MiniMed implantable pump

In the MiniMed implantable pump, a piston pump drives insulin through the delivery catheter. A patented solenoid motor controls the piston movement, to aspirate insulin from the reservoir chamber into the piston chamber and then push it through the insulin delivery catheter. 

Problems with insulin delivery in implanted pumps are difficult to correct. A change in Hoechst 21 pH-neutral semisynthetic insulin 400 U/ml in accordance with regulations of the European Pharmacopoeia (SEDA-20, 397) resulted in more frequent clogging when this insulin was used in the Minimed 2001 implantable pump (MIP 2001). From October 1995 to October 1996, 17 pumps were implanted (241). The refilling period was reduced from 90 to 30-45 days and the reservoirs were washed with insulin-free buffer before each refill. Backflow was seen in 13 pumps after a mean period of 7.2 months. Modification of the manufacturing process produced 21PH ETP insulin (human semisynthetic insulin, Genapol-stabilized) 400 U/ml, Hoechst, with improved stability since July 1997. All pumps were specifically cleaned before the new insulin was used for refill. The refill period was increased from 38 to 78 days. In 16 pumps, only one backflow was seen after 14 months. 

This study was designed to compare the efficacy of Oralin spray in subjects with type 1 diabetes implanted with a Minimed CSII pump to control post-prandial glucose levels. 

Subcutaneous in vivo testing of these polymers (13,14) has shown minimal tissue response—similar, in fact, to the response to poly-(tetrafluoroethylene). These materials are candidates for use in heart valves, heart pumps, blood vessel prostheses, or as coating materials for pacemakers or other implantable devices. 

Along with electronic transport improvements must come attention to substrate transport in such porous structures. As discussed above, introduction of gas-phase diffusion or liquid-phase convection of reactants is a feasible approach to enabling high-current-density operation in electrodes of thicknesses exceeding 100 jxm. Such a solution is application specific, in the sense that neither gas-phase reactants nor convection can be introduced in a subclass of applications, such as devices implanted in human, animal, or plant tissue. In the context of physiologically implanted devices, the choice becomes either milliwatt to watt scale devices implanted in a blood vessel, where velocities of up to 10 cm/s can be present, or microwatt-scale devices implanted in tissue. Ex vivo applications are more flexible, partially because gas-phase oxygen from ambient air will almost always be utilized on the cathode side, but also because pumps can be used to provide convective flow of any substrate. However, power requirements for pump operation must be minimized to prevent substantial lowering of net power output. 

Kempfert J, Blumenstein JM, Borger MA, et al. Minimally invasive off-pump valve-in-a-valve implantation the atrial transcatheter approach for re-operative mitral valve replacement. Eur Heart J 2008 29 2382-7. 

The primary limitation currently facing the development and use of these implantable micropumps is the precipitation of insulin on the pump components (7,11,14,31), although bicarbonate (33), certain serum components (25), or amino acides (32) may minimize or prevent insulin aggregation. These precipitates, if they accumulate, tend to occlude the flow channels in the pump and particularly the fine bore tubing or valves that are integral parts of these devices. Additional concern is related to the reliability and inherent safety of these devices and to their ability to use small, concentrated insulin reservoirs. 

Baclofen can be administered orally or intrathecally. Intrathecal administration is accomplished by means of an intrathecal catheter and a surgically implanted refiUable pump. Intrathecal administration is often preferred in patients with severe spasticity, as very little of the oral dose actually reaches the CSF. These patients may be unresponsive to oral baclofen and/or intolerant of its side effects at high doses. While intrathecal administration may minimize side effects, it poses the risk of potentially severe CNS depression. How supplied ... 

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