Freeze-Dried Microfluidic Monodisperse Microbubbles as a New Generation of Ultrasound Contrast Agents.

We succeeded in freeze-drying monodisperse microbubbles without degrading their performance, that is, their monodispersity in size and echogenicity. We used microfluidic technology to generate cryoprotected highly monodisperse microbubbles (coefficient of variation [CV] <5%). By using a novel retrieval technique, we were able to freeze-dry the microbubbles and resuspend them without degradation, that is, keeping their size distribution narrow (CV <6%). Acoustic characterization performed in two geometries (a centimetric cell and a millichannel) revealed that the resuspended bubbles conserved the sharpness of the backscattered resonance peak, leading to CVs ranging between 5% and 10%, depending on the geometry. As currently observed with monodisperse bubbles, the peak amplitudes are one order of magnitude higher than those of commercial ultrasound contrast agents. Our work thus solves the question of storage and transportation of highly monodisperse bubbles. This work might open pathways toward novel clinical non-invasive measurements, such as local pressure, impossible to carry out with the existing commercial ultrasound contrast agents.

Never too old for an autogenous dialysis fistula? Results of endovascular interventions in nonagenarians.

The number of elderly patients in hemodialysis has increased in recent years and nowadays there are significant numbers of nonagenarians. However, there is currently no information in the literature about arteriovenous fistula (AVF) outcomes in patients aged over 90 years after endovascular treatment for stenosis or thrombosis. This retrospective analysis of prospectively collected data included 38 consecutive patients aged over 90 years who were referred for endovascular evaluation and treatment of AVF nonmaturation (n = 11), dysfunction (n = 25), or thrombosis (n = 2) between 2005 and 2013. Median age was 93.9 years, and 24% were diabetic and 47% hypertensive patients. Immature and dysfunctional AVFs were treated by angioplasty, thrombosed fistulas by thromboaspiration. Fistula patency rates were calculated according to the Life-Table method. The immediate overall clinical success rate was 97.4%. Complications included four transient dilation-induced ruptures. Stents were placed for rupture control (n = 3) and major elastic recoil (n = 3), and to rectify a basilic vein pseudoaneurysm developed after dilation. Mean follow-up was 62.6 months. Primary patency rates were 60% and 43% at 1 and 2 years, respectively. Secondary patency rates were 95% and 92% at 1 and 2 years, respectively. Patency rates were not significantly different between immature and dysfunctional AVFs. Endovascular treatment of AVF complications appears to be a valuable approach in nonagenarian patients in view of the low invasiveness, low complication rate, and relatively good long-term patency rates.