Comparison 2. Overall perioperative and postoperative complications.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Seldinger (subclavian & IJ) versus venous cutdown (cephalic vein) ITT	7	1006	Odds Ratio (M‐H, Fixed, 95% CI)	1.16 [0.76, 1.75]
2 Seldinger (subclavian vein) versus venous cutdown (cephalic vein) ITT	5	672	Odds Ratio (M‐H, Fixed, 95% CI)	1.28 [0.78, 2.10]
3 Seldinger (IJ vein) versus venous cutdown (cephalic vein) ITT	2	367	Odds Ratio (M‐H, Fixed, 95% CI)	0.72 [0.40, 1.31]
4 Seldinger (subclavian & IJ) versus venous cutdown (cephalic vein). On‐treatment analysis	7	938	Odds Ratio (M‐H, Fixed, 95% CI)	0.93 [0.62, 1.40]
5 Seldinger (subclavian vein) versus venous cutdown (cephalic vein). On‐treatment analysis	5	618	Odds Ratio (M‐H, Fixed, 95% CI)	1.06 [0.66, 1.72]
6 Seldinger (IJ vein) versus venous cutdown (cephalic vein). On‐treatment analysis	2	332	Odds Ratio (M‐H, Fixed, 95% CI)	0.67 [0.37, 1.23]