Effects of prolonged head-down tilt on internal jugular vein cross-sectional area.

BACKGROUND Head-down tilt is often used to assist cannulation of the internal jugular vein (IJV). However, the optimal duration of tilt before cannulation is not well defined. METHODS Fifteen healthy volunteers were studied by B-mode duplex sonography to assess changes in cross-sectional area (CSA) of the right IJV during 10 degrees head-down tilt. RESULTS Median CSA in the supine position was 102 mm(2) [range 16-266, mean (SD) 113 (69)]. CSA increased to 139 mm(2) [23-388, 158 (93)] immediately after tilting (P<0.0001, repeated measures ANOVA). No significant further change was noted in the next 20 min. CSA returned to baseline level after return to the supine position. CONCLUSION The 10 degrees head-down tilt manoeuvre in healthy volunteers causes an immediate, significant increase in CSA in the right IJV. A longer tilt did not cause further increase in jugular CSA.