Secondary Logo

The Effect of Head Position on the Cross-Sectional Area of the Subclavian Vein

Kim, Hyerim, MD*; Chang, Jee-Eun, MD*; Lee, Jung-Man, MD, PhD*; Han, Sung-Hee, MD, PhD; Ryu, Jung-Hee, MD, PhD; Hwang, Jin-Young, MD, PhD*

doi: 10.1213/ANE.0000000000002446
Patient Safety: Brief Report
Free
SDC

In 41 healthy volunteers, we investigated the cross-sectional area (CSA) of the subclavian vein (SCV) in the following head positions: neutral and 30° head rotation toward the contralateral or ipsilateral sides. Significant differences were observed in the CSA of the SCV at 3 different head positions: contralateral 30° versus neutral, −0.05 cm2 (95% confidence interval, −0.08 to −0.03); contralateral 30° versus ipsilateral 30°, −0.15 cm2 (−0.19 to −0.12); neutral versus ipsilateral 30°, −0.10 cm2 (−0.13 to −0.07); all Pcorrected< .001). For SCV catheterization, 30° head rotation to the ipsilateral side provided significant improvements in the CSA compared with the other head positions.

From the *Department of Anesthesiology and Pain Medicine, SMG-SNU Boramae Medical Center, Seoul, Republic of Korea

Department of Anesthesiology and Pain Medicine, Seoul National University Bundang Hospital, Seongnam, Republic of Korea.

Published ahead of print August 31, 2017.

Accepted for publication July 27, 2017.

Funding: None.

The authors declare no conflicts of interest.

This study was conducted with written informed consent from the study subjects.

Clinical trial registration: The study was registered before patient enrollment. Registry URL: https://clinicaltrials.gov/show/NCT02860351.

ClinicalTrials.gov (trial ID: NCT02860351).

Institutional review board contact information: The Institutional Review Board of SMG-SNU Boramae Medical Center. Approved institutional review board number of this study: 20160616/16-2016-71/071.

Reprints will not be available from the authors.

Address correspondence to Jin-Young Hwang, MD, PhD, Department of Anesthesiology and Pain Medicine, SMG-SNU Boramae Medical Center, Boramae-ro, Dongjak-gu, Seoul 156-707, Republic of Korea. Address e-mail to mistyblue15@naver.com.

The subclavian vein (SCV) is the preferential site for central venous catheterization because of the lower risk of catheter-related infections, less collapsibility, and enhanced patient comfort.1,2 Unfortunately, catheterization of the SCV is clinically challenging and requires more training than alternative sites such as the internal jugular or femoral vein. Furthermore, improper SCV catheterization may lead to the development of potentially fatal complications, such as pneumothorax, hemothorax, chylothorax, or arterial injury.3,4

Ultrasonography-guided cannulation of the SCV has been reported to reduce the procedure-related complications compared with the landmark method.5 However, the concurrent use of ultrasonography may not be a viable option because of potential inaccessibility in the clinic. With the landmark method, securing a larger cross-sectional area (CSA) of the SCV can improve the likelihood of successful SCV puncture. In turn, these improvements provide further advantages when coupled with guided ultrasonography. It is interesting that previous investigations indicated that the CSA of the SCV may further be affected by the head positioning of the patient, and the effect of head position, either neutral or rotation to the contralateral side, on the CSA of the SCV has been controversial.6–8

Anatomically, the SCV runs posterior to the clavicle and anterior to the anterior scalene muscle, which separates the SCV from the subclavian artery. Furthermore, the anterior wall of the SCV is united to the fascia of the subclavian muscle.9 Although head rotation to the ipsilateral side may also affect the CSA of the SCV and the position of adjacent structures, it has not been determined yet. In this investigation of healthy adult volunteers, we compared the effect of head positioning with respect to the CSA of the SCV, the distances from the SCV to adjacent structures in the supine and Trendelenburg positions.

Back to Top | Article Outline

METHODS

This study was approved by the SMG-SNU Boramae Medical Center Institutional Review Board (No. 20160616/16-2016-71/071), and registered at ClinicalTrials.gov (NCT02860351). After obtaining written informed consent, healthy adult volunteers, 20 years of age and older, were enrolled. Exclusion criteria included treatment with medications affecting vascular tone, or patient history of clavicle fracture, lung and chest wall operations, or central venous catheterization.

The subjects were placed in the supine position on a horizontal operating table, with arms held alongside the body, and rested for 10 minutes before measurements for hemodynamic stabilization. A 2-dimensional 10-MHz linear probe (SonoSite MicroMaxx; SonoSite, Inc, Bothell, WA) was placed underneath the proximal aspect of the middle thirds of the clavicle, perpendicular to the long-axis of the SCV. A single experienced investigator examined the SCV and adjacent structures in 3 different head positions. Specifically, “neutral position” was defined as the head adjusted such that the top of the nasal bone was aligned with 0°. Furthermore, “30° rotation to the contralateral or ipsilateral side” was defined as the head rotated such that the upper nasal bone corresponded to the 30° rotation from neutral to each respective side. The subjects were instructed to breathe naturally, and all images were obtained at end-expiration. To conduct a blinded investigation with respect to head position, the subject was covered with a surgical drape, tented superior to the clavicle. Screened behind the surgical drape, an assisting investigator set the subject’s head position at the discretion of the assisting investigator. For each head position, we obtained 2 images, including a circular or nearly circular cross-sectional shape of the SCV and adjacent structures (subclavian artery, pleura, and skin; Figure). After recording images in the supine position, the operating table was adjusted to 20° of the Trendelenburg position and held static for 3 minutes before ultrasonographic examinations resumed. The ultrasonographic images for all 3 head positions were obtained as described for the supine positioning. The CSA of the SCV as assessed by planimetry, the minimal distance from the inferior wall of the SCV to the pleura, the minimal distance from the SCV to the subclavian artery, and the depth of the SCV from the skin surface were measured and averaged by an independent investigator blinded to both head and patient positions.

Figure

Figure

Data normality was tested using the Kolmogorov-Smirnov test. The variables of the CSA of the SVC, the depth of the SCV from the skin surface, and the minimal distance from the inferior wall of the SCV to the pleura passed the test (all P > .05). Data are expressed as mean ± standard deviation or number of subjects. The outcomes (the CSA of the SVC, the depth of the SCV from the skin surface, the minimal distance from the inferior wall of the SCV to the pleura, and the minimal distance from the SCV to the subclavian artery) were analyzed using repeated-measures analysis of variance, including 3 factors as follows: head position (3 levels: 30° rotation to the contralateral side/neutral/30° rotation to the ipsilateral side); patient position (2 levels: supine/Trendelenburg); and particular side (2 levels: right/left). When any significant differences were found in the main effect or interaction between the different factors, a paired t test with Bonferroni correction was performed. Bonferroni correction was applied by multiplying the uncorrected P value by the number of comparisons (ie, 3). P < .05 and Bonferroni-corrected P value (Pcorrected) < .05 were considered statistically significant.

The primary outcome of the present study was the CSA of the SCV. A pilot study was performed in 15 subjects to determine the sample size. In the pilot study, the CSA of the right SCV in the neutral head position was 0.75 ± 0.24 cm2 (mean ± standard deviation), and 38 patients were required to detect a 15% difference in the CSA at a significance level of 0.05 and a power of 80%. Considering a 10% dropout rate, 42 patients were enrolled. SPSS for Windows software (ver. 20; IBM Corp, Armonk, NY) was used to conduct all statistical analyses.

Back to Top | Article Outline

RESULTS

Ultrasonographic measurements were performed in 41 of 42 volunteers (20 men and 21 women; 31 ± 4 years of age; height, 168.3 ± 8.1 cm; weight, 63.9 ± 12.4 kg; body mass index, 22.4 ± 2.9 kg·m−2).

For each repeatedly measured outcome, the repeated-measures analysis of variance revealed no significant 2-way and 3-way interactions among the 3 factors. However, significant differences were observed in the CSA of the SCV by head position (F = 61.70; P < .001) and patient position (F = 24.73; P < .001), and in the depth of the SCV from the skin surface by head position (F = 4.50; P = .017).

The CSAs of the SCV in different head positions (30° rotation to the contralateral side, neutral, and 30° rotation to the ipsilateral side) were 0.78 ± 0.24, 0.83 ± 0.25, and 0.93 ± 0.27 cm2, respectively. The CSAs of the SCV in the supine and Trendelenburg positions were 0.78 ± 0.23 and 0.91 ± 0.27 cm2, respectively. After the pairwise comparison with Bonferroni correction, significant differences were observed in the CSA of the SCV in 3 different head positions (all Pcorrected < .001) and between the patient positions (P < .001; Table).

Table

Table

The depths of the SCV from the skin surface in different head positions (30° rotation to the contralateral side, neutral, and 30° rotation to the ipsilateral side) were 2.03 ± 0.51, 2.06 ± 0.51, and 2.07 ± 0.50 cm, respectively. After the pairwise comparison with Bonferroni correction, significant difference was observed in the depth of the SCV from the skin surface between the 2 head positions (contralateral 30° versus ipsilateral 30°, −0.04 cm [95% CI, −0.06 to −0.01]; Pcorrected = .013).

Back to Top | Article Outline

DISCUSSION

This study shows that 30° head rotation to the ipsilateral side provided significant improvements in the CSA of the SCV, compared with neutral head position and 30° head rotation to the contralateral side in both the supine and Trendelenburg positions.

The adventitia of the SCV is invested with the connective tissue of the clavicular periosteum, the costoclavicular ligament, and the fascia of the subclavian and anterior scalene muscles. These soft tissue attachments act as suspension for the SCV in space.10 Therefore, our findings on head position may be attributable to the distinct anatomical relationships between the SCV and the adjacent supporting structures.

This study has some limitations. First, spontaneous breathing and unanesthetized subjects were included in the study. Thus, these results may not be generalized to anesthetized patients with positive pressure ventilation. Second, this study was conducted with only healthy volunteers with normal body habitus and a mean body mass index of 22.4 kg·m−2, not in obese, critically ill, or hypovolemic patients. Third, we examined the SCV and adjacent structures by using ultrasonography in the absence of actual venous catheterization. As a result, clinical relevant issues such as time to cannulation, the success rate of SCV catheterization, and the incidence of clinical complications could not be determined with respect to head positioning.

In conclusion, compared with neutral head position and 30° head rotation to the contralateral side, 30° head rotation to the ipsilateral side produced the greatest increases in the CSA of the SCV. During SCV catheterization, head rotation to the ipsilateral side can be a simple and effective strategy to expand the CSA of the SCV in patients without limitations in head rotation or cervical instabilities. This technique may also provide optimal imaging conditions for ultrasonography-guided SCV cannulation.

Back to Top | Article Outline

ACKNOWLEDGMENTS

The authors would like to thank Sohee Oh, PhD, of the Department of Biostatistics in Seoul Metropolitan Government Seoul National University Boramae Medical Center for statistical advice.

Back to Top | Article Outline

DISCLOSURES

Name: Hyerim Kim, MD.

Contribution: This author helped design the study and analyze the data.

Name: Jee-Eun Chang, MD.

Contribution: This author helped design the study, conduct the study, and analyze the data.

Name: Jung-Man Lee, MD, PhD.

Contribution: This author helped conduct the study, analyze the data, and write the manuscript.

Name: Sung-Hee Han, MD, PhD.

Contribution: This author helped design the study, conduct the study, and analyze the data.

Name: Jung-Hee Ryu, MD, PhD.

Contribution: This author helped design the study, conduct the study, and analyze the data.

Name: Jin-Young Hwang, MD, PhD.

Contribution: This author helped design the study, conduct the study, analyze the data, and write the manuscript.

This manuscript was handled by: Richard C. Prielipp, MD.

Back to Top | Article Outline

REFERENCES

1. Citak A, Karaböcüoğlu M, Uçsel R, Uzel N. Central venous catheters in pediatric patients–subclavian venous approach as the first choice. Pediatr Int. 2002;44:83–86.
2. Arrighi DA, Farnell MB, Mucha P Jr, Iistrup DM, Anderson DL. Prospective, randomized trial of rapid venous access for patients in hypovolemic shock. Ann Emerg Med. 1989;18:927–930.
3. Parienti JJ, Mongardon N, Mégarbane B, et al; 3SITES Study Group. Intravascular complications of central venous catheterization by insertion site. N Engl J Med. 2015;373:1220–1229.
4. Merrer J, De Jonghe B, Golliot F, et al; French Catheter Study Group in Intensive Care. Complications of femoral and subclavian venous catheterization in critically ill patients: a randomized controlled trial. JAMA. 2001;286:700–707.
5. Fragou M, Gravvanis A, Dimitriou V, et al. Real-time ultrasound-guided subclavian vein cannulation versus the landmark method in critical care patients: a prospective randomized study. Crit Care Med. 2011;39:1607–1612.
6. Fortune JB, Feustel P. Effect of patient position on size and location of the subclavian vein for percutaneous puncture. Arch Surg. 2003;138:996–1000.
7. Lukish J, Valladares E, Rodriguez C, et al. Classical positioning decreases subclavian vein cross-sectional area in children. J Trauma. 2002;53:272–275.
8. Rodriguez CJ, Bolanowski A, Patel K, et al. Classical positioning decreases the cross-sectional area of the subclavian vein. Am J Surg. 2006;192:135–137.
9. Hoffman T, Du Plessis M, Prekupec MP, et al. Ultrasound-guided central venous catheterization: a review of the relevant anatomy, technique, complications, and anatomical variations. Clin Anat. 2017;30:237–250.
10. Bannon MP, Heller SF, Rivera M. Anatomic considerations for central venous cannulation. Risk Manag Healthc Policy. 2011;4:27–39.
© 2018 International Anesthesia Research Society