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Locating the optimal internal jugular target site for central venous line placement
Journal of Clinical Anesthesia (2016) 33, 198–202
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 structures. This paradigm is largely being displaced, as ultrasound has become routine practice, raising new considerations 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 tomography 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 thoracic cavity. Main results: We revealed that as the internal jugular descends into the thorax, the area of the vessel increases 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: [email protected]fl.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.
Optimal IJ target site for CVL placement
199
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 ipsilateral 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 tomography (CT) exams. These landmarks were chosen because radiologists 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).
200
C.R. Giordano et al.
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).
through CVL. We believe that in identifying a predictable anatomic change in IJ diameter, the traditional landmark IJ approach involving a more cephalad region can be replaced with a larger target that is more caudad. Subsequently, we believe this will result in more successful first attempts, thus resulting in less arterial punctures and other complications.
These locations were at the levels of the anterior margin of cervical 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
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 consecutive CT scans of the neck with intravenous contrast performed 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 suspended 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 laryngectomy and therefore had no available anatomic landmarks. On axial images, the maximum transverse diameter of bilateral IJ veins was measured at three different locations.
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 lower versus mid versus upper) likewise used an analysis of variance 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, given the application of repeated measurements per subject. Pairwise differences among main effects were calculated using least-squares differences applying the Tukey method for post hoc comparisons. Studentized residuals were examined to confirm 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).
Optimal IJ target site for CVL placement
201 In aggregate, the right IJ diameter [11.39 mm, 95% confidence 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]. Similarly, 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 significant 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
Fig. 3 (A) Coronal CT reconstruction of the bilateral internal jugular veins. (B) Sagittal CT reconstruction of the right internal jugular vein. (C) Sagittal CT reconstruction of the left internal jugular vein.
3. Results A total of 600 images from 100 adult CT images was initially 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.
Many medical atlases and textbooks (unintentionally or intentionally) 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 because 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 landmarks 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 locate 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
202
C.R. Giordano et al.
Fig. 4 Image from Grant's Atlas of Human Anatomy. Common depiction of the IJ vein as a perfectly cylindrical column exiting the cranial vault and joining the subclavian vein.
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 principles 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 progressively increases in size as it descends into the thoracic cavity. This translates into a larger target area for central line placement the farther caudally one accesses the neck, with understanding 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].
References [1] Botha R, van Schoor AN, Boon JM, Becker JH, Meiring JH. Anatomical considerations of the anterior approach for central venous catheter placement. Clin Anat 2006;19:101-5. [2] Troianos CA, Jobes DR, Ellison N. Ultrasound-guided cannulation of the internal jugular vein. A prospective, randomized study. Anesth Analg 1991;72:823-6. [3] Mallory DL, McGee WT, Shawker TH, et al. Ultrasound guidance improves the success rate of internal jugular vein cannulation. A prospective, randomized trial. Chest 1990;98:157-60. [4] Gray H. Gray's anatomy: the classics collectors. 28th ed. New York: Random House; 1966. [5] Agur A, Lee MJ. Grant's atlas of anatomy. 10th ed. Philadelphia: Lippincott, Williams, and Wilkins; 1999. [6] Netter F. Netter's atlas of human anatomy. Yardley, PA: ICON Learning Systems; 1989. [7] Lobato EB, Sulek CA, Moody RL, Morey TE. Cross-sectional area of the right and left internal jugular veins. J Cardiothorac Vasc Anesth 1999;13: 136-8. [8] Tartière D, Seguin P, Juhel C, Laviolle B, Mallédant Y. Estimation of the diameter and cross-sectional area of the internal jugular veins in adult patients. Crit Care 2009;13:R197. [9] Sulek CA, Blas ML, Lobato EB. A randomized study of left versus right internal jugular vein cannulation in adults. J Clin Anesth 2000;12:142-5. [10] Nassar B, Deol GR, Ashby A, Collett N, Schmidt GA. Trendelenburg position does not increase cross-sectional area of the internal jugular vein predictably. Chest 2013;144:177-82. [11] Botero M, White SE, Younginer JG, Lobato EB. Effects of Trendelenburg position and positive intrathoracic pressure on internal jugular vein cross-sectional area in anesthetized children. J Clin Anesth 2001;13:90-3. [12] Sulek C, Gravenstein N, Blackshear R, Weiss L. Head rotation during internal jugular vein cannulation and the risk of carotid artery puncture. Anesth Analg 1996;86:125-8.
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 structures. This paradigm is largely being displaced, as ultrasound has become routine practice, raising new considerations 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 tomography 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 thoracic cavity. Main results: We revealed that as the internal jugular descends into the thorax, the area of the vessel increases 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: [email protected]fl.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.
Optimal IJ target site for CVL placement
199
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 ipsilateral 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 tomography (CT) exams. These landmarks were chosen because radiologists 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).
200
C.R. Giordano et al.
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).
through CVL. We believe that in identifying a predictable anatomic change in IJ diameter, the traditional landmark IJ approach involving a more cephalad region can be replaced with a larger target that is more caudad. Subsequently, we believe this will result in more successful first attempts, thus resulting in less arterial punctures and other complications.
These locations were at the levels of the anterior margin of cervical 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
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 consecutive CT scans of the neck with intravenous contrast performed 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 suspended 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 laryngectomy and therefore had no available anatomic landmarks. On axial images, the maximum transverse diameter of bilateral IJ veins was measured at three different locations.
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 lower versus mid versus upper) likewise used an analysis of variance 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, given the application of repeated measurements per subject. Pairwise differences among main effects were calculated using least-squares differences applying the Tukey method for post hoc comparisons. Studentized residuals were examined to confirm 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).
Optimal IJ target site for CVL placement
201 In aggregate, the right IJ diameter [11.39 mm, 95% confidence 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]. Similarly, 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 significant 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
Fig. 3 (A) Coronal CT reconstruction of the bilateral internal jugular veins. (B) Sagittal CT reconstruction of the right internal jugular vein. (C) Sagittal CT reconstruction of the left internal jugular vein.
3. Results A total of 600 images from 100 adult CT images was initially 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.
Many medical atlases and textbooks (unintentionally or intentionally) 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 because 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 landmarks 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 locate 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
202
C.R. Giordano et al.
Fig. 4 Image from Grant's Atlas of Human Anatomy. Common depiction of the IJ vein as a perfectly cylindrical column exiting the cranial vault and joining the subclavian vein.
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 principles 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 progressively increases in size as it descends into the thoracic cavity. This translates into a larger target area for central line placement the farther caudally one accesses the neck, with understanding 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].
References [1] Botha R, van Schoor AN, Boon JM, Becker JH, Meiring JH. Anatomical considerations of the anterior approach for central venous catheter placement. Clin Anat 2006;19:101-5. [2] Troianos CA, Jobes DR, Ellison N. Ultrasound-guided cannulation of the internal jugular vein. A prospective, randomized study. Anesth Analg 1991;72:823-6. [3] Mallory DL, McGee WT, Shawker TH, et al. Ultrasound guidance improves the success rate of internal jugular vein cannulation. A prospective, randomized trial. Chest 1990;98:157-60. [4] Gray H. Gray's anatomy: the classics collectors. 28th ed. New York: Random House; 1966. [5] Agur A, Lee MJ. Grant's atlas of anatomy. 10th ed. Philadelphia: Lippincott, Williams, and Wilkins; 1999. [6] Netter F. Netter's atlas of human anatomy. Yardley, PA: ICON Learning Systems; 1989. [7] Lobato EB, Sulek CA, Moody RL, Morey TE. Cross-sectional area of the right and left internal jugular veins. J Cardiothorac Vasc Anesth 1999;13: 136-8. [8] Tartière D, Seguin P, Juhel C, Laviolle B, Mallédant Y. Estimation of the diameter and cross-sectional area of the internal jugular veins in adult patients. Crit Care 2009;13:R197. [9] Sulek CA, Blas ML, Lobato EB. A randomized study of left versus right internal jugular vein cannulation in adults. J Clin Anesth 2000;12:142-5. [10] Nassar B, Deol GR, Ashby A, Collett N, Schmidt GA. Trendelenburg position does not increase cross-sectional area of the internal jugular vein predictably. Chest 2013;144:177-82. [11] Botero M, White SE, Younginer JG, Lobato EB. Effects of Trendelenburg position and positive intrathoracic pressure on internal jugular vein cross-sectional area in anesthetized children. J Clin Anesth 2001;13:90-3. [12] Sulek C, Gravenstein N, Blackshear R, Weiss L. Head rotation during internal jugular vein cannulation and the risk of carotid artery puncture. Anesth Analg 1996;86:125-8.