Low doses of lidocaine given intravenously help control pain after ambulatory surgery procedures

Although lidocaine is most often used as a local anesthetic, low doses of lidocaine given intravenously can help to control pain after common ambulatory surgery procedures, suggests a study in the December issue of Anesthesia & Analgesia, official journal of the International Anesthesia Research Society (IARS).

Intravenous lidocaine may offer a safe, inexpensive, and effective option for improving pain control after minimally invasive or minor surgery, reports the new study led by Dr Danja S. Groves of University of Virginia, Charlottesville.

IV Lidocaine Reduces Need for Pain Medications

The study included 67 patients undergoing various types of ambulatory surgery (not requiring hospital admission). One group of patients received intravenous injection of lidocaine—the most commonly used local anesthetic—while the other group received a salt (saline) solution.

After surgery, pain was significantly reduced for patients in the lidocaine group. In the recovery room, average pain scores (on a scale of 0 to 10) was about 3 for patients receiving IV lidocaine, compared to 4.5 for those receiving saline solution. Patients in the IV lidocaine group also needed lower amounts of strong pain-relieving drugs (opioids) during and after surgery—about 40 percent less than those receiving saline solution. Intravenous lidocaine did not shorten the time until the patients were ready to go home, nor reduce the need for pain medications in the days after the procedure.

The results are surprising, because local anesthetics such as lidocaine are usually injected close to the nerve to numb the area for surgery. "Anesthesiologists often use local anesthetics to block the nerves that conduct pain," explains Dr. Steven L. Shafer of Columbia University, Editor-in-Chief of Anesthesia & Analgesia. "However, most anesthesiologists warn patients that the block is only as good as their marksmanship. Either they inject the local anesthesia right next to the nerve, numbing it up, or they miss the nerve, and the patient won't have any benefit."

Anesthesiologists generally try to avoid injecting local anesthetics into the bloodstream, as overdoses can be toxic. However, previous studies have found that that IV lidocaine injection is safe in small doses. Intravenous lidocaine has also shown pain-reducing effects in patients undergoing major surgery.

The new results suggest that low-dose IV lidocaine may also useful for less-invasive ambulatory surgery. "We don't know why lidocaine proved so effective," adds Dr. Groves. "It might be an effect on the nerves themselves, but a lot of evidence suggests that lidocaine has potent anti-inflammatory activity in addition to its effects on nerves. The lidocaine could simply be decreasing postoperative inflammation, which we know is a major cause of pain after surgery."

Giving IV local anesthetics is a promising new technique, especially since ambulatory procedures now account for most surgeries performed in the United States, according to an editorial by Drs. Christopher L. Wu of Johns Hopkins University and Spenser S. Liu of Cornell University. However, they point out that the reductions in pain were "much less gratifying" than in studies of IV lidocaine for major surgery. Drs. Wu and Liu believe anesthesiologists should play the leading role in evaluating this and other techniques for anesthesia and pain control in ambulatory surgery.