A simple anatomic topographical method for accurate central venous catheter (CVC) placement should decrease serious complications of CVC insertion, such as vascular perforation, arrhythmias, and hydrothorax or cardiac tamponade.
It is usually accepted that 20-cm (left side) or 16-cm (right side) length CVCs should be used in the majority of adult patients when inserting a catheter via the subclavian or jugular veins.1 This method is easy but may not be optimal in every patient. Insertion with electrocardiographic guidance and echocardiography are techniques that may assure correct CVC tip position, but such confirmatory techniques are not used routinely.2,3 Prior topographic methods also have limitations, in that they are only used for the right-sided central vein.4–6
The carina is a reliable landmark to guide appropriate and safe positioning of the CVC tip above the pericardial reflection and to minimize the risk of cardiac tamponade.7 The angle of Louis, the forward prominence formed by the manubriosternal joint, is a surface anatomical landmark that shares the same horizontal plane with the tracheal carina.8
The clavicular notch is an oval articular surface on each side of the sternal manubrium— directed upwards, backwards, and laterally—for articulation with the sternal end of the clavicle, and can be identified by palpation (Fig. 1).9 The internal jugular vein (IJV) and the subclavian vein (SCV) lie beneath the ipsilateral clavicular notch.8
The purpose of this study was to determine whether the measurement of surface landmarks along the course of central veins (IJV, SCV, brachiocephalic vein, superior vena cava) can estimate the approximate insertion depths of both right- and left-sided CVCs via the IJV and SCV.
After having obtained IRB approval and patients' written informed consent, the patients scheduled for neurosurgery or abdominal surgery requiring central venous catheterization were enrolled between March 2008 and September 2008. The patients were assigned randomly to 1 of 4 groups according to computer-generated sequence numbers (right IJV, left IJV, right SCV, and left SCV). Exclusion criteria included anatomical deformities of the neck or chest.
After antiseptic skin preparation and sterile draping, central venous catheterization was performed using a double-lumen CVC (Arrow International Inc., Reading, PA) with the Seldinger technique. The anterior approach, using the sternocleidomastoid muscle as a landmark, was used for IJV catheterization, and the infraclavicular approach was used for SCV catheterization. The patient's head and neck were placed in the neutral position after the insertion of the guidewire.5 To determine the adequate depth for catheter insertion, we performed topographical measurement by placing the catheter naturally with its own curvature over the draped skin (without direct contact with the skin), starting from the insertion point of the needle through the ipsilateral clavicular notch, and to the insertion point of the second right costal cartilage to the manubriosternal joint (Fig. 1). The CVC was then inserted and secured to the depth determined topographically.
The position of the CVC tip, in relation to the carina, was confirmed and measured on a postoperative full-inspiration chest radiograph (CXR) from the Picture Archiving & Communication System (PACS, Infinitt Healthcare Co., Ltd., Seoul, Korea). CVC tips positioned above the carina level were presented in positive values, and those below the carina were presented in negative values. We also measured the angle of the distal 1 cm of the tip to the vertical in the left-sided CVC lines. Assuming that the superior vena cava (SVC) lies approximately vertical, this angle approximates the angle of the CVC tip to the wall of the SVC. The vertical against which the angles were measured was a line connecting the vertebral spinous processes (Fig. 2).10
For the purposes of calculating power, 1 cm away from carina was regarded as a safe CVC tip level and an SD of 1.2 cm was used from a previous study.5 We calculated that a sample size of 48 measurements was needed for a type I error of 0.05 and a power of 80%. A t test was performed for statistical analysis. A P value of <0.05 was considered to be statistically significant. The 95% 2-sided prediction interval was calculated with the following equation:
where T−1[N − 1, τ] = the τth percentile of the Student t cumulative distribution function with (N − 1) df.
There were no patients excluded from enrollment in the study. Patient characteristics and CVC insertion depths are described in Table 1. Two hundred and nine patients were required to obtain 50 patients per group. Nine attempts of CVC insertion (1, right IJV; 3, right SCV; 2, left IJV; 3, left SCV) resulted in catheterization failure or catheter malposition, and were excluded from data analysis.
The confidence interval is for the bias; however, the prediction interval is the likely range for each patient and estimates the outcome of future samples, rather than estimating parameters. The CVC tip position of 50 CVCs placed via the right IJV was 0.1 (1.1) cm [mean (SD)] (P = 0.696 at test value = 0) above the carina (95% confidence interval [CI] = 0.3 cm below carina to 0.4 cm above carina; 95% prediction interval = 2.2 cm below carina to 2.3 cm above carina) and the tip position via the right SCV was 0.0 (0.9) cm (P = 0.834) in relation to the carina (95% CI = 0.3 cm below carina to 0.3 cm above carina; 95% prediction interval = 1.9 cm below carina to 1.8 cm above carina) (Fig. 2). The CVC tip position of 50 CVCs placed via the left IJV was 0.3 (1.0) cm (P = 0.021) above the carina (95% CI = 0.05 cm above carina to 0.6 cm above carina; 95% prediction interval = 1.7 cm below carina to 2.4 cm above carina) and the tip position via the left SCV was 0.2 (0.9) cm (P = 0.233) below the carina (95% CI = 0.4 cm below carina to 0.1 cm above carina; 95% prediction interval = 2.0 cm below carina to 1.7 cm above carina) (Fig. 3).
The relationship between the angle to the vertical and the catheter tip position in left-sided central venous catheterization is shown in Table 2 and Figure 4.
This study demonstrated that the CVC tip could be inserted to a location near the carina level when the CVC is inserted via the right IJV, left IJV, right SCV, or left SCV to a catheter depth measured by the topographical method.
There are no gold standards in estimating the exact CVC insertion depth. A previous study found an average insertion depth of 16.5 cm to the atrial–caval junction; however, internal jugular and subclavian approaches from both the left and right sides were included.1 A depth of 16.5 cm will clearly be too deep in many patients, especially if the right internal jugular or right subclavian approach is used. Moreover, this depth does not consider patient height, which may impact final catheter tip location. Right atrial electrocardiogram or transesophageal echocardiography-guided CVC placement is of value, but these techniques involve additional equipment and cost, and are thus not used routinely.2,3 Ryu et al.5 showed that the adequate CVC insertion depth could be achieved when the right-sided CVC was inserted to an adequate depth derived by adding the length between the needle insertion point to the clavicular notch and the vertical distance between the clavicular notch to the carina on a previous CXR. However, this technique is not suitable for those patients who have no CXR before central line insertion.
The CVC may remain intravascular and maintain the same curvature as contained in the manufactured box set. From this perspective, predicting the depth of CVC with the CVC itself, rather than using a straight measurement, seems reasonable. We inserted the CVC with its own curvature to be formed as a medial and cephalad convex arc to be fitted to the course of the central veins (Fig. 1). Although topographic landmarks including the right third intercostal space4 and angle of Louis6 were used for positioning the CVC to an adequate depth in other studies, those were only for the right IJV; there have been no previous studies of left-sided central catheterizations. The greatest advantage of the technique introduced in this study is that it can be used for measuring appropriate insertion depth in left-sided CVC approaches. Other benefits are that it does not require extra cost or devices.
The brachiocephalic veins can be projected onto the surface as broad bands 1.5 cm wide from the sternal end of the clavicle on each side to the formation of the SVC at the lower border of the first right costal cartilage. The SVC is 7 cm in length and 2 cm wide and partially behind the right margin of the sternum; it extends from the lower border of the first right costal cartilage to the lower border of the third right costal cartilage.11 The angle of Louis can be palpated easily near the second rib insertion to the manubriosternal joint. The tracheal carina was above the manubriosternal joint plane in 9 cases (17.6%), at the plane in 21 cases (41%), and below it in 21 cases (41%).12 Considering these measurements, we placed the tip of the CVC on the insertion point of the second right costal cartilage to the manubriosternal joint. We think that topographical methods such as ours may be difficult to apply in extremely obese patients; however, bony landmarks such as the clavicle, sternum, and second rib can be palpated in most people. The manubriosternal joint can be identified by palpating the second rib, or roughly measured at the junction of 1/4 and 3/4 of the total sternal length.13
It has been suggested that the more perpendicular the angle of the CVC tip is to the vessel wall, the greater the risk of vessel wall perforation.14 A high proportion of left-sided lines above the carina had a steep (≥40°) angle to the vertical, especially in the left IJV in this study, similar to previous reports.10,15 This phenomenon may have been due to the fact that the angles formed by 2 curves (the left IJV into the left innominate vein, and the left innominate vein into the SVC) are nearly 90° and opposite in convexity. A catheter inserted through the left IJV is distorted twice, in comparison with left SCV or right-sided lines. Therefore, it may be difficult to obtain the 2 objectives, that is, placing the tip above the carina and avoiding the abutment of the tip to the wall of the SVC at an acute angle in the left-sided lines. If the tip of the left-sided catheter is only 1 or 2 cm above the carina, then it is possible to be in the innominate vein or have a steep angle to the vertical. The optimal position of the catheter tip for CVCs remains controversial. The pericardium is attached to the SVC wall and ascends with the SVC for several centimeters. Thus, placement of the CVC tip just outside the heart does not preclude the risk of tamponade.7 Although we determined the insertion depth of a CVC by placing the tip of the CVC just on the level of the manubriosternal joint in this study, it may be optimal to target the tip slightly above the manubriosternal joint for right-sided insertion and a little below the manubriosternal joint for left-sided insertion. Another advantage of this method is that simple modification of the target point is possible by moving it above or below the manubriosternal joint (or carina) according to the operator's choice.
There were 8 patients in whom the initial target vein could not be located with a needle, or in whom the wire could not be inserted. In the event of failure in the assigned group, the next catheterization was attempted in another vein and then excluded from the study. In 1 patient in the right SCV group, the tip of the catheter was malpositioned in the right IJV, not the SVC, and was also excluded from analysis.
In conclusion, the topographical measurement with the CVC itself along the pathway of the central veins can estimate the approximate CVC insertion depth with no additional cost or time-consuming procedures.
Name: Myung-Chun Kim, MD, PhD.
Contribution: Study design.
Name: Keon-Sik Kim, MD, PhD.
Contribution: Conduct of study.
Name: Young-Kyoo Choi, MD, PhD.
Contribution: Conduct of study.
Name: Dong-Soo Kim, MD, PhD.
Contribution: Data analysis.
Name: Moo-Il Kwon, MD, PhD.
Contribution: Data analysis.
Name: Joon-Kyung Sung, MD.
Contribution: Manuscript preparation.
Name: Jee-Youn Moon, MD.
Contribution: Revision of manuscript.
Name: Jong-Man Kang, MD, PhD.
Contribution: Study design and preparation and revision of manuscript.
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