Ultrasound guidance for injecting local anaesthetics in children to block pain transmission


A regional blockade involves injecting a local anaesthetic into the spine or around the nerves to block pain transmission. It can be used to replace general anaesthesia or to treat pain after surgery. Finding an effective alternative to traditional painkillers (pills or injections containing morphine derivatives) is particularly important for children, as they might be more likely to suffer adverse effects from opioid painkillers, and also because pain in early life might do long-term harm (exaggerated response to pain later in life). Traditionally, finding the exact location where the local anaesthetic needs to be injected was done on anatomical landmarks, that is palpation of bones or a pulsatile vessel (artery, using fingers to feel a pulse). Later, an electric needle producing a muscle contraction (nerve stimulator) was advocated as being more precise. Over the past four decades, clinicians have started to use ultrasound to locate nerves. However, ultrasound machines are expensive (USD 22,000 versus USD 1000 for a nerve stimulator).

We wanted to know if ultrasound guidance can improve the success rate and reduce the incidence of complications of regional blockade in children. These complications may include lasting neurological complications, inadvertent needle entry into a blood vessel, and seizure or cardiac arrest from local anaesthetic excess or from inadvertent injection into a blood vessel.

Search date

The evidence is current to March 2018.

Study characteristics

We included 33 well-designed studies with a total of 2293 children in which ultrasound guidance was compared with another method of nerve localization (traditional landmarks techniques or nerve stimulator) for regional blockade in children.

Study funding sources

Sources of funding included a government organization (two studies), a charitable organization (two studies), and an institutional department (13 studies). Two studies declared that they received industry help (equipment loan). The source of funding was unclear for 14 studies.

Key results

Ultrasound guidance for regional blockade in children may decrease the occurrence of failed block. It may also increase duration of the block and reduce pain at one hour after surgery. Ultrasound guidance may decrease the number of needle passes required to perform the block. However, because the vast majority of blocks in children are performed with the child under deep sedation or general anaesthesia, the true value of this finding might be arguable. There were no major complications in the included trials. There may be little or no difference between study groups in risks of minor complications. Altogether, whether or not these findings justify the extra cost of ultrasound guidance should probably also take into account the anaesthesiologist's expertise and local resources. The five ongoing studies may alter the conclusions of the review once published and assessed.

Quality of the evidence

We assessed the quality of the evidence as moderate for decreased occurrence of a failed block and improved pain scores at one hour; high for prolonged block duration; and very low for decreased number of needle passes.

Authors' conclusions: 

Ultrasound guidance for regional blockade in children probably decreases the risk of failed block. It increases the duration of the block and probably decreases pain scores at one hour after surgery. There may be little or no difference in the risks of some minor complications. The five ongoing studies may alter the conclusions of the review once published and assessed.

Read the full abstract...

The use of ultrasound guidance for regional anaesthesia has become popular over the past two decades. However, it is not recognized by all experts as an essential tool, perhaps because it is unclear whether ultrasound reduces the risk of severe neurological complications, and the cost of an ultrasound machine (USD 22,000) is substantially higher than the cost of other tools. This review was published in 2016 and updated in 2019.


To determine whether ultrasound guidance offers any clinical advantage when neuraxial and peripheral nerve blocks are performed in children in terms of decreasing failure rate or the rate of complications.

Search strategy: 

We searched CENTRAL, MEDLINE, Embase, and two trial registers up to March 2018 together with reference checking to identify additional studies and contacted study authors to obtain additional trial information.

Selection criteria: 

We included all parallel randomized controlled trials that evaluated the effects of ultrasound guidance used when a regional blockade technique was performed in children. We included studies performed in children (≤ 18 years of age) undergoing any type of surgical procedure (open or laparoscopic), for which a neuraxial (spinal, epidural, caudal, or combined spinal and epidural) or peripheral nerve block (any peripheral nerve block including fascial (fascia iliaca, transversus abdominis plane, rectus sheath blocks) or perivascular blocks), for surgical anaesthesia (alone or in combination with general anaesthesia) or for postoperative analgesia, was performed with ultrasound guidance. We excluded studies in which regional blockade was used to treat chronic pain.

We included studies in which ultrasound guidance was used to perform the technique in real time (in-plane or out-of-plane), as pre-scanning before the procedure or to evaluate the spread of the local anaesthetic so the position of the needle could be adjusted or the block complemented. For control groups, any other technique used to perform the block including landmarks, loss of resistance (air or fluid), click, paraesthesia, nerve stimulator, transarterial, or infiltration was accepted.

Data collection and analysis: 

We used the standard methodological procedures expected by Cochrane. Our primary outcomes were failed blocks, pain scores at one hour after surgery, and block duration. Secondary outcomes included time to perform the block, number of needle passes, and minor and major complications. We used GRADE to assess the quality of evidence for each outcome.

Main results: 

We included 33 trials with a total of 2293 participants from 0.9 to 12 (mean or median) years of age. Most trials were at low risk of selection, detection, attrition, and reporting bias, however the lack of blinding of participants and personnel caring for participants resulted in 25 trials being judged as at high or unclear risk of bias. We identified five ongoing trials.

Ultrasound guidance probably reduces the risk of failed block (risk difference (RD) −0.16, 95% confidence interval (CI) −0.25 to −0.07; 22 trials; 1789 participants; moderate-quality evidence). When ultrasound guidance was used, there was a small to moderate reduction in pain one hour after surgery, equivalent to a reduction of 1.3 points on the revised Bieri FACES pain scale (scale; 0 = no pain, 10 = maximal pain) (standardized mean difference (SMD) −0.41, 95% CI −0.74 to −0.07 (medium effect size); 15 trials; 982 participants; moderate-quality evidence). Ultrasound guidance increases block duration by the equivalent of 42 minutes (SMD 1.24, 95% CI 0.72 to 1.75; 10 trials; 460 participants; high-quality evidence).

There is probably little or no difference in the time taken to perform the block (SMD −0.46, 95% CI −1.06 to 0.13; 9 trials; 680 participants; moderate-quality evidence). It is uncertain whether the number of needle passes required is reduced with the use of ultrasound guidance (SMD −0.63, 95% CI −1.08 to −0.18; 3 trials; 256 participants; very low-quality evidence).

There were no occurrences of major complications in either the intervention or control arms of the trials (cardiac arrest from local anaesthetic toxicity (22 trials; 1576 participants; moderate-quality evidence); lasting neurological injury (19 trials; 1250 participants; low-quality evidence)).

There may be little of no difference in the risk of bloody puncture (RD −0.02, 95% CI −0.05 to 0.00; 13 trials; 896 participants; low-quality evidence) or transient neurological injury (RD −0.00, 95% CI −0.01 to 0.01; 18 trials; 1230 participants; low-quality evidence). There were no occurrences of seizure from local anaesthetic toxicity (22 trials; 1576 participants; moderate-quality evidence) or block infections without neurological injury (18 trials; 1238 participants; low-quality evidence).