By Eleanor McDermid

J Clin Anesth 2011; 23: 87–89, 90–96

MedWire News: Ultrasound guidance achieves a higher success rate for regional block than do methods such as nerve stimulation, a meta-analysis reveals.

Christopher Wu (Johns Hopkins University, Baltimore, Maryland, USA) and colleagues say it is “not surprising” that ultrasound guidance improves the success of regional anesthesia.

“Ultrasound allows direct visualization of various peripheral nerves, resulting in precise localization of local anesthetic administration, which may increase success rates and be particularly useful in difficult patients,” they write in the Journal of Clinical Anesthesia.

The meta-analysis included 16 randomized controlled trials, with a total of 1264 patients who were undergoing elective surgical procedures. Fourteen of the studies compared ultrasound guidance with nerve stimulation, while the other two used surface landmarks and a transarterial technique.

Use of ultrasound guidance increased the chances of block success by 11% versus all other techniques and versus nerve stimulation only. Success was defined as sufficient block to conduct surgery without the need for additional anesthetic measures.

Ultrasound guidance improved block success for brachial plexus blocks, sciatic popliteal block, and brachial plexus axillary block, but not for brachial plexus infraclavicular block.

However, editorialists Toni Torrillo and Meg Rosenblatt (Mount Sinai School of Medicine, New York, USA) noted that two of the studies of infraclavicular blocks included in the meta-analysis reported that ultrasound guidance achieved success in a number of patients in whom nerve stimulation had failed to produce a successful block.

They speculated that the statistical technique used in the meta-analysis may have contributed to the lack of statistical significance.

But they also cautioned that the overall findings may not be generally applicable.

“The majority of the studies analyzed were performed by those considered experts in the field of UGRA [ultrasound-guided regional anesthesia], so the outcomes they report may not be reproducible by the occasional practitioner,” they said.

“An ultrasound machine itself does not replace physician judgment, experience, and knowledge of anatomy. It would be important to learn how novice skill level affects block success rates and other outcomes.”

Torrillo and Rosenblatt also noted that more and larger randomized controlled trials are needed, as those included in the meta-analysis were small and varied widely with respect to block type and the concentrations and volumes of anesthetics used.

But they concluded that “in the interim, the current meta-analysis… does represent an important step toward confirming the benefits” of ultrasound guidance.