An arterial catheter is a thin tube or line that can be inserted into an artery. Arterial catheters are used to monitor blood pressure during complex surgeries and during stays in intensive care. Ultrasound imaging (an image created with sound waves of soft tissue) allows anaesthesiologists and intensivists to see surrounding structures. Ultrasound can help medical practitioners accurately locate the artery and insert the catheter, and, particularly when surgeries involve children, ultrasound can prevent the need for multiple needle sticks. This reduces the occurrence of haematoma (a localized collection of blood outside the blood vessels) or damage to the artery, compared with other techniques such as palpation of the artery (feeling through the skin for the pulse) or Doppler auditory assistance (listening for a change to a higher pitch at the exact location of the artery). Our aim was to find out whether ultrasound offers any advantages over palpation of the artery or Doppler auditory assistance.
The evidence is current to January 2016. We found five eligible studies - four comparing ultrasound with palpation and one comparing ultrasound with Doppler auditory assistance.
We included in the review children aged one month to 18 years. We found that ultrasound increased the rate of successful cannulation at the first attempt and reduced the formation of haematomas. Ultrasound also increased the success rate within two attempts. It is likely that ultrasound is more useful for infants and small children than for older children. It is also likely that ultrasound is more useful if the practitioner is experienced in its use.
Quality of the evidence
We noted variation in the risk of bias of included studies. We rated the quality of evidence as moderate mainly because the number of studies was limited. For the same reason, we could not confirm the effect of age and expertise in ultrasound usage.
Our evidence suggests that ultrasound is superior to other techniques for arterial catheter insertion, particularly in babies and young children.
We identified moderate-quality evidence suggesting that ultrasound guidance for radial artery cannulation improves first and second attempt success rates and decreases the rate of complications as compared with palpation or Doppler auditory assistance. The improved success rate at the first attempt may be more pronounced in infants and small children, in whom arterial line cannulation is more challenging than in older children.
Arterial line cannulation in paediatric patients is traditionally performed by palpation or with Doppler auditory assistance in locating the artery before catheterization. It is not clear whether ultrasound guidance offers benefits over these methods.
To assess first attempt success rates and complication rates when ultrasound guidance is used for arterial line placement in the paediatric population, as compared with traditional techniques (palpation, Doppler auditory assistance), at all potential sites for arterial cannulation (left or right radial, ulnar, brachial, femoral or dorsalis pedis artery).
We searched CENTRAL, MEDLINE (Ovid) and Embase (Ovid). We also searched databases of ongoing trials (ClinicalTrials.gov (www.clinicaltrials.gov/), Current Controlled Trials metaRegister (www.controlled-trials.com/), the EU Clinical Trials register (www.clinicaltrialsregister.eu/) and the WHO International Clinical Trials Registry Platform (http://apps.who.int/trialsearch/). We tried to identify other potentially eligible trials by searching the reference lists of retrieved included trials and related systematic or other reviews. We searched until January 2016.
We included randomized controlled trials (RCTs) comparing ultrasound guidance versus palpation or Doppler auditory assistance to guide arterial line cannulation in paediatrics.
Two review authors independently assessed the risk of bias of included trials and extracted data. We used standard Cochrane meta-analytical procedures, and we applied the GRADE method to assess the quality of evidence.
We included five RCTs reporting 444 arterial cannulations in paediatric participants. Four RCTs compared ultrasound with palpation, and one compared ultrasound with Doppler auditory assistance.
Risk of bias varied across studies, with some studies lacking details of allocation concealment. It was not possible to blind practitioners in all of the included studies; this adds a performance bias that is inherent to the type of intervention studied in our review. Only two studies reported the rate of complications.
Meta-analysis showed that ultrasound guidance produces superior success rates at first attempt (risk ratio (RR) 1.96, 95% confidence interval (CI) 1.34 to 2.85, 404 catheters, four RCTs, moderate-quality evidence) and fewer complications, such as haematoma formation (RR 0.20, 95% CI 0.07 to 0.60, 222 catheters, two RCTs, moderate-quality evidence). Our results suggest, but do not confirm, that a possible advantage of ultrasound guidance for the first attempt success rate over other techniques is more pronounced in infants and small children than in older children. Similarly, our results suggest, but do not confirm, the possibility of a positive influence of expertise in the use of ultrasound on the first attempt success rate. We also found improved success rates within two attempts (RR 1.78, 95% CI 1.25 to 2.51, 134 catheters, two RCTs, moderate-quality evidence) with ultrasound guidance compared with other types of guidance. No studies reported data about ischaemic damage. We rated the quality of evidence for all outcomes as moderate owing to imprecision due to wide confidence intervals, modest sample sizes and limited numbers of events.