Table 4

Secondary outcomes: risk of bloody punctures with regard to different antithrombotic drug classes

	Controls without antithrombotics	Antiplatelet drugs	P value*	Anticoagulant drugs	P value*	Combined therapy†	P value*
Peripheral blocks
Group size/no of bloody taps (%)	25,299/318 (1.3)	855/11 (1.3)	0.939‡	7667/236 (3.1)	<0.001‡	852/30 (3.5)	<0.001‡
Crude OR (95% CI)	1	1.02 (0.56 to 1.89)	0.339	2.50 (2.10 to 2.96)	<0.001	2.87 (1.96 to 4.20)	<0.001
Adjusted§ OR (95% CI)	1	0.76 (0.41 to 1.40)	0.372	1.67 (1.37 to 2.04)	<0.001	2.11 (1.41 to 3.16)	<0.001
Neuraxial blocks
Group size/no of bloody taps (%)	19,506/591 (3.0)	788/35 (4.4)	0.025‡	9871/262 (2.7)	0.070‡	957/52 (5.4)	<0.001‡
Crude OR (95% CI)	1	1.49 (1.05 to 2.11)	0.026	0.87 (0.75 to 1.01)	0.070	1.84 (1.37 to 2.46)	<0.001
Adjusted§ OR (95% CI)	1	1.18 (0.80 to 1.68)	0.374	0.85 (0.72 to 1.00)	0.047	1.77 (1.31 to 2.40)	<0.001

*P value compares patients with antiplatelet, anticoagulant or a combined therapy to controls without antithrombotic medication.
†Combination of more than one antiplatelet and/or anticoagulant drug.
‡χ² test used to compare proportions.
§Adjusted for year of surgery, sex, age, body mass index, American Society of Anesthesiologists physical status, use of sedative drugs or general anesthesia during block performance, catheter use versus single shot approach, multiple skin punctures, and use of ultrasound.