What vessels are clamped during cardiopulmonary bypass (CPB) for cardiac surgeries?

Vessels Clamped During Cardiopulmonary Bypass

The ascending aorta is the primary vessel clamped (cross-clamped) during cardiopulmonary bypass for cardiac surgery, while vessels are cannulated rather than clamped for establishing the bypass circuit. 1

Understanding the Distinction: Clamping vs. Cannulation

The question conflates two distinct concepts in CPB. During cardiac surgery with CPB:

Vessels That Are Cross-Clamped

• The ascending aorta is cross-clamped to isolate the heart and create a bloodless operative field 1
• Cross-clamping the aorta allows cardioplegia delivery and cardiac arrest for the surgical procedure 1
• Manipulation and cross-clamping of the aorta can dislodge atheromatous debris, representing a significant stroke risk 1

Vessels That Are Cannulated (Not Clamped)

The CPB circuit requires cannulation of vessels to establish blood flow through the bypass machine:

Arterial cannulation sites (for blood return to the patient):

• Ascending aorta - most common site 1, 2
• Femoral artery - used in peripheral cannulation 3, 4, 2
• Axillary-subclavian artery - increasingly used, especially in aortic dissection, as these vessels permit antegrade flow and are usually atherosclerosis-free 1, 5
• Iliac artery - rarely used 1
• Distal aorta - alternative site 6

Venous cannulation sites (for blood drainage from the patient):

• Right atrium with bicaval, single atrial, or cavoatrial approaches 1, 2
• Superior vena cava 2
• Inferior vena cava 1, 2
• Femoral vein - for peripheral cannulation 3, 4

Critical Safety Considerations

Epiaortic ultrasonography should be considered before aortic cannulation and cross-clamping to detect atherosclerotic plaque in the ascending aorta, particularly in patients over 50-60 years with vascular disease history 1. This imaging can lead to relocation of cannulation sites in up to 29% of CABG patients and may improve neurological outcomes 1.

The "sand-blasting" effect from arterial cannula jets and manipulation during cross-clamping can dislodge embolic material, making careful technique and site selection critical for preventing perioperative stroke 1.