Beyond the Basics: Vascular Emergencies

CEU Review Form Vascular Emergencies (PDF)Valid until May 4, 2007

Vascular diseases, specifically of the arteries, have been and continue to be one of the major contributors to death in the United States. After peaking in the late 1960s, their incidence started to drop, largely due to changes in lifestyle. It has been leveling off as Americans realize the importance of risk factors such as a high-fat diet, lack of exercise and high-risk behaviors like smoking; however, vascular disease remains the pathologic origin for nearly half of all deaths in the U.S.

Basic Anatomy
     There are three types of vascular structures in the body: arteries, veins and lymphatics. Oxygenated blood is ejected from the left ventricle into the aorta, where it travels through an extensive network of arteries that decrease in lumen size and eventually branch into arterioles. The arterioles provide oxygenated blood to the capillary bed that perfuses tissue and organs like the brain, kidneys and liver. Following gas exchange in the capillary bed, the deoxygenated blood enters a venule, which then transports the blood to a vein. The blood travels through increasingly larger veins until it eventually enters the right atrium. The lymphatic system collects fluid from the body's tissues and provides filtration to it via the lymph nodes. This fluid is eventually returned to the venous system, where it mixes with the blood and returns to the heart.

     The walls of the arterial system, as well as of the venous system, are comprised of three layers. The innermost layer, the tunica intima (Latin for covering or coat), is a smooth interior surface of the blood vessel that minimizes unnecessary resistance to blood as it travels through the vessel. The middle layer, the tunica media, is also the thickest layer of the artery. The tunica media is comprised of elastic connective tissue and smooth muscle, which are circularly positioned around the artery and regulate the diameter of the vessel's lumen by contracting and relaxing. Interestingly, in the body's larger arteries, the tunica media is dominated by elastic tissue, whereas the smaller arteries and arterioles' tunica media are dominated by smooth muscle. The outermost layer of the blood vessel is called the tunica adventitia (adventitia in Latin means from afar). This outer layer is composed mainly of collagen and loosely organized connective tissue. Not only does this layer give the blood vessel its strength, the collagen also serves to anchor the blood vessel to nearby structures for added stability.

     While the intima and media are provided with oxygenated blood by a process of diffusion from the vessels' internal lumen, the adventitia and outer portion of the media are perfused by a network of small vessels that penetrate into these layers. The vasa vasorum are known as the "vessel of vessels."

Pathogenesis
     Essentially, the same vascular pathology underlies many of the cardiovascular, neurological and pulmonary emergencies seen in the prehospital setting. One may rationalize that a patient with diminished tactile sensation does not share anything in common with the patient who just suffered a debilitating stroke. In fact, the pathology of the two problems may well be one and the same. In order to understand this concept, an overview of specific arterial disease progression is necessary.

Arteriosclerosis
     Most disease processes that damage the arterial wall result in a reduction in the elasticity and flexibility of the vessel, which is known as sclerosis. The medical term applied to this condition as it relates to the arterial network of the body is arteriosclerosis, known to the layperson as "hardening of the arteries." In recent years, this term has fallen into disfavor, as it does not distinguish between the different types of arterial diseases. If left unqualified, the term usually means atherosclerosis, which is actually a form of arteriosclerosis.