Blood Vessel Anatomy

Microscopic Anatomy of Blood Vessels

• Blood vessels consist of three layers or tunics, barring capillaries.
• The tunica intima provides a friction-reducing lining, composed of endothelium.
• The tunica media is made up of smooth muscle and elastic tissue, controlled by the sympathetic nervous system.
• The tunica externa, composed mostly of fibrous connective tissue, is the protective outermost layer that supports the vessel.

Structural Differences in Blood Vessels

• Arteries possess a heavier, stronger, and stretchier tunica media than veins for pressure resistance.
• Veins have a thinner tunica media compared to arteries and operate under low pressure.
• Valves are present in veins to prevent the backflow of blood.
• The lumen, or inside space, of veins is larger than that of arteries.
• Skeletal muscle aids in circulating blood in veins towards the heart.

Capillaries

• Have only one cell layer thick, which is the tunica intima.
• Capillaries facilitate exchange between blood and tissue.
• Networks of capillaries form capillary beds, including a vascular shunt and true capillaries.
• Microcirculation is the term for blood flow through a capillary bed.

Great Vessels

• The ascending aorta is a segment of the aorta.
• The aortic arch is a section of the aorta.
• The thoracic aorta is another portion of the aorta.
• The abdominal aorta is a major segment of the aorta.

Aneurysm Basics

• An aneurysm is a permanent dilation of an artery that enlarges it to over twice its normal diameter.
• Fusiform aneurysms feature diffuse dilation around the entire arterial circumference.
• Saccular aneurysms are characterized by an outpouching affecting a limited portion of the artery.
• Aneurysms most commonly occur in the abdominal aorta, despite the fact that they can occur at specific anatomical sites.
• An aneurysm results from the weakening of the middle layer (tunica media) of the artery, leading to stretching of the inner (tunica intima) and outer layers (tunica adventitia).
• The risk of arterial rupture increases as the aneurysm grows.
• Atherosclerosis is the most common cause, with hypertension and cigarette smoking as contributing factors.

Diagnosis and Treatment of Aneurysms

• Many aneurysms are asymptomatic, discovered during routine exams or radiographic studies for other reasons.
• Symptoms include steady, gnawing abdominal, flank, or back pain, especially with abdominal aortic aneurysms (AAA).
• Rupturing AAAs may present with hypotension, diaphoresis, mental obtundation, oliguria, and dysrhythmias indicating hypovolemic shock.
• X-rays may reveal an "eggshell" appearance in cases of AAA.
• As a standard tool, a CT scan is used to determine the size and location of the aneurysm.
• Ultrasonography is a noninvasive method for accurate diagnosis and information on the size and location of AAA.
• Monitoring aneurysm growth via CT scans and maintaining blood pressure at normal levels to reduce rupture risk are components of nonsurgical treatment.
• Surgical management involves abdominal aortic aneurysm resection to excise the aneurysm and prevent or repair rupture.
• The goal of surgical management is to ensure stable aortic integrity and tissue perfusion throughout the body.

Peripheral Vascular Disease (PVD)

• PVD encompasses disorders altering natural blood flow in arteries and veins outside of the heart.
• The lower extremities are most frequently affected.
• Inadequate blood flow from pump failure, vessel alterations, or circulatory insufficiency can lead to ischemia and cellular necrosis.
• Inadequate blood flow can result from conditions such as obstruction and trauma, atherosclerosis, and arteriosclerosis.
• Left-sided heart failure (LSHF) leads to pulmonary congestion, while right-sided heart failure (RSHF) results in systemic congestion.

Arterial vs. Venous Insufficiency

Peripheral Arterial Disease (PAD) and Related Concepts

• Arteriosclerosis is the thickening or hardening of arterial walls and atherosclerosis is a type of arteriosclerosis involving plaque formation within the artery wall.
• PAD inflow obstruction involves the distal aorta and iliac arteries located above the inguinal ligament.
• PAD outflow obstruction involves the femoral, popliteal & tibial arteries found below the superficial femoral artery.
• Atherosclerosis is the most common cause of PAD.
• Risk factors include hypertension, hyperlipidemia, diabetes mellitus, cigarette smoking, obesity, and familial predisposition.
• A symptom of PAD is intermittent claudication and rest pain:
  • Inflow disease causes discomfort in the lower back, buttocks, or thighs.
  • Outflow disease causes burning or cramping in the calves, ankles, feet, and toes.
• PAD assessment reveals hair loss on the lower calf, ankle, and foot, dry/scaly/dusky/pale/mottled skin, and thickened toenails.
• A cold/cyanotic extremity with pallor upon elevation and diminished/absent peripheral pulses may also be present.
• Arteriography, segmental systolic blood pressure measurements, ankle-brachial index, and exercise tolerance testing can be used for diagnostic assessment:
  • Ankle-Brachial Index (ABI) - An ABI of <0.9 in either leg is diagnostic of PAD (derived by dividing the ankle BP by the brachial BP).
• PAD nursing interventions involve exercise and promoting arterial circulation and vasodilation:
  • Refrain from raising the legs above the heart level
  • Avoid crossing the legs and wearing restrictive clothing
  • Provide warmth to the affected extremity and prevent long periods of exposure to cold
  • Avoid emotional stress, caffeine, and nicotine
• PAD pharmacologic interventions involve pentoxifylline (Trental) which increases flexibility of RBCs and decreases blood viscosity by inhibiting platelet aggregation & fibrinogen and aspirin.
• Surgical interventions involve percutaneous transluminal angioplasty (PTA), laser-assisted angioplasty (clients with smaller occlusions in distal superficial femoral, proximal popliteal & common iliac arteries) and bypass procedures (grafts preferred are saphenous vein, cephalic or basilic arm veins, synthetic materials such as polytetrafluoroethylene, Gore-Tex & Dacron).

Buerger's Disease (Thromboangiitis Obliterans/ TAO)

• It is a reoccurring inflammation of the intermediate and small arteries and veins of the lower and upper extremities.
• Buerger's Disease involves male, young adults, and cigarette smoking is a risk factor; the cause is unknown.
• Clinical manifestations include pain, instep claudication, digital rest pain, and aggravation by emotional disturbances, nicotine, or chilling.
• Affected individuals experience sensitivity to cold, dependent rubor, absent or diminished radial/ulnar pulses, and digital ulceration and gangrene.
• Assessment and diagnostic methods include segmental limb blood pressures, duplex ultrasonography, and contrast angiography.
• Nursing interventions involve complete abstinence from tobacco in all forms and avoidance of extreme cold to prevent vasoconstriction.

Raynaud's Disease

• Is caused by vasospasm of the arterioles and arteries of the upper and lower extremities.
• Clinical manifestations of Raynaud's Phenomenon involve blanching of the extremities followed by cyanosis and numbness, coldness, pain, swelling, and ulcers may also be present.
• Raynaud's Disease is managed using calcium channel blockers (potent vasodilator) such as Nifedipine, as a first choice, or Sympathectomy.

Venous Thromboembolism (VTE) and Deep Vein Thrombosis (DVT)

• Risk factors include hip surgery, total knee replacement, open prostate surgery, pregnancy, ulcerative colitis, heart failure, immobility, invasive procedures, autoimmune disease, polycythemia vera, oral contraceptives, trauma, adenocarcinoma of the visceral organs.
• Acute calf pain and localized edema are indicative of a possible DVT.
• Diagnostic tests include contrast venography (Gold Standard), duplex ultrasonography, Doppler flow studies, impedance plethysmography and MRI.
• Main focus of treatment is to prevent complications/ pulmonary emboli and prevent further thrombus formation/ increasing in size of the thrombus.
• Management includes strict rest and elevation of the extremity; DO NOT Massage the affected extremity.
• Drug therapy involves anticoagulants (Unfractionated Heparin Therapy, Warfarin Therapy; Works in the liver to inhibit synthesis of the four vitamin K-dependent clotting factors, takes 3-4 days before it can exert therapeutic anticoagulation) or Thrombolytic Therapy (recombinant tissue plasminogen activator, Alteplase, Reteplase etc).
• Health teaching - STOP smoking, avoid the use of oral contraceptives to decrease the risk of recurrence.

Varicose Veins

• These are dilated tortuous veins, often occurring in the saphenous leg veins but also in the rectum (hemorrhoids) and esophagus (esophageal varices).
• Incompetent valves, poor venous return, and thrombophlebitis are the main causes.
• Assessment: legs feel heavy & tired particularly after prolonged standing (patient will say that activity or elevation of the legs relieves the discomfort) and tortuous veins that appear swollen under the skin.
• Four stages include Reticular or spider veins, Varicose veins or venous nodes, Edema of the lower legs or varicose eczema or trophic ulcer.
• Treatment for mild to multiple Varicose Veins includes exercise (walking, swimming), losing weight, wearing elastic support stockings, avoidance of prolonged sitting & standing.
• Treatment for severe Varicose Veins includes Vein ligation, with veins tied off above & below the area of incompetent valves, but the dysfunctional vein still present, Vein stripping (ligated veins are severed & removed) and schlerotherapy.