression about 1 inch anterior to the angle of the lower jaw.
* The temporal artery, which may be pressed against the side of the skull just anterior to the ear to stop hemorrhage on the side of the face and around the ear;
* The common carotid artery in the neck, which may be pressed back against the spinal column for bleeding in the neck and the head. Avoid prolonged compression, which can result in lack of oxygen to the brain.
* The subclavian artery, which may be pressed against the first rib by a downward push with the thumb to stop bleeding from the shoulder or arm;
* The brachial artery, which may be pressed against the humerus (arm bone) by a push inward along the natural groove between the two large muscles of the arm. This stops hand, wrist, and forearm hemorrhage.
* The femoral artery (in the groin), which may be pressed to avoid serious hemorrhage of the lower extremity.
It is important not to leave the pressure on too long, as this may cause damage to tissues supplied by arteries past the pressure point.
Figure 11-15 Stages in atherosclerosis.
* Leg cramps, pain, and sudden lameness while walking may be caused by insufficient blood supply to the lower extremities resulting from arterial damage.
* Headaches, dizziness, and mental disorders may be the result of cerebral artery sclerosis.
* Hypertension may result from a decrease in lumen size within many arteries throughout the body. Although hypertension may be present in young people with no apparent arterial damage, and atherosclerosis may be present without causing hypertension, the two are often found together in elderly people.
* Palpitations, dyspnea (difficulty in breathing), paleness, weakness, and other symptoms may be the result of coronary artery arteriosclerosis. The severe pain of angina pectoris may follow the lack of oxygen and the myocardial damage associated with sclerosis of the vessels that supply the heart.
* An increase in the amount of urine with the appearance of albumin. Albumin is a normal plasma protein usually found in the urine only if there is kidney damage. Other symptoms referable to the kidneys may be caused by renal artery damage.
* Ulceration and tissue necrosis (death) as a result of ischemia (lack of blood supply), especially in the extremities. If the dead tissue is invaded by bacteria, the result is gangrene. The arterial damage that is caused by diabetes, for example, often leads to gangrene in the extremities of elderly diabetic patients.
Treatment for Arterial Degeneration Stents, small tubes inserted to keep vessels open, also discussed in relation to the heart, are used for other vessels as well. An additional treatment approach is endarterectomy, removal of the thickened, atheromatous lining of a vessel. Common sites for this procedure are the carotid artery or vertebral artery leading to the brain and the common iliac or femoral arteries leading to the lower limbs. Surgeons can remove a blockage by direct incision of a vessel. More commonly, they use a cutting tool inserted with a catheter through the vessel opening to remove plaque.
Figure 11-16 A cerebral aneurysm in the circle of Willis.
The word shock has a number of meanings. In terms of the circulating blood, it refers to a life-threatening condition in which there is inadequate blood flow to the body tissues. A wide range of conditions that reduce effective circulation can cause shock. The exact cause is often not known. However, a widely used classification is based on causative factors, the most important of which include the following:
* Cardiogenic shock, sometimes called pump failure, is often a complication of heart muscle damage, as occurs in myocardial infarction. It is the leading cause of shock death.
* Septic shock is second only to cardiogenic shock as a cause of shock death. It is usually the result of an overwhelming bacterial infection.
* Hypovolemic shock is caused by a decrease in the volume of circulating blood and may follow severe hemorrhage or burns.
* Anaphylactic shock is a severe allergic reaction to foreign substances to which the person has been sensitized.
When the cause is not known, shock is classified according to its severity.
In mild shock, regulatory mechanisms relieve the circulatory deficit. Symptoms are often subtle changes in heart rate and blood pressure. Constriction of small blood vessels and the detouring of blood away from certain organs increase the effective circulation. Mild shock may develop into a severe, life-threatening circulatory failure.
Severe shock is characterized by poor circulation, which causes further damage and deepening of the shock. Symptoms of late shock include clammy skin, anxiety, low blood pressure, rapid pulse, and rapid, shallow breathing.
Heart contractions are weakened, owing to the decrease in the heart’s blood supply. The blood vessel walls also are weakened, so that the vessels dilate. The capillaries become more permeable and lose fluid, owing to the accumulation of metabolic wastes.
The victim of shock should first be placed in a horizontal position and covered with a blanket. If there is bleeding, it should be stopped. The patient’s head should be kept turned to the side to prevent aspiration (breathingin) of vomited material, an important cause of death in shock cases. Further treatment of shock depends largely on treatment of the causative factors. For example, shock resulting from fluid loss, as in hemorrhage or burns, is best treated with blood products or plasma expanders (intravenous fluids). Shock caused by heart failure should be treated with drugs that improve heart muscle contractions. In any case, all measures are aimed at supporting the circulation and improving the output of the heart. Oxygen is frequently administered to improve oxygen delivery to the tissues.
Formation of a blood clot in a vessel is thrombosis. A blood clot in a vein, termed deep venous thrombosis (DVT), most commonly develops in the deep veins of the calf muscle, although it may appear elsewhere. Thromboses typically occur in people who are recovering from surgery, injury, or childbirth or those who are bedridden. Clot formation may also be associated with some diseases, with obesity, and with certain drugs, such as hormonal medications. Symptoms are pain and swelling, often with warmth and redness below or around the clot. Thrombosis can be diagnosed with ultrasound or with magnetic resonance imaging (MRI). A dangerous complication of thrombosis is formation of an embolus, a piece of the clot that becomes loose and floats in the blood. An embolus is carried through the circulatory system until it lodges in a vessel. If it reaches the lungs, sudden death from pulmonary embolism may result. Prevention of infections, early activity to promote circulation after an injury or an operation, and the use of anticoagulant drugs when appropriate have greatly reduced the incidence of this condition. Phlebitis, inflammation of a vein, may contribute to clot formation, in which case the condition is called thrombophlebitis.
Varicose veins are superficial veins that have become swollen, distorted and ineffective. They may occur in the esophagus or rectum, but the veins most commonly involved are the saphenous veins of the lower extremities (Fig. 11-17). This condition is found frequently in people who stand for long periods, such as salespeople, because blood tends to pool in the legs and put pressure on the veins. Pregnancy, with its accompanying pressure on the pelvic veins, may also be a predisposing factor. Varicose veins in the rectum are called hemorrhoids, or piles. The general term for varicose veins is varices; the singular form is varix.
Figure 11-17 Varicose veins.