Opioids may be an effective means of post-operative pain relief, but they're also potentially addictive. With this drawback in mind, scientists at Boston Children's Hospital have developed a new pain management system that incorporates ultrasound and liposomes (microscopic man-made sacs) full of a nerve-blocking agent.

The idea is that patients would receive a pain-killer when at the hospital for surgery, plus some of the liposomes would be injected into their body at the wound site. They would then be sent home with a portable ultrasound device.

Once the pain-killer wore off and the discomfort commenced, they would use the device to non-invasively send pulses of ultrasound through their body tissue to the liposomes. This would cause molecules known as sono-sensitizers – located in the walls of the liposomes – to break down, thus releasing the nerve-blocking agent right where it was needed. The process could be performed multiple times.

Developed by a team led by Dr. Daniel Kohane, the liposomes can be activated up to three days after injection. The degree of nerve block can then be controlled simply by adjusting the duration and intensity of the ultrasound.

"Opioid abuse is a growing problem in healthcare," says Kohane. "In the future, this system could potentially combat that by giving patients access to non-opioid, effective nerve-blocking drugs."

An article on the research was published this week in the journal Nature Biomedical Engineering.