title: The effects of the Trendelenburg position and intrathoracic pressure on the subclavian cross-sectional area and distance from the subclavian vein to pleura in anesthetized patients.
abstract: BACKGROUND
  The effects of maneuvers to increase intrathoracic pressure and of Trendelenburg position on the cross-sectional area (CSA) of the subclavian vein (SCV) and the relationship between the SCV and adjacent structures have not been investigated.
  
  
  METHODS
  In ultrasonography-guided SCV catheterization (N = 30), the CSA of the SCV and the distance between the SCV and pleura (DSCV-pleura) were determined during 10-second airway opening, and 10-second positive inspiratory hold with 20 cm H2O in the supine position (S-0, and S-20) and the 10° Trendelenburg position (T-0, and T-20). In addition to a statistical significance of P < 0.05, CSA and DSCV-pleura differences of ≥15% were defined as clinically relevant changes.
  
  
  RESULTS
  CSA (mean [95% confidence interval]) in S-20, T-0, and T-20 (1.02 [0.95-1.14] cm(2), 1.04 [0.95-1.15] cm(2), and 1.14 [1.04-1.24] cm(2), respectively) was significantly larger than a CSA in S-0 (0.93 [0.86-1.00] cm(2), all P < 0.001). However, only the increase of CSA in T-20 vs S-0 (0.21 cm(2), 23.2%) was clinically meaningful (≥15%). The number of patients who showed CSA increase ≥15% was more in S-0 to T-20 (57%) compared with those in S-0 to S-20 (23%) and S-0 to T-0 (27%). DSCV-pleura measurements (mean) in S-20 and T-20 (0.61 and 0.60 cm) were significantly shorter than those in S-0 (0.70 cm, all P < 0.001), but the reductions of DSCV-pleura were not clinically meaningful (≥15%).
  
  
  CONCLUSIONS
  The combined application of inspiratory hold and Trendelenburg position provided a greater and more relevant degree of CSA increase without compromising DSCV-pleura, which may facilitate SCV catheterization. Further investigations are needed to determine whether these results affect the success rate of catheterization and the risk of procedural injury.
authors.affiliation: Department of Anesthesiology, Konkuk University Medical Center, Research Institute of Biomedical Science, Konkuk University School of Medicine, 4-12 Hwayang-dong, Gwangjin-gu, Seoul 143-729, Korea.
authors.forename: Mi-Young
authors.initials: MY
authors.lastname: Kwon
authors.forename: Eun-Kyung
authors.initials: EK
authors.lastname: Lee
authors.forename: Hye-Ju
authors.initials: HJ
authors.lastname: Kang
authors.forename: Ho-Young
authors.initials: HY
authors.lastname: Kil
authors.forename: Kee-Hoon
authors.initials: KH
authors.lastname: Jang
authors.forename: Min-Seok
authors.initials: MS
authors.lastname: Koo
authors.forename: Gunn-Hee
authors.initials: GH
authors.lastname: Lee
authors.forename: Myung-Ae
authors.initials: MA
authors.lastname: Lee
authors.forename: Tae-Yop
authors.initials: TY
authors.lastname: Kim
mesh_terms: D000328:Adult; D000368:Aged; D019412:Anatomy, Cross-Sectional / Q000379:methods*; D000768:Anesthesia, General / Q000379:methods*; D002405:Catheterization, Central Venous / Q000379:methods*; D005260:Female; D018475:Head-Down Tilt / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D010994:Pleura / Q000000981:diagnostic imaging*; D013350:Subclavian Vein / Q000000981:diagnostic imaging*; D016896:Treatment Outcome; D014463:Ultrasonography