This Cochrane review found that nerve blocks to provide local anaesthesia in the arms or legs of adults before a surgical procedure were safe and effective when guided by ultrasound compared to other guidance techniques.
They were successful about nine times out of ten with ultrasound guidance, compared to about eight times out of ten when using other techniques, such as nerve stimulation. Overall, guided blocks were quicker by one minute and caused fewer side effects, such as the accidental puncture of blood vessels.
The review did not look at cost-effectiveness, or whether one or another technique was best in a particular block or a particular group of patients.
The improved success rates, reduced adverse effect rate and quicker performance time suggest that the use of ultrasound guidance when performing a nerve block for surgery may lead to patient benefits and improved satisfaction. These results support NICE guidance but the costs of ultrasound imaging systems, specialised needles and the training of anaesthetists would also need to be considered in an assessment of affordability and cost-effectiveness of this technique.
Why was this study needed?
A nerve block is an injection of local anaesthetic to numb the nerves supplying a particular part of the body, such as the arm or leg. It may allow for an operation with the person awake, without the need for a general anaesthetic. Blocks, as an adjunct to a general anaesthetic can improve pain control. It is important to place the injection close to the correct nerve in order to get the maximum benefit and avoid potential complications, such as damaging the nerves or nearby blood vessels.
Various nerve-locating techniques are used. One approach is to use anatomical landmarks, such as bones or arteries. An alternative is electrical nerve stimulation via the injection needle. Muscles supplied by the nerve twitch in time with the pulses of current as the needle nears the nerve. Another approach is to locate the nerve using the images created by ultrasound scan. This is the technology assessed in this review.
What did this study do?
This was a systematic review with meta-analyses of 32 randomised controlled trials that compared ultrasound-guided arm or leg nerve blocks in adults with at least one other method of nerve location. It was an update of a previous 2009 review to include new trials. Twenty-six trials looked at nerve blocks in the arm or hand, and six in the leg or foot. Trials were excluded if they looked at postoperative pain relief only, or were for the treatment of chronic pain.
Seventeen trials compared ultrasound with nerve stimulation while nine compared ultrasound in combination with nerve stimulation versus nerve stimulation alone. The remaining six studies looked at a variety of other techniques.
The review used reliable Cochrane systematic review methods. However, there was a high risk of bias across all included studies caused by, for example, a lack of blinding and missing information on how the procedure was performed. Therefore, the findings need to be treated with caution.
What did it find?
- Ultrasound guided nerve blocks were successful, i.e. giving sufficient anaesthesia for surgery, about 90% of the time, compared to a success rate of about 80% when using other techniques (odds ratio [OR] 2.94, 95% confidence interval [CI] 2.14 to 4.04). They were also less likely to need supplementary nerve blocks or general anaesthetic (OR 0.28, 95%CI 0.20 to 0.39).
- Accidental puncture of blood vessels was a complication in about two in 100 ultrasound-guided nerve blocks compared to nearly ten in 100 procedures using other techniques (OR 0.19, 95% CI 0.07 to 0.57). Ultrasound also led to fewer nerve-related complications such as ‘pins and needles’ - about eight per 100 compared with 17 per 100 with other techniques (OR 0.42, 95% CI 0.23 to 0.76). However, the quality of this evidence was low, with wide variation in results between trials.
- Ultrasound-guided nerve blocks were performed about one minute faster than when using other guidance techniques (nerve blocks typically take about five to ten minutes to do). Again, the reliability of this evidence was assessed as very low.
What does current guidance say on this issue?
NICE 2009 guidance supports the use of ultrasound-guided regional nerve blocks. It recommends that clinicians wishing to perform the procedure should be experienced in the administration of regional nerve blocks and trained in ultrasound guidance techniques.
What are the implications?
The evidence in this review confirms and supports NICE guidance that ultrasound may be useful to guide nerve block in adults requiring local anaesthesia in the arms or legs. The review did not assess cost-effectiveness. However, as ultrasound guidance is more effective and takes less time to perform than other regional techniques, its increased use may result in some cost savings. Balancing the effectiveness, safety, cost and training requirements for undertaking procedures by regional anaesthesia compared to general anaesthesia is an important consideration not addressed by this review. Given the overall high costs associated with surgery under general anaesthesia and the possible changes to treatment pathways that result from increased use of nerve blocks, further real world data on activity and cost would help commissioning decisions in this area.
It should be noted that these results are only applicable to nerve blocks of the upper and lower limbs in adults for operative pain relief. Further systematic reviews would be required to assess whether these findings are consistent with other nerve blocks. Neither did the included studies consistently describe who performed the nerve block. Therefore it is not possible to say whether the success of ultrasound-guided nerve block is influenced by experience or the level of technical expertise.
Regional anaesthesia has become more commonly used in the UK in the last decade and there are implications for the training of anaesthetists and surgical/anaesthetic pathways from any further increases in use of ultrasound guidance.
Lewis SR, Price A, Walker KJ, et al. Ultrasound guidance for upper and lower limb blocks. Cochrane Database Syst Rev. 2015;9:CD006459.
NHS Chocies. Local anaesthesia. London: NHS Choices; 2015.
NHS Chocies. Ultrasound scan. London: NHS Choices; 2015.
NICE. Ultrasound-guided regional nerve block. IPG285. London: National Institute for Health and Care Excellence; 2009.
Marhofer P, Harrop-Griffiths W, Kettner SC, et al. Fifteen years of ultrasound guidance in regional anaesthesia: Part 1. Br J Anaesth. 2010;104(5):538-546.
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