Peripheral Vascular System Overview

The Venous System

Unlike the high-pressure arterial system, veins operate in a low-pressure environment to return deoxygenated blood and metabolic waste products back to the heart. Because the pressure is low, veins require auxiliary mechanisms to ensure blood continues to move toward the heart:

1. Intraluminal Valves: These prevent the backflow of blood.
2. Skeletal Muscle Contraction: As muscles move, they compress the veins, pushing blood upward.
3. Pressure Gradients: The act of breathing creates pressure changes (decreasing thoracic pressure and increasing abdominal pressure) that assist venous return.

Venous Pathologies

• Deep Vein Thrombosis (DVT): A blood clot that forms in a deep vein, often caused by stasis (lack of movement) or hypercoagulability. DVT is a significant concern because the clot can break loose and travel to the lungs, causing a pulmonary embolism.
• Deep Venous Thrombophlebitis: This is the occlusion of a deep vein by a thrombus, which results in inflammation, reduced venous return, edema, and cyanosis.

The Lymphatic System and Related Organs

The lymphatic system acts as a drainage and filtration network. Its primary roles are to retrieve excess fluid from tissue spaces, filter it, and return it to the bloodstream. This process helps conserve plasma proteins and forms a major component of the immune system.

The system drains into two main trunks:

• Right Lymphatic Duct: Drains the right side of the head, neck, and heart, as well as the right arm, lung, pleura, and the upper section of the liver. It empties into the right subclavian vein.
• Thoracic Duct: Drains the rest of the body and empties into the left subclavian vein.

Supporting Organs

Several organs are integral to the lymphatic and vascular health:

• Spleen: Located in the Left Upper Quadrant (LUQ), it filters microorganisms from the blood, destroys old red blood cells, stores red blood cells, and creates antibodies.
• Tonsils: Located at the entrance of the respiratory and gastrointestinal tracts, they respond to local inflammation.
• Thymus Gland: Located in the superior mediastinum; while vital in development, it has no significant function in adults.
• Bone Marrow: Located in the center of bones, it is the site for the creation of T and B lymphocytes.

Clinical Assessment: Edema and Circulation

When assessing the peripheral vascular system, clinicians focus on several key indicators: color, temperature, capillary refill, pulses, symmetry, and edema.

Edema and Lymphedema

Edema is the accumulation of excess fluid in the interstitial tissues. Lymphedema specifically refers to swelling caused by a blockage or malfunction in the lymphatic system.

Clinicians often assess pitting edema by pressing firmly over a bony surface (such as the tibia) for five seconds and noting the depth and duration of the indentation.

Edema Grading Scale

• 1+: Mild pitting; slight indentation; no perceptible swelling of the limb.
• 2+: Moderate pitting; indentation subsides rapidly.
• 3+: Deep pitting; indentation remains for a short time; the limb looks swollen.
• 4+: Very deep pitting; indentation lasts a long time; the limb is very swollen and significantly distorted.

Physical Examination Techniques

A thorough exam includes checking capillary refill (which should be $< 2$ seconds) and grading pulses on a scale from 0 to +3. If a peripheral pulse is too weak to palpate, a Doppler ultrasonic stethoscope can be used. This device magnifies the "swishing" or "whooshing" pulsatile sounds from the blood vessels.

Exam Tip: Using a Doppler To use a Doppler, place a drop of coupling gel on the handheld transducer. Place the transducer over the pulse site at a 45-degree angle and apply very light pressure to locate the sound.

Summary of Clinical Findings