The Venerable Subclavian Line.

In this treatise, we will address one of the higher-risk procedures, subclavian vein cannulation, that a practitioner may undertake in the care of complex patients. All cardiothoracic surgeons and their trainees will need, on occasion, to put in central lines in a variety of circumstances, including in the operating room, in the intensive care unit, in emergency circumstances, and, occasionally, when other practitioners have been unsuccessful in their attempts to place a central line. We will describe, in detail, the anatomy of the subclavian vein, the preparation of the patient for subclavian vein cannulation, the infraclavicular approach to cannulation of the vein, and a few notes about the supraclavicular approach to the subclavian vein. It is self-evident that the priorities of central venous cannulation include safety of insertion, minimizing clot formation, and avoiding infection. We will dwell primarily on the principles of safe subclavian line insertion.

Effects of ipsilateral tilt position on the cross-sectional area of the subclavian vein and the clinical performance of subclavian vein catheterization: a prospective randomized trial.

BACKGROUND: The cross-sectional area of the subclavian vein (csSCV) is a crucial factor in the successful catheterization of the subclavian vein. This randomized controlled study investigated the effects of the csSCV on landmark-based subclavian vein catheterization. METHODS: This study was performed using a two-stage protocol. During stage I, the csSCV was measured in 17 patients placed in the supine, 20° ipsilateral tilt, and 20° contralateral tilt positions in a random order. During stage II, landmark-based subclavian vein catheterization was randomly performed in patients placed in either the supine (group S, n = 107) or the ipsilateral tilt (group I, n = 109) position. The primary outcome measure was the csSCV in stage I and the primary venipuncture success rate in stage II. Secondary outcome measures were the time to successful venipuncture, the total catheterization time, the first-pass success rate, and the incidence of mechanical complications during catheterization. RESULTS: The csSCV was significantly larger in the ipsilateral tilt than in either the supine or contralateral tilt position (1.01 ± 0.35 vs. 0.84 ± 0.32 and 0.51 ± 0.26 cm2, P = .006 and < .001, respectively). The primary venipuncture success rate did not differ significantly between the group S and I (57.0 vs. 64.2%, P = .344). There were also no significant differences in the secondary outcome measures of the two groups. CONCLUSIONS: The csSCV was significantly larger in patients placed in the ipsilateral tilt than in the supine position, but the difference did not result in better clinical performance of landmark-based subclavian vein catheterization. TRIAL REGISTRATION: NCT03296735 for stage I ( ClinicalTrials.gov , September 28, 2017) and NCT03303274 for stage II ( ClinicalTrials.gov , October 6, 2017).

Anatomical variations in distal portion of the thoracic duct-A systematic review.

The objective of this study was to identify and analyze the anatomical variations in the termination of the thoracic duct (TD) in cadavers or patients by anatomical dissections and surgical or radiological procedures for better knowledge of the interindividual variations through a systematic review. The search strategy included PubMed and reference tracking. Studies were identified by searching the electronic Medline databases. The search terms included "TD," "Jugular Vein," "Subclavian Vein," or "Cervical," and the protocol used is reported herein. These search results yielded 20 qualitative review articles out of the 275 articles consulted. We collected all the important data from these 20 articles with 1,352 TD analyzed by varying sources in our search. Regarding the characteristics of the studies and the anatomy of the TD, the results were heterogeneous. The TD most commonly terminates in the internal jugular vein in 54.05% of cases (95% confidence interval [CI]: 54.03; 54.07), in the jugular-venous angle in 25.79% (95% CI: 25.77; 25.81), and in the subclavian vein in 8.16% of cases (95% CI: 8.14;8.18). Other terminations were found in 12% of cases. This systematic review provided an overview of the variations in the distal portion of the TD. This study can be helpful for surgeons in selecting the most appropriate methods to achieve successful surgical results and avoid complications, such as chylothorax; it also offers detailed information on the cervical termination of the TD in new diagnostic and therapeutic methods involving the TD. Clin. Anat. 32:99-107, 2019. © 2019 Wiley Periodicals, Inc.

Effect of lumbar elevation on dilatation of the central veins in normal subjects.

BACKGROUND: Increasing the size of the central veins is required to increase the success rate of central line placement and decrease complication risk. Right-sided approach for the central veins, Valsalva maneuver, and Trendelenburg position have been recommended, but these may not be available for some cases. This study aimed to determine a more convenient patient position that can result in the largest central vein diameter. METHODS: Recruited subjects were placed in 60° and 30° upper body elevation, supine position, and 30° and 60° lower body elevation, and lumbar elevation (LE) was consecutively performed, with one position maintained for 10 min. Diameters of the subclavian vein (SCV) and internal jugular vein (IJV) were measured using high-resolution two-dimensional ultrasonography at each position. RESULTS: The most suitable position on the ordinary bed for increasing central vein diameter was LE. The maximum and minimum SCV and IJV diameters in LE were significantly larger than those in the supine position (SCV: coefficients -0.633 and -0.863, p = 0.08 and 0.011, respectively; IJV: coefficients -1.09 and -1.15, p < 0.001 and = 0.001, respectively). Leg elevation for 10 min failed to dilate the central vein diameter. CONCLUSION: The LE without leg elevation produced a greater and more significant increase in central vein diameter than the supine position and may be useful for central line placement.

Redefining the morphometry of subclavian vessels for clavicle fracture treatments.

PURPOSE: Clavicle fractures are common injuries in adults and children. Although neurovascular damage is rarely seen, acute subclavian artery pseudoaneurysms and injuries to subclavian vessels were reported for closed fractures of the clavicle. The aim of this study was to identify the morphological details of the subclavian vessels and their relation to the sternoclavicular joint and body of the clavicle. METHODS: 127 patients (66 females and 61 males) were evaluated using reconstructed three-dimensional computed tomographic angiographies. The point at which the subclavian artery crossed posterior to the clavicle was detected as a landmark. The medio-lateral distance between the sternal end of the clavicle, landmark, antero-posterior distance between the clavicle and the subclavian artery, diameter of the artery and vein, angle between the subclavian artery and vein, distance of the subclavian vein to the subclavian artery and the clavicle at the landmark were measured. Measurements were compared according to gender and right and left sides, and age correlation was determined. RESULTS: Morphometric relationship between the subclavian vessels and clavicle presented differences between genders. We measured the antero-posterior distance between the subclavian artery and the clavicle to be less than 1 cm (0.91 cm). CONCLUSION: The subclavian artery travelled longer distances in men than women to reach the point that it crossed the clavicle. Our results demonstrated that the subclavian artery does not pass from the inferior margin of the clavicle, thus, superior plate osteosynthesis does not have any risk to injury against the subclavian vessels during the management of the clavicle fractures.

The Effect of Head Position on the Cross-Sectional Area of the Subclavian Vein.

In 41 healthy volunteers, we investigated the cross-sectional area (CSA) of the subclavian vein (SCV) in the following head positions: neutral and 30° head rotation toward the contralateral or ipsilateral sides. Significant differences were observed in the CSA of the SCV at 3 different head positions: contralateral 30° versus neutral, -0.05 cm (95% confidence interval, -0.08 to -0.03); contralateral 30° versus ipsilateral 30°, -0.15 cm (-0.19 to -0.12); neutral versus ipsilateral 30°, -0.10 cm (-0.13 to -0.07); all Pcorrected< .001). For SCV catheterization, 30° head rotation to the ipsilateral side provided significant improvements in the CSA compared with the other head positions.

Subclavian and axillary vessel anatomy: a prospective observational ultrasound study.

PURPOSE: The primary objective of this study was to define the ultrasound-derived anatomy of the axillary/subclavian vessels. As a secondary objective, we evaluated the relationship between the vascular anatomy and demographic, anthropometric, and hemodynamic data of patients. METHODS: This observational anatomical study used bedside ultrasound with 150 cardiac surgical patients in the operating room. Bilateral axillary and subclavian anatomy was determined using a high-frequency ultrasound probe with fixed reference points. Images were recorded and analyzed, and correlation with demographic, anthropometric, and hemodynamic data was performed. RESULTS: The images were adequate to evaluate potential anatomical variations in 97.4% of patients with a body mass index as high as 46.4 kg·m-2. The mean (standard deviation) diameter of the axillary vein was 1.2 (0.3) cm on the right side and 1.1 (0.2) cm on the left side. The dimensions of the axillary vein were larger on the right side in 69% of patients. The vein was located directly over the artery in the mid-clavicular view in 67% of the patients and in lateral-clavicular view in only 7% of the patients. As we moved the probe laterally, the vein was lateralized in relation to the artery in 89% of patients. There was no significant correlation between the hemodynamic data and vessel size, although direct correlation was found between body mass index and the depth of the vessel (P < 0.001). The axillary vein area was smaller in females than in males (P < 0.002), and in 4% of patients, the axillary vein was in an aberrant position. CONCLUSIONS: In patients undergoing cardiac surgery, axillary vessel anatomy varied considerably, and the patients' hemodynamics could not predict the size of the axillary vessels. Only the patients' weight correlated moderately with the depth of the vein.

A novel "shrug technique" for totally implantable venous access devices via the external jugular vein: A consecutive series of 254 patients.

BACKGROUND: The external jugular vein (EJV) approach for totally implantable venous access devices (TIVADs) is safe. However, the success rate is unsatisfactory because of the difficulty in catheterization due to the acute angle between the EJV and the subclavian vein (SCV). A novel "shrug technique" to overcome this difficulty was developed, and its efficacy was assessed in a consecutive case series. METHODS: TIVAD placement was performed via the EJV cut-down approach. "Shrug technique," a simple way to straighten the EJV-SVC angle by shrugging the patient's shoulder, was applied to facilitate the passage of the guidewire and sheath-introducer when there was acute angulation between the EJV and SCV. RESULTS: A total of 254 patients underwent TIVAD implantation by the EJV cut-down approach. The "shrug technique" was applied in 51 cases (20%), and catheterization was successful in all cases. Thus, TIVAD implantation was successfully completed in all 254 cases (100%) in a single operative setting. The median operating time was 38 [IQR 30-45] min. Eleven complications (4%) were observed, but none of them were EJV-specific. CONCLUSION: The "shrug technique" is simple but very useful to achieve a higher success rate and safer insertion of TIVADs from the EJV. J. Surg. Oncol. 2017;115:291-295. © 2016 Wiley Periodicals, Inc.

A supraclavicular cephalic vein drained into the subclavian vein.

Although the cephalic vein follows a fairly consistent course, numerous variants have been reported. We found a rare anatomical presentation of the cephalic vein in a 75-year-old Korean male cadaver. The left cephalic vein was identified in the deltopectoral groove, ascended over the clavicle, and terminated into the left subclavian vein just before its union with the left internal jugular vein. The detailed knowledge on the variations of the cephalic vein is important for clinicians as well as anatomists since the approach through the axillary base is favored in many invasive clinical procedures.

A rare variant between the left superior vena cava and the azygos vein.

During the educational dissection of a 68-year-old Chinese male cadaver, an azygos vein (AV) coursing on the left side with double superior vena cava was observed. The left superior vena cava (LSVC) began from the confluence of the left internal jugular and left subclavian veins, and extended downwards medially into the left edge of the dilated coronary sinus. The right superior vena cava was formed by the union of the right internal jugular and right subclavian veins, and drained into the right atrium from the above. The AV was formed by the union of the right and left ascending lumbar veins at the level of the tenth thoracic vertebra. It ascended along the left margin of the thoracic vertebra, receiving almost the bilateral posterior intercostal veins and then extended into the LSVC on the left wall via the azygos arch. Better understanding of these variations will reduce unnecessary and potential harmful testing, and unneeded patient anxiety.

Comprehensive Imaging Review of the Superior Vena Cava.

The superior vena cava (SVC) is the largest central systemic vein in the mediastinum. Imaging (ie, radiography, computed tomography [CT], magnetic resonance [MR] venography, and conventional venography) plays an important role in identifying congenital variants and pathologic conditions that affect the SVC. Knowledge of the basic embryology and anatomy of the SVC and techniques for CT, MR imaging, and conventional venography are pivotal to accurate diagnosis and clinical decision making. Congenital anomalies such as persistent left SVC, partial anomalous pulmonary venous return, and aneurysm are asymptomatic and may be discovered incidentally in patients undergoing imaging evaluation for associated cardiac abnormalities or other indications. Familiarity with congenital abnormalities is important to avoid image misinterpretation. Acquired abnormalities such as intrinsic and extrinsic strictures, fibrin sheath, thrombus, primary neoplasms, and trauma can produce mild narrowing to complete occlusion, the latter leading to SVC syndrome. Each imaging modality plays a role in evaluation of the SVC, helping to determine the site, extent, and cause of pathologic conditions and guide appropriate management. Commonly performed interventional procedures for fibrin sheath and benign and malignant strictures include low-dose thrombolytic infusion, fibrin sheath disruption, venous angioplasty, and stent placement.

Ultrasonographic anatomic variations of the major veins in paediatric patients.

BACKGROUND: The aim of our study was to describe the anatomic relationships in internal jugular (IJV), subclavian (SCV), and femoral (FV) vein sites. METHODS: One hundred and forty-two children had a two-dimensional (2D) ultrasound (US) evaluation of IJV, SCV, and FV sites. They were enrolled according to their age: 0-1 month old (n=9), 1 month old to 2 yr old (n=61), 2-6 yr old (n=22), 6-12 yr old (n=32), and 12-18 yr old (n=18). RESULTS: We found about 7.7% variation for the IJV. The most common anatomic variations were a lateral (nine children) or anterior (nine children) position of the IJV to the carotid artery. Regardless of the age category, about 9.8% of the anatomic variations were found for the FV. The most common anatomic variation in our study was that the FV ran anteromedially to the femoral artery (17 children). Anatomic variation of the SCV, regardless of age category, was about 7.4%. The most common anatomic variation was the SCV, which ran medially (10 children) to the subclavian artery. CONCLUSIONS: The relevant percentages of anatomic variations obtained for all these areas support at least a systematic US screening before attempting to obtain central venous access, ideally using a US-guided technique.

Predicting the optimal depth of left-sided central venous catheters in children.

The aim of this study was to predict the optimal depth for insertion of a left-sided central venous catheter in children. Using 3D chest computed tomography angiography, we measured the distance from a point where the internal jugular vein is at the superior border of the clavicle, and from a point where the subclavian vein is inferior to the anterior border of the clavicle, to the junction of the superior vena cava and the right atrium in 257 children. Linear regression analysis revealed that the distances correlated with age, weight and height. Simple formulae for the depth of a central venous catheter via the left internal jugular vein (0.07 × height (cm)) and the left subclavian vein (0.08 × height (cm)) were developed to predict placement of the central venous catheter tip at the junction of the superior vena cava with the right atrium. Using these fomulae, the proportion of catheter tips predicted to be correctly located was 98.5% (95% CI 96.8-100%) and 94.0% (95% CI 90.8-97.3%), respectively.

Ultrasound-guided subclavian venous catheterisation - is this the way forward? A narrative review.

Central venous catheterisation is a commonly performed procedure in anaesthesia, critical care, acute and emergency medicine. Traditionally, subclavian venous catheterisation has been performed using the landmark technique and because of the complications associated with this technique, it is not commonly performed in the United Kingdom - where the accepted practice is ultrasound-guided internal jugular vein catheterisation. Subclavian vein catheterisation offers particular advantages over the internal jugular and femoral vein sites such as reduced rates of line-related sepsis, improved patient comfort and swifter access in trauma situations where the internal jugular vein may not be easily accessible. There is a growing body of evidence to suggest a potential emerging role for ultrasound-guided subclavian vein catheterisation. Barriers to this approach include many physicians still believing that the clavicle obscures imaging of the vein. In this article, we review the evidence supporting ultrasound-guided subclavian vein catheterisation and ask the question whether, in view of it potential advantages, it could be the way forward?

Teaching a sonographically guided invasive procedure to first-year medical students using a novel finger transducer.

OBJECTIVES: The exposure to ultrasound technology in medicine is increasing at multiple training levels. Ultrasound transducers have evolved to provide higher-resolution imaging for more accurate structural identification, with few improvements in ease of use. This study investigated a novel finger ultrasound transducer used by first-year medical students conducting structural identification and practicing an invasive procedure. METHODS: A literature search was conducted on texts, specialty journals, and websites regarding the anatomy of internal jugular and subclavian vein central line placement with sonographic guidance and the use of a finger transducer. First-year medical students performed timed sonographically guided cannulation on the internal jugular and subclavian veins on a phantom torso and identified the internal jugular and subclavian veins on a healthy volunteer using the finger transducer and a conventional transducer. After exposure to both transducers, a survey was taken regarding transducer preference. RESULTS: The literature search revealed no studies comparing finger and classic transducers or sonographically guided central line techniques being conducted by first-year medical students. The students identified and cannulated the internal jugular and subclavian veins using both transducers. Survey results revealed that 70% of the students preferred the finger transducer. CONCLUSIONS: This study showed that first-year medical students could interpret sonographic anatomy while conducting a clinical procedure. The finger transducer proved successful in structure identification and was preferred to the classic transducer because of its combined tactile presence. This pilot study of a novel finger transducer showed the benefits of combining palpatory skills with ultrasound technology in teaching first-year medical students to perform invasive procedures.

Descriptive anatomy of the interscalene triangle and the costoclavicular space and their relationship to thoracic outlet syndrome: a study of 60 cadavers.

OBJECTIVE: Thoracic outlet syndrome classically results from constrictions in 1 or more of 3 specific anatomical locations: the interscalene triangle, costoclavicular space, and coracopectoral tunnel. Magnetic resonance and computed tomographic imaging studies suggest that, of the 3 potential locations for constriction, the costoclavicular space is the most susceptible to compression. This study of human cadavers aims to expand on the descriptive anatomy of the interscalene triangle and associated costoclavicular space. METHODS: The interscalene angle, interscalene triangle base, and costoclavicular space were measured on 120 sides of embalmed human cadavers. Linear distances and angles were measured using a caliper and protractor, respectively. The data were analyzed by calculating the mean, range, and standard deviation. RESULTS: The range for the interscalene base was 0 to 21.0 mm with a mean of 10.7 mm. For the interscalene angle, the range was 4° to 22° with a mean of 11.3°. Measurements for the costoclavicular space ranged from 6 to 30.9 mm with a mean of 13.5 mm. CONCLUSIONS: No significant differences were observed between left and right interscalene triangles or costoclavicular spaces; furthermore, there were no differences between the sexes concerning these 2 locations.

Position of valves within the subclavian and axillary veins.

BACKGROUND: The aim of this explorative morphologic study was to determine the position and frequency of the valves in the axillary and subclavian veins. METHODS: The position and frequency of the valves in the subclavian and axillary veins were studied macroscopically in 59 limbs from 30 cadavers. We measured in situ with a measuring tape, starting from the venous angle toward the initiation of the axillary vein. All cadavers were bequeathed by informed consent. RESULTS: A terminal valve existed in all subclavian veins within the range of 0.0 to 27.5 mm (mean: left, 13.87 mm; right, 9.78 mm) distally to the venous angle; a second valve existed in one left and one right subclavian vein at a distance of 30.0 and 30.5 mm, respectively. All left axillary veins had a "most proximal" valve (mean, 103.4 mm), 73.3% also possessed a second valve (mean, 140.48 mm), and 16.7% had a third valve (mean, 153.9 mm). All right axillary veins possessed at least one valve (mean, 100.07 mm), 75.86% had a second valve (mean, 134.55 mm), 34.48% also had a third valve (mean, 157.30 mm), and 10.3% had a fourth valve (mean, 140.0 mm). CONCLUSIONS: All of the axillary and subclavian veins in our specimens possessed at least one valve. All the valves in the subclavian veins were concentrated to the proximal half, resulting in a valveless distal half. The subclavian vein rarely had a second valve. The valves in the axillary veins were located in the distal half, resulting in a valveless proximal half. The axillary vein can have one to four valves. No relation was evident between the frequency of the valves and the age of the donors when they died. Many other factors may influence the frequency of the valves in the axillary vein.

Variable anatomical relationship of phrenic nerve and subclavian vein: clinical implication for subclavian vein catheterization.

BACKGROUND: During subclavian vein catheterization, a potential, but rare, hazard is the phrenic nerve injury, which compromises respiratory function. We conducted a cadaver study focused on the possible anatomical relationships between the subclavian vein and the phrenic nerve. METHODS: Forty-two adult cadavers (84 heminecks) were dissected. Special attention was given to the topography of the phrenic nerve and subclavian vein. RESULTS: In all but three cases (81 of 84), normal topography was present, that is, the nerve was posterior to the vein. In two cases, the phrenic nerve crossed anterior to the subclavian vein and in one case traversed the anterior wall of the subclavian vein. CONCLUSIONS: Variants of the relationship of the subclavian vein and the phrenic nerve should be familiar to anaesthesiologists during subclavian vein cannulation in order to achieve successful vein approach without causing phrenic nerve palsy.

Sonoanatomy of the vasculature at the supraclavicular and interscalene regions relevant for brachial plexus block.

BACKGROUND: Our aim in this observational study was to utilize ultrasound, as well as anatomic dissection, to document the frequency with which branches of the subclavian vessels are found in close association with the brachial plexus at the locations of supraclavicular and interscalene brachial plexus block. METHODS: Ultrasound was utilized to document the presence of branches of the subclavian vein and artery, adjacent to the brachial plexus in the supraclavicular and in the interscalene region in 50 patients undergoing shoulder surgery. The position, depth, and dimensions of the vessels were described, and the origin determined when possible. In addition, the posterior triangle of the neck on both sides of three non-preserved cadavers was dissected to evaluate the vascular anatomy and correlate the ultrasound findings. RESULTS: Ultrasound scanning revealed an arterial branch adjacent to, or passing directly through, the brachial plexus in the supraclavicular region in 43/50 (86%) patients. Within the interscalene region, an artery was identified coursing in a lateral direction in 45/50 (90%) of cases, while a corresponding small vein, coursing medial to lateral in this area, was noted in 23/50 (46%) of cases. CONCLUSIONS: Small branch vessels from the subclavian artery and vein were frequently evident, on ultrasound imaging, in close association with the nerve elements of the brachial plexus in the supraclavicular and interscalene regions. Appreciation of the presence of these vessels and their likely origin and course will aid the anesthesiologist in planning a safe nerve block.

Anatomy of the thoracic duct.

The thoracic duct is a major anatomic structure of the upper part of the abdomen, chest, and the lower part of the neck. This article reviews the embryology, anatomy, and multiple variations of the thoracic duct. Proper knowledge of this anatomy should ease understanding the pathophysiology of diseases involving the lymph channels and also prevent injury to the duct during major procedures in which the duct or its tributaries can be involved.