Is US guidance of radial artery catheterizations effective compared to standard methods of palpation/Doppler in either adult or pediatric patients?

• Design 

Systematic review and meta-analysis 

• Population 

Adult or pediatric patients requiring radial artery catheterization, inclusion criteria varied by study. 

• Intervention 

Ultrasound-guided radial artery catheterization compared to doppler-assisted or landmark technique.

• Outcomes  

First attempt success rate and complications from attempts at radial artery catheterization.

7 RCTs were used to calculate a pooled estimate of first-attempt success

• • Rate of first-attempt success in US group: 48.5%
  • Rate of first-attempt success in control group: 30.7%
  • US-guided radial arterial catheterization was associated with increased first-attempt success (RR 1.55, 95% CI, 1.02 to 2.35, P = 0.04)
  • US-guided radial arterial catheterization significantly reduced mean attempts to success (WMD −1.13, 95% CI −1.58 to −0.69, P <0.001), mean time to success (WMD −72.97 seconds, 95% CI −134.41 to −11.52, P = 0.02), and incidence of hematoma (RR 0.17, 95% CI 0.07 to 0.41, P <0.001)

Subgroup Analyses

• • No difference in primary outcome between elective insertion (five trials, RR 1.91, 95% CI, 1.45 to 2.53) and emergency insertion (two trials, RR 1.05, 95% CI, 0.38 to 2.83) 
  • US-guided radial arterial catheterization was associated with significantly increased first-attempt success in small children/infants (RR 1.94, 95% CI, 1.31 to 2.88, P = 0.001)

Strengths:

Well-performed systematic review and meta-analysis with a clear primary outcome and relevant secondary outcomes.

Limitations:

• • There were major differences in ultrasound experience of operators, ranging from those without any experience and only an observational training period to expert operators.
  • Overall, the studies had small sample sizes and only a small number of studies met inclusion criteria for the review.
  • Not enough samples to conduct additional subgroup analyses of patients who might be characterized as difficult-to-insert, including hypotension, obesity, edematous, and pulseless.
  • Lack of inclusion of other potential factors including patient pain or patient/operator satisfaction.
  • Lack of comment and description on specific US-guidance techniques

 

"US guidance is an effective and safe technique for radial artery catheterization, even in small children and infants. However, results should be interpreted cautiously due to the heterogeneity among studies."

Though data from RCTs is limited, with proper operator training US-guidance can be an effective method of improving radial artery catheterization accuracy, especially in small children/infants with smaller and more difficult-to-palpate anatomy.

Conflicting results in previously conducted RCTs may be attributed to differences in operator training or lack of a proper observational training period and thus careful consideration of the operator should be conducted in future RCTs. A physician who has performed dozens of A-lines using the palpation technique, who is unfamiliar with bedside ultrasonography, is unlikely to benefit significantly from adding this modality to their procedure, while residents who are trained with ultrasounds in their hands will likely benefit more. 

Future RCTs should focus on patient populations that have been characterized as difficult-to-insert including hypotension which is in particular significant to emergency medicine, as well as edematous or obese patients.

This post was written by Jessica Wen, MS4 at UCSD School of Medicine, Charles Murchison, MD and Amir Aminlari, MD. 

Gu W, Tie H, Zeng X. Efficacy of ultrasound-guided radial artery catheterization: a systematic review and meta-analysis of randomized controlled trials. Critical Care. 2014; 18(3): R93 doi:10.1186/cc13862