Cannula Size Selector
Get suggested CPB cannula sizes based on patient weight.
Input Parameter
Enter patient weight to see suggestions.
Clinical Context & Significance
Cannulation is the critical interface between the patient and the heart-lung machine. Selecting the correct size is a balance between achieving adequate flow and minimizing trauma to the blood vessels.
Arterial Cannulation
Arterial cannulae are characterized by their pressure drop across the tip. High pressure drops (>100 mmHg) can lead to hemolysis and jetting, which may cause aortic dissection or plaque dislodgement.
Venous Drainage
Venous drainage is primarily skeletal and dependent on gravity or vacuum assistance. Inadequate venous cannula size is a leading cause of "air lock" and poor pump flow during bypass.
Clinical Tip: Always verify the internal diameter (ID) of the cannula, as different manufacturers may have varying wall thicknesses for the same French (Fr) size. Use this tool as a baseline guide and adjust based on surgical access and specific patient anatomy.
Vascular Access, Cannulation Hemodynamics, and Vessel Sizing
Physiological Principles & Clinical Context
Cardiopulmonary bypass requires established vascular access to securely drain deoxygenated blood from the patient's venous system and return oxygenated blood to the arterial tree. Choosing appropriate cannula sizes is a critical decision: an undersized arterial cannula creates high resistance, leading to hemolysis, high circuit pressure, and high-velocity jet flow that can cause aortic wall dissection. Conversely, an undersized venous cannula limits gravitational drainage, depleting the venous reservoir and causing circuit air entrainment. Appropriate selection is highly dependent on patient weight and planned flow requirements.
Clinical Targets & Safe Ranges
- •Maximum Arterial Line Velocity: Keep below 4.0 to 4.5 m/s to prevent endothelial damage.
- •Maximum Cannula Pressure Gradient: Target less than 100 mmHg across the arterial cannula.
- •Adult Arterial Cannula Sizes: Standardly ranges from 18 Fr to 24 Fr based on flow requirements.
- •Venous Drainage Strategies: Options include Dual-Stage (draining RA and IVC), Bicaval (separate SVC and IVC cannulas), or Peripheral Femoral drainage.
Mathematical Formulation
- ƒReynolds Number (fluid dynamics): Re = (velocity × diameter × density) / viscosity
- ƒPoiseuille's Law (resistance): Flow Resistance ∝ Length / Radius⁴
- ƒPressure Drop (ΔP): ΔP = Flow × Resistance
Academic & Clinical References
- Reed CC, Stafford TB. Cardiopulmonary Bypass. 2nd ed. Houston: Medical Academic Press; 1985.
- Groom RC. Extracorporeal technology and cardiopulmonary bypass circuit design. In: Sellke FW, del Nido PJ, Swanson SJ, eds. Sabiston and Spencer's Surgery of the Chest. 9th ed. Philadelphia: Elsevier; 2016.