Effect of patient position on size and location of the subclavian vein for percutaneous puncture.

HYPOTHESIS Large-bore subclavian intravenous access is important during trauma resuscitation and to provide central access in the intensive care unit. Controversy exists as to the patient position that best facilitates the insertion of this line. Duplex scanning of the subclavian vein in different body positions may help define which provides the largest vein size and distance from the clavicle. DESIGN Prospective comparison study in healthy humans. SETTING Clinical research laboratory. SUBJECTS Ten healthy volunteers. INTERVENTIONS We examined the left subclavian vein diameter, position from clavicle, and flow in subjects placed in 5 different positions advocated for subclavian vein puncture. A duplex scanner was used to image the subclavian vein with B-mode ultrasonography and to detect flow rates with a Doppler probe. The different subject positions were as follows: (1) flat (or supine), head and shoulders neutral; (2) flat, head neutral, shoulders arched; (3) flat, head opposite, shoulders arched; (4) Trendelenburg, head opposite, shoulders arched; and (5) Trendelenburg, head and shoulders neutral. RESULTS The mean (SEM) diameter of the subclavian vein is largest in position 5 (0.99 [0.06] cm) and smallest in position 2 (0.84 [0.05] cm). The distance of the vein from the clavicle is greatest in position 1 (0.94 [0.08] cm) and least in position 4 (0.75 [0.07] cm). Using an analysis of variance with Dunnett's comparison, all positions were compared with position 5. For vein diameter, all positions had significantly smaller size. In position 4, the vein was significantly closer to the clavicle. There was no statistical difference in flow rates among all positions. CONCLUSIONS These data demonstrate that arching of the shoulders and turning of the head may reduce target size and provide an unsatisfactory position for subclavian puncture. The Trendelenburg position with no other positioning maneuvers may be helpful.