In the landmark technique, the subclavian vein or the internal jugular vein on either side was chosen for access depending on surgeon's preference. An infraclavicular approach was used for the subclavian vein, and an anterior approach was used for the internal jugular vein. If venous flash could not be achieved after three attempts on the initial chosen site using the landmark technique, the study was terminated and the surgeon was free to use either ultrasound or landmark at any other site. A single pass of the needle was defined as a single episode of needle advancement and withdrawal. A second pass occurred if the needle was re-advanced or removed and reinserted. A failed attempt was recorded if aspiration resulted in no venous flash, arterial puncture (bright red blood, pulsatile flow), or air.

In the ultrasound-guided group, the internal jugular vein on either side was accessed depending on surgeon's preference. An ultrasound console with a linear 11 Hz probe was used. The patient was then put into Trendelenburg position. The head was positioned away from the insertion side. The ultrasound probe was placed at the apex of the triangle formed between the two heads of the sternocleidomastoid muscle and the clavicle. The internal jugular vein and common carotid artery were visualized, with the vein identified by its larger size, relative anatomic position, and compressibility. After a flashback of dark venous blood was noted in the syringe, the standard Seldinger technique was followed for the catheter insertion. After 3 failed attempts using the ultrasound at the specified site, the surgeon was free to further attempts using landmark or ultrasound approaches at any other site.

In the landmark technique, the subclavian vein or the internal jugular vein on either side was chosen for access depending on surgeon's preference. An infraclavicular approach was used for the subclavian vein, and an anterior approach was used for the internal jugular vein. If venous flash could not be achieved after three attempts on the initial chosen site using the landmark technique, the study was terminated and the surgeon was free to use either ultrasound or landmark at any other site. A single pass of the needle was defined as a single episode of needle advancement and withdrawal. A second pass occurred if the needle was re-advanced or removed and reinserted. A failed attempt was recorded if aspiration resulted in no venous flash, arterial puncture (bright red blood, pulsatile flow), or air.

In the ultrasound-guided group, the internal jugular vein on either side was accessed depending on surgeon's preference. An ultrasound console with a linear 11 Hz probe was used. The patient was then put into Trendelenburg position. The head was positioned away from the insertion side. The ultrasound probe was placed at the apex of the triangle formed between the two heads of the sternocleidomastoid muscle and the clavicle. The internal jugular vein and common carotid artery were visualized, with the vein identified by its larger size, relative anatomic position, and compressibility. After a flashback of dark venous blood was noted in the syringe, the standard Seldinger technique was followed for the catheter insertion. After 3 failed attempts using the ultrasound at the specified site, the surgeon was free to further attempts using landmark or ultrasound approaches at any other site.

In the landmark technique, the subclavian vein or the internal jugular vein on either side was chosen for access depending on surgeon's preference. An infraclavicular approach was used for the subclavian vein, and an anterior approach was used for the internal jugular vein. If venous flash could not be achieved after three attempts on the initial chosen site using the landmark technique, the study was terminated and the surgeon was free to use either ultrasound or landmark at any other site. A single pass of the needle was defined as a single episode of needle advancement and withdrawal. A second pass occurred if the needle was re-advanced or removed and reinserted. A failed attempt was recorded if aspiration resulted in no venous flash, arterial puncture (bright red blood, pulsatile flow), or air.

In the ultrasound-guided group, the internal jugular vein on either side was accessed depending on surgeon's preference. An ultrasound console with a linear 11 Hz probe was used. The patient was then put into Trendelenburg position. The head was positioned away from the insertion side. The ultrasound probe was placed at the apex of the triangle formed between the two heads of the sternocleidomastoid muscle and the clavicle. The internal jugular vein and common carotid artery were visualized, with the vein identified by its larger size, relative anatomic position, and compressibility. After a flashback of dark venous blood was noted in the syringe, the standard Seldinger technique was followed for the catheter insertion. After 3 failed attempts using the ultrasound at the specified site, the surgeon was free to further attempts using landmark or ultrasound approaches at any other site.

In the landmark technique, the subclavian vein or the internal jugular vein on either side was chosen for access depending on surgeon's preference. An infraclavicular approach was used for the subclavian vein, and an anterior approach was used for the internal jugular vein. If venous flash could not be achieved after three attempts on the initial chosen site using the landmark technique, the study was terminated and the surgeon was free to use either ultrasound or landmark at any other site. A single pass of the needle was defined as a single episode of needle advancement and withdrawal. A second pass occurred if the needle was re-advanced or removed and reinserted. A failed attempt was recorded if aspiration resulted in no venous flash, arterial puncture (bright red blood, pulsatile flow), or air.

In the ultrasound-guided group, the internal jugular vein on either side was accessed depending on surgeon's preference. An ultrasound console with a linear 11 Hz probe was used. The patient was then put into Trendelenburg position. The head was positioned away from the insertion side. The ultrasound probe was placed at the apex of the triangle formed between the two heads of the sternocleidomastoid muscle and the clavicle. The internal jugular vein and common carotid artery were visualized, with the vein identified by its larger size, relative anatomic position, and compressibility. After a flashback of dark venous blood was noted in the syringe, the standard Seldinger technique was followed for the catheter insertion. After 3 failed attempts using the ultrasound at the specified site, the surgeon was free to further attempts using landmark or ultrasound approaches at any other site.