Study finds no clear advantage of ultrasound guidance for pain relief in nerve block procedures

Using ultrasound to guide the performance of nerve blocks—in which anesthetics are directly targeted to a specific nerve or group of nerves—has contributed to the increased use of regional anesthesia. However, available research doesn't show that ultrasound-guided nerve block procedures lead to increased pain relief, according to a report in the October issue of Anesthesia & Analgesia, official journal of the International Anesthesia Research Society (IARS).

"[T]here is insufficient evidence at this time to define the effects of ultrasound guidance compared to traditional nerve localization techniques on acute pain and related outcomes," concludes the study by Drs. Stephen Choi and Richard Brull of University of Toronto. Meanwhile, an accompanying editorial suggests that the lack of difference is good news—if the ultimate result is that more patients derive the benefits of regional anesthesia.

No Consistent Improvement in Pain Relief…
Drs. Choi and Brull searched the research literature to identify studies comparing ultrasound guidance versus traditional nerve localization procedures for nerve blocks. The findings were analyzed to determine the effectiveness of ultrasound-guided nerve blocks in reducing pain. The analysis included data from 23 studies in which a total of 1,674 patients were randomly assigned to ultrasound-guided versus traditional nerve block techniques.

The results showed no clear advantage of ultrasound guidance in terms of pain relief. Of 16 studies evaluating pain severity, eight found less pain with ultrasound-guided nerve block. However, the pain reductions were generally small: just one study found more than a one-point difference on the standard ten-point pain rating scale.

There were also mixed results in terms of the duration of nerve block or the need for strong pain medications (opioids). Most other outcomes showed no difference between ultrasound guidance and traditional nerve localization techniques. "Ultrasound guidance was not found to be inferior to traditional nerve localization techniques for any outcome," according to Drs. Choi and Brull.

Ultrasound has been a driving force behind the increased use of nerve blocks for a widening range of purposes—especially surgical anesthesia and postoperative pain control. With traditional techniques, anatomical landmarks or electrical nerve stimulation is used to localize the nerve for local anesthetic injection. Using ultrasound allows the anesthesiologist (or other professional) to visualize the nerve directly.

…But Ultrasound Guidance Helps Promote Effective Regional Anesthesia
Most studies of ultrasound guidance have focused on the technical aspects of the nerve block procedure—particularly its success rate in avoiding the need for "conversion" to general anesthesia. The new study assembles the best available data on how ultrasound guidance affects pain control achieved with nerve block.

The results show no consistent evidence that ultrasound guidance leads to more pain reduction, compared to traditional nerve localization—at least so far. In the near future, Drs. Choi and Brull expect to see an increasing number of new studies focusing specifically on the pain-relieving effects of ultrasound-guided nerve block techniques.

But is it even necessary to show that ultrasound guidance leads to superior pain control? In an accompanying editorial, Drs. John Antonakakis and Brian Sites outline the case that the equivalent results of ultrasound-guided versus traditional nerve block techniques is actually good news. They believe that the research focus on technical issues is appropriate—especially in light of the advantages offered by regional anesthesia for surgery.

"We would argue that equivalence is actually a victory for ultrasound," Drs. Antonakakis and Sites write. "Given the wide popularity of ultrasound-guided regional anesthesia, we are confident that ultrasound will continue to expand the application of regional anesthesia, allowing clinical benefits to be realized by a maximum number of patients."