Optimized venous return with a self-expanding cannula: from computational fluid dynamics to clinical application

Abstract

The Smart canula concept allows for collapsed cannula insertion, and self-expansion within a vein of the body. (A) Computational fluid dynamics, and (B) bovine experiments (76+/-3.8 kg) were performed for comparative analyses, prior to (C) the first clinical application. For an 18F access, a given flow of 4 l/min (A) resulted in a pressure drop of 49 mmHg for smart cannula versus 140 mmHg for control. The corresponding Reynolds numbers are 680 versus 1170, respectively. (B) For an access of 28F, the maximal flow for smart cannula was 5.8+/-0.5 l/min versus 4.0+/-0.1 l/min for standard (P<0.0001), for 24F 5.5+/-0.6 l/min versus 3.2+/-0.4 l/min (P<0.0001), and for 20F 4.1+/-0.3 l/min versus 1.6+/-0.3 l/min (P<0.0001). The flow obtained with the smart cannula was 270+/-45% (20F), 172+/-26% (24F), and 134+/-13% (28F) of standard (one-way ANOVA, P=0.014). (C) First clinical application (1.42 m2) with a smart cannula showed 3.55 l/min (100% predicted) without additional fluids. All three assessment steps confirm the superior performance of the smart cannula design.

Routine use of self-expanding venous cannulas for cardiopulmonary bypass: benefits and pitfalls in 100 consecutive cases☆

“…A new generation of venous cannulas that can change its shape within the body [3] was originally designed for remote access perfusion where, by definition, the access vessel is smaller than the target vessel to be drained. Interestingly, there is increasing evidence, that venous cannulation relying on the 'collapsed insertion and expansion in situ' concept is not only beneficial in remote venous cannulation, where unmatched flow rates can be achieved with gravity drainage alone [4], but also for central cannulation [5,6].…”

Superior flow for bridge to life with self-expanding venous cannulas

“…As reported previously, the selfexpanding venous cannulas [7][8][9][10] can be stretched and collapsed with a hollow mandrel, inserted into the venous vasculature over a guide wire through an access orifice similar to the size of the peripheral vein or even smaller [11] and expanded to its nominal diameter of 36 F within the vena cava (typical diameter in adults is >20 mm or 60 F) or to the available luminal width of the access vessel (typical diameter of the femoral vein is 8 mm or 24 F). Already at the iliac level, the vein diameter increases, and, therefore, the narrow segment of a well-positioned self-expanding cannula is relatively short.…”

“…The superiority of the self-expanding cannula design resulting in a short reduction of its diameter at the point of insertion has also been demonstrated by both computation fluid dynamics [7,13] and bench tests [14]. For the set-up presented here, the negative pressure required to achieve adequate venous drainage with the self-expanding venous cannula accounts for approximately 31% of the 19 F standard rectilinear design at negative pressures reaching 200 mmHg and more.…”

“…We have previously reported the functional principles of the self-expanding venous cannulas mainly for applications with gravity drainage that is, open heart surgery and miniinvasive cardiac surgery [7][8][9][10]. Briefly, the self-expanding cannula can be stretched and collapsed with a hollow mandrel, inserted into the venous vasculature, for example, through a femoral vein, over a guide wire in open, semi-open or percutaneous fashion [11].…”

“…The present study was designed to assess the potential performance increase by the introduction of next-generation, self-expanding venous cannulas [7][8][9][10] despite a relatively small access orifice. In contrast to the previous reports about the self-expanding cannula, a readyfor-use centrifugal pump is an integral part of this set-up, hence providing, by definition, augmentation of venous drainage.…”