Study	Reason for exclusion
Kaiser 1981	Allocation: Randomized, table of random numbers. Participants: Patients requiring selective central venous cannulation. Interventions: Internal jugular site insertion n=49, Subclavian site insertion n=51. Substantial missing data: No description about participants' age and sex, duration of catheterization and setting.
Senagore 1987	Allocation: Randomized, no further details. Participants: Patients admitted to ICU and have pulmonary artery catheters placed. Interventions: Internal jugular site insertion n=26, Subclavian site insertion n=40. Outcomes: No usable data‐ no group detail about infectious complications. Substantial missing data: No description about participants' age, sex.
Richet 1990	Allocation: Prospective, observational study.
Schillinger 1991	Allocation: Prospective, observational study.
Trottier 1995	Allocation: Randomized. Participants: Patients from a medical‐surgical ICU requiring no emergent central venous catheterization. Interventions: Upper access site (internal jugular and subclavian vein) n=21 Lower access site (femoral vein) n=24 Outcomes: No usable data‐unclear how many participants originally randomized to internal jugular and subclavian vein group respectively.
Goetz 1998	Allocation: Prospective, observational study.
Dhawan 2001	Allocation:Prospective, observational study.
Lorente 2005	Allocation: Prospective observational study.
Deshpande 2005	Allocation: Prospective observational study.
Torgay 2005	Allocation: Prospective, observational study.
Moretti 2005	Allocation: Prospective observational study.
Young 2005	Allocation: Prospective, observational study.
Araujo 2008	Allocation: Prospective, non‐randomized, observational, study.
Chen 2008	Allocation: Prospective observational study.
Cui 2008	Allocation: Retrospective study from another report of the same study.
Gowardman 2008	Allocation: Prospective, observational Study.
Moini 2009	Allocation: Randomized. Participants: Patients requiring short‐term central venous catheterization. Interventions: Central venous group (internal jugular and subclavian vein) n=34. External jugular group n=34. Outcomes: No usable data, participants not randomized to internal jugular and subclavian vein group respectively.
Mer 2009	Allocation: Prospective, observational study.
Huang 2009	Allocation: Randomized, no further detail. Participants: Patients with various kinds of chronically renal disease. Interventions: Femoral (n=40), internal jugular (n=52), subclavian (n=53). Outcomes: No usable data‐ There were 13 participants changed their catheter in the original site through a guidewire, Huang et al added the data of second catheterization into the first catheterization, but the second catheterization was not randomized and the data for the first catheterization were not available.
Pang 2009	Allocation: Prospective observational study.
Miao 2010	Allocation: quasi‐randomized trials. Allocation by participants' own intention.
Fan 2011	Allocation: not randomized trial. The intervention was selected by the patient's condition.
Wang 2011	Allocation: quasi‐randomized trials. It allocated by the sequence.