Medtronic Inc. said Thursday that 14 patient deaths have been associated with problems involving its SynchroMed implantable drug pump. A day earlier, the device was the subject of recalls from the U.S. Food and Drug Administration.

Two patient deaths have been associated with a blockage in the catheter that delivers medication from the pump to the area being treated, Medtronic said; 11 deaths were attributed to medication being inadvertently injected into tissue around the implanted pump, called "the pocket" rather than into the reservoir in the pump. Medtronic said one death is connected to a short-circuit of the pump.

The deaths occurred between May 1996 and April 2013.

The Fridley-based company said it told customers previously about potential problems, and again in early June when it issued special instructions for its use. Medtronic made a broader announcement Wednesday after learning that the U.S. Food and Drug Administration has classified that correspondence as a Class I recall, meaning "there is a reasonable probability that use of these products will cause serious adverse health consequences or death," according to the FDA.

The SynchroMed pump is used to deliver drugs directly to the cerebral spinal fluid in patients with intractable pain or who have severe spasticity and for whom oral medication is ineffective. Despite the problems with the pump, Medtronic spokeswoman Donna Marquard said the SynchroMed pump "continues to demonstrate strong overall reliability, and Medtronic remains confident in its ability to deliver safe and effective therapy for those who need it."

The first reason for the recall involves what is called the "priming bolus function," which is used to quickly move medication from the pump reservoir to the tip of the catheter that delivers the drug to the spinal fluid. Medtronic found that anytime the function is used with the pump, the drug mixes with the sterile water or spinal fluid already in the catheter. That can result in the unintended delivery of drug, as well as dilution of some of the drug remaining in the catheter. This can increase the risk of drug overdose — or underdose — following the initial implant of the pump or a replacement of the pump.

The effects of an overdose or underdose vary depending on the drug being infused, but may include a reduced level of consciousness or a return of underlying symptoms. Medtronic said it is recommending that doctors continue using the priming bolus function to ensure therapy is initiated while a patient is under medical supervision. Recommendations are being provided for performing a priming bolus, which involves monitoring patients after they're implanted.

Marquard said Thursday that the company has not established "with certainty a direct causal relationship between the priming bolus and specific adverse events, due to a number of other potentially contributing factors, including drug dosage, patient medical history and the use of other systemic drugs during intrathecal therapy."

The second reason for recall involves the potential of an electrical short circuit. Medtronic said a short within the pump could make the pump motor stall and lead to a loss of therapy. That can result in a return of the patient's underlying symptoms or drug withdrawal symptoms. Medtronic said the pump is equipped with alarms and will sound if the motor stalls. The cumulative failure rate of the pump due to this issue is less than 1 percent after seven years, the company said. Because of that, Medtronic is not recommending removal of the device unless a pump shows signs of malfunction. Medtronic officials said they are developing design updates to deal with this issue.

The third recall has to do with the pump's Sutureless Connector (SC) catheter. Medtronic said it has redesigned the catheter to reduce the potential for blockage due to misalignment at the point where the catheter connects to the pump. As a result, the company said it has initiated a voluntary removal of unused catheters that were made before the design change. To reduce the risk of blockage, Medtronic is recommending that customers discontinue use of all SC catheter models 8709SC, 8731SC, 8596SC and 8578, made before the design change. Those products have a "use by" date of Aug. 25, 2014.

A safety update

In addition to those three recalls, Medtronic announced a safety update to the SynchroMed Implantable Infusion Pump refill procedure, which continues a 2011 recall. The update reflects revised product labeling approved by the FDA to help health care professional reduce the potential of making inadvertent injections of the drug into the area under a patient's skin where the pump in placed instead of into the pump itself.

Marquard said more than 200,000 patients worldwide receive what is called "intrathecal" drug therapy using the pump. Based on Medtronic's registry, 98.8 percent of SynchroMed II pumps continue to perform according to specifications after three years. After six years, 94.4 percent continue to perform according to specifications, she said.

Still, she said, if patients experience any problems or a return of symptoms — or hear a device alarm — they should contact their doctor immediately.

"Patient safety is our top priority and we take these notifications seriously," Marquard said. "As new information becomes available, we share it with our customers."

James Walsh • 612-673-7428