Medical Device Daily Washington Editor

Stem cells and biologic therapies and drugs might not be ready to restore spinal function in those with impaired neurological systems, but researchers at one academic center are working on a what they hope is a promising device strategy in this area: the use of small jolts of electricity to bring back a measure of independence for those dealing with incontinence due to damage to the lower spine.

Researchers at Duke University (Durham, North Carolina) have developed what they characterize as a "smart bladder pacemaker," designed to precisely mimic the nerve activity that the body uses to control the bladder sphincter muscle.

Warren Grill, PhD, a researcher at Duke's Pratt School of Engineering, and several others have demonstrated in felines that tweaking the frequency of electrical pulses in the nerves leading to the bladder can invoke both the hold-and-release functions of the bladder, and by making use of the pudendal nerve, can avoid directly stimulating the bladder to achieve the desired effect.

Grill told Medical Device Daily that "The size of a bladder pacemaker would be comparable to that of an implantable cardiac pacemaker." He noted that battery technology is improving, so that the latest battery will have a better power-to-size ratio, which will be essential to keeping the device's size to a minimum.

He added: "The power consumption of neurostimulators is generally higher than pacemakers because rather than stimulating once a second, you're stimulating many times a second." Because the electronic circuitry is very small, the size of the unit, he said, is "determined totally by the battery."

Grill said that in humans, the pudendal nerve originates from the lumbo-sacral spine and can be accessed through the gluteal muscle behind the pelvis.

"We would likely put the stimulator in the abdomen and run a wire to the electrode, which would sit on the pudendal nerve."

Grill said that the research team is pursuing "ongoing feasibility studies in humans, and the purpose of these studies is to determine whether the reflexes we've seen in animal models are present in humans."

The surgeons make use of the latest non-invasive surgical techniques in implanting the necessary electrical leads for the tests.

"If those are successful, the next challenge will be to identify the appropriate technology," Grill said, adding that Duke would probably not attempt to design and build the hardware but would develop it with a company that already makes similar hardware.

At the risk of trotting out a cliché, the multidisciplinary approach to research has played a vital role in this development process, according to Grill.

"One thing that has allowed us to make this progress is collaboration between engineers and physicians here at Duke, and that partnership has enabled a lot of this to go forward," he said.

Similar devices may well offer a similar benefit for a different function down the road as well.

Grill pointed out that this type of technology is becoming "fairly widespread," adding that the Cleveland Functional Electrical Stimulation Center (Cleveland, Ohio) is working on how implants might restore limb function to those with nerve damage or paralysis of traumatic origin.

Grill said that at present, he has no plans to tackle other issues related to spinal damage.

"Right now, we're focused on this bladder control problem, and it's more than enough to fill our plates."

Off-pump CABG no better for cognitive function

The negative downstream effects of coronary artery bypass surgery (CABG) have worried doctor and patient for decades, but until angioplasty came along, patients with severe blockage had few options. Even today, some patients are simply not realistic candidates for stents and other treatment regimes, and they must undergo a thoracic procedure that is long on trauma and short on desirability.

The use of a heart-lung machine to maintain cardiopulmonary function is as old as the CABG, but has some drawbacks. The tubing may carry infectious agents or foreign matter, and blood cells are prone to damage.

However, one of the more notorious side effects of bypass surgery is a decline in cognitive function, and researchers have wondered if avoiding the pump offered a drop in the impairment of cognitive function.

The procedure, which requires the use of pharmaceuticals to slow the heart rate, is already known to be less expensive, and because it requires a smaller opening, allows patients to head home sooner. However, it was not known whether the lower rate of dislodged aortic accumulations would translate to better cognitive outcomes.

In 1998, a team of researchers at the University Medical Center Utrecht (Utrecht, the Netherlands) drew up and started a study to examine whether the off-pump procedure was less stress on cognitive function. The resulting article, which appeared in the Feb. 21 edition of the Journal of the American Medical Association, notes that not only can the intervention in the ascending aorta dislodge accumulations in the aorta, "leading to stroke," but it also can increase the permeability of the blood-brain barrier and trigger the accumulation of atherosclerotic tissues in blood vessels, "which may adversely affect cognitive function."

The authors state that the cognitive decline in CABG on-pump patients is often measured at 5%-30%, depending on the measure, and that about 3% of CABG patients experience a stroke.

These factors have led to "a renewed interest in bypass surgery on the beating heart," but the off-pump procedure "is technically more demanding," the article points out. However, the trial of more than 280 patients, dubbed the Octopus Study, presented researchers with more questions than answers.

"In the Octopus Study, we found a trend toward better cognitive outcomes after three months after surgery, but the difference disappeared at 12 months and now appears to remain absent at five years." The team opined that "this is remarkable because several studies have demonstrated that off-pump CABG surgery is associated with less cerebral embolization" than surgeries using the heart-lung machine. And the authors hypothesize that "factors other than cardiopulmonary bypass may be responsible for cognitive decline, such as anesthesia and the general inflammatory response that is associated with major surgical procedures."

The authors, however, did not address the potential role of high doses of corticosteroids, which are commonly used to suppress swelling after surgeries, in cognitive impairment.