The internal jugular vein (IJV) approach for central venous access is now widely used by physicians, surgeons and anesthesiologists. There are many effective methods to achieve IJV cannulation, but there is no accepted standard technique. Which approach and optimal condition is best remains controversial.1,2 In the absence of direct visualization of the vessels, external anatomic landmark-based techniques have been proposed for decades but are unlikely to allow practitioners to address common causes of catheterization failure or eliminate certain complications. Laceration of neck vessels, inadvertent arterial puncture, hematoma, pneumohemothorax, catheter malposition, fragment embolization, air embolism, venous thrombosis and infection are the most common central venous access complications.3–5 A simple venous access procedure may actually cause debilitating or fatal stroke.6 Although the general anatomic landmarks and relationship between the IJV and the common carotid artery (CCA) are known and have been reported in the literature,6,7 there are variations in position and relationship between the IJV and the CCA that may lead to inadvertent carotid artery punctures which range from 3% to 10%.4 The degree of overlap between the IJV and CCA has been reported to be different in previous studies.8,9 The incidence of accidental puncture of the CCA is decreased with an increase in the practitioner's experience and by palpation of the CCA during central venous access. However, the risk of this complication is never eliminated. Accidental CCA puncture could be disastrous and life-threatening when it results in accidental intraarterial cannulation, cerebrovascular accident, hemothorax, IJV-carotid artery fistula, or airway compromise secondary to hematoma.10–13 Ultrasound can be used to locate the IJV and provide guidance of single-wall puncture of the IJV. However, portable ultrasound is not widely used in China, especially in emergency settings and for bedside venous access needs. Awareness of the expected location of the IJV and anatomic variation is very important.
The aim of this study was to demonstrate the anatomic relationship of the IJV with the CCA in Chinese people, in order to find the optimal entry point, improve the procedural success rate and help reduce the need for multiple needle advances and decrease the chance of complications during central venous access.
The research protocol was approved by the Institutional Ethical Committee of People's Liberation Army General Hospital (Beijing, China) and conducted with the informed consent of each participant. Between January 1, 2009 and April 31, 2009, two hundred and twenty noncardiac (general, thoracic, urologic, gynecologic or orthopedic) elective surgical patients, American Society of Anesthesiologists physical status I and II, requiring central venous access were enrolled. All the patients fasted 8—12 hours and were under general anesthesia, in the supine position with no pillow under the occiput, and were controlled by mechanical ventilation (tidal volume 8 ml/kg). Patients with previous neck surgery (including carotid endarterectomy), history of head and neck masses or cancer, superior vena cava syndrome, or reported limited neck mobility were excluded from the study. No patient was hypotensive or hemodynamically unstable at the time of data collection.
Portable ultrasonography (iLOOKTM 25, Sonosite Company, USA) was used to collect information on the diameters of bilateral IJV and anatomic position in relation to the skin and CCA. During examination of the neck vessels before the IJV puncture was performed, the patient was lying supinely on the operating table with the operator standing by the patient's head, looking at the patient from head to toe. Therefore the right side of the patient coincided with the right side of the operator. The heads were tilted approximately 30° to the opposite side and kept at the exact position by a plastic pillow placed beside the opposite side of the head. Transverse scans at three cross sections (the upper border of the thyroid cartilage, the cricoid cartilage and the second tracheal ring which represent the high, middle and low approaches to the IJV6,14,15) were performed holding the probe perpendicular to the skin and perpendicular to the tracheal axis, without significant compression, to maintain the normal shape and location of the vessel. The probe was placed transversely to obtain a cross-sectional view of the vessel. These three scan levels were easily identified by touching the skeletal marks. Mechanical ventilation was temporarily suspended when the image was collected and then immediately continued. Measurements of the position and relationship of the IJV and the CCA were obtained after freezing the real-time image. All procedures were performed by an anesthesiologist who was qualified and experienced with ultrasonography test.
Regardless of the puncture site, the right and left IJV positions were registered in a circular disposition.6 The center of the circle was the center of the CCA, and an imaginary line was drawn to the direction of the center of the IJV. For instance, if the IJV was just above the CCA, this position was registered as 0° on either the right or left side. If the IJV was truly lateral to the CCA, it was registered as 90° on either the right or left side. If the IJV was truly medial to the CCA, it was registered as —90° (Figure). The percent overlap of the IJV and CCA was calculated by the following formula: Overlap(%) = Overlap (cm)/Carotid artery diameter (cm) ×100%.14
Sample size and statistical analysis
Sample size was determined on the basis of our pilot study in which the SD of the angle between IJV and CCA was approximately 17°. A minimum sample size of 182 patients was required to provide alpha level of 0.05 and beta level of 0.01 (power=0.99) to detect a 5° difference of the angle between the IJV and CCA. Two hundred and twenty patients were enrolled to compensate for possible dropouts. All data were tested for normal distribution and for homogeneity of variances. Statistical analyses between right and left sides of the neck at the same scan level were carried out with Student's t test. The comparisons among different transverse scan levels at the same side of the neck were performed by analysis of variance (ANOVA) followed by a post hoc test. The proportion of medially positioned IJV and CCA furcation rate at the level of the upper border of the thyroid cartilage at the right side vs. left side were tested with the Fisher's exact χ2 test. The SPSS for Windows 11.0 was used for statistical analysis (SPSS Inc., Chicago, USA). A P value <0.05 was considered statistically significant.
On the basis of exclusionary criteria, 20 patients were excluded from participation. Three of the patients were excluded because they had previous neck surgery, four for limited neck mobility, two had neck masses, and the other 11 patients had already been cannulated at the ward before surgery. Therefore, there were 119 male and 81 female patients remained, ranging in age from 20 to 85 years old, ((53±16) years), body weight ranged from 45 kg to 110 kg ((67±12) kg), height from 150 to 183 cm ((167±7) cm), and body mass index (BMI) (calculated as the body weight divided by the square of the height, kg/m2) ranged from 16.6 to 34.7 kg/m2 ((23.7±3.7) kg/m2).
Adjacent relationship of IJV, CCA and skin
From the upper border of the thyroid cartilage level to the second tracheal ring level, the IJV became gradually more superficial while the CCA became deeper at both sides of the neck. The right IJV was more superficial than the left IJV and the right CCA was deeper than the left CCA (P <0.05 and P <0.01 respectively). The distance between CCA and IJV was longer at the right side than at the left side (P <0.05 and P <0.01 respectively) (Table 1).
Diameters of IJV and CCA
The right IJV was wider than the left IJV at all three scan levels. The average width of CCA at both sides was similar but a little wider at the level of the second tracheal ring on the left side. From up to down, the diameter of the IJV gradually became larger while the diameter of CCA gradually smaller at both sides of the neck (P <0.05 and P <0.01, respectively) (Table 2).
Adjacent relationship of IJV and CCA
The IJV position was lateral to or on the CCA in most patients. However, there were 11 patients whose IJV location was medial to the CCA at one or more transverse scan levels (involved in two cases of medially positioned IJV at the right side and 18 cases at the left side, P <0.01). The average age of the 11 patients was older than that of patients being studied in this research ((62.45±14.27) vs. (52.57±15.53) years old) (P <0.05).
From up to down, the IJV went from parallel (lateral) to the CCA to gradually move to the front of the CCA, so the angle between the IJV and CCA became smaller and the percent overlap of IJV and CCA was gradually increased at both sides of the neck (P <0.05 and P <0.01, respectively). The angle was larger at the right side than at the left side at two scan levels (P <0.01). The percent overlap was smaller on the right than on the left at the level of the upper border of the thyroid cartilage (P <0.05) (Tables 3 and 4).
CCA had already furcated at the level of the upper border of the thyroid cartilage in seven patients (3.5%) at the right side of the neck and in 12 patients (6%) at the left side of the neck (left side vs. right side, P >0.05).
Analysis of the angle between IJV and CCA
There was no correlation among gender, weight, height or BMI with the angle of IJV and CCA (data not shown). The angle between the IJV and CCA was significantly smaller in patients over 53 years old (Table 5).
Cannulation of the right IJV at the level of the cricoid cartilage was successfully achieved in 191 patients after location of IJV by skin-surface marking with the assistance of ultrasonography. Ultrasonographic imaging in real time method was used in another five patients for whose IJV were positioned medially or directly above the CCA. The diameter of the right IJV was too small (<0.5 cm) in four of the 200 patients, and alternative approaches (subclavian or external jugular vein) were used. No inadvertent CCA puncture, hematoma, or pneumohemothorax occurred in these 200 patients.
Several entry sites for central venous cannulations such as subclavian, jugular, femoral venous route are described.16 The IJV is routinely cannulated for central venous access. Normally, the IJV follows the vascular bundle, down the neck, and most commonly becomes anterior and lateral to the CCA.8 Jugular vein cannulation using the traditional blind technique, guided by external landmarks, can be extremely hazardous both to patients with distorted anatomy of the neck and to coagulopathic individuals. Awareness of the expected location of the IJV and anatomic variation is very important.
The right IJV is usually preferred because it has a straighter path into the superior vena cava, thus providing an easier pass for the catheter. The left IJV carries the risk of thoracic duct injury. Our results showed that the diameter of IJV and the distance between IJV and CCA were wider at the right side, and the angle between IJV and CCA was also larger at the right side. Variations in position and relationship between the IJV and the CCA were found more frequently at the left side. This all indicates that it is relatively safer to cannulate at the right side of the neck than at the left side. This result for Chinese people is consistent with the Sulek et al4 study which had 12 westerners.
Inconsistent with our results, Sulek et al4 noted that overlap of the CCA and the IJV did not differ between 2 and 4 cm above the clavicle at the same degree of head rotation. Their study consisted of only 12 departmental volunteers. In our result from a sample of 200, we found that the percent overlap of IJV and CCA increased significantly from the top to down. We recommend that IJV cannulation is not attempted at a relatively low position, which is at the level of the second tracheal ring. The increased overlap of the CCA and IJV increases the risk of inadvertent puncture of the carotid artery associated with the common occurrence of transfixion of the IJV before it is identified during needle withdrawal. Although ultrasound may decrease the rate of inadvertent CCA puncture,17 location of the IJV just above the CCA (0°), even slightly lateral to CCA, can cause inadvertent arterial puncture. In addition, puncture at the low position has a higher probability of pneumothorax and hemothorax complications.
Our study showed that the angle between the IJV and CCA was significantly smaller in elderly patients, which indicated that they had a higher probability of inadvertent CCA puncture during central venous access. This result is consistent with previous study by Troianos et al.8 In the study, the degree of head rotation was not measured and the heads rotated as far to the opposite side as comfortable. Our study recorded all the location with the head tilted 30° to the opposite side according to the finding that more head rotation will increase the percent overlap of IJV and CCA. We reached the same conclusion that the patient's age as well as their head rotation contributed to the degree of overlap. It is likely due to the fact that the IJV and CCA become enlarged, elongated and tortuous as age increases, presumably from hypertension and arteriosclerosis. During IJV cannulation, venous blood return may not be achieved until the needle is withdrawn because the pressure of the advancing needle can cause the IJV to collapse; the incidence of which is reported to be 50%.18 This may result in puncture of the posterior wall of the vessel (through-and-through puncture of the IJV/double-wall puncture) rather than entering in its lumen, and then puncture of the carotid artery when the two vessels overlap. The incidence depends on needle gauge, needle bevel, speed of needle insertion, patient age, the degree of contralateral head rotation, and the operator's level of training or experience.8,9,19–22 Unfortunately, we did not examine the effect of different head rotations on the relationship of the IJV and the CCA.
Our results showed that during IJV cannulation at the level of the upper border of the thyroid cartilage, the operator must be attentive, because that we found the CCA had already furcated at this level in seven patients (3.5%) on the right side of the neck and in 12 patients (6.0%) on the left side of the neck. IJV cannulation using the traditional blind technique, guided by artery pulsation, can be hazardous to these patients. The pulsation of the two arteries will confuse the estimation of the IJV location and may cause artery puncture (finger touched the external carotid artery) or failure of IJV puncture (finger touched the internal carotid artery). In addition, the IJV at the upper level is thinner and deeper under the skin than at a lower level, although the percent overlap of IJV and CCA is less at the upper level.
In our study, the diameters of the IJV and the CCA in Chinese people are both smaller than those reported in a previous study.8 The reason may lie in the fact that the Chinese have less body weight and height than the Western people. They also fasted 8—12 hours before the procedure, which could perhaps increase the difficulty of puncture.
However, we can not explain why the medially positioned IJV occurred more frequently on left side and the proportion of variation was higher than that reported in a previous study.6 It needs further study with a large sample size. Another limitation to this study is the lack of standardization of patients on the basis of medication regimen and intestinal preparation before surgery which affects the vascular tone and intravascular volume. Therefore, the data may not be as precise as we would have liked. Furthermore, our observation was limited to adult surgical patients and did not evaluate infants, children or patients at extremely old age, all of whom are needed further study.
Our results are important to help physicians, surgeons and anesthesiologists to improve the procedural success rate and help reduce the need for multiple needle advances and decrease the chance of complications during central venous access; especially when ultrasound imaging is not available. We report our clinical and anatomic data here in order to make practitioners aware of the potential problems in common procedures, and to inform them about the expected location and anatomic variations of the IJV in the proximity of the CCA.
In conclusion, there are variations in position and relationship between the IJV and the CCA. It is impossible to predict which patients have a “safe” anatomic relation and which have a “dangerous” anatomic relation (IJV overlies CCA). It is relatively more difficult to puncture at the left side of the neck, at lower position or in elderly patients. On the contrary, it is relatively easier to puncture at the right side of the neck, at the level of the cricoid cartilage or in younger patients. Ultrasound-guided access to the IJV is recommended, especially when blinded attempts by a skilled operator are unsuccessful. Ultrasound can quickly establish the reason for failure and safely guide venous access, minimizing the risk to the patient.
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Keywords:© 2010 Chinese Medical Association
central venous; jugular veins; carotid artery; ultrasonography