Crescent vs Avalon ECMO Cannula: Key Differences

Extracorporeal membrane oxygenation (ECMO) supports patients with severe respiratory or cardiac failure. Dual-lumen cannulas streamline venovenous ECMO by enabling simultaneous blood drainage and reinfusion through a single vessel, reducing the need for multiple access points.

The Crescent and Avalon dual-lumen ECMO cannulas are widely used but differ in design and function. Understanding these differences is essential for optimizing patient outcomes and procedural efficiency.

Architecture Of Dual-Lumen Cannulas

The design of dual-lumen cannulas dictates blood flow dynamics, positioning, and overall efficiency in gas exchange. These devices facilitate simultaneous drainage and reinfusion through a single vessel, typically the internal jugular vein, minimizing vascular trauma and reducing complications associated with multiple access points. Their structure must balance hemodynamic efficiency with mechanical stability to ensure optimal performance.

A key feature of dual-lumen cannulas is the presence of separate lumens for blood withdrawal and reinfusion, positioned to prevent recirculation—where oxygenated blood is inadvertently drawn back into the drainage lumen instead of reaching systemic circulation. Manufacturers incorporate directional flow control mechanisms, such as strategically placed side ports and tapered lumens, to optimize blood movement. Computational fluid dynamics (CFD) modeling has refined these designs, improving flow distribution and reducing shear stress, which can contribute to hemolysis and thrombogenesis.

Material composition is also critical. Most dual-lumen ECMO cannulas are made from biocompatible polyurethane or silicone, chosen for flexibility and durability. These polymers must maintain structural integrity while minimizing endothelial irritation. Heparin-bonded or hydrophilic coatings are often applied to reduce thrombogenicity and enhance hemocompatibility, lowering clot formation and improving circuit longevity.

Crescent Device Configuration

The Crescent dual-lumen ECMO cannula is designed for hemodynamic efficiency and stability during prolonged venovenous support. Its asymmetric lumen arrangement directs blood flow to minimize shear stress and turbulence, reducing the risk of hemolysis and endothelial damage.

A notable feature is its tapered distal tip, which facilitates atraumatic insertion and aligns with the internal jugular vein’s curvature, reducing malposition risks. This design enhances stability, particularly during patient repositioning or transport. Radiopaque markers along its length allow for precise visualization under fluoroscopy or ultrasound, aiding accurate placement and minimizing repositioning needs.

Flow optimization is enhanced by the Crescent cannula’s side port configuration, designed to maximize oxygenated blood delivery while minimizing recirculation. Studies indicate improper side port orientation can reduce gas exchange efficiency. CFD modeling has helped refine its flow pattern, ensuring reinfused blood reaches the right atrium rather than being immediately withdrawn by the drainage lumen. This is particularly beneficial for patients with high cardiac output, where clear separation between drainage and reinfusion streams is crucial.

Constructed from a flexible, biocompatible polyurethane blend, the Crescent cannula balances durability with pliability, easing insertion while maintaining structural integrity. Heparin-bonded coatings further reduce thrombotic risk, improving circuit longevity and minimizing anticoagulation adjustments.

Avalon Device Configuration

The Avalon dual-lumen ECMO cannula was one of the first commercially available designs to streamline venovenous support through a single vessel. Its symmetrical triple-port design, with a centrally located reinfusion port flanked by two drainage ports, promotes balanced blood flow distribution and reduces preferential drainage from a single venous segment. Unlike traditional ECMO cannulas, which require precise angulation to prevent recirculation, the Avalon inherently directs reinfused blood toward the tricuspid valve, minimizing flow disturbances.

Insertion requires careful imaging guidance due to its relatively rigid structure and the need for precise positioning. While its reinforced walls provide stability, they can make advancement challenging, particularly in patients with tortuous vasculature or altered venous anatomy. Most clinicians rely on transesophageal echocardiography (TEE) or fluoroscopic guidance to ensure proper alignment. Incorrect placement can significantly impact ECMO efficiency, with malpositioned Avalon cannulas leading to recirculation fractions exceeding 30%, compromising oxygen delivery and necessitating repositioning.

Designed to accommodate higher flow rates, the Avalon cannula suits patients with significant oxygenation demands. Its wider luminal diameter enhances drainage capacity, particularly beneficial in severe acute respiratory distress syndrome (ARDS) cases requiring high extracorporeal blood flow. However, this larger diameter necessitates adequate vascular access, which may not be feasible in patients with small or stenotic veins. Ultrasound evaluation before cannulation is recommended to ensure proper fit and minimize vascular injury risks.

Hemodynamic Flow Pathways

Effective hemodynamic flow in ECMO depends on precise blood movement through the dual-lumen cannula, ensuring adequate venous drainage and efficient reinfusion into the central circulation. Blood flow direction and velocity significantly impact oxygenation and carbon dioxide removal, particularly in patients with high cardiac output or altered venous pressures. Flow resistance, influenced by cannula diameter, positioning, and vessel compliance, directly affects perfusion efficiency. CFD modeling has shown that suboptimal flow alignment can increase turbulence, leading to shear stress, hemolysis, and endothelial irritation.

Managing the interaction between drainage and reinfusion streams is crucial to preventing recirculation, where oxygenated blood is inadvertently withdrawn by the ECMO circuit instead of reaching systemic circulation. Factors such as atrial pressure gradients and cannula orientation influence this phenomenon. Studies using Doppler ultrasound and intracardiac echocardiography indicate even minor misalignments can elevate recirculation fractions above 20%, reducing oxygen delivery. Clinicians frequently adjust pump flow rates and cannula positioning in real time to optimize these dynamics, ensuring venous return is efficiently directed toward the tricuspid valve while avoiding interference with drainage ports.