The influence of passive leg elevation on the cross-sectional area of the internal jugular vein and the subclavian vein in awake adults.
The aim of this study was to evaluate the influence of passive leg elevation and Trendelenburg position on the cross-sectional area (CSA) of the internal jugular (IJ) and subclavian veins (SCV). Ultrasound imaging was used for the following measurements of both the IJV and SCV baseline in the supine position (control); Trendelenburg position 15[degrees]; reverse Trendelenburg position 15[degrees] and passive leg elevation 50[degrees]. Twenty healthy male volunteers were studied. Mean CSA of the IJV was 1.12 [+ or -] 0.57 [cm.sup.2] in control, 1.66 [+ or -] 0.67 [cm.sup.2] in the Trendelenburg position (P <0.0001 vs. control), 0.38 [+ or -] 0.23 [cm.sup.2] in the reverse Trendelenburg position (P <0.0001 vs. control), and 1.40 [+ or -] 0.64 [cm.sup.2] during passive leg elevation (P <0.0001 vs. control). Mean CSA of the SCV was 0.92 [+ or -] 0.23 [cm.sup.2] in control, 0.98 [+ or -] 0.17 [cm.sup.2] in the Trendelenburg position, 0.86 [+ or -] 0.21 [cm.sup.2] in the reverse Trendelenburg position and 0.93 [+ or -] 0.18 [cm.sup.2] during passive leg elevation. The results indicate that passive leg elevation increases the CSA of the IJV, but has little effect on the SCV The CSA of the IJV appears to be influenced more by gravitational factors than the SCV
Key Words: internal jugular vein, subclavian vein, Trendelenburg
The internal jugular vein (IJV) and the subclavian vein (SCV) are the most popular routes for central venous access. Successful cannulation is assisted by distension of the veins. The Trendelenburg position, Valsalva manoeuvre and abdominal compression have been suggested to increase the cross-sectional area (CSA) of the IJV and SCV (1-6).
Unfortunately, the Valsalva manoeuvre or abdominal compression may be cumbersome and create discomfort to patients who are awake. The Trendelenburg position requires a tilt table in order to place the head in the down position. In addition, the Trendelenburg position can have adverse effects on patients such as increased intracranial pressure.
Leg elevation redistributes more blood from the lower extremity into the central veins and is commonly used for hypovolaemic shock. In addition, passive leg elevation can be performed relatively easily. However, the effect of leg elevation on the CSA of the central veins has not been previously investigated.
We hypothesised that passive leg elevation might be an alternative method for increasing the CSA of the IJV and the SCV during central venous cannulation. This study evaluated the effect of passive leg elevation and Trendelenburg position on the CSA of the IJV or the SCV using ultrasound imaging.
MATERIALS AND METHODS
After obtaining approval from our Institutional Review Board and informed written consent, 20 healthy male volunteers were studied. Subjects who were taking any medication, who had a history of prior central venous catheterisation or who had prior neck surgery were excluded. The subjects were within 15% of their ideal body weight.
A two-dimensional 4.0-13.3 MHz linear array probe was used to obtain ultrasound images of the right IJV or right SCV The same investigator (YJ) obtained all images in order to achieve consistency in measurements. The probe was applied with the lightest pressure possible and held perpendicular to the skin of the subjects in horizontal supine position. All images of the IJV were obtained at the level of the cricoid cartilage, with the head rotated 15[degrees] to the left side. The CSA of the SCV was obtained at the junction of the medial and middle third of the clavicle. The probe was directed inferiorly so that the SCV could be visualised under the clavicle.
The following four measurements of the CSA of the IJV and the SCV were made with the probe held in the same position: 1) baseline in the supine position (control), 2) Trendelenburg position 15[degrees], 3) reverse Trendelenburg position 15[degrees] and 4) passive leg elevation 50[degrees]. The subjects were kept in each position for at least one minute before taking any measurement.
In order to eliminate the respiratory effect, the investigator selected the image showing the largest CSA and the area was measured by planimetry. The circumference of the IJV or the SCV was delineated using the electronic marker (Vivid I[R] ultrasound machine, GEMSI ultrasound, Tirat Carmel, Israel). Two investigators measured the CSA and the mean value was used. Before this study, it had been confirmed that our inter-observer variation in assessing CSA was less than 5%.
A 20% change in the CSA was considered clinically relevant. The distribution of data was determined using Kohnogorov-Smirnov analysis. The data was analysed using a paired t-test (normally distributed data) or Wilcoxon signed rank test (non-normally distributed data). Each P value for the test was adjusted using a Bonferroni correction at an overall significant level <0.05.
[FIGURE 1 OMITTED]
The characteristics of the subjects were as follows (mean [+ or -] SD): age, 27.6 [+ or -] 1.9 years; height, 175.5 [+ or -] 4.1 cm and weight, 72.9 [+ or -] 6.1.
The CSA of the IJV was changed significantly in each position in relation to the control. Leg elevation increased the CSA of the IJV by 25% (P <0.0001). However, it was less than the 48% increase by the Trendelenburg position (P <0.0001). The reverse Trendelenburg position decreased the CSA of the IJV by 66% (P <0.0001) (Table 1, Figure 1).
There were no clinically relevant changes (>20%) in the CSA of the SCV with the Trendelenburg position, reverse Trendelenburg position or leg elevation (Table 1, Figure 2).
[FIGURE 2 OMITTED]
To our knowledge, this is the first study to examine the effect of passive leg elevation on the CSA of the central veins in subjects who are awake. These results show that passive leg elevation, as in Trendelenburg position, increases the CSA of the IJV In contrast, the CSA of the SCV is not increased significantly by either the Trendelenburg position or passive leg elevation. This suggests that passive leg elevation can be helpful for the central venous cannulation of the IJV
The Trendelenburg position and leg elevation are commonly used to treat hypotension. It is well known that both these positional changes shift the blood from the lower part of the body into the central veins and affect the haemodynamics (7-9). However, there may be a difference on the amount of recruited blood between the two positions. The blood from the body below the IJV can be recruited during the Trendelenburg position, while only blood from the lower extremities can be recruited during leg elevation position. Moreover, with the Trendelenburg position, the abdominal contents may press on the diaphragm, increasing the intrathoracic pressure, which can interfere with the venous return in the IJV. This may be another reason why the CSA of the UV by Trendelenburg position was greater than that by leg elevation. Consequently, in the IJV, the Trendelenburg position is more effective in increasing the CSA than passive leg elevation alone and there is no reason to recommend passive leg elevation alone for routine cannulation into the UV However, passive leg elevation can be an alternative to the Trendelenburg position when the Trendelenburg position is contraindicated, such as the increased intracranial pressure or when a tilt table is unavailable.
In contrast to the IJV, the CSA of the SCV was not significantly changed by the Trendelenburg position, leg elevation or the reverse Trendelenburg position. The effect of the Trendelenburg position on the CSA of SCV is controversial. In some studies (5,6), the Trendelenburg position increased the CSA of the SCV However, this was not observed in a previous study (10) or the present study. The anterior wall of the SCV adheres to the fascia of the subclavian muscle. Posteriorly, the vein is invested with pre-tracheal fascia. These facial attachments maintain the calibre of the vein during respiration". The SCV wall is reinforced by a thick tunica fibrosa as well as its adherence to the adjacent ligaments, fascia and periosteum. Consequently, the SCV does not collapse as easily, or is as easily displaced, even during shock (12-14).
The results of this study were obtained from normal awake volunteers. The results from patients with cardiovascular disease or under anaesthesia with positive pressure ventilation might be different. Indeed, the mean CSA of IJV has been shown to increase by 37% after administering anaesthesia and positive pressure ventilation (15). The degree of increase in the CSA of the IJV and the SCV is dependent on the vessel compliance and the venous volume from the legs. Therefore, there might be individual variations in the increase of the CSA of the IJV and the SCV In addition, the real success rate of cannulation could not be determined because catheterisation was not performed in this study. The small sample size also reduced the power of this study.
In conclusion, a passive leg elevation to 50[degrees] increases the CSA of the IJV in healthy volunteers. Although the increase by passive leg elevation was smaller than that by the Trendelenburg position, passive leg elevation might be an alternative to the Trendelenburg position, particularly in situations where the Trendelenburg position is inappropriate. In contrast, passive leg elevation and gravitational position has little effect on the CSA of the SCV.
Accepted for publication on September 6, 2007.
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J.-T. KIM *, H.-S. KIM *, Y.-J. LIM *, J.-H. BARK *, K.-H. LEE *, C.-S. KIM *, S.-D. KIM *, Y. JEON * Department of Anesthesiology and Pain Medicine, Seoul National University Hospital, Seoul, Korea
* M.D., Anesthesiologist and Professor.
Address for reprints: Dr Y. Jeon, Department of Anesthesiology and Pain Medicine, Seoul National University Hospital, Seoul National University College of Medicine, #28 Yongon-Dong, Jongno-Gu, Seoul 110-744, Korea.
TABLE 1 Cross-sectional area of the central veins Control Trendelenburg CSA of IJV ([cm.sup.2]) 1.12 [+ or -] 0.57 1.66 [+ or -] 0.67 * CSA of SCV ([cm.sup.2]) 0.92 [+ or -] 0.23 0.98 [+ or -] 0.17 Reverse Trendelenburg Leg elevation CSA of IJV ([cm.sup.2]) 0.38 [+ or -] 0.23 * 1.40 [+ or -] 0.64 * ([dagger]) CSA of SCV ([cm.sup.2]) 0.86 [+ or -] 0.21 0.93 [+ or -] 0.18 Data are mean [+ or -] standard deviation. CSA=cross-sectional area, IJV= internal jugular vein, SCV=subclavian vein. Compared with the control group * P <0.0001. Compared with the Trendelenburg group ([dagger]) P <0.0001.
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|Author:||Kim, J.-T.; Kim, H.-S.; Lim, Y.-J.; Bahk, J.-H.; Lee, K.-H.; Kim, C.-S.; Kim, S.-D.; Jeon, Y.|
|Publication:||Anaesthesia and Intensive Care|
|Article Type:||Clinical report|
|Date:||Jan 1, 2008|
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