Sono-anatomy of the supraclavicular region for ultrasound-guided subclavian vein catheterization: revaluation of a former method

Abstract

Background/Objective

Ultrasound-guided subclavian vein (SCV) catheterization offers an alternative approach to the classical jugular vein catheterization for central venous catheter placement. The objective of this study was to evaluate the anatomy of the supraclavicular region in healthy volunteers using ultrasonography, specifically for the catheterization of the subclavian vein. Additionally, we aimed to determine specific sonographic measurements of this anatomic region.

Methods

This was a prospective observational study and received approval from the local ethical board. Twenty healthy volunteers (10 male and 10 female) were included in the study. The supraclavicular region of the volunteers was scanned using ultrasonography. The diameter of the subclavian vein (SCV), the distance from the SCV to the skin, the distance from the SCV to the sternocleidomastoid muscle (SCM), as well as the distances from the SCV to the pleura and from SCV to the clavicle were measured. The changes in the SCV-skin distance and SCV diameter before and after performing a caudal traction maneuver on the arm were noted. Additionally, we determined the optimal probe position for visualizing the SCV in the long axis at supraclavicular fossa and identified the ideal needle insertion point.

Results

The mean diameter of the subclavian vein (SCV) was 9.47 ± 1.78 mm. The mean distance from the SCV to the skin was 10.55 ± 2.01 mm, the mean distance from the SCV to the pleura was 9.16 ± 1.26 mm at the medial one-third of the clavicle. The optimal angle for probe positioning was determined 12.75 ± 7.16 degrees from the coronal plane. The ideal needle insertion point was found 4.53 ± 0.70 cm lateral to the medial head of the clavicle. The SCV diameter and SCV-skin distances did not significantly differ from the neutral position after caudal traction of the arm.

Conclusion

In the present study, the normal sonographic anatomy of the subclavian vein, the optimal ultrasound (US) probe angle to visualize the SCV, and the ideal needle insertion point for SCV cannulation in the supraclavicular region were identified for adults. This information serves as a valuable guide for clinicians performing either a blind or ultrasound-guided placement of SCV catheter at the supraclavicular fossa. Additionally, the diameter of the SCV did not change significantly after applying caudal traction to the arm, indicating that this maneuver is unnecessary.

Introduction

Central venous catheterization (CVC) is a commonly performed procedure in selected cases within intensive care units (ICU) and operating rooms. A previous meta-analysis have demonstrated that the use of ultrasonography (USG) increases the success rate of catheter placement and reduces the risk of complications [1]. The development of micro-convex ultrasound probes with smaller footprints has allowed clinicians to explore novel and safer catheterization techniques.

The supraclavicular approach to subclavian vein (SCV) catheterization was first described by Yoffa in 1965 as a blind technique [2]. With advancements in ultrasound technology, the supraclavicular approach has recently gained popularity for central catheterization in both adult and pediatric patients, having potential advantages over the traditional jugular vein catheterization technique [3-7].

Imaging of the SCV using USG in the supraclavicular area has been found to be easier and faster compared to the infraclavicular area [8]. Recent studies recommend the supraclavicular approach, as it has been shown to be noninferior to the infraclavicular approach while offering several potential advantages [9, 10]. The supraclavicular ultrasound-guided approach to the subclavian vein has been previously investigated in several computerized tomography and ultrasonography studies and basic anatomical parameters have been described [11-14]. While the mean diameter of the subclavian vein and the skin-to-vein distance have been addressed in these studies, there remains a need for a standardized assessment of multiple variables such as the optimal ultrasonography probe angle for visualizing the SCV and the optimal needle insertion point to reach the vein. In particular, providing a more comprehensive overview of the clinical and sonographic anatomy of this area may be beneficial for clinicians interested in performing supraclavicular SCV catheterization.

Our study aims to build upon this existing literature by providing a detailed ultrasonography mapping of supraclavicular region in particular for subclavian vein catheterization. Our goal was to enhance clinicians’ understanding of the sonographic anatomy of this region through the results we obtained. As secondary endpoints of this study, we sought to determine the optimal ultrasound probe placement for visualization of the SCV in long axis and optimal needle insertion point to puncture the subclavian vein for SCV cannulation.

Methods

The present study is a prospective observational study involving volunteers, conducted at Sakarya University Faculty of Medicine. The study received approval from the institutional clinical research ethics committee on September 14, 2022, under the approval number E-16214662-050.01.04-176646-113.

Following the approval, 20 healthy volunteers participated in the study between October 1, 2022, and December 30, 2022. Written informed consent was obtained from all volunteers for allowing the use of recorded ultrasound images for scientific purposes.

The exclusion criteria for the study included a history of previous subclavian vein catheter placement, and any prior pathology affecting the anterior or posterior triangles of the neck. The research utilized the Sonosite M-Turbo (Bothell, WA, USA) and the HM70 EVO (Samsung Healthcare, Seoul, South Korea) with a linear high-frequency (3.0–16.0 MHz) ultrasound probe. Data were collected from a total of 20 volunteers, consisting of 10 males and 10 females. Throughout the study, the right side SCV of the volunteers was examined. The age, gender, weight, height, and body mass index (BMI) of the participants were recorded.

The ultrasonography procedures were performed in a dedicated operating room set aside for this study. Volunteers were placed on an operating table in the supine position, with their heads turned 30 degrees to the left. Subsequently, the right clavicle was measured from the sternal joint to the shoulder joint and recorded (Fig. 1a). The clavicle was then divided into three sections, which were marked with a surgical marker pen as the medial third, middle third, and lateral third (Fig. 1b).

Fig. 1.

The clavicle is divided into three regions using a ruler and marked with a surgical pen. These regions are labeled as medial one-third, middle one-third, and lateral one-third

The ultrasound probe was positioned on the supraclavicular fossa and tilted toward the coronal plane (Fig. 2a) until a long-axis image of the subclavian vein (SCV) was visualized.

Fig. 2.

The measurements at the junction of the subclavian vein and the brachiocephalic vein in the supraclavicular fossa. a The probe position at the medial one-third of the clavicle, slightly moved medially to visualize the junction. b A long-axis image of the subclavian vein is shown. The diameter of the subclavian vein and the distance from the subclavian vein to the skin are measured at the junction of the subclavian vein and the brachiocephalic vein. c The distance from the subclavian vein to the pleura is measured at the same junction. SCV: Subclavian vein, BCV: Brachiocephalic vein

The diameter of the SCV was measured at the junction with the brachiocephalic vein (BCV) (Fig. 2), at the medial one-third of the clavicle (Fig. 3), and at the mid one-third of the clavicle (Fig. 4). The SCV-skin distances were also measured at the same three locations: the SCV-BCV junction (Fig. 2b), the medial one-third of the clavicle (Fig. 3), and the mid one-third of the clavicle (Fig. 4). The SCV was not visualized at the lateral one-third of the clavicle; therefore, no measurement was performed in that area. The distances and diameters were measured using minimal probe pressure to prevent tissue and vessel collapse.

Fig. 3.

Showing the measurements at the medial one third of the clavicle in the supraclavicular fossa. a The probe position at the medial one-third of the clavicle. b Measurement of the subclavian vein diameter and skin-subclavian vein distance at the medial one-third of the clavicle. SCV: Subclavian vein, SCM: Sternocleidomastoid muscle

Fig. 4.

Showing the measurements at the mid one third of the clavicle. a The probe position at the mid one-third of the clavicle. b Measurement of the subclavian vein diameter and skin-subclavian vein distance at the mid one-third part of the clavicle. SCV: Subclavian vein

The distances between the SCV and the pleura were also assessed at three points: the SCV-BCV junction (Fig. 2c), the medial one-third part of the clavicle, and the mid one-third part of the clavicle. Subsequently, the SCV-sternocleidomastoid muscle (SCM) distances were measured at the SCV-BCV junction and the medial one-third of the clavicle. The measurement of SCV-SCM distance at the mid one-third of the clavicle was not applicable because the lateral border of the sternocleidomastoid muscle does not extend to that area.

The SCV-clavicle distance was measured at the mid one-third of the clavicle by placing the ultrasound probe sagittal on the clavicle. If the SCV was not adequately visualized using the supraclavicular fossa approach, a short-axis image of the right jugular vein was obtained by positioning the ultrasound probe in the horizontal plane at the level of the thyroid cartilage. The jugular vein was then tracked by sliding the ultrasound probe caudally until the junction of the SCV with the BCV was located in long-axis imaging. The SCV was visualized in both short and long-axis images, which were confirmed by Doppler imaging. The measurements were conducted during the expiratory phase of respiration.

After completing all measurements, we assessed the optimal position of the ultrasound probe for visualization of the SCV. This position was defined as the specific transducer angle in the coronal plane that yields the maximum achievable cross-sectional diameter of the subclavian vein with the clearest visualization of the vessel walls and surrounding anatomical structures in long-axis imaging at the medial third of the clavicle. The angle of the probe in the coronal plane was measured with the help of a goniometer(Fig. 5a).

Fig. 5.

a The optimal position of the ultrasound probe is defined as the angle in the coronal plane where the maximum cross-sectional diameter of the subclavian vein is visualized in long-axis imaging at the medial third of the clavicle. b Identification of the optimal needle entry point, Primarily, the SCV was visualized at the location closest to the skin. This point was then marked and the distance from the sternoclavicular joint to this point was measured

To determine the optimal needle entry point, we visualized the SCV at the location closest to the skin. This point was then marked and the distance was measured from the sternoclavicular joint to this point, which was determined to be the ideal needle entry point for catheter placement (Fig. 5b).

The SCV diameter measured before and after arm traction maneuvers was compared to determine if there is a significant difference due to the application of the arm traction maneuver. The SCV-skin distance was also compared before and after arm traction maneuvers. All measurements were recorded with the patient’s arm in neutral position and after an assistant slightly pulled the arm to caudal. The ultrasonography procedures and the measurements were performed by single operator to prevent inter-observer variability and minimize measurement errors. The operator is a medical doctor and senior Anesthesiology resident (AZB) in Sakarya University Hospital who has three years of experience in ultrasound guided regional anesthesia and catheterization procedures and has four years of experience in residency. The measurements are performed under supervision of a senior Anesthesiologist and Associate Professor (OB), given the importance of precise of the probe angle and distance measurements. However, owing to the descriptive characteristic of the study and a single operator measurement, intra-observer variability remains as a possible source of bias.

The Statistical Package for the Social Sciences (SPSS) software (IBM Corp, Armonk, NY) was utilized for statistical analysis of the data. Descriptive statistical methods were applied to evaluate the study results. Simple descriptive statistics were used to characterize the features of vascular structures. Qualitative data were expressed in numbers and percentages, while quantitative data were presented as mean ± standard deviation. The Shapiro-Wilk test was conducted to assess the normality of the data. A paired t-test was used to compare the size of the SCV before and after the caudal traction maneuver of the arm, provided the data followed a normal distribution. P-value of less than 0.05 was considered statistically significant.

Results

The mean age of the volunteers was 29.60 ± 5.30 years, the mean body weight was 72.35 ± 12.85 kg, the mean height was 170.95 ± 11.08 cm, and the mean BMI was 24.59 ± 2.52. The mean clavicle length of the patients was recorded as 14.23 ± 1.14 cm.

In measurements where the subclavian vein (SCV) merges into the brachiocephalic vein (BCV), the mean diameter of the SCV was found to be 10.57 ± 1.76 mm. After pulling the arm caudally, this diameter was measured 10.37 ± 1.36 mm. The difference was not statistically significant (p = 0.683).

The distance between the SCV and the skin was measured 13.89 ± 3.09 mm in neutral position and it was measured 13.30 ± 2.70 mm after caudal traction of the arm, with no statistically significant difference (p = 0.163) (Table 1).

Table 1.

Changes in subclavian vein-skin distance and subclavian vein diameter before and after caudal traction of the arm maneuver measured by supraclavicular ultrasonography at different localizations

	Before traction of the arm	After traction of the arm	P value
SCV diameter (mm):
SCV-BCV merge point	10.57 ± 1.76	10.37 ± 1.36	0.683
Medial 1/3 part of clavicle	9.47 ± 1.78	9.87 ± 1.75	0.257
Mid 1/3 part of clavicle	9.91 ± 1.96	10.38 ± 1.69	0.217
SCV-skin distance (mm):
SCV-BCV merge point	13.89 ± 3.09	13.30 ± 2.70	0.163
Medial 1/3 part of clavicle	10.55 ± 2.01	10.44 ± 2.67	0.789
Mid 1/3 part of clavicle	13.17 ± 3.65	13.36 ± 3.91	0.686

Data presented as mean ± standard deviation. BCV Brachiocephalic vein, SCV Subclavian vein, SCM Sternocleidomastoid muscle

Additionally, the SCV-to-pleura distance was recorded as 8.83 ± 1.37 mm, while the distance between the SCV and the sternocleidomastoid (SCM) muscle was measured 7.05 ± 3.94 mm (Table 2).

Table 2.

Sonographic anatomy measurements obtained from volunteers and the optimal ultrasound probe angle

	SCV-BCV junction	Medial 1/3 part of clavicle	Mid1/3 part of clavicle
SCV-Pleura distance (mm)	8.83 ± 1.37	9.16 ± 1.26	5.61 ± 0.43
SCV-SCM distance (mm)	7.05 ± 3.94	3.93 ± 2.30	N/A
SCV-Clavicula distance (mm)	N/A	N/A	14.86 ± 3.47
Optimal probe angle	N/A	12.75 ± 7.16	38 ± 11.52

Data presented as mean ± standard deviation. *BCV Brachiocephalic vein, SCV Subclavian vein, SCM Sternocleidomastoid muscle, N/A Not applicable

In measurements taken at the medial one-third of the clavicle, the diameter of the subclavian vein (SCV) was recorded as 9.47 ± 1.78 mm. After applying traction to the arm, the diameter increased to 9.87 ± 1.75 mm. However, this difference was not statistically significant (p = 0.257). The distance from the SCV to the skin was measured 10.55 ± 2.01 mm, and after traction, this distance changed to 10.44 ± 2.67 mm, which was also not significant (p = 0.789) (Table 1).

Additionally, the distance between the SCV and the pleura was found 9.16 ± 1.26 mm, while the distance between the SCV and the sternocleidomastoid (SCM) muscle was measured as 3.93 ± 2.30 mm.

In the measurements at the middle third of the clavicle, the diameter of the subclavian vein (SCV) was found 9.91 ± 1.96 mm. After applying traction to the arm, the SCV diameter increased to 10.38 ± 1.69 mm. However, this difference was not statistically significant (p = 0.217).

Additionally, the SCV-skin distance was measured at 13.17 ± 3.65 mm in the neutral position, and 13.36 ± 3.91 mm after the arm traction maneuver. No statistically significant difference was observed (p = 0.686) (Tables 1 and 2).

In the short-axis measurements in the sagittal plane at the middle third of the clavicle, the distance between the upper wall of the SCV and the lower border of the clavicle was measured to be 14.86 ± 3.47 mm (Table 2).

The optimal angle of the ultrasound probe relative to the coronal plane was determined to be 12.75 ± 7.16 degrees (Table 2).The optimal point for needle insertion for supraclavicular SCV catheterization was identified as 4.53 ± 0.70 cm lateral from the medial head of the clavicle.

Discussion

The present study highlighted the important sonographic anatomy of the supraclavicular fossa by measuring the mean diameter of the subclavian vein and the average distances from the subclavian vein to the skin, pleura, sternocleidomastoid muscle, and the clavicle. The supraclavicular approach, as described by Yoffa, has been underutilized for many years. One possible reason for this underuse could be the fear of pleural puncture and damage to vital structures [15]. This fear may stem from a limited understanding of the anatomy in this area, uncertainty about the optimal position for the ultrasound probe, or the correct needle entry point. However, catheterization of the subclavian vein via the supraclavicular approach is a viable technique and offers several advantages over catheterization through the infraclavicular approach [16, 17].

The SCV is relatively superficial in the supraclavicular fossa, requiring a shorter distance to puncture the vein. A recent study found that the supraclavicular route is faster and relatively safer, with fewer complications [18]. Additionally, the supraclavicular approach reduces the failure rate and the incidence of malposition [19]. Thrombosis and infection rates are significantly lower, patient tolerance and comfort are higher, and central venous catheter placement is often easier in fluid-deficient patients, as the clavipectoral fascia helps maintain the vein’s patency [20].

Comparisons of the supraclavicular approach to the subclavian vein with the modern and commonly preferred technique of internal jugular vein catheterization are rare. In a study by Shin et al., the complication rates for internal jugular vein (IJV) catheterization were found to be very low, similar to those of subclavian vein catheterization. The complication rates for both methods are comparable, suggesting that the SCV approach is as safe as the IJV approach [21].

The SCV approach enables real-time needle insertion in a long-axis orientation, providing excellent control over the needle tip. As the patient breathes, the pleura can be seen in real time as a sliding echogenic structure, typically located caudal to the confluence of the brachiocephalic vein (BCV) and the subclavian vein (SCV) over the dome of the lung. We have demonstrated that the pleura is very close to the posteromedial wall of the SCV at the BCV-SCV confluence. The first rib serves as a safety barrier and can be visualized posterolateral to the SCV. However, the anatomical findings suggest that to maintain a low angle of needle insertion and avoid deep needle penetration may prevent puncturing the posteromedial wall and damaging the pleura. The subclavian artery is typically located posterior to the SCV, and it is usually not visualized in images obtained with the ultrasound probe angles. Therefore, arterial puncture seems unlikely when using the supraclavicular approach, particularly when employing the preferred long-axis in-plane technique. To differentiate between the subclavian artery and the SCV, clinicians can check for venous valves or use color flow Doppler to observe arterial pulsations.

There are several studies utilizing three-dimensional computed tomography (3D CT) to investigate the anatomy of the supraclavicular region. In a study conducted by Jung et al., the diameter of the subclavian vein was measured in 45 adults using 3D CT, reporting an average diameter of 12.9 ± 3.4 mm (ranging from 6.5 to 22.5 mm) based on images obtained from the medial one-third of the clavicle [11]. Another CT study assessed the surface cross-sectional area at the junction of the brachiocephalic vein and the subclavian vein and found 1.24 ± 0.33 cm² [12]. When measurements were done at the middle one-third section of the clavicle, the surface cross-sectional area was reported as 1.28 ± 0.34 cm².

On the other hand, ultrasonography studies are infrequent; Fortune et al. reported a subclavian vein (SCV) diameter of 8.8 mm, measured via ultrasound at the medial third of the clavicle in 10 adults [13]. Similarly, a study by Salari et al. performed ultrasound measurements from the lateral part of the right clavicle, reporting an SCV diameter of 7.47 ± 2.13 mm [14]. In our study, the mean SCV diameter was found to be within the ranges reported in these previous studies.

The optimal probe position determined in the present study aligns with the needle advancement angle suggested by Yoffa. Yoffa emphasizes that successful procedures hinge on accurately defining the clavi-sternomastoid angle, formed by the junction of the lateral head of the sternocleidomastoid muscle and the clavicle. According to his guidelines, the needle should be placed one centimeter lateral to the lateral head of the sternocleidomastoid muscle and one centimeter cephalad to the clavicle, directed towards the contralateral nipple at a 45-degree angle, which is 15 degrees below the coronal plane. Utilizing ultrasonography can make these maneuvers unnecessary. However, the anatomical findings propose that if a blind technique is employed, the needle insertion should be steeper than the mentioned angles especially when performing a medial puncture.

Our study also explored how the diameter of the subclavian vein (SCV) and the SCV-to-skin distance changed with the application of caudal traction on the ipsilateral arm. Kim et al. noted that the length of the puncturable SCV may increase after applying caudal traction to the arm, and the diameter of the SCV may slightly increase as well [22]. However, we could not find any data supporting the use of caudal traction on the arm to significantly enlarge the SCV diameter.

This study has several limitations. The observational nature of the research and the lack of a control group make it difficult to determine if one method is superior to another. The measurements were performed by a single operator, and neither intra- nor inter-observer variability was assessed. The single experienced operator ensured a standardized measurement protocol and eliminated individual technique variations, however, the lack of reliability testing for the specific angles and measured distances may limit the generalizability of these parameters. We obtained only ultrasonographic images and did not perform any catheterization. Therefore, we were unable to observe how the ultrasound probe and arm positions affected catheterization success and complications and our findings require further validation through outcome-based studies. Since we only used the right side of the body in our study, our findings may not be applicable to the left side. Another limitation is the potential for measurement bias related to ultrasound probe pressure. Although we adhered to a ‘minimal probe pressure’ technique to prevent vessel compression, this approach remains subjective and was not objectively monitored.

In conclusion, this study presents the normal sonographic anatomy of the subclavian vein and the supraclavicular region in a group of adults, specifically for the purpose of the subclavian vein catheterization using the supraclavicular approach. Additionally, our findings indicate that applying caudal traction to the ipsilateral arm does not significantly alter the diameter of the subclavian vein or the distance between the subclavian vein and the skin. Therefore, this maneuver may not be necessary during the procedure. Since our study did not evaluate procedural success or complication rates, the measurements should be interpreted as anatomical guidance rather than clinical recommendations.

Abbreviations

SCV

Subclavian vein

SCM

Sternocleidomastoid muscle

US

Ultrasound

CVC

Central venous catheterization

ICU

Intensive care unit

USG

Ultrasonography

BMI

Body mass index

BCV

Brachiocephalic vein

SPSS

Statistical Package for the Social Sciences

IJV

Internal jugular vein

3D CT

Three-dimensional computed tomography

Authors' contributions

Ahmet Zeki Berk, conceived and designed the study, drafted the manuscript and performed the study. Onur Balaban interpreted the data and supervised the study, Ali Eman and Bayazit Dikmen revised the manuscript. All authors made substantial contributions to study conception and design. All authors read and approved the final manuscript.

Funding

This study received no specific grant from any funding agency in the public, commercial, or not-for‐profit sectors.

Data availability

The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.

Declarations

Ethics approval and consent to participate

The study was approved by Sakarya University Ethics Committee of Sakarya University Faculty of Medicine with the approval number: E-16214662-050.01.04-176646-113. The study was conducted in accordance with the Declaration of Helsinki. All participants signed written informed consent before enrollment.

Consent for publication

All human participants provided signed informed consent for the trial and for publishing the data and photographs.

Competing interests

The authors declare no competing interests.