Inferior vena cava surgical cannulation for infants needing veno-venous extracorporeal membrane oxygenation

INTRODUCTION

Femoral cannulation for veno-venous extracorporeal membrane oxygenation is challenging in infants because of the diameter of the vein.

CASE REPORT

Prolonged ECMO support (67 days) was necessary for an 8-month-old (8 kg) girl with acute respiratory distress syndrome that was caused by H1N1 influenza. After 30 days on ECMO support and using a single 16 Fr double-lumen cannula (internal jugular vein), a second cannula was necessary to ensure adequate flow. This second 12 Fr single-lumen cannula was surgically placed through the right common iliac vein. An excellent flow profile was then achieved and ECMO continued successfully for 37 more days.

DISCUSSION

As a lifesaving option, this double caval configuration successfully optimized the flow profile and oxygenation, outweighing the related risks.

CONCLUSION

In small children, a surgical approach to the inferior vena cava can be considered safe, especially in those cases where there is a shortage of adequate cannulas, or when central venous access is difficult.

Flattening of Diluted Species Profile via Passive Geometry in a Microfluidic Device

In recent years, microfluidic devices have become an important tool for use in lab-on-a-chip processes, including drug screening and delivery, bio-chemical reactions, sample preparation and analysis, chemotaxis, and separations. In many such processes, a flat cross-sectional concentration profile with uniform flow velocity across the channel is desired to achieve controlled and precise solute transport. This is often accommodated by the use of electroosmotic flow, however, it is not an ideal for many applications, particularly biomicrofluidics. Meanwhile, pressure-driven systems generally exhibit a parabolic cross-sectional concentration profile through a channel. We draw inspiration from finite element fluid dynamics simulations to design and fabricate a practical solution to achieving a flat solute concentration profile in a two-dimensional (2D) microfluidic channel. The channel possesses geometric features to passively flatten the solute profile before entering the defined region of interest in the microfluidic channel. An obviously flat solute profile across the channel is demonstrated in both simulation and experiment. This technology readily lends itself to many microfluidic applications which require controlled solute transport in pressure driven systems.

Optimal B-spline Mapping of Flow Imaging Data for Imposing Patient-specific Velocity Profiles in Computational Hemodynamics

OBJECTIVE

We propose a novel method to map patient-specific blood velocity profiles obtained from imaging data such as 2D flow MRI or 3D colour Doppler ultrasound) to geometric vascular models suitable to perform CFD simulations of haemodynamics. We describe the implementation and utilisation of the method within an open-source computational hemodynamics simulation software (CRIMSON).

METHODS

The proposed method establishes point-wise correspondences between the contour of a fixed geometric model and time-varying contours containing the velocity image data, from which a continuous, smooth and cyclic deformation field is calculated. Our methodology is validated using synthetic data, and demonstrated using two different in-vivo aortic velocity datasets: a healthy subject with normal tricuspid valve and a patient with bicuspid aortic valve.

RESULTS

We compare our method with the state-of-the-art Schwarz-Christoffel method, in terms of preservation of velocities and execution time. Our method is as accurate as the Schwarz-Christoffel method, while being over 8 times faster.

CONCLUSIONS

Our mapping method can accurately preserve either the flow rate or the velocity field through the surface, and can cope with inconsistencies in motion and contour shape.

SIGNIFICANCE

The proposed method and its integration into the CRIMSON software enable a streamlined approach towards incorporating more patient-specific data in blood flow simulations.