Applying Acoustic Shading Facilitates Orientation of Radial Artery Puncture and Cannulation Teaching in Standardized Resident Education: A Randomized Controlled Trial | BMC medical training | SehndeWeb


The present study aimed to compare traditional ultrasound-guided teaching with ultrasound-guided teaching facilitated by acoustic shading and to determine which of the two methods may be more helpful for beginners in learning puncture technique. of the radial artery.

study design

The present study was designed as a randomized, prospective, single center controlled trial. This study complied with applicable CONSORT guidelines and was approved by the Ethics Committee of Qingdao Municipal Hospital, Qingdao University.

Study population

All postgraduate students who underwent SRTP at the anesthesia department of Qingdao Municipal Hospital were eligible for the study. Inclusion criteria were postgraduate students who had not previously performed radial artery puncture or received relevant training. The sample size was calculated based on our preliminary experience, in which the first puncture success rates in the new and traditional ultrasound groups were 73.91% and 45.45%, respectively. The “two-proportion comparison formula” was used to calculate the sample size, with the type I error (α) set at 0.05, the power (1-β) was 0.8 and the sampling rate was 1. The sample size per group was calculated as 43. Considering a dropout rate of 20%, each group ultimately contained 52 participants. Since all postgraduate medical students signed a training agreement before entering the hospital and professional training is an inherent requirement of the SRTP, no other written informed consent was required, such as approved by the ethics committee.

Patients undergoing elective surgery requiring the use of invasive blood pressure monitoring, as determined by the treating anesthesiologist, were eligible for inclusion in this study. The exclusion criteria were as follows: (1) Age less than 18 years old or more than 65 years old; (2) BMI ≥ 30 kg/m2; (3) negative Allen test; (4) patients who had had multiple arterial punctures or radial artery cannulation in the previous 30 days; (5) patients with peripheral vascular disease, hemorrhagic shock, atherosclerosis, coagulation disorders or Raynaud’s disease. Written informed consent was obtained for all patients or their legally authorized representatives.


All students are tested on their theoretical medical knowledge after entering the anesthesiology rotation to assess their knowledge base. The students involved were randomly grouped according to the entrance examination results by the stratified randomization method, including the Acoustic Shading Facilitated Ultrasound Guided Teaching (ASFU-G) group and the traditional ultrasound guided teaching (TU-G).


The pedagogical secretary provided the first training on aseptic operating techniques, basic anesthesia operations and fundamental theories. Specific researchers who have qualifications for standardized resident training gave theoretical training on radial artery puncture techniques for all students, explaining the anatomical position of the radial artery, puncture preparations, the process puncture and complications. Subsequently, two groups of participants observed the demonstration and explanation in 30 cases of catheterization by arterial puncture. Among them, the ASFU-G group learned the radial artery puncture technique under ultrasound guidance assisted by acoustic shadowing; the TU-G group learned the radial artery puncture technique under traditional ultrasound guidance. In a later period, both groups of participants performed 30 radial artery puncture placements under the guidance of their respective investigators.

Teaching methods in the ASFU-G group

The modification of the ultrasound probe was made by referring to the literature with minor modifications [4]. The metal-containing strand of X-ray detectable surgical gauze is separated and placed over the ultrasound probe to make it perpendicular to the long axis of the ultrasound probe. The ultrasound coupler and sterile 3 M membrane were applied to the ultrasound probe to secure the ultrasound probe and metal-containing strand as shown in Fig. 1. Patients were placed in the supine position with the operative upper limb abducted 30° with the palm facing upwards and the wrist elevated 3 cm. The skin around the puncture site was sterilized with povidone iodine solution. The ultrasound probe was equipped with sterile disposable plastic caps. The probe, with a frequency of 11 MHz and a depth of 1.5 cm, has been adjusted to obtain the highest quality ultrasound. Using the short-axis out-of-plane procedure, the probe was adjusted by moving left to right so that the radial artery was positioned between the middle of the two low-density shadows on the ultrasound image. The central point of the junction between the two visible lines and the skin was the projection point of the radial artery. The needle was inserted at a 30° angle to the skin between the two visible lines on the probe. The needle tip, located between the low-echo acoustic shadows of the line of sight, appears as a hyperechoic shadow on the ultrasound screen. Once the needle entered the radial artery, the angle of the needle was reduced from 30° to 15°, and the needle was slowly pushed forward 1-2 mm. Then the cannula was placed, fixed and connected to the arterial transducer. The relationship between the developing line and the radial artery on the ultrasound screen is shown in Fig. 2. With the guidance of scholars who explained the anatomy of the radial artery, the methods and essentials of arterial puncture, the causes and analysis of puncture failures, the students performed 30 cases of puncture and radial artery catheterization under the guidance of acoustic shadowing facilitated ultrasound (not limited to the same day).

Fig. 1
Figure 1

The double development lines were attached on the ultrasound probe perpendicular to the long axis. A Design of an ultrasonic probe for double development lines. B Ultrasound image of the radial artery (arrow) and acoustic shading of the evolving double line (arrowheads)

Figure 2
Figure 2

Principle diagram of the acoustic occultation of the double development line. D1 (purple line) represents the transverse diameter of the radial artery; D2 (yellow line) represents the longitudinal diameter of the radial artery; D3 (green line) represents the depth of the skin at the center of the radial artery

Teaching methods in the TU-G group

The radial artery puncture and catheterization procedure was performed as described above, but the ultrasound probe was not modified. The radial artery was located using the short axis out-of-plane approach. Radial artery puncture and catheterization were performed using color Doppler flow imaging or central function (M-line). With the guidance of researchers who explained the anatomy of the radial artery, arterial puncture methods, and the essentials, causes, and analysis of puncture failures, the students performed 30 cases of puncture and catheterization of the radial artery (not limited to the same day).

Outcome measures

At the end of the student training, patients were randomly selected for examination. The general condition of the patients was recorded. The diameter of the radial artery under ultrasound and the distance from the skin to the center of the internal diameter of the radial artery were measured. The primary endpoint was to compare the success rate of puncture and catheterization at the first attempt, and the secondary endpoints were ultrasound localization time, puncture time and incidence vascular complications. We defined ultrasound localization time as beginning with placement of the ultrasound probe on the skin to contact of the patient’s skin with the puncture needle, and catheterization time was the time from contact of the puncture needle with the patient’s skin and successful insertion. of the cannula in the radial artery. All times measured have been documented by a third party. All measured times were recorded by two researchers and the average values ​​were calculated. A successful first attempt radial puncture was defined as entry of the puncture needle into the vessel (ultrasound imaging revealed a puncture needle entering an artery or regurgitation of arterial blood into the puncture needle). puncture), regardless of subsequent successful cannula placement. However, successful first attempt catheterization was defined not only by entry of the puncture needle into the artery, but also by successful placement of the arterial cannula. During the final test, each student had only one opportunity. If the puncture failed, the researcher would take over and perform the next puncture operation. After completing the experiment, participants were asked to complete a questionnaire about their satisfaction with the teaching.

statistical analyzes

Statistical analysis was performed using IBM SPSS Statistics for Windows, version 21.0 (IBM Corp., Armonk, NY, USA). The normality of the data was assessed by the Kolmogorov-Smirnov test. Enumeration data is expressed as percentages, measurement data with a normal distribution is expressed as mean ± SD, and non-normally distributed measurement data is expressed as median values ​​(quartile spacing). For two groups with continuous variables, the two-sample independent t-test was used when each data set was normally distributed with homogeneous variance; otherwise, the Mann-Whitney U test was used. Count data were analyzed using the chi-square test or Fisher’s exact probability method. Differences were declared statistically significant if p<0.05.

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