1. Original contribution
Locating the optimal internal jugular target site
for central venous line placement☆
Chris R. Giordano MD (Assistant Professor of Anesthesiology; Liver Transplant Division
Chief; Anesthesiology Clerkship Director)⁎,
Kevin R. Murtagh MD (Resident in Radiology)1
, Jaime Mills (Undergraduate Student)2
,
Lori A. Deitte MD (Professor of Radiology)3
,
Mark J. Rice MD (Professor of Anesthesiology)3
,
Patrick J. Tighe MD, MS (Assistant Professor of Anesthesiology; Program Director,
Perioperative Analytics Group; Joint Assistant Professor of Orthopedics)
Department of Anesthesiology, University of Florida, Gainesville, FL 32610, USA
Received 24 March 2015; revised 16 March 2016; accepted 17 March 2016
Keywords:
Internal jugular size
differences;
Central line placement;
Ultrasound guidance;
Internal jugular anatomy;
Neck external landmarks
Abstract
Study objective: Historically, the placement of internal jugular central venous lines has been accomplished
by using external landmarks to help identify target-rich locations in order to steer clear of dangerous struc-
tures. This paradigm is largely being displaced, as ultrasound has become routine practice, raising new con-
siderations regarding target locations and risk mitigation. Most human anatomy texts depict the internal
jugular vein as a straight columnar structure that exits the cranial vault the same size that it enters the thoracic
cavity. We dispute the notion that the internal jugulars are cylindrical columns that symmetrically descend
into the thoracic cavity, and purport that they are asymmetric conical structures.
Design: The primary aim of this study was to evaluate 100 consecutive adult chest and neck computed to-
mography exams that were imaged at an inpatient hospital. We measured the internal jugular on the left and
right sides at three different levels to look for differences in size as the internal jugular descends into the tho-
racic cavity.
Main results: We revealed that as the internal jugular descends into the thorax, the area of the vessel in-
creases and geometrically resembles a conical structure. We also reconfirmed that the left internal jugular
is smaller than the right internal jugular.
Conclusions: Understanding that the largest target area for central venous line placement is the lower portion
of the right internal jugular vein will help to better target vascular access for central line placement. This is
☆
This work was supported by the Departments of Anesthesiology and Radiology, and by a K23 grant to Dr. Patrick Tighe (no. K23 GM102697).
⁎ Corresponding author at: Department of Anesthesiology, University of Florida College of Medicine, 1600 SW Archer Road, PO Box 100254, Gainesville, FL
32610, USA. Tel.: +1 352 222 7855; fax: +1 352 392 7029.
E-mail address: cgiordano@anest.ufl.edu (C.R. Giordano).
1
Present address: St. Joseph's Hospital, 3001 West Dr. Martin Luther King Jr. Blvd., Tampa, FL 33607, USA.
2
Present address: Nova Southeastern University, 3301 College Ave., Fort Lauderdale, FL 33314, USA.
3
Present address: Vanderbilt University College of Medicine, 2215 Garland Ave., Nashville, TN 37232, USA.
http://dx.doi.org/10.1016/j.jclinane.2016.03.070
0952-8180/© 2016 Elsevier Inc. All rights reserved.
Journal of Clinical Anesthesia (2016) 33, 198–202

2. the first study the authors are aware of that depicts the internal jugular as a conical structure as opposed to the
commonly depicted symmetrical columnar structure frequently illustrated in anatomy textbooks. This target
area does come with additional risk, as the closer you get to the thoracic cavity, the greater the chances for
lung injury.
© 2016 Elsevier Inc. All rights reserved.
1. Introduction
Historically, the placement of internal jugular (IJ) central
venous lines (CVL) has been accomplished by using external
landmarks to help identify target-rich locations along with
steering clear of dangerous structures such as the carotid
artery or the lung [1]. Some of these landmarks include the
laryngeal cartilage, the carotid pulse, the bifurcation of the
sternocleidomastoid muscle, the sternal notch, and the ipsilat-
eral nipple. This paradigm has largely been abandoned with
the advent of ultrasound (US)-guided CVL placement [2,3],
and now other considerations (including the plane of the US
probe, the approach angle of the needle, and the needle entry
site) are emerging.
Measurement of the varying size of the IJ vein as it courses
the neck has not been, to the best of our knowledge, previously
investigated. The primary aim of this study was to measure the
IJ on the left and right sides at three different levels, including
cervical vertebra one, the hyoid bone, and the cricoid cartilage,
by evaluating 100 consecutive adult neck computed tomogra-
phy (CT) exams. These landmarks were chosen because radi-
ologists frequently use these anatomical areas as points of
demarcation for dividing and measuring. This knowledge
should aid in elucidating the largest target area for IJ access
Fig. 1 Size of internal jugular versus side of neck. The right internal jugular diameter (11.39 mm, 95% CI 10.90–11.90 mm) was greater than
the left side (9.95 mm, 95% CI 9.54–10.36 mm; mean difference 1.44 mm, 95% CI 0.79–2.09 mm, P b .0001).
199Optimal IJ target site for CVL placement

3. through CVL. We believe that in identifying a predictable an-
atomic change in IJ diameter, the traditional landmark IJ ap-
proach involving a more cephalad region can be replaced
with a larger target that is more caudad. Subsequently, we be-
lieve this will result in more successful first attempts, thus
resulting in less arterial punctures and other complications.
2. Materials and methods
The study protocol was approved by the University of
Florida Institutional Review Board (#404–2011), which
determined that informed consent was not necessary for this
retrospective study. A convenient sample of the first 100 con-
secutive CT scans of the neck with intravenous contrast per-
formed from the beginning of May 2012 was included in the
study. All studies performed met an inclusion criteria for a
slice thickness of 3 mm or less to appropriately define small
anatomic changes, and were retrospectively reread specifically
for this study by two board-certified radiologists. All patients
received intravenous contrast for the study, and all imaging
was performed with the patient in a supine position during sus-
pended inspiration. Pediatric patients, defined as those less
than or equal to 17 years old, were excluded. One patient
was excluded because of postoperative changes after total lar-
yngectomy and therefore had no available anatomic land-
marks. On axial images, the maximum transverse diameter
of bilateral IJ veins was measured at three different locations.
These locations were at the levels of the anterior margin of cer-
vical vertebra one, the inferior/anterior border of the hyoid
bone, and the anterior/inferior border of the cricoid cartilage.
Last, the mean diameters of each of the three divisions of the
right and left sides were compared against each other.
2.1. Statistical analysis
Normal distribution was presumed via the Central Limit
Theorem. Comparison of IJ measurements between sides (left
versus right) were made using the t-test, and for level of neck
(lower versus mid versus upper) via an analysis of variance
with post hoc corrections using the Tukey–Kramer method.
A comparison of each site (left versus right, coupled with low-
er versus mid versus upper) likewise used an analysis of vari-
ance along with the Tukey–Kramer method for post hoc
comparison corrections.
For multivariate modeling, we used a mixed model with
subject identification included as a random effect. The main
effects included level of neck, side of neck, and an interaction
term combining level and side of neck. Degrees of freedom
were calculated using the method of Kenward and Roger, giv-
en the application of repeated measurements per subject. Pair-
wise differences among main effects were calculated using
least-squares differences applying the Tukey method for post
hoc comparisons. Studentized residuals were examined to con-
firm normal distribution. alpha was set at P = .05 for all tests.
Analyses were conducted using SAS 9.3 and JMP 10.0.2
(SAS Institute, Cary, NC, USA).
Fig. 2 Size of internal jugular versus level of neck. There were significant aggregate differences between the upper (8.74 mm, 95% CI
8.21–9.26 mm), middle (10.83 mm, 95% CI 10.26–11.39 mm), and lower (12.46 mm, 95% CI 11.85–13.07 mm; P b .0001).
200 C.R. Giordano et al.

4. 3. Results
A total of 600 images from 100 adult CT images was ini-
tially considered for analysis. Six images from a single patient
were excluded because the patient had a laryngectomy that
prevented using the predefined landmarks outlined above.
No missing data were present in the subjects studied.
In aggregate, the right IJ diameter [11.39 mm, 95% confi-
dence interval (CI) 10.90–11.90 mm] was greater than the left
side (9.95 mm, 95% CI 9.54–10.36 mm; mean difference
1.44 mm, 95% CI 0.79–2.09 mm, P b .0001) [Fig. 1]. Simi-
larly, there were significant aggregate differences between
the upper (8.74 mm, 95% CI 8.21–9.26 mm), middle
(10.83 mm, 95% CI 10.26–11.39 mm), and lower
(12.46 mm, 95% CI 11.85–13.07 mm; P b .0001). Post hoc
comparisons demonstrated that the differences were signifi-
cant for upper versus lower (mean difference 3.72 mm, 95%
CI 2.83–4.61), upper versus mid (mean difference 2.09 mm,
95% CI 1.2–2.98, P b .0001), and mid versus lower (mean
difference 1.63 mm, 95% CI 0.74–2.52 mm, P b .0001) IJ
sites [Fig. 2].
In the mixed model, significant main effects included
lower level of neck (estimate 4.41 mm, 95% CI
8.51–9.97 mm, P b .0001), middle level of neck (estimate
2.06 mm, 95% CI 1.23–2.88 mm, P b .0001), left side of
neck (estimate −1.01 mm, 95% CI −0.83 to −0.18 mm,
P = .02), and the interaction between lower neck and left side
of neck (estimate −1.37 mm, 95% CI −2.54 to −0.20 mm,
P = .02). Fig. 3 (a–c) demonstrates in coronal and sagittal
views the increasing diameter of the IJ veins as they exit the
cranial vault and enter the thoracic cavity.
4. Discussion
Many medical atlases and textbooks (unintentionally or in-
tentionally) depict the IJ vein as a perfectly cylindrical column
coursing through the neck as it leaves the cranial vault and
joins the subclavian vein [Fig. 4] [4–6]. This misconception
has had little impact on the external landmarks technique be-
cause locating these external areas was of sole importance
and the varying diameter of the IJ was unknown. Coupled with
this need to identify landmarks was the fear of pneumothorax,
which was generally the main advantage of the IJ approach
over the subclavian vein. Now, with the routine use of US
guidance to assist CVL placement, identifying external land-
marks has fallen by the wayside. Directly viewing the IJ with
US guidance has become the standard for many institutions,
which includes appreciating other internal structures to avoid,
in addition to navigating optimum needle trajectory. Thus, the
correct anatomic depiction of the IJ as it courses through the
neck becomes more appreciable [7].
We believe this is the first study to show that the diameter
of the IJ vein increases as it leaves the cranial vault and joins
the subclavian vein in the chest. The further caudal one
accesses the IJ vein, the larger the diameter the vein will be,
and thus a larger target will be acquired. This must be balanced
with the risk of the needle entering the chest cavity and placing
the cupola of the lung in jeopardy. We believe that US readily
identifies this area at risk for lung injury, and can be used to lo-
cate the largest target as well as structures to avoid. This study
also reaffirms [8,9] that the left IJ vein is smaller in all three
Fig. 3 (A) Coronal CT reconstruction of the bilateral internal jugu-
lar veins. (B) Sagittal CT reconstruction of the right internal jugular
vein. (C) Sagittal CT reconstruction of the left internal jugular vein.
201Optimal IJ target site for CVL placement

5. measured divisions compared to the right-sided divisions of
the IJ vein.
One of the limitations of this study is that the CT images
were acquired with suspended inspiration from patients who
were lying supine and not in the Trendelenburg position. A tenet
of CVL placement is to place the patient in the Trendelenburg
position to avert venous air embolism in the spontaneously
breathing patient and to engorge the vein to increase target size.
This augmentation to the cross-sectional area of the IJ has been
disputed in previous studies, thus its impact may be negligible
[10,11]. Our patients were also not intubated, and positive
pressure ventilation may change the geometry of the vessel
in a similar fashion as Trendelenburg positioning, depending
on when in the cycle airflow ceases. Another limitation is
our postulation that the IJ vein forms a circle that is a simple
shape of Euclidean geometry, which abides by axiomatic prin-
ciples permitting its area for measurement, i.e., area =π × r2.
A final consideration is that none of these imaged patients
had their heads rotated away from the insertion point,
which is a common technique used during IJ placement
and changes the location of the carotid artery relative to
the IJ vein.
We conclude that the IJ vein exits the cranial vault and pro-
gressively increases in size as it descends into the thoracic cav-
ity. This translates into a larger target area for central line
placement the farther caudally one accesses the neck, with un-
derstanding that the more cephalad one approaches the IJ, the
smaller the target area will be, and thus the more likely one will
be to miss the accessing structure altogether [12].
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202 C.R. Giordano et al.