Vascular Access - Basics - General Anatomy
General Anatomy
Here we shall take a look at the anatomy of the vasculature and the surrounding tissues at different cuts to help us identify the relevant key structures.
1. Short Axis
2. Long Axis
3. Artery vs Vein
Here we shall take a look at the anatomy of the vasculature and the surrounding tissues at different cuts to help us identify the relevant key structures.
1. Short Axis
2. Long Axis
3. Artery vs Vein
1. Short Axis:
Here is an image of a vein localized at the flexion portion of the forearm. The vein is imaged from the short axis perspective. From superficial to deep, the first structure that the ultrasound beam images is the skin. The heterogenous hypoechoic structures underneath are the subcutaneous tissue. In this particular patient, the arm was quite edematous, you can see little anechoic pockets within the subcutaneous tissue representing the edema. The vein is the circular or ovoid at about 1-1.5cm deep.
Here is an image of a vein localized at the flexion portion of the forearm. The vein is imaged from the short axis perspective. From superficial to deep, the first structure that the ultrasound beam images is the skin. The heterogenous hypoechoic structures underneath are the subcutaneous tissue. In this particular patient, the arm was quite edematous, you can see little anechoic pockets within the subcutaneous tissue representing the edema. The vein is the circular or ovoid at about 1-1.5cm deep.
2. Long Axis:
This is the same vein as the one imaged above though image in its long axis.
Notice the vein, now, is tubular in structure. In addition, some of the fascial planes can be seen running horizontally.
This is the same vein as the one imaged above though image in its long axis.
Notice the vein, now, is tubular in structure. In addition, some of the fascial planes can be seen running horizontally.
3. Artery vs Vein
Artery:
Vein:
Artery:
- Thicker vascular wall (media)
- Need high pressure to collapse the vessel especially during systole (unless hypotensive) - however, usually the pressure that suffices to collapse arteries during diastole would collapse veins in BOTH systole and diastole
- Visible pulsation
- Pulsation on doppler
Vein:
- Thin vascular wall
- Little pressure can collapse the lumen during the entire cardiac cycle
- Usually no pulsation
- No flow, or continuous flow on doppler - can be accentuated with distal muscular contraction
Key Message:
- Be sure you know what you are imaging (what you are looking for) and what you are looking at (image interpretation):
- Not all anechoic circular/tubular structures are vessels: Mimics are nerves, muscle, tendons. Look for the differentiating features.
- Is it an artery or a vein: Assess for multiple differentiating features
- Are you sure the vessel you see is the ONE you are looking for: eg.) Inferior epigastric vessels mistaken for femoral vessels. Know your surface and internal anatomy.