Author:
Kai Knudsen
Updated:
8 October, 2024
An arterial catheter is inserted to monitor continuous invasive blood pressure and to obtain frequent blood samples. It allows for repeated measurement of blood gases and arterial acid-base status. Typically, arterial catheters are used in critically ill patients, those with unstable hemodynamics, and patients with respiratory difficulties requiring ongoing blood gas monitoring.
Arterial Needle
A common arterial catheter for an adult patient measures 45 mm in length with a diameter of 1.1 mm, corresponding to 20G. An arterial catheter is typically connected to a pressure set (pressure line system/pressure doom) with an electronic transducer that can register and measure blood pulsations, displayed graphically as an arterial pressure curve. The pulsations in the arterial pressure curve can measure pulse, blood pressure, and give an indication of current blood volume.
The arterial catheter is most often inserted into the radial artery on the left or right side. For difficult-to-cannulate patients, the catheter can be placed in the brachial artery or femoral artery. A typical arterial catheter includes a stylet (mandrin) that is removed after the artery is penetrated. The vessel is usually punctured with the stylet fully inserted, then the stylet is withdrawn by one centimeter, and the catheter is advanced until free backflow is observed. The catheter is then inserted over the stationary stylet, which is subsequently removed. The catheter’s flow switch is locked, and the catheter is secured with tape. The arterial catheter is then connected to the pressure line system.
Arterial Needle in Children
Arterial Needles in Small Children
- Can be placed at the same sites as in adults
- Arterial needles in children usually lack a flow switch valve
- Brachial artery is a good alternative to the radial artery but can result in poor circulation in the arm
- Femoral artery is usually the best option in urgent situations or when high reliability is needed (may cause impaired circulation—should be avoided in children < 3 kg)
- Heparin is recommended in the flush line for arterial pressure monitoring in children (APTT and similar tests cannot be taken from the artery)
- Ultrasound is often helpful for insertion
Arterial Needle Size
- < 6 months – 0.7 mm (yellow needle)
- > 6 months – 0.9 mm (blue needle)
- > 25 kg – adult needle
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