Nerve blocks are used to numb all or part of the arms or legs (peripheral blockade) for surgery or to provide good pain relief after the operation, or both. For instance, nerve blocks may be used as the sole anaesthetic for operations involving arms or legs or be used in combination with other anaesthetic techniques for more major operations such as joint replacements. Serious complications of nerve blocks are rare although do happen occasionally. Using ultrasound, anaesthetists can 'see' vital structures below the skin, which should allow them to place the local anaesthetic injection accurately and avoid damaging other tissues or organs.
The review authors searched the medical literature for controlled clinical trials comparing ultrasound with another nerve-locating technique in adult patients. They found 18 studies including a total of 1344 patients. Most of the studies compared ultrasound with electrical nerve stimulators. Most of the studies were of moderate quality. As the methods used in the included studies were very varied, the review authors were unable to pool the results using statistical tests. The findings of the review are based on the interpretation of individual studies.
The use of ultrasound was not found to make a significant difference to whether a nerve block was successful or not. Using ultrasound reduced bruising. Ultrasound may reduce the time taken to do the block and also resulted in the block working more quickly. Two studies found ultrasound allowed a reduction in the amount of local anaesthetic. No differences were found in length of time the nerve block lasted. No serious complications were reported in any of the studies and there was no evidence of adverse effects from ultrasound itself.