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Anatomy and sites
Site: Radial artery at the wrist is the most commonly used site.
Other sites include brachial, axillary, ulnar, dorsalis pedis and femoral arteries.
Location: The distal end of the radius between the tendons of the brachioradialis and flexor carpi radialis
Modified Allen test: Radial artery has a collateral circulation, via the ulnar artery, which helps to minimize the risk of ischaemic damage should the radial artery thrombose following cannulation. The collateral supply of the ulnar artery can be demonstrated using the modified Allen test (With the hand open, release the pressure on the ulnar artery and observe the return in color, which should occur within 6 seconds)
- Continuous beat-to-beat heart rate and blood pressure monitoring.
- Frequent blood sampling without the need for repeated arterial puncture.
- Frequent arterial blood gas sampling.
- Inotropic (or vasopressor) support
- Monitoring of waveform for cardiac output and end-diastolic volume estimation.
- Inadequate collateral flow – limbs where the collateral circulation has been demonstrated to be poor
- Active infection or ischemia
- Surgical shunt, such as for renal dialysis
- Anticoagulation & Coagulopathy – hemorrhage may be difficult to control and a hematoma can also lead to distal ischemia
- Hematoma – reduced through minimizing movement of the catheter and by applying adequate pressure
- Risk of infection at the site of puncture – Minimise by cannulae should not be left in place longer than absolutely necessary
Reasons for dampened/no waveform
- Cannula displacement into tissues
- Cannula clotting
- Cannula kinking
- Cannula tip against the vessel wall
- Bubbles in the catheter or system
- Improper zero or transducer calibration
- Incorrect stopcock position
- Loose connection
- Compliant tubing
- Loss of counterpressure from the bag
- Loss of IV fluid
- Tubing kink
- Monitor off/incorrect settings