Intra-arterial catheters: An evidence-based review of device design, function and application

Table 1 Approximate dimensions for needles, wires and cannulae utilized in arterial catheterization; note that minor variability exists between manufacturers, products, and measurement systems

Needle or catheter gauge	Needle or catheter outer diameter (mm)	Matching guidewire thickness (inches)	Gravity flow rate (mL/minute)
22G	0.7-0.9	0.014	35
21G	0.8-0.9	0.018	60
20G	0.9-1.1	0.025	65
18G	1.2-1.3	0.035	100