Ultrasound‐guided arterial cannulation in the paediatric population
Abstract
Background
In arterial line cannulation in children and adolescents, traditional methods of locating the artery include palpation and Doppler auditory assistance. It is unclear whether ultrasound guidance is superior to these methods. This is an update of a review originally published in 2016.
Objectives
To evaluate the benefits and harms of ultrasound guidance compared with traditional techniques (palpation, Doppler auditory assistance) for assisting arterial line placement at all potential sites in children and adolescents.
Search methods
We searched CENTRAL, MEDLINE, Embase, and Web of Science from inception to 30 October 2022. We also searched four trials registers for ongoing trials, and we checked the reference lists of included studies and relevant reviews for other potentially eligible trials.
Selection criteria
We included randomised controlled trials (RCTs) comparing ultrasound guidance versus other techniques (palpation or Doppler auditory assistance) to guide arterial line cannulation in children and adolescents (aged under 18 years). We planned to include quasi‐RCTs and cluster‐RCTs. For RCTs with both adult and paediatric populations, we planned to include only the paediatric population data.
Data collection and analysis
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 certainty of evidence.
Main results
We included nine RCTs reporting 748 arterial cannulations in children and adolescents (under 18 years of age) undergoing different surgical procedures. Eight RCTs compared ultrasound with palpation, and one compared ultrasound with Doppler auditory assistance. Five studies reported the incidence of haematomas. Seven involved radial artery cannulation and two involved femoral artery cannulation.
The people performing arterial cannulation were physicians with different levels of experience. The risk of bias varied across studies, with some studies lacking details of allocation concealment. It was not possible to blind practitioners in any case; this adds a performance bias that is inherent to the type of intervention studied in our review.
Compared to traditional methods, ultrasound guidance probably causes a large increase in first‐attempt success rates (risk ratio (RR) 2.01, 95% confidence interval (CI) 1.64 to 2.46; 8 RCTs, 708 participants; moderate‐certainty evidence) and probably causes a large reduction in the risk of complications such as haematoma formation (RR 0.26, 95% CI 0.14 to 0.47; 5 RCTs, 420 participants; moderate‐certainty evidence). No studies reported data about ischaemic damage. Ultrasound guidance probably improves success rates within two attempts (RR 1.78, 95% CI 1.25 to 2.51; 2 RCTs, 134 participants; moderate‐certainty evidence) and overall rate of successful cannulation (RR 1.32, 95% CI 1.10 to 1.59; 6 RCTs, 374 participants; moderate‐certainty evidence). In addition, ultrasound guidance probably reduces the number of attempts to successful cannulation (mean difference (MD) −0.99 attempts, 95% CI −1.15 to −0.83; 5 RCTs, 368 participants; moderate‐certainty evidence) and duration of the cannulation procedure (MD −98.77 seconds, 95% CI −150.02 to −47.52, 5 RCTs, 402 participants; moderate‐certainty evidence).
More studies are needed to confirm whether the improvement in first‐attempt success rates is more pronounced in neonates and younger children compared to older children and adolescents.
Authors' conclusions
We identified moderate‐certainty evidence that ultrasound guidance for arterial cannulation compared with palpation or Doppler auditory assistance improves first‐attempt success rate, second‐attempt success rate and overall success rate. We also found moderate‐certainty evidence that ultrasound guidance reduces the incidence of complications, the number of attempts to successful cannulation and the duration of the cannulation procedure.
PICO
Plain language summary
Ultrasound use for insertion of arterial catheters in children
Background
An arterial catheter is a thin tube that can be inserted into an artery to monitor blood pressure during complex surgeries and during stays in intensive care. Ultrasound (an imaging method that uses sound waves to capture live images of soft tissue) can help doctors to locate the artery and insert the catheter. In children in particular, ultrasound may reduce the need for multiple needle sticks, the occurrence of haematoma (a collection of blood outside the blood vessels) and 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).
What did we want to find out?
We aimed to find out whether ultrasound offers any advantages over palpation of the artery or Doppler auditory assistance. Specifically, we wanted to find out if ultrasound improved the following outcomes.
1. How often doctors can successfully insert the catheter on first attempt
2. The occurrence of complications such as haematoma and injury caused by reduced blood flow
3. How often doctors can successfully insert the catheter on the first two attempts
4. How often doctors can successfully insert the catheter after several attempts
5. The average number of attempts needed to insert the catheter
6. How long it takes to insert the catheter
What did we do?
We searched the literature for controlled clinical studies comparing use of ultrasound with traditional ways of placing a catheter into an artery in children under the age of 18 years. We compared and summarised the results of the studies and rated our confidence in the evidence based on factors such as study methods and sizes.
What did we find?
We found nine eligible studies: eight comparing ultrasound with palpation and one comparing ultrasound with Doppler auditory assistance. Seven studies were of radial artery cannulation and two studies were of femoral artery cannulation. Four studies did not mention any funding source and five studies had departmental funds. The studies included children aged from under one month to 18 years.
Main results
We found that ultrasound guidance compared with traditional methods probably increases the rate of successful cannulation on first attempt, within the first two attempts, and after several attempts. Ultrasound guidance probably reduces the occurrence of haematoma, the number of attempts needed to successfully place an arterial catheter, and the time needed to perform successful cannulation. The evidence suggests that ultrasound is probably superior for arterial cannula insertion in children and adolescents, including very young children.
Limitations of the evidence
Our confidence in the evidence is only moderate because it was impossible to mask the doctors performing the cannulation (they knew which children had ultrasound‐assisted cannulation), and because the studies included few children and reported few events.
How up to date is the evidence?
The evidence is up to date to October 2022.
Authors' conclusions
Summary of findings
| Ultrasound‐guided arterial cannulation compared with palpation or Doppler guidance for children and adolescents | |||||
| Patient or population: children and adolescents | |||||
| Outcomes | Anticipated absolute effects (95% CI) | Relative effect | No. of participants | Certainty | |
|---|---|---|---|---|---|
| Risk with other techniques (palpation/Doppler) | Risk with US‐guided arterial cannulation | ||||
| First‐attempt success rate | Study population | RR 2.01 (1.64 to 2.46) | 708 | ⊕⊕⊕⊝ | |
| 242 per 1000 | 487 per 1000 | ||||
| Incidence of complications (haematoma) | Study population | RR 0.26 (0.14 to 0.47) | 420 | ⊕⊕⊕⊝ | |
| 218 per 1000 | 57 per 1000 | ||||
| Successful cannulation within first 2 attempts | Study population | RR 1.78 | 134 | ⊕⊕⊕⊝ | |
| 358 per 1000 | 638 per 1000 (448 to 899) | ||||
| Overall successful cannulation after multiple attempts
| Study population | RR 1.32 (1.10 to 1.59) | 374 | ⊕⊕⊕⊝ | |
| 606 per 1000 | 800 per 1000 | ||||
| Number of attempts to successful cannulation
| Study population | — | 368 | ⊕⊕⊕⊝ | |
| The mean number of attempts to successful cannulation was 2.12 attempts | MD 0.99 attempts fewer (1.15 fewer to 0.83 fewer) | ||||
| Duration of cannulation procedure
| Study population | — | 402 (5 RCTs) | ⊕⊕⊕⊝ | |
| The mean time to successful cannulation was 331.3 seconds | MD 98.77 seconds shorter (150.02 shorter to 47.52 shorter | ||||
| CI: confidence interval; ICU: intensive care unit; RCT: randomised controlled trial; RR: risk ratio; US: ultrasound. | |||||
| GRADE Working Group grades of evidence | |||||
| a Downgraded one level owing to risk of bias concerns (selection bias and performance bias). | |||||
Background
Description of the condition
Arterial line cannulation is an intervention that is commonly performed during major surgery and in the intensive care unit (ICU) for continuous blood pressure monitoring and arterial blood sampling in children and adolescents. Arterial line cannulation can be more challenging in children and adolescents compared with adults because their arteries are smaller.
Description of the intervention
The most common site for arterial cannulation is the radial artery; other sites include the femoral, axillary, brachial, ulnar, dorsalis pedis, tibial posterior and temporal arteries. There are many possible techniques for arterial cannulation in the paediatric population, including palpation, Doppler auditory assistance and ultrasound guidance (Ueda 2013).
Palpation of the pulse
Pulse palpation to identify a landmark is the traditional approach to inserting an arterial catheter. The site of cannulation is usually selected, positioned and prepped. The physician locates the artery by palpating the pulse before initiating cannulation. Accurate localisation of small arteries is technically difficult, especially in small children and infants (Varga 2013). This may complicate placement and threading of the catheter (Schindler 2005). Dehydration or haemodynamic instability weakens the pulse and makes it difficult to find, further complicating the procedure.
Ultrasound guidance
Ultrasound guidance represents an alternative to the traditional palpation technique for insertion of arterial catheters. It is commonly used for placement of central venous catheters (CVCs). Numerous randomised controlled trials (RCTs) and systematic reviews have found that use of ultrasound reduces complications and increases first‐attempt success for CVC placement compared with traditional landmark techniques (Hind 2003; Milling 2005; Randolph 1996).
Doppler auditory assistance
Doppler auditory assistance has been described as another traditional technique for insertion of arterial catheters. The Doppler tone changes to a higher pitch at the exact location of the artery, which may facilitate arterial cannulation. This technique has a reported success rate of 46% (Ueda 2013).
Potential complications
Although rare, devastating complications associated with arterial line cannulation may occur, such as permanent ischaemic damage, sepsis and pseudoaneurysm formation (Scheer 2002). Less serious complications such as arterial occlusion, haematoma and nerve injury are more frequent (King 2008).
How the intervention might work
Intervention
Real‐time ultrasound guidance technique
Through an out‐of‐plane technique, the physician positions the artery in the middle of the screen, holding the probe in their left hand, perpendicular to the skin. With the right hand, the physician introduces a cannula of an appropriate size below the ultrasound probe, and tissue movement is observed on the ultrasound screen. They then redirect the cannula or repeat the manoeuvre until adequate arterial flow allows easy insertion of the guidewire or cannula.
Comparator
Palpation technique
With this approach, the physician uses their non‐dominant hand to palpate the artery, while their dominant hand manipulates the intravascular needle or catheter, which they insert at a 30‐ to 45‐degree angle and advance slowly until pulsatile blood flow returns. They then advance the outer cannula into the artery directly from the needle or with the aid of a guidewire.
Doppler auditory assistance
The Doppler probe identifies the artery by locating the area with maximum frequency. During cannulation, the physician uses the Doppler probe to identify the exact position of the artery and to guide needle or cannula insertion.
Why it is important to do this review
The importance of this Cochrane Review stems from the large number of arterial lines placed in children and adolescents undergoing major surgery or hospitalised in an ICU, or both. UK guidelines for placement of CVCs have recommended use of an ultrasound‐guided technique, given associated reductions in the rate of failure and in mechanical complications (NICE 2002). The American Society of Anesthesiology Task Force has issued practice guidelines for central venous access, in which they recommended real‐time ultrasound guidance for vessel localisation and venipuncture when the internal jugular vein is selected for cannulation (ASA 2012). One systematic review found that ultrasound can offer small gains in safety and quality compared with an anatomical landmark technique when used for subclavian or femoral vein cannulation for central vein catheterisation (Brass 2015). Ultrasound guidance may also significantly reduce the number of haemodialysis catheters successfully inserted on the first attempt, the risk of arterial puncture and haematomas and the time taken for successful venipuncture (Rabindranath 2011). While some studies support the use of ultrasound for arterial line insertion (Schwemmer 2006), others oppose this approach (Ganesh 2009). Ultrasound guidance is a common and broadly used intervention, mainly based on the evidence from adults (Flumignan 2021). No guidelines are available on use of ultrasound for arterial line placement in children and adolescents. Several RCTs have published findings on this topic (Anantasit 2017; Ganesh 2009; Ishii 2013; Min 2019; Salik 2021; Schwemmer 2006; Siddik‐Sayyid 2016; Tan 2015; Ueda 2013), but meta‐analyses for the paediatric population still include a limited number of studies restricted to radial artery cannulation (Aouad‐Maroun 2016; White 2016). This Cochrane Review will provide an objective assessment of the benefits and harms of using ultrasound guidance compared with traditional techniques (palpation, Doppler auditory assistance) for arterial line placement in children and adolescents. This information can help doctors to make educated choices and reduce potential complications of arterial line placement.
Objectives
To evaluate the benefits and harms of ultrasound guidance compared with traditional techniques (palpation, Doppler auditory assistance) for assisting arterial line placement at all potential sites in children and adolescents.
Methods
Criteria for considering studies for this review
Types of studies
We included RCTs.
Types of participants
We limited participants of interest to children and adolescents (under the age of 18 years) undergoing arterial line placement.
Types of interventions
The intervention was ultrasound guidance, and the comparators were pulse palpation and Doppler auditory assistance.
Types of outcome measures
Primary outcomes
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First‐attempt success rate
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Incidence of complications
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Haematoma
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Ischaemic damage
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Secondary outcomes
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Successful cannulation within the first two attempts
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Overall successful cannulation after multiple attempts
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Number of attempts to successful cannulation
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Duration of cannulation procedure
Search methods for identification of studies
Electronic searches
We searched the following databases from inception to 30 October 2022.
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Cochrane Central Register of Controlled Trials (CENTRAL; 2022)
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MEDLINE (via Ovid)
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Embase (via Ovid)
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Web of science
We searched the following trials registries to 30 October 2022.
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U.S. National Institutes of Health (NIH) ongoing trials register ClinicalTrials.gov (clinialtrials.gov)
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The ISRCTN registry (www.isrctn.com)
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The EU Clinical Trials register (www.clinicaltrialsregister.eu)
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World Health Organization (WHO) International Clinical Trials Registry Platform (trialsearch.who.int)
We also combined the searches (where appropriate) with RCT filters provided in the Cochrane Handbook for Systematic Reviews of Interventions (Lefebvre 2021), searched for citations of retrieved included trials, searched for relevant systematic reviews, and checked for errata and retraction notices related to the included studies.
We searched for potentially eligible trials in the following websites.
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Society for Pediatric Anesthesia (pedsanesthesia.org)
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American Society of Anesthesiologists (www.asahq.org)
We did not limit our search by language, publication date or publication format.
See Appendix 1, Appendix 2, Appendix 3, and Appendix 4 for details of our searches.
We continuously applied the basic search strategy of the 'My NCBI' (National Center for Biotechnology Information) email alert service of PubMed to identify newly published studies. We performed a completely updated search of all specified databases in October 2022.
Searching other resources
We tried to identify other potentially eligible trials or ancillary publications by searching the reference lists of included trials, related systematic or other reviews and health technology assessment reports.
Data collection and analysis
Selection of studies
We planned to include quasi‐RCTs and cluster‐RCTs. For RCTs with both adult and paediatric populations, we planned to include only the paediatric population data, if presented separately. Two review authors (CR, NHC) independently assessed every retrieved citation for potential eligibility. We retrieved the full texts for all citations judged potentially eligible by at least one of the two review authors. The two review authors then independently assessed the full texts in duplicate using a standardised and pilot‐tested screening form. We compared results and resolved disagreements by consensus, or with the help of a third review author (MAM) when needed. Before starting the selection process, CR and NHC conducted calibration exercises to ensure the validity of the process.
Data extraction and management
Two review authors (CR, NHC) independently extracted relevant data in duplicate, using standard data extraction forms. Abstracted data included characteristics of the population, interventions, controls and outcomes. We also extracted statistical data needed for the meta‐analysis. We resolved disagreements by discussion or, if required, by consulting a third review author (MAM). We contacted one study author for clarification and additional data. After completing the data extraction forms, the two review authors (CR, NHC) entered the data into Review Manager Web (RevMan Web 2022).
Dealing with duplicate publications and companion papers
In the event of duplicate publications, companion documents or multiple reports of a primary study, we planned to maximise the yield of information by collating all available data. We planned to resolve remaining uncertainties by attempting to contact study authors when possible.
Assessment of risk of bias in included studies
Two review authors (CR, NHC) assessed the risk of bias of each included study independently and in duplicate, using the Cochrane risk of bias tool (RoB 1; Higgins 2011). RoB 1 includes the following domains.
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Random sequence generation (selection bias)
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Allocation concealment (selection bias)
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Blinding of participants, providers, data collectors, outcome adjudicators and data analysts (performance bias and detection bias)
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Incomplete outcome data (attrition bias)
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Selective outcome reporting (outcome reporting bias)
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Other bias
We assessed outcome reporting bias by comparing outcomes listed in a trial protocol, at registration and in the methods section versus outcomes for which data were reported in the results section (Kirkham 2010). We judged trials as having 'low risk', 'high risk' or 'unclear risk' of bias and evaluated individual bias items as described in the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011). For blinding of participants and personnel (performance bias), blinding of outcome assessors (detection bias) and incomplete outcome data (attrition bias), we intended to evaluate risk of bias separately for subjective and objective outcomes (Hróbjartsson 2013). We planned to consider the implications of missing outcome data for individual participants.
Measures of treatment effect
We planned to express dichotomous data as risk ratios (RRs) or hazard ratios (HRs) with 95% confidence intervals (CIs). We planned to express continuous data as mean differences (MDs) with 95% CIs when all studies reported the outcome using the same scale, and as standardised mean differences (SMDs) when studies reported the outcome using different scales.
If included studies had reported rate data (i.e. counts measured for each participant along with observation time), we would have pooled rate ratios.
When studies reported median and interquartile range (IQR), we assumed the median was representative of the mean, and we used guidance in the Cochrane Handbook for Systematic Reviews of Interventions to calculate standard deviations (SDs; Higgins 2021).
Unit of analysis issues
When studies randomised individual participants, we considered the participant as the unit of analysis. For cluster‐RCTs or trials with multiple catheters per person, we planned to use estimates from the included studies adjusted for correlation. Whenever this was not reported, we treated the trial as a parallel group trial. For studies with multiple intervention arms, we omitted groups that were irrelevant to our comparison of interest.
Dealing with missing data
We planned to use a complete case approach in the main analysis and to conduct sensitivity analyses using plausible assumptions about the outcomes of participants with missing outcome data to test the robustness of our findings, as outlined in Akl 2013 and Ebrahim 2013. However, there were no missing data.
Assessment of heterogeneity
We assessed statistical heterogeneity (inconsistency) by visually inspecting the forest plots and by using a standard Chi2 test with a significance level of 0.1. In view of the low power of this test, we also considered the I2 statistic, which quantifies inconsistency across studies, to assess the impact of heterogeneity on the meta‐analysis (Higgins 2002; Higgins 2003). We considered an I2 statistic of 50% or more as indicative of a considerable level of statistical heterogeneity (Higgins 2021).
We planned to conduct subgroup analyses to explore whether any clinical or methodological factor could explain cases of considerable statistical heterogeneity (see Subgroup analysis and investigation of heterogeneity). If the subgroup analysis identified a subgroup effect (i.e. statistical heterogeneity was explained), we planned to present results stratified by relevant subgroups. If the subgroup analysis did not identify a subgroup effect (i.e. statistical heterogeneity remained unexplained), we planned to refrain from meta‐analysis of studies.
We expected the following characteristics to introduce clinical heterogeneity.
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Expertise of the physician
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Academic versus non‐academic setting
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Age group of participants (infants versus older children versus adolescents)
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Site of cannulation (radial or other arteries)
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Experience of the physician with ultrasound
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Studies at low versus high risk of bias
We made a post‐hoc decision to conduct subgroup analyses that we judged clinically relevant even in the absence of statistical heterogeneity.
Assessment of reporting biases
We planned to examine funnel plots to assess the potential for publication bias if we found 10 or more studies reporting on a particular outcome (Sterne 2011); however, we included only nine studies in total.
Data synthesis
We synthesised and analysed data using RevMan Web (RevMan Web 2022). We calculated agreement between the two independent review authors for assessment of full‐text eligibility using the kappa statistic. For categorical data, we calculated RRs separately for each study for the event rate of outcomes by treatment arm, then pooled the results of different studies using a random‐effects model. For continuous data, we pooled data from different studies using a random‐effects model. For both types of data, we used a fixed‐effect model when meta‐analysing two studies.
Subgroup analysis and investigation of heterogeneity
We planned to investigate potential reasons for heterogeneity by conducting subgroup analyses. We planned to investigate interactions by conducting subgroup analyses based on the following characteristics.
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Expertise of the physician
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Academic versus non‐academic setting
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Age group of participants (neonates versus infants versus children versus adolescents)
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Site of cannulation (radial or other arteries)
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Experience of the physician with ultrasound
However, there were insufficient data for some characteristics: expertise of the physicians varied widely among the included studies and all studies were performed in university hospitals. Therefore, we analysed data according to age groups of participants (though we could not obtain these data for one study), site of cannulation and experience with ultrasound.
Sensitivity analysis
We planned to perform sensitivity analyses to explore the influence of the following factors (when applicable) on effect size.
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Restricting the analysis to published studies.
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Restricting the analysis to studies with low risk of bias.
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Making plausible assumptions about the outcomes of participants with missing data.
Summary of findings and assessment of the certainty of the evidence
Using the GRADE approach, we classified the certainty of the evidence for each outcome into one of four possible categories: high, moderate, low and very low (Guyatt 2011a). This approach takes into account the study design, as well as risk of bias, imprecision, inconsistency, indirectness, publication bias, large effect size, dose‐response effect and confounding. We used the principles of the GRADE system to assess the certainty of the body of evidence associated with the following specific outcomes in our review.
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First‐attempt success rate
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Incidence of complications
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Haematoma
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Ischaemic damage
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Successful cannulation within the first two attempts
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Overall successful cannulation after multiple attempts
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Number of attempts to successful cannulation
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Duration of cannulation procedure
We used GRADE software to construct a summary of findings table (GRADEpro GDT). The GRADE approach appraises the certainty of a body of evidence according to the extent to which one can be confident that an estimate of effect or association reflects the item being assessed.
Results
Description of studies
See Characteristics of included studies table.
Results of the search
Of the 1729 records identified through database searching (excluding duplicates), we retrieved 43 full‐text articles that we considered potentially eligible. Of these 43 titles, nine met our eligibility criteria (Anantasit 2017; Ganesh 2009; Ishii 2013; Min 2019; Salik 2021; Schwemmer 2006; Siddik‐Sayyid 2016; Tan 2015; Ueda 2013). We excluded 34 studies (Abdelbaser 2021; Aouad‐Maroun 2016; Bhattacharjee 2018; Bobbia 2013; Chi 2015; Gu 2014; Guan 2016; Ijiri 2016; Jung 2021; Kiberenge 2018; Lee 2016; Liu 2019; Nakayama 2014; Oulego‐Erroz 2019; Polat 2019; Quan 2019; Schults 2020; Selldén 1987; Sethi 2017; Seto 2010; Seto 2013; Shiloh 2010; Sobolev 2015; Song 2016; Sorrentino 2020; Staudt 2019; Takeshita 2015; Takeshita 2021; Varga 2013; White 2016; Ye 2020; Zhang 2020; Zhefeng 2019; Zhou 2016). We found no ongoing studies or studies awaiting classification.
We have further illustrated these findings in the study flow diagram (Figure 1; Liberati 2009).
Study flow diagram.
Included studies
We included nine studies published between 2006 and 2021, all in English. The studies involved a total of 748 participants, including 369 ultrasound‐assisted arterial catheterisations, 327 palpation‐assisted catheterisations and 52 Doppler‐assisted catheterisations.
Seven RCTs studied radial artery cannulation (Anantasit 2017; Ganesh 2009; Ishii 2013; Min 2019; Schwemmer 2006; Tan 2015; Ueda 2013), while two studied femoral artery cannulation (Salik 2021; Siddik‐Sayyid 2016). Eight studies randomised participants, while Ishii 2013 randomised multiple arteries (right and left) of the same participants.
Eight RCTs evaluated ultrasound‐guided arterial catheterisation versus palpation‐guided arterial catheterisation, and Ueda 2013 evaluated ultrasound‐guided arterial catheterisation versus Doppler‐guided arterial catheterisation. The median sample size across studies was 94 (IQR 84 to 104). These studies took place in university hospital settings in Germany, Japan, Lebanon, Thailand, Singapore, Turkey, the USA and Canada. All studies included participants of both sexes, with ages ranging from under one month to 18 years.
The exclusion criteria were as follows.
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Skin erosion or haematoma, a visible recent catheterisation scar or an arterial puncture site from one month earlier (Anantasit 2017; Ishii 2013; Ueda 2013)
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Signs of skin infection near the puncture site (Min 2019)
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Absence of an amplitude of radial or femoral pulsation (Anantasit 2017; Salik 2021)
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Prominent differences in arterial pressure between left and right arms (Ishii 2013)
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Diagnosed vascular abnormality or variation (Min 2019)
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Anticipated circulatory instability after anaesthesia induction, such as pulmonary hypertension or severe heart failure (Min 2019; Salik 2021; Siddik‐Sayyid 2016; Tan 2015)
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Allergy to ultrasound gel (Salik 2021)
Types of surgery included elective cardiac surgeries (Ishii 2013; Min 2019; Salik 2021; Siddik‐Sayyid 2016), major neurosurgery (Schwemmer 2006), and other major surgeries (Ueda 2013). Two studies were performed in the paediatric intensive critical care unit (Anantasit 2017; Tan 2015).
The people performing cannulation were medical doctors with different levels of expertise, including inexperienced anaesthesiology fellows (Anantasit 2017; Tan 2015), paediatric subspecialty trainee anaesthesiologists with a minimum of two years (Ueda 2013) or three years of training in anaesthesia (Ganesh 2009; Ishii 2013; Siddik‐Sayyid 2016), a mix of consultant paediatric anaesthesiologist and trainees (Ganesh 2009), cardiac anaesthesia fellows (Ueda 2013) and a specialist with at least three years of experience in paediatric cardiac anaesthesia (Salik 2021).
Some physicians had minimal experience with ultrasound (Anantasit 2017; Ganesh 2009; Siddik‐Sayyid 2016; Tan 2015; Ueda 2013), while others were advanced users (Ishii 2013; Min 2019; Salik 2021; Schwemmer 2006).
Four studies did not mention any funding source (Anantasit 2017; Ishii 2013; Salik 2021; Schwemmer 2006), and five studies had departmental funding (Ganesh 2009; Min 2019; Siddik‐Sayyid 2016; Tan 2015; Ueda 2013).
Excluded studies
We excluded 34 studies. The main reasons for exclusion were related to the type of study design (not an RCT), the age group (adults) and the outcomes.
Ongoing studies
We identified no ongoing studies.
Awaiting classification
We identified no studies awaiting classification.
Risk of bias in included studies
Figure 2 shows the risk of bias summary, which reflects judgements about each risk of bias item for each included study.
Risk of bias summary: review authors' judgements about each risk of bias item for each included study.
Allocation
The included studies used different methods of random sequence generation.
Ganesh 2009, Min 2019 and Tan 2015 used computer‐generated random number sequence for assignment to one of two groups, whereas Ishii 2013 and Salik 2021 utilised the envelope method. Schwemmer 2006 tossed a coin and allocated 'heads' to the ultrasound technique and 'tails' to the palpation technique. Siddik‐Sayyid 2016 and Ueda 2013 assigned participants by randomised block design to the control group or the ultrasound‐guided technique group. Anantasit 2017 did not clearly describe the randomisation method. Ishii 2013, Min 2019, Salik 2021, Siddik‐Sayyid 2016, and Ueda 2013 ensured allocation concealment via the envelope method, whereby assignments were contained in prepared opaque envelopes that were opened just before cannulation. However, Anantasit 2017, Ganesh 2009, Schwemmer 2006 and Tan 2015 did not mention the method of concealment. For random sequence generation, all studies were judged to be at low risk of bias except Anantasit 2017 (unclear risk). Regarding allocation concealment, we judged Ishii 2013, Min 2019, Salik 2021, Siddik‐Sayyid 2016 and Ueda 2013 at low risk, and Anantasit 2017, Ganesh 2009, Schwemmer 2006 and Tan 2015 at unclear risk.
Blinding
Risk of performance bias for participants in all nine included studies was low because all participants underwent induction of general anaesthesia before catheter insertion. However, risk of performance bias was high for the anaesthesiologist, who cannot be blinded during the intervention and is aware of the allocated technique before performing arterial catheterisation. Since the outcomes depend on the operator, we judged all studies to be at high risk of performance bias.
Ganesh 2009, Min 2019 and Salik 2021 considered aspiration of blood from the distal end of the arterial cannula as the endpoint, and Ishii 2013, Siddik‐Sayyid 2016 and Ueda 2013 deemed the procedure successful when the artery was cannulated and an arterial waveform was recorded. Tan 2015 classified the procedure as successful when the artery was cannulated. Schwemmer 2006 mentioned only that in the ultrasound technique, when the cannula appeared to be within the vessel, the transducer was removed and catheterisation was considered successful, but the study did not describe the endpoint for the palpation technique. All these endpoints are unequivocal, so we considered the studies at low risk of detection bias.
Incomplete outcome data
Risk of attrition bias was low in six studies because outcome data were complete and no participants withdrew or were lost to follow‐up (Ganesh 2009; Ishii 2013; Min 2019; Schwemmer 2006; Tan 2015). Salik 2021, Siddik‐Sayyid 2016, and Ueda 2013 were at low risk of attrition bias because only a few participants were excluded from the analysis. In Ueda 2013, two cases were withdrawn and were counted as failures in the intention‐to‐treat analysis. The first of these occurred because an unintentional femoral arterial cannulation was performed on a participant who had been allocated to the ultrasound‐guided technique; in the second case, a participant in the Doppler‐assisted group dropped out because the operator who would have performed the procedure was unavailable. In Siddik‐Sayyid 2016, two participants from each group were excluded because the residents were unavailable to perform the procedures, and in Salik 2021, three participants were removed after randomisation because they had haematomas at the selected site of cannulation due to previous interventions.
Selective reporting
Regarding our primary outcomes, eight studies reported first‐attempt success rate (Anantasit 2017; Ganesh 2009; Ishii 2013; Min 2019; Salik 2021; Schwemmer 2006; Siddik‐Sayyid 2016; Ueda 2013), and five of those studies also reported incidence of complications (Anantasit 2017; Ishii 2013; Min 2019; Salik 2021; Ueda 2013). We judged them at low risk of reporting bias. Although the methods of Ganesh 2009 included stratification according to age group (younger than two years, two to five years, older than five years), investigators did not report results according to this stratification, so we judged the study at high risk of reporting bias. The primary endpoint for Tan 2015 was time to successful cannulation using the primary randomisation method, and the secondary endpoints were number of attempted sites, number of attempts by practitioner and estimated cost of the procedure. We judged Tan 2015 at low risk of reporting bias.
Other potential sources of bias
Differences in the definitions of outcome measures among the included studies may be another source of bias. All studies except Ganesh 2009 defined a specific duration of procedure or number of attempts that would represent an unsuccessful cannulation. Ueda 2013 had two other potential sources of bias: firstly, haemodynamic manipulation of the size of a radial artery (by volume load or vasopressor effect) could improve the success rate of cannulation; and secondly, the investigated terminated the trial after recruiting only 50% of the original sample size.
Min 2019 and Siddik‐Sayyid 2016 set a time limit of 10 minutes for successful cannulation, which might have affected the outcome duration of cannulation. In Min 2019, the participants' age and height were significantly different between the two groups, which could have affected all outcomes.
In Anantasit 2017, the operators included seven fellows with different levels of experience. Although the study authors performed a multiple logistic regression analysis to reduce bias related to operators' experience, a potential source of bias cannot be ruled out.
Effects of interventions
See: Summary of findings 1 Summary of findings table
Primary outcomes
1. First‐attempt success rate
Eight studies reported first‐attempt success rate (Anantasit 2017; Ganesh 2009; Ishii 2013; Min 2019; Salik 2021; Schwemmer 2006; Siddik‐Sayyid 2016; Ueda 2013). Meta‐analysis of their results showed that ultrasound guidance compared with palpation or Doppler probably causes a large increase in the first‐attempt success rate of cannulation in children and adolescents (RR 2.01, 95% CI 1.64 to 2.46; P < 0.001; 8 RCTs, 708 participants; Analysis 1.1; Figure 3). We judged the certainty of evidence as moderate owing to small sample sizes and risk of bias concerns, mainly selection bias and performance bias (summary of findings Table 1).
Subgroup analysis based on artery site
We conducted a subgroup analysis based on artery site (radial/femoral; Figure 4).
Six studies that reported first‐attempt success rate provided data for radial artery cannulation (Anantasit 2017; Ganesh 2009; Ishii 2013; Min 2019; Schwemmer 2006; Ueda 2013), while Salik 2021 and Siddik‐Sayyid 2016 provided data for femoral artery cannulation.
We found that the superior performance of ultrasound guidance applied to both the radial site (RR 1.98, 95% CI 1.57 to 2.48; P < 0.001; 6 RCTs, 562 participants) and the femoral site (RR 2.16, 95% CI 1.37 to 3.42; P = 0.001; 2 RCTs, 146 participants). The test of subgroup difference was not statistically significant (P = 0.73).
Subgroup analysis based on age
We conducted a subgroup analysis based on age (Figure 5).
Ganesh 2009 included children from a wide age group, but most were older children, with a mean age of 99 months. This study showed no difference between the use of ultrasound and palpation.
Seven studies reported data on neonates and children aged up to four years, with a mean age under 48 months (Anantasit 2017; Ishii 2013; Min 2019; Salik 2021; Schwemmer 2006; Siddik‐Sayyid 2016; Ueda 2013). When we meta‐analysed their results, we found a clear difference in first‐attempt success rate in favour of ultrasound guidance (RR 2.11, CI 95% 1.71 to 2.60; P < 0.001; 7 RCTs, 556 participants).
The difference between ultrasound guidance and traditional techniques appears to be greater in children aged up to four years compared with older children; however, the test for subgroup differences was not statistically significant (P = 0.08).
Subgroup analysis based on the operator's experience with ultrasound
We conducted a subgroup analysis based on the experience of the operator performing the arterial cannulation in ultrasound use (Figure 6).
In Ganesh 2009, anaesthesiologists had experience with fewer than 10 ultrasound‐guided arterial cannulations, and in Siddik‐Sayyid 2016 and Ueda 2013, anaesthesiologists had experience with fewer than five ultrasound‐guided arterial cannulations. Meta‐analysis suggested that ultrasound guidance led to increased first‐attempt success rates in the paediatric population compared with palpation or the Doppler technique when the operator had minimal experience with ultrasound‐guided cannulation (RR 1.66, 95% CI 1.11 to 2.46; P = 0.01; 3 RCTs, 362 participants).
In Ishii 2013, the operators performing arterial cannulation were familiar with the ultrasound‐guided technique for central venous catheterisation in adults and children. Fellows who performed the cannulation in Anantasit 2017 assisted a vascular access course and had experience with more than 10 paediatric ultrasound‐guided arterial cannulation procedures prior to the study. Anaesthesiologists in Min 2019, Salik 2021 and Schwemmer 2006 had experience with more than 20 paediatric ultrasound‐guided arterial cannulation procedures. Meta‐analysis suggested that ultrasound guidance led to increased first‐attempt success rates in the paediatric population compared with palpation when the operator was more experienced in performing ultrasound‐guided radial artery cannulation (RR 2.11, 95% CI 1.66 to 2.67; P < 0.001; 5 RCTs, 346 participants).
The test of subgroup effects showed that ultrasound guidance compared to traditional techniques leads to a similar increase in first‐time success rates regardless of the operators' experience with ultrasound (P = 0.31).
2. Incidence of complications (haematoma or ischaemia)
Five studies reported incidence of haematoma (Anantasit 2017; Ishii 2013; Min 2019; Salik 2021; Ueda 2013).
Meta‐analysis of their results showed that ultrasound guidance compared with palpation or the Doppler technique probably causes a large reduction in the rate of haematoma during arterial cannulation in the paediatric population (RR 0.26, 95% CI 0.14 to 0.47; P < 0.001; 5 RCTs, 420 participants; Figure 7). We judged the certainty of evidence as moderate owing to imprecision and risk of bias concerns, mainly regarding selection bias and performance bias (summary of findings Table 1).
No studies reported ischaemia as an outcome.
Secondary outcomes
1. Successful cannulation within the first two attempts
Two studies reported successful cannulation within the first two attempts (Schwemmer 2006; Ueda 2013). Meta‐analyses of their results showed that ultrasound guidance compared with palpation or the Doppler technique probably increases the rate of successful radial artery cannulation within the first two attempts in the paediatric population (RR 1.78, 95% CI 1.25 to 2.51; P = 0.001; 2 RCTs, 134 participants). We judged the certainty of evidence as moderate owing to imprecision and risk of bias concerns, mainly regarding selection bias and performance bias (summary of findings Table 1, Figure 8).
2.Overall successful cannulation after multiple attempts
Six studies reported overall successful cannulation after multiple attempts (Anantasit 2017; Min 2019; Salik 2021; Schwemmer 2006; Siddik‐Sayyid 2016; Tan 2015). Meta‐analysis of their results showed that ultrasound guidance compared with palpation probably increases overall successful cannulation in the paediatric population (RR 1.32, 95% CI 1.10 to 1.59; P = 0.003; 6 RCTs, 374 participants; Figure 9). We judged the certainty of evidence as moderate owing to imprecision and risk of bias concerns, mainly regarding selection bias and performance bias (summary of findings Table 1).
3. Number of attempts to successful cannulation
Five studies reported the number of attempts to successful cannulation as a secondary outcome (Ishii 2013; Min 2019; Salik 2021; Schwemmer 2006; Siddik‐Sayyid 2016). We found that ultrasound‐guided arterial cannulation compared with palpation in the paediatric population probably reduces the number of attempts to successful cannulation (MD −0.99 attempts, 95% CI −1.15 to −0.83; P < 0.001; 5 RCTs, 368 participants; Figure 10). We judged the certainty of evidence as moderate owing to small sample sizes and risk of bias concerns, mainly regarding selection bias and performance bias (summary of findings Table 1).
4. Duration of cannulation procedure
Seven studies reported time to successful cannulation (Anantasit 2017; Ganesh 2009; Min 2019; Salik 2021; Schwemmer 2006; Siddik‐Sayyid 2016; Tan 2015); however, we could not include Anantasit 2017 or Tan 2015 in the meta‐analysis owing to missing data.
Anantasit 2017 reported that the median time to success was significantly shorter in the ultrasound‐guided group than in the palpation group (3.3 minutes versus 10.4 minutes; P < 0.001; 84 participants); no SDs were provided. Tan 2015 (40 participants) reported a mean of 7.8 minutes for the ultrasound group and 12.7 minutes for the palpation group but provided no SDs or P values.
When we meta‐analysed data from the remaining five studies, we found that ultrasound‐guided radial artery catheterisation probably reduces mean time to success (MD −98.77 seconds, 95% CI −150.02 to −47.52; P = 0.001; 5 RCTs, 402 participants; Figure 11). We judged the certainty of evidence as moderate owing to imprecision and risk of bias concerns, mainly regarding selection bias and performance bias (summary of findings Table 1).
Min 2019 reported the median (IQR) "procedural time(s) until successful catheterization", which we converted to mean and SD. A sensitivity analysis excluding Min 2019 did not change the results of the analysis (Figure 12).
Discussion
Summary of main results
The results of our review indicate that ultrasound usage for arterial cannulation probably causes a large increase in the first‐attempt success rate and a moderate increase in the success rate after two attempts, compared with traditional techniques (palpation or Doppler auditory assistance). Moreover, ultrasound guidance probably causes a large reduction in haematoma formation, which was the only reported complication. We found that ultrasound probably improves the overall rate of successful cannulation. although definitions of this outcome varied among studies. What is more relevant than the success rate is the number of attempts and time needed to secure successful cannulation, both of which are probably lower with ultrasound‐guided cannulation.
A subgroup analysis per age group included only one study with children aged over four years (Ganesh 2009), and seven studies in which participants were neonates and smaller children aged up to four years (Anantasit 2017; Ishii 2013; Min 2019; Salik 2021; Schwemmer 2006; Siddik‐Sayyid 2016; Ueda 2013). More studies are needed to confirm whether ultrasound guidance is more beneficial in younger children versus older children (P = 0.08).
Overall completeness and applicability of evidence
We identified moderate‐certainty evidence suggesting that ultrasound guidance for arterial cannulation improves first‐attempt success rates, success rates within two attempts, and overall success rates compared with palpation or Doppler auditory assistance. We also found moderate‐certainty evidence suggesting that ultrasound guidance for arterial cannulation probably reduces the incidence of complications, the number of attempts to successful cannulation and the duration of the cannulation procedure.
The evidence suggests that ultrasound guidance is preferable to traditional techniques even when operators have little experience with ultrasound. However, an ultrasound device might not be present or readily available in the operating room in all institutions, which may limit the applicability of our evidence.
We did not restrict the systematic review to a particular arterial site, but eligible studies included cannulation of the radial and femoral arteries only. Therefore, the results of our review are only directly applicable to cannulation of the radial and femoral arteries, which are the most common sites of arterial cannulation in paediatrics.
We did not limit our comparator to the palpation technique; however, most included studies compared ultrasound with palpation, and only one study compared ultrasound with Doppler assistance. As a result, we could not explore a subgroup effect related to different comparators.
Quality of the evidence
Risk of bias in the included studies varied across assessed factors. Details of allocation concealment were inconsistent across studies. In addition, as it is impossible to blind the anaesthesiologist or the intensivist to the method of arterial line insertion, all studies were at increased risk of performance bias. Another potential bias concerns the lack of a standardised definition of the primary outcome. It is unclear whether a "first pass successful arterial cannulation" includes or excludes redirection of the needle. Moreover, some studies included children with a broad age interval (e.g. Ganesh 2009), and we were unable to obtain additional data from study authors.
We graded the certainty of evidence as moderate for the first‐attempt success rate and for the number of attempts to successful cannulation owing to a relatively small number of events and sample sizes for the outcomes. In addition, the incidence of complications, rate of successful cannulation within two attempts, overall rate of success, and the duration of cannulation were graded as moderate certainty, mainly owing to imprecision, relatively small number of events and small sample sizes for these outcomes (Guyatt 2011b).
Potential biases in the review process
We identified one article written in Chinese by cross‐checking the reference lists of identified articles. However, we were unable to find or retrieve this article (Liu 2013). One meta‐analysis mentioned this article, and its results seem to be consistent with our findings (Zhang 2020). According to the meta‐analysis, the study reported a higher first‐attempt success rate in the ultrasound group (25/30) than in the palpation group (18/30). Therefore, it is unlikely that its inclusion would have modified our results.
We carried out a thorough search of appropriate electronic databases. We also used citation tracking and searched clinical trials registers. We attempted to contact study authors for additional study details.
Agreements and disagreements with other studies or reviews
This is an update of a review first published in 2016, which was the first to compare real‐time ultrasound use versus palpation or Doppler guidance for arterial cannulation exclusively in children (Aouad‐Maroun 2016). For this update, we added new data published since 2016.
Our results are consistent with those of previous meta‐analyses that gathered data from both adult and paediatric populations and showed an improved first‐attempt success rate with the use of ultrasound guidance compared with palpation (Gao 2015; Gu 2014; Shiloh 2011; Tang 2014; White 2016).
Study flow diagram.
Risk of bias summary: review authors' judgements about each risk of bias item for each included study.
Comparison 1: Ultrasound (US)‐guided arterial cannulation versus other techniques (palpation/Doppler), Outcome 1: First‐attempt success rate
Comparison 1: Ultrasound (US)‐guided arterial cannulation versus other techniques (palpation/Doppler), Outcome 2: First‐attempt success rate (per artery site)
Comparison 1: Ultrasound (US)‐guided arterial cannulation versus other techniques (palpation/Doppler), Outcome 3: First‐attempt success rate (per age group)
Comparison 1: Ultrasound (US)‐guided arterial cannulation versus other techniques (palpation/Doppler), Outcome 4: First‐attempt success rate (per experience with ultrasound)
Comparison 1: Ultrasound (US)‐guided arterial cannulation versus other techniques (palpation/Doppler), Outcome 5: Incidence of complications (haematoma)
Comparison 1: Ultrasound (US)‐guided arterial cannulation versus other techniques (palpation/Doppler), Outcome 6: Successful cannulation within first two attempts
Comparison 1: Ultrasound (US)‐guided arterial cannulation versus other techniques (palpation/Doppler), Outcome 7: Overall successful cannulation after multiple attempts
Comparison 1: Ultrasound (US)‐guided arterial cannulation versus other techniques (palpation/Doppler), Outcome 8: Number of attempts to successful cannulation
Comparison 1: Ultrasound (US)‐guided arterial cannulation versus other techniques (palpation/Doppler), Outcome 9: Duration of cannulation procedure (seconds)
Comparison 1: Ultrasound (US)‐guided arterial cannulation versus other techniques (palpation/Doppler), Outcome 10: Duration of the cannulation procedure (seconds) – sensitivity analysis
| Ultrasound‐guided arterial cannulation compared with palpation or Doppler guidance for children and adolescents | |||||
| Patient or population: children and adolescents | |||||
| Outcomes | Anticipated absolute effects (95% CI) | Relative effect | No. of participants | Certainty | |
|---|---|---|---|---|---|
| Risk with other techniques (palpation/Doppler) | Risk with US‐guided arterial cannulation | ||||
| First‐attempt success rate | Study population | RR 2.01 (1.64 to 2.46) | 708 | ⊕⊕⊕⊝ | |
| 242 per 1000 | 487 per 1000 | ||||
| Incidence of complications (haematoma) | Study population | RR 0.26 (0.14 to 0.47) | 420 | ⊕⊕⊕⊝ | |
| 218 per 1000 | 57 per 1000 | ||||
| Successful cannulation within first 2 attempts | Study population | RR 1.78 | 134 | ⊕⊕⊕⊝ | |
| 358 per 1000 | 638 per 1000 (448 to 899) | ||||
| Overall successful cannulation after multiple attempts
| Study population | RR 1.32 (1.10 to 1.59) | 374 | ⊕⊕⊕⊝ | |
| 606 per 1000 | 800 per 1000 | ||||
| Number of attempts to successful cannulation
| Study population | — | 368 | ⊕⊕⊕⊝ | |
| The mean number of attempts to successful cannulation was 2.12 attempts | MD 0.99 attempts fewer (1.15 fewer to 0.83 fewer) | ||||
| Duration of cannulation procedure
| Study population | — | 402 (5 RCTs) | ⊕⊕⊕⊝ | |
| The mean time to successful cannulation was 331.3 seconds | MD 98.77 seconds shorter (150.02 shorter to 47.52 shorter | ||||
| CI: confidence interval; ICU: intensive care unit; RCT: randomised controlled trial; RR: risk ratio; US: ultrasound. | |||||
| GRADE Working Group grades of evidence | |||||
| a Downgraded one level owing to risk of bias concerns (selection bias and performance bias). | |||||
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
| 1.1 First‐attempt success rate Show forest plot | 8 | 708 | Risk Ratio (M‐H, Random, 95% CI) | 2.01 [1.64, 2.46] |
| 1.2 First‐attempt success rate (per artery site) Show forest plot | 8 | 708 | Risk Ratio (M‐H, Random, 95% CI) | 2.01 [1.64, 2.46] |
| 1.2.1 Radial artery | 6 | 562 | Risk Ratio (M‐H, Random, 95% CI) | 1.98 [1.57, 2.48] |
| 1.2.2 Femoral artery | 2 | 146 | Risk Ratio (M‐H, Random, 95% CI) | 2.16 [1.37, 3.42] |
| 1.3 First‐attempt success rate (per age group) Show forest plot | 8 | 708 | Risk Ratio (M‐H, Random, 95% CI) | 2.01 [1.64, 2.46] |
| 1.3.1 Children aged over four years | 1 | 152 | Risk Ratio (M‐H, Random, 95% CI) | 1.01 [0.46, 2.24] |
| 1.3.2 Neonates and children aged up to four years | 7 | 556 | Risk Ratio (M‐H, Random, 95% CI) | 2.11 [1.71, 2.60] |
| 1.4 First‐attempt success rate (per experience with ultrasound) Show forest plot | 8 | 708 | Risk Ratio (M‐H, Random, 95% CI) | 1.98 [1.61, 2.42] |
| 1.4.1 Little experience with US | 3 | 362 | Risk Ratio (M‐H, Random, 95% CI) | 1.66 [1.11, 2.46] |
| 1.4.2 More experience with US | 5 | 346 | Risk Ratio (M‐H, Random, 95% CI) | 2.11 [1.66, 2.67] |
| 1.5 Incidence of complications (haematoma) Show forest plot | 5 | 420 | Risk Ratio (M‐H, Random, 95% CI) | 0.26 [0.14, 0.47] |
| 1.6 Successful cannulation within first two attempts Show forest plot | 2 | 134 | Risk Ratio (M‐H, Fixed, 95% CI) | 1.78 [1.25, 2.51] |
| 1.7 Overall successful cannulation after multiple attempts Show forest plot | 6 | 374 | Risk Ratio (M‐H, Random, 95% CI) | 1.32 [1.10, 1.59] |
| 1.8 Number of attempts to successful cannulation Show forest plot | 5 | 368 | Mean Difference (IV, Random, 95% CI) | ‐0.99 [‐1.15, ‐0.83] |
| 1.9 Duration of cannulation procedure (seconds) Show forest plot | 5 | 402 | Mean Difference (IV, Random, 95% CI) | ‐98.77 [‐150.02, ‐47.52] |
| 1.10 Duration of the cannulation procedure (seconds) – sensitivity analysis Show forest plot | 4 | 328 | Mean Difference (IV, Random, 95% CI) | ‐99.99 [‐160.30, ‐39.68] |
