Ultrasound (US)-guided central venous catheterization is now considered standard of care according to recent clinical evidence, at least considering jugular vein approach. Recent trials suggested that even US-guided subclavian approach could be more effective that landmark technique. However, studies comparing both sites employing US are still lacking.

We, therefore, designed a non-inferiority randomized controlled trial to compare these sites, both using US guidance, according to immediate complications following central venous catheterization.

Inclusion Criteria:

• critically ill patients; central venous access indicated.

Exclusion Criteria:

• cardiac arrest; at least one side of each vein available for insertion; pacemaker insertion; pulmonary artery catheter insertion; non-corrected coagulopathy; thrombolytics in the past 24 hours.