Intravenous literature: Kwon, M.Y., Lee, E.K., Kang, H.J., Kil, H.Y., Jang, K.H., Koo, M.S., Lee, G.H., Lee, M.A., and Kim, T.Y. (2013) 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. Anesthesia & Analgesia. 117(1), p.114-118.
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] cm2, 1.04 [0.95–1.15] cm2, and 1.14 [1.04–1.24] cm2, respectively) was significantly larger than a CSA in S-0 (0.93 [0.86–1.00] cm2, all P < 0.001). However, only the increase of CSA in T-20 vs S-0 (0.21 cm2, 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.