Philips harnesses echo probes for nerve blocks

Volumetric imaging may be the key to an emerging opportunity for ultrasound in anesthesiology. Researchers at the Mayo Clinic in Jacksonville, FL, adapted real-time echocardiography to produce 3D images of nerves, clearing the way for faster and more accurate nerve blocks using local anesthesia.

Two Mayo anesthesiologists, Steven Clendenen and Neil Feinglass, have been using real-time ultrasound technology from Philips Medical Systems to guide needles to nerve endings before anesthesia is released to inactivate them. Such nerve blocks can reduce the time needed for interventions, which helps make the procedure run more efficiently and spares patients the consequences of general anesthesia.

The physicians have employed two Philips probes designed for echocardiography: the x3-1 and x7-2 Matrix array transducers. The best results were obtained with the x7-2 Matrix array, which was customized to image infant hearts.

"With the 7.2 matrix, we were able to actually see the nerve roots coming out," Clendenen said.

Real-time volumetric data allows visualization of the nerve longitudinally and from all angles - a far cry from what can be done with the 2D probes typically used to guide nerve blocks.

"The problem with 2D ultrasound is finding the tip of the needle," he said. "You have to manipulate the probe and jiggle the needle to find it. With 3D ultrasound, you manipulate the image."

The Mayo physicians have used this technique to place blocks on nerves in the neck, under arms, below collarbones, and in the back upper portion of legs. Such regional blocks exert less stress on patients' hearts, thus promoting recovery and improved rehabilitation, Clendenen said. Also, through detailed guidance, a miniature catheter can be placed alongside the nerves. This allows for at-home administration of anesthetic.

"We can send people home the day of or the day after surgery instead of keeping them in the hospital with a morphine infusion," he said. "It is cutting-edge technology."

Clendenen has discussed with Philips executives how this technology might be packaged for anesthesiology. One idea is the development of a tailored system with presets for optimal nerve imaging and the removal of other echocardiography features. He has also has suggested boosting the frequency from 7 MHz to 9 MHz to improve resolution in the near field, as well as expanding the width of the probe for more coverage.