AccuRx Constant Flow Implantable Pump. The AccuRx Constant Flow Implantable Pump (St. Jude Medical, Plano, TX) is an implantable device that stores and dispenses medication at a constant factory-set flow rate to a specific site. The pumps are available in a range of flow rates to allow physicians to tailor therapy to the needs of the patient. 

The AccuRx Constant Flow Implantable Pump consists of a single sealed chamber formed between a rigid titanium shell and a polymeric diaphragm. The chamber holds the drug to be infused. The diaphragm exerts pressure on the drug causing the drug to flow out of the chamber, through a series of filters and a flow restrictor, and then out the catheter (see below) to the delivery site. The AccuRx Constant Flow Implantable Pump is refilled through a raised refill port in the center of the titanium shell. Refilling the pump expands the diaphragm outward and starts the pump on the next cycle of drug infusion. 

DuraCath Intraspinal Catheter. The DuraCath Intraspinal Catheter (Advanced Neuromodulation Systems, Plano, TX) is designed for long-term intraspinal (epidural or intrathecal) implantation. The trimmable, flexible, elastic radiopaque catheter incorporates insertion depth markings and a removable guide wire to facilitate implantation. This catheter has a closed tip and multiple side-exit channels to facilitate dispersion of the drug to reduce the probability of catheter tip complications. There are one- and two-piece versions of the DuraCath Intraspinal Catheter to suite a variety of clinical needs. The DuraCath Intraspinal Catheter is made from silicone and has a small connector made from 316L stainless steel. 

MAGNETIC RESONANCE IMAGING (MRI) INFORMATION
Exposure of AccuRx Constant Flow Implantable Pump and DuraCath Intraspinal Catheter to magnetic resonance imaging (MRI) fields of 1.5-Tesla has demonstrated no impact on pump or catheter performance and a limited effect on the quality of the diagnostic information. Testing performed on the AccuRx Constant Flow Implantable Pump and DuraCath Intraspinal Catheter has established the following with regard to MRI safety and diagnostic issues:

Static Magnetic Field. Testing demonstrated that a 1.5-Tesla magnetic resonance environment produced no measurable magnetic field interactions (i.e., translational attraction and torque) for the AccuRx Constant Flow Implantable Pump and DuraCath Intraspinal Catheter. 

Heating During MRI. Testing demonstrated that there was very little heating for the AccuRx Constant Flow Implantable Pump in association with MR imaging conducted using an excessive amount of RF energy (i.e., a whole-body averaged specific absorption rate of 1.5 W/kg; spatial peak SAR of 2.9 W/kg). Furthermore, this amount of heating is considered to be physiologically inconsequential and will not impose an additional risk to the patient undergoing an MR procedure under the conditions used for the evaluation. In the unlikely event that the patient experiences warmth near the pump, the MRI procedure should be stopped immediately.

Peripheral Nerve Stimulation. The presence of the AccuRx Constant Flow Implantable Pump may potentially cause a one-fold increase (doubling) of the induced gradient current in tissues near this device. This increase in the induced gradient current is similar to that already present elsewhere in the body (e.g., at bone-tissue interfaces) and, as such, is unlikely to enhance the propensity for nerve stimulation. In the unlikely event that the patient reports stimulation during the scan, the MRI procedure should be stopped immediately. 

REFERENCE
AccuRX Constant Flow Implantable Pumps, Technical Manual, St. Jude Medical, Plano, TX.