An Innovative Approach to Minimizing Downtime in Continuous Kidney Replacement Therapy.

Continuous kidney replacement therapy (CKRT) is often utilized to stabilize patients with severe acute kidney injury associated with significant electrolyte abnormalities and/or oliguria and concomitant fluid accumulation. Circuit downtime may reduce daily treatment time and affect delivered doses of CKRT. Studies have found clotting to be the leading cause of downtime and underdosing, which are associated with negative treatment outcomes. The NxStage Cartridge Express with Speedswap (NxStage Medical, Inc.) was designed to minimize downtime by allowing filter priming to occur in parallel with ongoing CKRT and by permitting filter exchanges without the need to replace the entire cartridge. Data from pilot studies suggest that filter exchanges using this system interrupt treatment by an average of 4 minutes per exchange-a considerable reduction from traditional systems that require treatment to be discontinued while the filter is primed, which can take 30 minutes or more. In addition to increasing patient time on therapy, this system has the potential to reduce costs for patients who require a high number of filter changes, and reduce nursing labor and environmental impact (reduced plastic waste). Future studies should confirm whether patients at higher risk of clotted/clogged filters benefit from CKRT with a system designed for rapid filter changes.

Design Concepts and Preclinical Results of a Miniaturized HeartWare Platform: The MVAD System.

OBJECTIVE: Ventricular assist device (VAD) miniaturization is one design trend that may result in less-invasive implantation techniques and more versatility with patient selection. The MVAD System is a miniature, continuous-flow device implanted in the ventricle. The pump is capable of delivering between 0 and 7 L/min of flow at a mean arterial pressure of 75 mm Hg. The impeller was optimized from its original design to improve hydraulic performance, minimize shear regions, and enhance the impeller's radial stiffness. These studies evaluated the MVAD System with modified impeller in the preclinical setting. METHODS: This modified pump design was tested through chronic studies (n = 6) in a healthy ovine model where 4 animals were implanted for a duration of 30 ± 5 days and 2 animals were implanted for a duration of 90 ± 5 days. The pump was placed in the left ventricular apex with the outflow graft anastomosed to the descending aorta. Postoperatively, no anticoagulant or antiplatelet therapies were administered throughout the study duration. RESULTS: All 6 animals reached their elective date of kill, demonstrating no evidence of organ compromise or device-related complications. Average pump parameters did not deviate significantly, and average rotational speed, pump flow, and power consumption were 14095 ± 139 RPM, 4.1 ± 0.4 L/min, and 4.3 ± 0.1 W, respectively. Examination of pump components postexplant demonstrated no mechanical wear or thrombus formation. CONCLUSIONS: Hemocompatibility and biocompatibility of the modified MVAD System were demonstrated through pump parameters, blood chemistry panels, and histopathology analysis.

Design concepts and principle of operation of the HeartWare ventricular assist system.

Implantable left ventricular assist devices provide circulatory support for patients at risk of death from refractory, end-stage heart failure. Rotary blood pumps have been designed for increased reliability and smaller size for use in a broader population of patients than the first-generation pulsatile devices. The design concepts and principle of operation of the HeartWare System are discussed. The HeartWare Ventricular Assist System (HVAD) is a small centrifugal flow pump with a displacement volume of 50 ml and an output capacity of 10 L/min. A unique wide-blade impeller is suspended by hybrid passive magnets and hydrodynamic forces. An integrated inflow cannula is inserted into the left ventricle and is held in position by an adjustable sewing ring; the pump is positioned in the pericardial space. The 10-mm outflow graft is anastomosed to the ascending aorta. External system components include the microprocessor-based controller, a monitor, lithium-ion battery packs, alternating current and direct current power adapters, and a battery charger. Physiologic control algorithms are incorporated for safe operation. Preclinical life cycle tests have shown the HVAD to be highly reliable. This system design offers reliability, portability, and ease of use for ambulatory patients.