Ice and Nanoparticles for Postoperative Pain?

Two new pain management approaches that can decrease postoperative pain as well as the need for opioid pain relievers were presented this week at the 2013 Clinical Congress of the American College of Surgeons. One strategy involved the use of ice packs, and the other strategy involved a prolonged drug delivery method using nanotechnology in animals.

Previous research has shown that cryotherapy is a safe and effective method of pain control after orthopedic surgery. However, a new study has found that the application of ice to the surgical wound after open abdominal surgery is a simple but nonstandard method of pain control.

The ice pack study involved the application of soft ice packs to the incision area after open abdominal operations in 27 patients, compared with the use of no ice in 28 patients. Patients in the cryotherapy group could apply ice packs to the wound at desired intervals for at least 24 hours. They also had the option of taking opioids. The no-cryotherapy group received only opioids for pain control.

Patients in the cryotherapy group reported significantly less pain-about 50% less on day 1 and day 3-than the no-ice control group. In addition, the cryotherapy group used 22.5% less opioid pain medication than those in the control group. In fact, some patients in the cryotherapy group reportedly used no additional pain medication.

Viraj A. Master, MD, PhD, FACS, principal investigator and associate professor of urology at Emory University School of Medicine in Atlanta, suggests that surgeons recommend that their patients who have had open abdominal surgery intermittently apply ice packs to the surgical wound.

“An ice pack is safe and inexpensive, gives the patient a sense of empowerment because it is self-care, and doesn’t require high-teck devices,” said Dr. Master.

In contrast to the low-tech ice pack, the second pain management approach used nanoparticles to create a controlled-release delivery system for lidocaine, a non-opioid numbing medication.

The research team, led by Jeffrey L. Van Eps, MD, a research associate at the Houston Methodist Research Institute, first developed an injectable hydrogel containing lidocaine. The hydrogel was able to hold microscopic spheres of biodegradable polymer called polylactic-co-glycolic acid (PLGA), which has been FDA-approved for drug delivery. The polymer acts as an “envelope” for nanoparticles, which are molecular-sized structures, of the mineral silica, which has spongelike holes that take up the lidocaine gel, Dr. Van Eps explained.

“Nanotechnology with PLGA makes an ideal drug delivery system because we can tailor the nanoparticles to allow prolonged delivery,” said Dr. Van Eps. In animal studies, the drug's delivery time was extended to last all 7 days of the study, providing adequate pain relief throughout.

The researchers to date have limited their testing to rats, and planned studies in larger animals must occur before this technology can be tested in humans, explained Dr. Van Eps. Using mechanical-force withdrawal testing and daily scoring of pain-related adaptive behaviors, the researchers were able to assess the pain-control effect in rats. According to the researchers, the best study results were seen with combination therapy using lidocaine gel and daily NSAIDs, the effects of which were equivalent to those of daily opioid narcotic pain control.

References:

American College of Surgeons. Surgeons report 2 new approaches to lessen postoperative pain [press release]. Available here. Accessed October 8, 2013.