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Anatomic Basis of Safe Percutaneous SubclavianVenous Catheterization

Bien-Keem Tan, MBBS(Sing), FRCS(Ed), Soo-Wan Hong, MBBS(Sing), FRCS(Glasg), FAMS(Plast Surg),

Martin H. S. Huang, MBBS(Sing), FRCS(Ed), FRCS(Glasg), MMed Surg(Sing), FAMS(Plast Surg), and

Seng-Teik Lee, MBBS(Adel), FRCS(Ed), FAMS(Plast Surg)

Background: The technique of percutaneous catheterizationof the subclavian vein by the infraclavicular approach is depen-dent on the location of the subclavian vein in relation to theclavicle. The purpose of this study was to analyze the anatomicrelationship between these two structures and how it is influ-enced by changes in shoulder positioning.

Methods: Dissections of the infraclavicular region were per-formed in seven fresh cadavers and linear measurements madeto determine the extent of overlap between the vein and the

clavicle in different shoulder positions.Results: When the shoulder was in neutral position, the sub-

clavian vein was overlapped by the medial third or more of theclavicle and this segment of bone was able to serve as a land-

mark for the vein. However, shoulder elevation displaced theclavicle cephalad and reduced the degree of overlap. Mild shoul-der retraction increased the area of contact between the veinand the undersurface of the clavicle, whereas protraction liftedthe clavicle off the vein.

Conclusion: Infraclavicular subclavian venipuncture shouldbe performed with shoulders in a neutral position and also inslight retraction. An appreciation of the anatomic relationshipbetween the clavicle and the subclavian vein is the key to suc-

cessful execution of this technique.Key Words: Subclavian venipuncture, Infraclavicular ap-

proach, Cadaveric dissections, Anatomic relationship, Shoulderpositioning.

Percutaneous catheterization of the subclavian vein by

means of the infraclavicular approach has been estab-

lished as a relatively safe and reliable method of access

to the central veins since it was introduced by Aubaniac in

1952.1 However, it is a blind procedure, because the subcla-

vian vein cannot be visualized or palpated. Serious compli-

cations of this technique have been reported in the

literature,26

the major hazards being pneumothorax and sub-clavian artery injury. Accidental puncture of the pleura can

occur because, beyond the protective edge of the first rib, the

pleura lies only 5 mm posterior to the subclavian vein.3 The

subclavian artery is also vulnerable to injury because it lies

just behind and slightly superior to the path of the subclavian

vein.

Because the clavicle is used as a landmark for locating the

subclavian vein, an understanding of the relationship between

these two structures is critical to the successful execution of

this technique. This important relationship changes with dif-

ferent shoulder positions. For example, if the shoulder is

elevated, the acromial end of the clavicle moves cephalad andthe vein assumes a more inferior and medial relationship to it

(Fig. 1). This was pointed out in a radiologic study by Land

who demonstrated on single-view venograms that the subcla-

vian vein, which was in the path of the needle when the

shoulder was in neutral position, may be out of its path when

the shoulder was abducted or elevated.7,8

By using his observations as a basis for further investiga-

tion, anatomic dissections were performed to study the spatial

relationship between the clavicle and the subclavian vein,

correlating this with surface markings pertinent to the tech-

nique of subclavian venipuncture. Changes in the relationship

were studied in two planes with the shoulder elevated, de-pressed, retracted or protracted. Shoulder elevation is defined

as shrugging the shoulders. Shoulder depression is the

reverse movement. Protraction refers to forward movement

of the shoulder, as in pushing, thrusting, or punching. Back-

ward movement, as in bracing the shoulders, is termed re-

traction.

Submitted for publication January 29, 1998.

Accepted for publication October 6, 1999.From the Department of Plastic Surgery, Singapore General Hospital,

Singapore.

This study was supported by a grant from the Department of ClinicalResearch, Ministry of Health, Singapore.

Address for reprints: Bien-Keem Tan, MBBS(Sing), FRCS(Ed), Depart-ment of Plastic Surgery, Singapore General Hospital, Outram Road, Singa-

pore 169608.

FIG 1. Positional relationship of the subclavian vein to the clavicle is expressed by

the ratio VJ:LC. Comparison of shoulder elevation (A) with neutral position (B)

shows that during elevation, the vein is in a more medial and inferior position,

hence VJ:LC decreases. Triangles, midpoint of clavicle. The asterisk is the point

along the lower border of the clavicle where the center of the vein crosses it. VJ,

distance between the sternoclavicular joint and the point on the lower border of the

clavicle where the center of the vein crosses it. LC, length of the clavicle.

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Vol. 48, No. 1

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MATERIALS AND METHODS

Anatomic dissections of the infraclavicular region and the

root of the neck were performed on seven adult fresh cadav-

ers (four men and three women). A skin incision was made

along the entire length of the clavicle, beginning from the

sternoclavicular joint to the acromioclavicular joint. The sub-

clavian vein was exposed by detaching the clavicular origins

of the pectoralis major and the subclavius muscles. Superi-orly, a skin-platysmal flap was raised cephalad to expose the

root of the neck. The internal jugular vein was uncovered by

dividing the sternal and clavicular heads of the sternocleido-

mastoid muscle. This vessel was then traced to its junction

with the subclavian vein from which the brachiocephalic vein

arose, behind the sternoclavicular joint.

Two linear measurements were made (Fig. 1): the length of

the clavicle (LC), and, the distance between the sternoclavic-

ular joint and the point on the lower border of the clavicle

crossed by the center of the subclavian vein (VJ). These

measurements were made with the cadaver supine, simulating

clinical practice. The shoulders were kept in neutral positionand with the arms by the sides. Similar linear measurements

were then made with the shoulders maximally elevated

(shrugged) for comparison. The effect of shoulder protraction

on the positional relationship between the clavicle and the

subclavian vein was also examined. All measurements were

made within the limits of normal shoulder movement, with all

articulations of the shoulder girdle intact to minimize abnor-

mal shoulder mobility.

RESULTS

The relationship of the subclavian vein to the clavicle at the

point where the vein crossed its lower border was expressed

as a ratio formulated by Land.7 This was derived by taking

the distance from the center of the vein to the sternoclavicular

joint (VJ) and dividing this by the length of the clavicle (LC)

(Fig. 1).

In neutral position, the median VJ:LC ratio on the right

side was 0.40 (range, 0.32 to 0.46); whereas on the left, the

median VJ:LC ratio was 0.34 (range, 0.26 to 0.41). When the

shoulders were maximally elevated, the median VJ:LC ratio

for the right was 0.34 (range, 0.23 to 0.38) compared with the

left, which was 0.31 (range, 0.23 to 0.35) (Table 1). Nogender difference was noted. These results indicate that the

point at which the subclavian vein crossed the inferior border

of the clavicle shifted medially when the shoulders were

elevated (Figs. 1, 2, and 3). The extent of medial displace-

ment of this point ranged from 0.5 to 1.5 cm, depending on

the degree of shoulder elevation.

Retraction of the shoulders increased the area of contact

between the vein and the undersurface of the clavicle (Fig. 4).

Conversely, protraction lifted the clavicle off the vein and

reduced the segment of vein in contact (Fig. 5). The relation-

ship between bone and vein was most consistent medially

where the subclavian vein joined the internal jugular vein.

DISCUSSION

Several practical points have been highlighted in the

literature712 to improve both the safety and success of in-

fraclavicular subclavian venipuncture. Among these, patient

positioning and the technique of needle insertion seem to bethe most important. However, although these recommenda-

TABLE 1. Ratio of the distances (VJ:LC) expresses the positional relationship of

the subclavian vein to the clavicle a

CadaverNo.

VJ:LC

Right Shoulder Position Left Shoulder Position

Neutral Elevated Neutral Elevated

1 0.32 0.26 0.26 0.23

2 0.34 0.31 0.34 0.31

3 0.40 0.34 0.34 0.31

4 0.41 0.35 0.35 0.325 0.43 0.38 0.34 0.31

6 0.46 0.35 0.41 0.35

7 0.33 0.23 0.36 0.26

a VJ, distance between the sternoclavicular joint and the point on

the lower border of the clavicle where the center of the vein crosses

it. LC, length of the clavicle.

FIG 2. Infraclavicular region (right side, anterior view). The shoulders have been

placed in the neutral position. The vein crosses the lower border of the clavicle

slightly lateral to its medial third in this specimen. Midpoint of clavicle (arrow).

FIG 3. Infraclavicular region (right side, anterior view). The shoulders have been

elevated. The vein crosses the lower border of the clavicle within the medial third

of the bone. The midpoint of the clavicle (arrow) has moved cephalad in relation to

the path of the vein.

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tions have been widely accepted, their anatomic basis re-

mains unclear.

Patient Positioning

It is usually recommended that the patients shoulders be

placed in an anatomically neutral position and the arms kept

by the side. In addition, a small sandbag or pillow should be

inserted underneath the vertebral column between the scap-

ulae.

The findings of the present study suggest that placing the

shoulders in a neutral position brings the vein and the clavicle

together (Figs. 1 and 2). However, it is a common mistake to

assume that the shoulders are in neutral position as long as the

arms are by the side. This is because there is a naturaltendency for the shoulders to slide cephalad when the body is

in the Trendelenburg position, a position routinely used for

the procedure. Therefore, a conscious effort should be made

to counter this tendency by applying gentle traction in a

caudal direction on both shoulders.

Another recommendation is to place a small sandbag be-

neath the vertebral column between the scapulae to allow theshoulders to fall back. This maneuver serves two purposes:

first, it prevents interference with the path of needle insertion

by the humeral head,9 thus ensuring that the needle and

syringe are always parallel to the coronal plane. Second, it

brings the subclavian vein into close contact with the under-

surface of the clavicle (Fig. 4), which is desirable for accurate

identification of the vein.

Technique of Needle Insertion

Three techniques have been described for the infraclavicular

approach. They differ in the point of insertion of the needle in

relation to the midpoint of the clavicle (Fig. 6).

Most authors3,13,14 use the midpoint approach, which was

originally described by Aubaniac1 in 1952 (Fig. 6). The

surface marking of the entry point of the needle is 1 to 2 cm

inferior to the lower border of the clavicle along the midcla-

vicular line. The needle tip is directed at the upper border of

the suprasternal notch, keeping parallel to the coronal plane.

If this landmark is not clearly defined, a finger tip can be

placed in the suprasternal notch as a target. Constant negative

pressure is applied on the syringe as the needle is advanced

posterior to the clavicle, keeping close to its undersurface. A

flashback of blood indicates that the vein has been entered,

and this entrance should occur at the junction between the

middle and medial thirds of the clavicle. The technique aims

to enter the subclavian vein just when it begins its passage

underneath the clavicle. Neutral shoulder positioning sets the

correct bone-vein relationship for this point of entrance to

occur. On the other hand, shoulder elevation and protraction

disrupt this relationship, thereby reducing the reliability of

anatomic landmarks.

Tofield10 in 1969 advocated a more lateral approach in

which the point of needle insertion was lateral (precise dis-

tance was not given) to the midclavicular line. The author

stated that this approach improved the safety of the procedure

but did not provide the anatomic basis of the recommenda-

tion. The rationale for this approach can be understood by

FIG 4. Root of the neck in a decapitated cadaver (right side, superior view). The

shoulders have been retracted by placing a sandbag under the vertebral column.

The needle tip is resting against the wall of the right subclavian vein. IJV, internal

jugular vein; BP, brachial plexus; T, trachea; C6, body of the sixth cervical

vertebra.

FIG 5. Root of the neck (right side, superior view). The shoulders have been

protracted. The clavicle has been lifted off the subclavian vein. The needle passed

along the undersurface of the bone has missed the vein. IJV, internal jugular vein;

SCV, subclavian vein; SA, scalenus anterior; BP, brachial plexus.

FIG 6. Infraclavicular approaches to the subclavian vein. 1: Aubaniac (1952)1;

Wilson et al. (1962)13; 2: Davidson et al. (1963)15, Corwin and Moseley (1966)16,

Morgil et al. (1967)9; 3: Tofield (1969) 10.

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considering the infraclavicular contour of the upper chest.

The clavicle is a long bone whose shaft has a double curve in

the horizontal plane. The medial two-thirds of the bone is

convex anteriorly, whereas the lateral third is concave ante-

riorly. A needle inserted along this concavity and maintained

level will automatically find the vein along the undersurface

of the bone. Although this lateral approach is safe, the needle

may not be sufficiently long in patients who have thick chest

walls or who are obese.Morgil et al.,9 Davidson et al.,15 and Corwin and

Moseley16 (Fig. 6) described a medial approach in which the

needle was inserted at the junction between the middle and

inner thirds of the lower border of the clavicle. Christensen et

al.4 described a point of insertion located even more medially,

which was adjacent to the lateral palpable margin of the

costoclavicular ligaments. The needle was directed at a point

just above the suprasternal notch, and aimed to penetrate the

vein as it runs in the groove between the clavicle and the first

rib. The main advantage of this medial approach is the rela-

tively constant course of the vein in relation to the bone.

Because the site of the costoclavicular ligaments is the ful-crum of clavicular movements,17 bone-vein relationships re-

main fairly constant at this point. Furthermore, a broad target

formed by portions of the three great veins, i.e., the subcla-

vian, the internal jugular, and the innominate, increases the

likelihood of success.

But, the following anatomic caveats should be recognized

when attempting to puncture the vein by using the medial

approach: It is more difficult to maintain the needle in a

horizontal position when the point of insertion is medial; The

thickness of the clavicle increases from lateral to medial.

(The diameter of the sternal end is 1.5 to 2 times the diameter

of the lateral half of the clavicle). Thus, it is more difficult toinsinuate the tip of a straight needle under the medial part of

the clavicle because the increased thickness of the bone

mandates a steeper approach; The needle has to pass through

a thicker layer of intervening soft tissue, including the cos-

toclavicular ligaments. A large-bore needle can sometimes

cut a core of tissue in its lumen.

The cannulation failure rate has been reported to be be-

tween 6 and 20% by authors who use the medial approach.4,15

It seems logical that these factors could be contributory to

failure. Christensen et al.,4 Morgil et al.,9 and Corwin and

Moseley16 have attributed their failures to obesity and chest

wall thickness. Clearly, cannulation failure in these cases isdue to insufficient cannula length for a lateral and level

approach to the vein. Furthermore, excessive fat distributed

around the arms and upper chest in grossly obese patients

may prevent neutral positioning of the shoulders.

The consistent relationship between the vein and clavicle

when the shoulder is in neutral position was documented by

Land.7 In this study, right subclavian venograms were per-

formed in 70 adult patients undergoing intravenous urogra-

phy. Land demonstrated that in 67% of patients examined in

the neutral position, the vein passed beneath the clavicle. In

30% of the 70 cases, the vein ran more cephalad. Only in one

patient did the vein not pass beneath the clavicle. In another

study, Land showed that on the left side, the vein was sited

more medially in relation to the clavicle.8

The findings of the present study suggest that gentle shoul-

der retraction brings the clavicle and the subclavian vein

together, whereas shoulder protraction lifts the clavicle off

the subclavian vein. One should be aware of this in patients

who have neck or shoulder stiffness caused by underlying

joint pathologic conditions. In such instances, the clavicle

may be a poor landmark for the subclavian vein becauseneutral positioning is difficult to achieve.

On the other hand, excessive shoulder retraction may result

in compression of the vein in the groove between the first rib

and the clavicle. This was demonstrated by Jesseph et al.12

who showed on magnetic resonance imaging in five individ-

uals that there was a decrease in the anteroposterior diameter

of the subclavian vein when the shoulders were braced back-

ward. However, this change should not be an issue if the

attempt to cannulate the vein is made lateral to this narrow

groove.

In clinical situations in which correct shoulder positioning

cannot be achieved, such as the presence of cervical spine andshoulder joint pathologic conditions, obesity, or edema of the

chest wall and upper limbs attributable to extensive burns, a

more medial approach may be attempted. Although the vein

may bear a more constant relationship with the clavicle me-

dially, the hazards of the medial approach should be recog-

nized; in attempting to negotiate the needle under a thick

clavicular head, there is a risk of injury to deep structures.

Subclavian Venipuncture in Children

Eichelberger et al. reported that central venous catheteriza-

tion in neonates and children by using the infraclavicular

route is safe.18,19 According to the authors technique, the

skin puncture is made at the deltopectoral groove, and by

advancing the needle at a gradual angle, the subclavian vein

is located in the groove between the clavicle and the first rib.

In neonates the subclavian vein position is more cephalad,

hence the needle is directed at a point midway between the

chin and the sternal notch. In older children, the course of the

subclavian vein becomes less cephalad and the syringe sys-

tem is directed more medially and toward the sternal notch.18,19

Despite anatomic differences attributable to growth and devel-

opment, Eichelberger et al. have shown that the vein can be

consistently located within the medial third of the clavicle. This

finding concurs with our observation that the relationship be-

tween the vein and clavicle is more constant medially, and

consequently less affected by shoulder positioning.

Supraclavicular Approach to the Subclavian Vein

Since its original description by Yoffa in 1965,20 this tech-

nique has gained popularity because of the relatively short

and direct approach to the vein.21,22 The needle is inserted in

the angle formed by the clavicular head of the sternomastoid

muscle and the upper border of the clavicle. Once the skin is

entered, the syringe is depressed 15 degrees below the coro-

nal plane and the needle is directed at an angle 45 degrees to

the sagittal plane. The vein is met at an average depth of 1 to

1.5 cm from the skin. From an anatomic standpoint, this

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approach is reliable because of the constant relationship be-

tween the subclavian vein and the medial third of the clavicle.

And as long as the depth and direction of needle penetration

are controlled, the method is safe.

CONCLUSIONS

The findings of this anatomic investigation indicate that the

subclavian vein passes posterior to the clavicle close to the

junction between the inner and middle thirds of the bone.

Elevation of the shoulder alters this relationship. The vein is

more caudad in these situations, and the point at which it

crosses the clavicle is more medial. Therefore, during percu-

taneous puncture of the subclavian vein, the vein which is in

the path of the puncture needle with the arm in the neutral

position may be out of its path when the shoulder is elevated.

The subclavian vein is closely positioned to the posterior

surface of the inner third of the clavicle as the vein passes

medially to join the internal jugular vein. Protraction of the

shoulders moves the clavicle anteriorly away from the vein.

In this position, a needle which is advanced along the poste-

rior surface of the medial third of the bone will not find thesubclavian vein.

Thus, infraclavicular subclavian venipuncture should be

performed with shoulders in the neutral position and in slight

retraction. Understanding the variable anatomic relationship

between the clavicle and the subclavian vein is critical to the

success and safety of subclavian venipuncture.

Acknowledgments

The authors thank Professor T. C. Chao, Director of the Institute ofScience and Forensic Medicine, Ministry of Health, Singapore forproviding the specimens; Dr. Peter Mack, Director of the Depart-ment of Experimental Surgery, Singapore General Hospital, for theuse of facilities; Mr. Robert Ng, for technical support, and Dr. S. C.Aung for critique of the manuscript.

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