A Sound Approach to Radial Artery Cannulation: A Comparison between the Conventional Palpatory Method and Ultrasound-Guided Technique

INTRODUCTION

Intra-arterial cannulation enables beat-to-beat blood pressure monitoring, assessment of fluid responsiveness, and frequent blood sampling in the intraoperative period as well as in the intensive care unit (ICU).^[1] The radial artery is the most cannulated artery due to its consistent anatomy, easy accessibility due to superficial location, lesser incidences of complications like infection and ischemia of the hand (due to availability of rich collateral circulation in the hand).^[2] Other sites where arterial cannulation can be done are the femoral artery, dorsalis pedis artery, and anterior and posterior tibial artery and ulnar artery.^[3] Current techniques used for radial artery cannulation include puncturing the vessel and then using the Seldinger technique to advance the catheter over a guidewire, puncturing the vessel and then directly advancing the catheter into the artery, a surgical cut-down to provide direct vessel visualization, use of Doppler ultrasound (USG), and direct vessel visualization with two-dimensional USG guidance.^[4] This study compared radial artery cannulation (using the Seldinger technique) by the landmark technique (by palpating the radial arterial pulse) and by the USG guidance method.

MATERIAL AND METHODS

This is one of the earliest studies undertaken in the Indian sub-continent that compared the conventional palpatory method to the USG-guided approach to radial artery cannulation. This prospective observational study was conducted at a tertiary care hospital located in one of the metropolitan cities of India between the years 2019 and 2022. Adult patients above the age of 18 years, patients undergoing major surgery, patients with cardiac dysfunction undergoing cardiac surgery and non-cardiac surgery, patients who required repeated arterial blood gas analysis, and patients admitted to ICU on inotropic support were included in the study. Patients with peripheral vascular disease, patients with failed Allen test, and patients or next of kin not willing to participate in the study were excluded from the study. Approval from the Institutional Ethics Committee was obtained, and written informed consent from all 80 patients was taken. After simple randomization (drawing lots), 40 patients were categorized into Group A (USG-guided method) and 40 were categorized into Group B (digital palpatory method). Patients in Group A underwent radial artery cannulation using USG guidance, and patients in Group B underwent radial artery cannulation using the conventional digital palpatory (anatomical landmark) method. Leadercath arterial catheter (Polytetrafluoroethylene, single lumen, 20 G, 8 cm length) [ Figure 1] was used to catheterize the radial artery after the Allens’ test [Figure 2] using the “classic” Seldinger technique [Figure 3] in all patients under strict aseptic precautions.^[5]

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Figure 1:

(a) 2% Lignogaine loaded in hypodermic syringe for local anesthesia. (b) 18 G arterial needle. (c) Guidewire. (d) Leadercath (20 G, 8 cm).

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Figure 2:

Allen’s test. (a) Note the pallor in the patient’s palm when radial and ulnar arteries are occluded. (b) Pallor disappears as soon as compression over ulnar artery is released.

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Figure 3:

Classic Seldinger technique. (a) Radial artery is punctured using an arterial needle. (b) A guidewire is threaded through the needle and thereafter the needle is removed. (c) Leadercath is inserted over the guidewire and finally, the guidewire is removed.

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All patients were subjected to the modified Allen’s Test to assess collateral blood flow to the hands^[5,6] before radial artery cannulation [Figure 2]. Local anesthesia using 2% Lignocaine infiltrated subcutaneously was given to all patients [Figure 1a]. After attaching monitors, baseline vitals were noted. A sterile tray was prepared with assembly of 18G cannula for percutaneous arterial puncture[Figure 1b], guide wire [Figure 1c] and the catheter i.e. leadercath[Figure 1d]. In Group A, the radial artery was cannulated under USG guidance. The radial artery was identified by its pulsatile nature and confirmed by color Doppler. After confirmation, arterial puncture was done with 18 G needle [Figure 3a], guide wire was inserted [Figure 3b], needle was removed and leadercath was threaded over the guide wire[Figure 3c]. Then guidewire was removed and leadercath was connected to transducer for invasive blood pressure measurement. Time taken for cannulation was measured as the time from cutaneous puncture to the appearance of arterial waveform on the monitor. The number of re-directions was counted as the number of times needle was redirected without coming out of the skin. The number of attempts was counted as the number of cutaneous punctures required for successful radial artery cannulation. A hematoma was noted for the appearance of swelling and vasospasm when the pulse could no longer be felt. In Group B, the radial artery was cannulated by digital palpation (anatomical landmark method) of the radial pulse.

A sample size of 80 was calculated using the formula: n = [z²p(1-p)]/d² with a power of 80% and precision error of 0.06. The data obtained were subjected to statistical analysis using Student’s unpaired t-test and Chi-square test to find out a significant difference between the groups and Mann and Whitney nonparametric test was used for qualitative data. For statistical comparison, a difference was considered significant when P-value was found to be <0.05. Data were statistically described in terms of mean (±standard deviation), frequency (number of cases), and percentage when appropriate. Results were graphically represented in Microsoft Excel 2010, and the Statistical Package for the Social Sciences ver. 20 was used for statistical analysis.

RESULTS

Distribution of patients in both the groups was compared for differences in age and sex represented in the Table 1 for distribution of age, [Table 2] for distribution of sex), and there was no significant difference between the two groups as per Student’s t-test.

USG-guided method showed lesser time for cannulation; the mean time for cannulation was found to be significantly low in Group A as compared to Group B [Table 3]. While 90% (n = 36) of patients in Group A (USG-guided method) required only a single cutaneous puncture to achieve successful cannulation of the radial artery, 55% (n = 22) of patients in Group B needed two or more cutaneous punctures for achieving the same. About 5% (n = 2) of patients in Group B required more than three cutaneous punctures [Table 4].

The number of redirections was significantly less in USG guided group as compared to conventional palpatory method with p value of 0.0024 [Table 5]. Two complications, namely, hematoma formation and vasospasm, were recorded in the study. It was observed that while the instances of hematoma formation were equal (10%, n = 4) in both the groups, incidences of radial artery vasospasm were higher in Group B (0%, n = 0 v/s. 12.5%, n = 5), with P = 0.05 [Graph 1].

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Graph 1:

Distribution of patients according to complications.

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DISCUSSION

In this study, it was observed that the mean time taken for successful cannulation of the radial artery amongst patients of Group A (USG-guided method) was significantly lower than that among patients in Group B (digital palpation method) by 35.62%. This is quite similar to the results of a study conducted by Yeap et al., where the average time taken for arterial cannulation by USG-guided method was found to be faster than the traditional blind palpation (TBP) method by 29.62% (mean times 171.1 ± 16.7 s versus 243.6 ± 23.5 s, P = 0.012).^[7] Anand et al.,^[8] in their randomized controlled trial assessing USG to cannulate the dorsalis pedis artery showed that cannulation time was significantly higher in the palpation group (17.5 s [12–36 s]) versus. 11.5 s (9–15 s) among USG group. In other words, dorsalis pedis artery cannulation took 34.28% more time by the digital palpation method than when done by the USG method. These results are comparable to our study results.

A study conducted by Wilson et al.^[9] observed that the average number of cutaneous punctures taken for successful arterial cannulation by USG guidance to be 1.3 (±0.596) whereas that by the palpation method to be 2.0 (±0.928). Our study also observed comparable figures when the average number of punctures required for successful radial artery cannulation was compared between Group A and Group B (1.13 ± 0.40 in Group A v/s. 1.75 ± 1.03 in Group B).

Bhattacharjee et al.,^[10] in their meta-analysis of randomized controlled trials compared USG-guided radial artery cannulation with the digital palpation technique and found an overall cannulation success rate which was similar between USG-guided technique and digital palpation. Our study showed that the first-attempt success rate among Group A (USG-guided method) to be 90% (n = 36) and that among Group B to be 55% (n = 22). This was significantly higher than the observations by Levin et al.^[11] who found the first attempt success rate with USG to be 62% compared to the 34% using palpatory method alone in 69 adult patients who underwent elective surgery. However, observations (regarding first-attempt success rates) of Shiver et al. were comparable to our study. Shiver et al., in their study based in an emergency setting, showed first pass success rate of 87% in the USG group when compared to 50% in the palpatory group.^[12]

In the study, the number of redirections was significantly lower in Group A compared to Group B (P < 0.05, as per Chi-square test). This is in concordance to the studies of Yeap et al.,^[7] Wilson et al.^[9] and Cao et al.^[13] Even in the elderly, USG-guided arterial cannulation is preferred over traditional palpation, as it achieves a higher first attempt success rate of cannulation and has fewer complications.^[14]

It was observed in the study that an equal number (10%, n = 4) of patients from both groups had instances of hematoma while attempting to catheterize the radial artery. However, 12.5% (n = 5) of patients in Group B had experienced vasospasm of the radial artery. None of the patients in Group A (USG-guided method) encountered vasospasm as a complication. Wilson et al. observed that the incidence of hematoma formation was almost twice amongst patients who underwent arterial cannulation using TBP method.^[9]

CONCLUSION

USG-guided radial artery cannulation was found to be superior to the traditional digital palpation method in terms of time taken for successful catheterization, first-attempt success rate, number of skin punctures required, number of re-directions required, and lesser instances of vasospasm. These advantages of the USG-guided method of arterial cannulation translate to better patient experience during arterial catheterization.

The study adds to the existing realm of knowledge that compares the USG-guided approach to be a superior technique as compared to the traditional palpatory approach and offers initial data insights in the era when the USG approach to cannulation was still evolving in clinical practice. Larger multi-center trials using randomized approaches and meta-analysis are needed to further collate the findings of this study and those of similar ones undertaken subsequently.