Arterial catheterisation is often challenging. Although ultrasound guidance may increase the success rate, it is not used routinely; rather it is experience and technique that are essential.1–3
In this observational study we evaluated the feasibility of a new ultrasound-guided technique for routine placement of arterial catheters in the ICU. Our technique focuses on visualisation and continuous tracking of the bevel line. This is a direct ultrasonic sign of the needle tip: its exact position is at the distal end of the bevel line. When an over-the-needle type cannula is used, after entering the lumen, we forward the introducer needle a few millimetre upward under direct visual control to secure the passage of the plastic cannula into the vessel (Fig. 1, see also Videos, Supplemental Digital Content 1–2, http://links.lww.com/EJA/A94 and http://links.lww.com/EJA/A95, which demonstrate the tracking of the bevel line during needle advancement into the radial artery).4,5
All arterial cannulations performed in our adult ICU by any of four participating study physicians (GR, CL, MM. and RV) were included between 1 July 2012 and 31 December 2012; 20G over-the-needle type arterial cannula was preferred but Seldinger technique was also available. We used a LOGIQ Book XP Pro ultrasound machine (GE Medical Systems Co., Ltd., Wuxi, China) and a 10 MHz linear transducer.
Our primary outcome was the total success rate of the ultrasound-guided procedure. Detailed data were obtained in nonurgent cases only when the operator had sufficient time for data acquisition and an independent person was also available for time measurements. These included diameter and depth of the artery, presence of potential factors of difficult cannulation (i.e. shock, obesity, coagulopathy, previous cannulas, weak/absent arterial pulsation, local tissue oedema, diameter of the radial artery less than 2 mm and vascular abnormalities), number of attempts and cannulation time (from skin puncture to successful cannula placement). We used the Wilson test for confidence interval calculations and χ2 test to compare proportions. Intercooled STATA 8.2 software (StataCorp, Texas, USA) was used for calculations and P less than 0.05 was accepted as statistically significant. Ethical approval (Ethical Committee, IKEB/UDARC/2012/2) was provided by the Institutional Research Ethics Board of Markhot Ferenc Hospital, Eger, Hungary (Chairperson Dr Laszlo Hernadi) on 8 May 2012.
All consecutive cannula placements (n = 66) were attempted with the presented technique. Success rate of the ultrasound-guided intervention was 100% (95% confidence interval, 94.5 to 100); 58 cannulae were placed in the radial artery and eight cannulae in the brachial artery.
Detailed data are available for 37 cannulations. At least one factor potentially leading to difficult cannula placement was identified in 26 cases (70.3%) and 15 patients (40.5%) had more than one risk factor. First-pass success rate was 75.7% and only one patient required more than two attempts (mean number of attempts: 1.27 per cannula placement). Over-the-needle cannula was used for the majority of cases, Seldinger technique was used in only one case. Median and mean catheterisation time was 92 and 113.5 s, respectively (range: 27 to 142; SD, 113.0). Mean diameter of the cannulated arteries was 2.54 mm and the diameter of the smallest artery successfully cannulated was 1.4 mm. The bevel line was visualised in 83% of all attempts and it was significantly more visible in successful than in failed attempts (34/37 vs. 5/10, P = 0.002).
In our opinion, correct and precise identification of the needle tip is crucial to successful ultrasound-guided catheterisation of small vessels. Modifications of the out-of-plane technique that allow for relatively accurate tracking of the needle tip have been described and used with success.6,7 The advantage of the in-plane technique is that it enables continuous visualisation of the advancing needle; unfortunately, misalignment of the needle to the ultrasound beam and loss of the needle tip are common. As the bevel line is a direct ultrasonic sign of the needle tip, by focusing on this line and keeping it on screen during needle advancement, loss of the needle tip can be avoided. We were able to visualise the bevel line in over 80% of attempts even with the poor quality ultrasound machine that was available during the study period. In our experience, it is virtually always recognisable with modern ultrasound equipment.
The main limitation of our study is that we did not compare our technique with other approaches. Meta-analyses have already proven that ultrasound guidance is superior to blind arterial catheterisation and our first-pass success rate was significantly higher than pooled first-pass rates with the palpation technique when combining either all individual studies (P = 0.001) or studies in adults (P = 0.039).3 It would be more interesting to compare our results with other ultrasound-guided approaches. Unfortunately, as we are aware of the meaning of the bevel line and automatically track it during the procedures, we could not compare our technique with the standard in-plane technique (i.e. without tracking of the bevel line) in a blinded manner. Of note, visualisation of the bevel line significantly increased the rate of successful attempts in our study, and this finding indirectly supports the usefulness of our modification to the standard in-plane approach.
Another limitation is that we did not collect detailed data for all catheterisations. Collecting these time-consuming measurement data was not possible in the cases of emergency cannulations.
In conclusion, we modified the standard in-plane ultrasound guidance technique, emphasised that tracking of the bevel line allows precise needle manipulation, and evaluated our technique for routine ultrasound-guided arterial catheterisation. We achieved 100% success rate and a high first-pass success rate in a critically ill patient population despite a high proportion of difficult-to-cannulate patients. We conclude that our approach (continuous tracking of the bevel line during in-plane ultrasound guidance) is feasible for routine placement of arterial catheters with catheter-over-needle technique.
Acknowledgements relating to this article
Assistance with the letter: we would like to thank Dr Szilvia Kovacs for her assistance with the study.
Financial support and sponsorship: none.
Conflicts of interest: none.
1. Shiloh AL, Savel RH, Paulin LM, et al. Ultrasound-guided catheterization of the radial artery: a systematic review and meta-analysis of randomized controlled trials. Chest
2. Gu WJ, Tie HT, Liu JC, et al. Efficacy of ultrasound-guided radial artery catheterization: a systematic review and meta-analysis of randomized controlled trials. Crit Care
3. Gao YB, Yan JH, Gao FQ. Effects of ultrasound-guided radial artery catheterization: an updated meta-analysis. Am J Emerg Med
4. Reusz G, Langer C, Jakab L, Morvay Z. Ultrasound-guided vascular access: the importance of the needle bevel. Can J Anesth
5. Reusz G, Sarkany P, Gal J, et al. Needle-related ultrasound artifacts and their importance in anaesthetic practice. Brit J Anaesth
6. Quan Z, Tian M, Chi P, et al. Modified short-axis out-of-plane ultrasound versus conventional long-axis in-plane ultrasound to guide radial artery cannulation: a randomized controlled trial. Anesth Analg
7. Clemmesen L, Knudsen L, Sloth E, et al. Dynamic needle tip positioning: ultrasound guidance for peripheral vascular access. A randomized, controlled and blinded study in phantoms performed by ultrasound novices. Ultraschall Med