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

Background

A local anaesthetic can be injected into the spine or around the nerves to block pain transmission to avoid putting the patient to sleep for surgery or to treat postoperative pain. This is called ‘regional blockade’. Finding an effective alternative to general anaesthetics or traditional painkillers is particularly important for children because they might be more likely to suffer adverse effects from general anaesthesia or opioid painkillers, and because pain in early life might do long-term harm. Regional blockade can be performed by inserting a needle into the skin at a place that is determined by palpation of bones or a pulsatile vessel. An electric needle producing a muscle contraction can also be used to find a suitable location. Over the past three decades, clinicians have started to use ultrasound to locate the nerves, but these machines are expensive and require additional clinician expertise. A Cochrane review has already found that ultrasound guidance does not increase the rate of success of regional blockade but does reduce harmful effects in adults. We wanted to know whether effects in children are the same.

Search date

Evidence is current to March 2015.

Study characteristics

We included 20 randomized controlled trials in which ultrasound was compared with another method of nerve localization for regional blockade in children.

Study funding sources

Sources of funding included a government organization (two studies), a charitable organization (one study) and an institutional department (four studies). Two studies declared that they received help from the industry (equipment loan). The source of funding was unclear for 11 studies.

Key results

Ultrasound guidance decreased the occurrence of a failed block (actual rate without ultrasound 25%). If six blocks were performed, one fewer participant would have a failed block if ultrasound guidance was used. The identified studies used children from different age groups. If we compare results by age, we find that the younger the child, the greater was the reduction in failed blocks. Pain scores at one hour after surgery were reduced when ultrasound guidance was used, but the reduction in pain was small. When ultrasound guidance was used, the time that lapsed before the child needed additional painkillers after surgery was increased by approximately 62 minutes from the usual mean time ranging from 11 minutes to seven hours. Here again, the younger the child, the longer was the difference in delay to the appearance of pain. Time to perform the block was reduced when ultrasound guidance was used for pre-scanning before a block in the spine was performed (equivalent to 2.4 minutes less from a mean time of 3.2 minutes in the control group). Ultrasound guidance reduced the number of needle passes required to perform the block: mean 0.6 needle pass per participant (from a mean of 1.6 in the control group). Data are needed to show whether ultrasound guidance also reduces the number of unwanted needle entrances into a blood vessel (actual rate without ultrasound 14%). No major complications were reported in any of the 1241 participants.

Quality of evidence

The quality of the evidence was rated as high for decreased occurrence of a failed block, improved pain scores at one hour, increased block duration, reduced time needed to perform regional blockade when ultrasound guidance was used as pre-scanning before a block in the spine and a decreased number of needle passes. The level of evidence was rated as low for the number of unwanted needles entered into a blood vessel.

Authors' conclusions: 

Ultrasound guidance seems advantageous, particularly in young children, for whom it improves the success rate and increases the block duration. Additional data are required before conclusions can be drawn on the effect of ultrasound guidance in reducing the rate of bloody puncture.

Read the full abstract...
Background: 

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. The cost of an ultrasound machine is substantially higher than the cost of other tools such as a nerve stimulator.

Objectives: 

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

Search strategy: 

We searched the following databases to March 2015: Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (OvidSP), EMBASE (OvidSP) and Scopus (from inception to 27 January 2015).

Selection criteria: 

We included all parallel randomized controlled trials (RCTs) that evaluated the effects of ultrasound guidance used when a regional blockade technique was performed in children, and that included any of our selected outcomes.

Data collection and analysis: 

We assessed selected studies for risk of bias by using the assessment tool of The Cochrane Collaboration. Two review authors independently extracted data. We graded the level of evidence for each outcome according to the GRADE (Grades of Recommendation, Assessment, Development and Evaluation) Working Group scale.

Main results: 

We included 20 studies (1241 participants) for which the source of funding was a government organization (two studies), a charitable organization (one study), an institutional department (four studies) or an unspecified source (11 studies); two studies declared that they received help from the industry (equipment loan). In 14 studies (939 participants), ultrasound guidance increased the success rate by decreasing the occurrence of a failed block: risk difference (RD) -0.11 (95% confidence interval (CI) -0.17 to -0.05); I2 = 64%; number needed for additional beneficial outcome for a peripheral nerve block (NNTB) 6 (95% CI 5 to 8). Blocks were performed under general anaesthesia (usual clinical practice in this population); therefore, haemodynamic changes to the surgical stimulus (rather than classic sensory/motor blockade evaluation) were used to define success. For peripheral nerve blocks, the younger the child, the greater was the benefit. In eight studies (414 participants), pain scores at one hour in the post-anaesthesia care unit were reduced when ultrasound guidance was used; however, the clinical relevance of the difference was unclear (equivalent to -0.2 on a scale from 0 to 10). In eight studies (358 participants), block duration was longer when ultrasound guidance was used: standardized mean difference (SMD) 1.21 (95% CI 0.76 to 1.65; I2 = 73%; equivalent to 62 minutes). Here again, younger children benefited most from ultrasound guidance. Time to perform the procedure was reduced when ultrasound guidance was used for pre-scanning before a neuraxial block (SMD -1.97, 95% CI -2.41 to -1.54; I2 = 0%; equivalent to 2.4 minutes; two studies with 122 participants) or as an out-of-plane technique (SMD -0.68, 95% CI -0.96 to -0.40; I2 = 0%; equivalent to 94 seconds; two studies with 204 participants). In two studies (122 participants), ultrasound guidance reduced the number of needle passes required to perform the block (SMD -0.90, 95% CI -1.27 to -0.52; I2 = 0%; equivalent to 0.6 needle pass per participant). For two studies (204 participants), we could not demonstrate a difference in the incidence of bloody puncture when ultrasound guidance was used for neuraxial blockade, but we found that the number of participants was well below the optimal information size (RD -0.07, 95% CI -0.19 to 0.04). No major complications were reported for any of the 1241 participants. We rated the quality of evidence as high for success, pain scores at one hour, block duration, time to perform the block and number of needle passes. We rated the quality of evidence as low for bloody punctures.

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