Blood draws are a common medical procedure, providing healthcare professionals with valuable insights into a patient’s health and aiding in the diagnosis of various conditions. A frequent question is whether blood is collected from veins or arteries.
The Primary Source: Veins
For most routine blood tests, blood is drawn from veins. Veins are blood vessels that carry deoxygenated blood back towards the heart. They are located closer to the skin’s surface, making them accessible for medical procedures. Venipuncture, the medical term for drawing blood from a vein, commonly uses several sites:
- The median cubital vein in the inner elbow, often chosen for its size and visibility.
- The cephalic vein, running along the outer forearm.
- The basilic vein, located on the inner forearm.
- Dorsal hand veins, used for minor draws or when arm veins are difficult to access.
The blood obtained is known as venous blood. It is suitable for most diagnostic purposes, including complete blood counts, cholesterol panels, and glucose level assessments.
Why Veins Are Chosen
Veins are the preferred choice for blood collection due to several physiological and practical advantages. Their superficial location makes them easily accessible and visible, simplifying the venipuncture procedure. Blood pressure in veins is considerably lower than in arteries, which contributes to a safer and less painful experience for the patient. This lower pressure also reduces the risk of complications such as hematoma formation, where blood collects under the skin.
Collecting blood from veins poses less risk of damaging surrounding tissues or nerves compared to arterial punctures. The walls of veins are thinner than those of arteries and have less nerve innervation, resulting in less discomfort when pierced. Additionally, venous blood is appropriate for the majority of standard laboratory tests, making it the practical choice for routine diagnostics.
Specific Cases: Arterial Blood Draws
While rare for routine examinations, blood can be drawn from arteries for specific diagnostic purposes. Arteries are vessels that transport oxygenated blood away from the heart to the rest of the body. The primary reason for an arterial blood draw is an Arterial Blood Gas (ABG) analysis. This test measures oxygen, carbon dioxide, and pH levels, providing insights into lung function and metabolic status.
Common sites for arterial blood collection include the radial artery in the wrist, though other sites like the femoral artery in the groin may be used in certain situations. Arterial draws are more complex and can be more painful than venous draws due to the deeper location and higher pressure within arteries. These procedures also carry a higher risk of complications such as bleeding, hematoma, or nerve damage. Consequently, arterial blood draws are performed only when medically necessary and by healthcare professionals with specialized training.