Ultrasound-Guided Radial Artery Access by a Non-Ultrasound Trained Interventional Cardiologist Improved First-Attempt Success Rates and Shortened Time for Successful Radial Artery Cannulation

Abstract: Background. Use of the radial artery for cardiac catheterization and percutaneous coronary intervention (PCI) continues to expand. Cannulating the radial artery can be one of the most challenging aspects of the radial approach. Ultrasound-guided vascular access may be a method to improve first-attempt success rates and shorten time to radial artery access. Methods. Fifty consecutive patients underwent ultrasound-guided radial artery access (UGRAA) by a senior interventional cardiologist with little prior experience with UGRAA. The operator had 20 run-in cases before enrolling subjects. Time to establish access and number of attempts required for each patient were recorded. Ultrasound was also used to measure radial arterial diameter and the distance between the skin and the anterior wall of the radial artery. Results. All patients had successful UGRAA, 80% on the first attempt and 92% on the first or second attempt. The median time for access was 35 seconds, with an interquartile range of 31-55 seconds. Conclusion. UGRAA improved first-attempt success rates and shortened the time needed for radial artery cannulation when compared to historical data of palpation-directed radial artery access. A large randomized trial of palpation versus UGRAA will be required to confirm this finding. Furthermore, this technique is easy to learn and incorporate into everyday practice in the cardiac catheterization lab.  

J INVASIVE CARDIOL 2013;25(12):676-679

Key words: transradial approach, cardiac catheterization, percutaneous coronary intervention

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In recent years, use of the radial artery as an access site for cardiac catheterization and percutaneous coronary intervention (PCI) has been increasing. The reasons for this include fewer access-site complications, lower bleeding risks, shorter hospital stays, lower costs, and possible mortality benefits in ST-elevation myocardial infarction (STEMI).^1-3 Greater postprocedure comfort and patient acceptability are other important reasons for growing radial preference.

Cannulating the radial artery can be one of the most challenging aspects of the radial approach.⁴ The radial artery diameter is typically between 2 and 3 mm, which is very close to the 2 mm limit of two-point discrimination of the fingertip.^5-7 This physiological limitation to palpation may make radial artery cannulation by manual palpation difficult. Multiple attempts to puncture the radial artery can lead to hematoma formation, intimal dissection, and arterial spasm, rendering radial cannulation unsuccessful.   

Studies in critical care medicine, emergency medicine, anesthesia, and pediatrics have documented the advantages of using ultrasound during venous and arterial line placement. In one prospective randomized study in the critical care literature comparing ultrasound-guided radial artery catheter placement to palpation guided radial artery catheterization, the first-attempt success rate with ultrasound guidance was nearly twice that of the palpation technique (62% vs 34%; P=.03). Significantly fewer attempts were taken to cannulate the radial artery under ultrasound guidance as compared to palpation (1.6 ± 1.0 vs 3.1 ± 2.4; P=.003).⁸ Another study in the emergency medicine literature showed that the use of ultrasound significantly reduced the time (107 seconds vs 314 seconds; P<.001), number of attempts (1.2 vs 2.2; P=.001) and number of sites (1.1 vs 1.6; P=.001) required to establish radial arterial access.⁹ A recent meta-analysis in the critical care literature showed 71% improvement in first-attempt success rates with ultrasound-guided radial arterial catheterization.¹⁰ The American Society of Echocardiography and the Society of Cardiovascular Anesthesiologists recommend the use of ultrasound during cannulation of the radial artery with a category A, level 1 evidence of its efficacy.¹¹ 

In spite of growing evidence in support of ultrasound-guided vascular access, real time ultrasonography is remarkably under-utilized in the cardiac catheterization lab. The recent Femoral Arterial Access With Ultrasound Trial (FAUST) demonstrated that ultrasound guidance was associated with fewer attempts (1.3 vs 3.0; P<.001), greater first-pass success rate (83% vs 46%; P<.001), shorter median time to access (136 seconds vs 148 seconds; P<.003), lower risk of venipuncture (2.4% vs 15.8%; P<.001), and vascular complications (1.4% vs 3.4%; P<.04) during femoral arterial access as compared to fluoroscopy-assisted palpation-guided femoral access. The FAUST trial did not show an improvement, however, in the rate of common femoral artery (CFA) cannulation except in patients with high CFA bifurcation.¹² Data on the use of ultrasound in obtaining radial access in the cardiology literature are extremely sparse.  Can real-time ultrasound-guided radial artery access (UGRAA) improve first-attempt success rates and shorten the time needed to obtain access during cardiac catheterization and PCI? This prospective observational study was performed to work toward answering this question.

Methods

Fifty consecutive patients underwent UGRAA performed by a senior interventional cardiologist with little prior UGRAA experience between July 14, 2011 and October 3, 2011. The operator had 20 run-in cases prior to enrolling patients in the study. Written informed consent was obtained in accordance with the Baptist Hospital of Miami Institutional Review Board.  Subjects were included in the study if they were at least 18 years of age and able to give informed consent. Patient exclusion criteria included an abnormal pulse-oxymetry Allen’s test (Barbeau class D), STEMI, pregnancy, and inability to give informed consent.

A baseline ultrasound diameter of each patient’s radial artery was performed using a SonoSite M Turbo portable ultrasound machine and an L25X 13-6 MHz vascular transducer (SonoSite, Inc). The patient was then prepped and draped by the cath lab’s standard procedure and given a sublingual nitroglycerin (SL NTG) tablet (0.4 mg). The ultrasound transducer was then placed in a sterile CIV-Flex Transducer cover (Civco Medical Solutions), and the radial artery diameter was re-measured 2 to 5 minutes after the SL NTG was given. Subcutaneous 2%  lidocaine was then given under ultrasound guidance. Radial artery access was then obtained under direct ultrasound guidance in a transverse (short-axis) view, using the “single anterior wall puncture” technique with a 2.5 cm, 21 gauge, thin-wall needle (Cook Medical). A Cope 0.018˝ stainless-steel guidewire (Cook Medical) was then inserted through the needle and an Avanti radial non-hydrophilic coated sheath (Cordis Corporation) was inserted into the radial artery over the Cope wire after a skin nick was made with a No. 11 scalpel. A 5 Fr sheath was used if the baseline radial artery diameter was <2.0 mm and a 6 Fr sheath if the diameter was ≥2.0 mm. Seven Fr sheaths were used for complex interventions if the diameter was ≥2.4 mm.

The primary endpoint was successful cannulation of the radial artery. Secondary endpoints were first-attempt success rates, total number of attempts required for successful cannulation, and time to establish access. Time to establish access was measured from the moment the needle was first inserted into the skin until the sheath was inserted into the artery. A single attempt was defined as both the forward movement of the needle and the withdrawal of the needle. A subsequent forward motion of the needle, after previous withdrawal, was counted as an additional attempt.

Additional study measurements were the radial artery diameter at baseline and 2-5 minutes after SL NTG administration, as well as the distance from the skin to the anterior wall of the radial artery. Baseline and post-SL NTG radial artery diameters were measured in two perpendicular axes, at the “9 o’clock to 3 o’clock” and the “6 o’clock to 12 o’clock” positions. The average of the two was then reported as the diameter. 

Variables are expressed as median (interquartile range [IQR]), mean ± standard deviation, or percentages. Pearson’s correlation coefficient was used to compare continuous variables and t-test was performed when suitable. Comparisons of outcomes based on gender (Tables 1 and 2) were completed with unpaired t-tests. A P-value of ≤.05 was considered to be significant. Statistical analysis was performed with SPSS version 19.0 (SPSS, Inc).

Results

Seventy four percent of the patients enrolled in the study were men. The average age of the study population was 59 ± 10 years. The average body mass index was 30.3 ± 4.4. Access was obtained via the right radial artery in all cases. A 6 Fr sheath was used in 42 patients, while 5 Fr sheaths were used in 7 patients and a 7 Fr sheath was used in 1 patient. See Table 1 for specific patient characteristics by gender. 

All fifty patients had successful UGRAA, 80% (n = 40) on the first attempt, 92% (n = 46) on the first or second attempt, and 98% (n = 49) on the first, second, or third attempt (Figure 1). The median time from start to sheath insertion was 35 seconds (IQR, 31-55 seconds) and the mean time was 61 ± 93.6 seconds (Figure 2). Two cases in the series that required 295 and 640 seconds to cannulate skewed the mean to the right. The first was due to inadvertent subintimal wire passage and the second was prolonged due to spasm. In both cases, the needle was pulled, pressure held for 2 minutes, and the artery was then cannulated 1 cm proximal to the original puncture site under ultrasound guidance.  

The mean distance between the skin and the anterior wall of the radial artery was 3.3 ± 1.2 mm. The average radial artery diameter at baseline and at 2-5 minutes after SL NTG was 2.6 ± 0.52 mm and 2.8 ± 0.57 mm, respectively. There was a weak negative correlation between the baseline radial artery diameter and the time to establish access (Pearson’s correlation coefficient, -0.295; P=.04). 

There was no significant relationship between gender, skin to radial artery distance, body mass index, post SL NTG radial artery diameter, and number of attempts for successful cannulation or time to establish access. Baseline and post-SL NTG radial artery diameters were significantly greater in men than in women. See Table 2 for specific procedural measures by gender.

Discussion

This study showed very high first-attempt success rates and short times to cannulation. The first-attempt success rates were higher than previously reported by Levin et al⁸ and Schwemmer et al¹⁰ during ultrasound-guided radial artery cannulation. The median time to establish access was also much lower than observed in previous studies on ultrasound-guided radial artery cannulation.⁹ It is not clear why the times and first-attempt success rates are better than previously reported in the non-cardiology literature. All 50 cases were performed by one very experienced interventional cardiologist. No fellows or less-experienced cardiologists participated in this study.

Sublingual nitroglycerin was given 2-5 minutes prior to radial access to observe if there was an increase in the diameter of the radial artery. We did find that the radial artery diameter increased by a very small amount (0.16 mm; 95% confidence interval, 0.098-0.225 mm; P<.001) following SL NTG administration. However, the clinical relevance of this finding needs further exploration.   

Knowing the precise diameter of the radial artery is helpful. Palpation cannot help discriminate the diameter. A large radial artery (ie, 3.0 mm) that is deep may feel “weak and small” and a small (ie, 1.8 mm) but superficial radial artery may feel large and bounding. Five Fr sheaths can be appropriately placed in smaller radial arteries to prevent injury and spasm. Many arteries are large enough to accept a 7 Fr sheath, which easily allows one to perform almost any complex intervention. Knowing the radial artery diameter before cannulation can be helpful, as it allows one to confidently size up to a larger sheath when necessary.

Knowing the radial artery anatomy before cannulation can be important, if there are variations from normal. One significant variation is the dual radial artery system, in which two radial arteries run parallel to one another and are usually separated by a distance of 1 to 2 mm. One’s finger tip cannot discern this variant. Both dual radial arteries are usually small and come to a confluence 2-3 cm proximal to the typical location of radial access. If one simply follows the dual radial arteries proximally with the ultrasound transducer, one can then insert the needle into the confluent single radial artery, which is almost always of normal size. Although not a common variation, inadvertently placing a 6 Fr sheath in a small dual radial artery may cause severe spasm and extreme difficulty in removing a sheath, especially with non-hydrophilic sheaths. Another anatomic variation is the radial artery being smaller than the ulnar artery. If a small-diameter radial artery is seen on ultrasound, one can quickly slide the ultrasound transducer over to the ulnar artery. If the ulnar artery is larger than the radial, one can then use the ulnar artery for access.

Finally, there was a weak negative correlation between time taken to establish access and the diameter of the radial artery at baseline. That is, larger arteries required less time to cannulate as compared to smaller radial arteries. However, since the correlation was weak, this finding has to be further validated. A study with a larger sample size would be necessary.

UGRAA is simple to learn and apply in everyday practice. The extra set-up time of 1-2 minutes is offset by the extremely fast cannulation process. With experience and mastery of UGRAA, one almost never encounters those infrequent but prolonged attempts at radial cannulation, and the multiple unsuccessful sticks that can cause radial artery spasm, necessitating the switch to a different access site. The difficult radial case cannot be predicted by palpation. 

Study limitations. This study had a number of limitations. It was performed at a single center by only one senior interventional cardiologist. It was an uncontrolled study with a small sample size. 

Conclusion

Use of radial artery access is increasing and is the dominant access site in many institutions and countries throughout the world. UGRAA is a technique that is easy to learn and allows for predictably high first-attempt success rates and shorter access times. Set-up time is short. UGRAA essentially eliminates a “difficult radial stick,” a barrier that has possibly kept some operators who use the femoral approach from embracing the radial approach. Is UGRAA “better” than palpation-guided access? A recently completed large randomized trial of palpation versus UGRAA will hopefully answer this question.  

References

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From the ¹Baptist Cardiac & Vascular Institute, Baptist Hospital of Miami, Miami, Florida, and ²Florida International University Herbert Wertheim College of Medicine, Miami, Florida. 

Funding: This research was supported by the BCVI Research and Outcomes Division.

Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. The authors report no conflicts of interest regarding the content herein.

Manuscript submitted May 13, 2013, provisional acceptance given June 10, 2013, final version accepted August 5, 2013.

Address for correspondence: Jonathan S Roberts, MD, FACC, FSCAI, Baptist Cardiac and Vascular Institute, Baptist Hospital of Miami, 8950 N Kendall Drive, Suite 601, Miami, FL 33176. Email: drjakes@aol.com