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Circulation - Arterial line insertion (radial)


Blood pressure monitoring

Haemodynamic instability

Failed non-invasive monitoring

Titrating drug therapies


Frequent arterial blood sampling

Contraindications (absolute in bold)

Proximal traumatic injury (absolute)

Deficient collateral circulation

Site infection



Non-invasive blood pressure monitoring

Informed consent

Medical emergency

Consent is not required if the patient lacks capacity or is unable to consent

Brief verbal discussion is recommended if the situation allows


Verbal consent

Less complex non-emergency procedure with low risk of complications

Potential complications


Failure or sampling error (air in sample, venous blood, improper mixing, transportation delay)

Arterial injury (haematoma, haemorrhage, pseudoaneurysm, arterial dissection)

Nerve injury

Thrombosis and distal ischaemia


Procedural hygiene

Standard precautions

Surgical aseptic non-touch technique

PPE: sterile gloves, surgical mask, eye protection, sterile ultrasound probe cover, gown (provider-dependent)


Resuscitation bay or monitored acute bed


Procedural clinician and assistant


Ultrasound (recommended)

Rolled towel and tape (for arm positioning)

Drawing up needle for lignocaine, 25g needle and 5ml syringes

Arterial cannula (long 20g), integral guidewire cannula set or arterial line set

Non-absorbable suture or transparent adhesive dressing

Fluid giving set primed with 500ml of sterile 0.9% sodium chloride in pressure bag at 300mmHg

Transducer set

Arm board

Pre-heparinised 3ml blood gas syringe and non-injectable red bung


Supine with arm and wrist extension (radial artery)

Hand and wrist immobilised in mild dorsiflexion (rolled towel under wrist)


1-2ml lignocaine 1%

Sequence (insertion)

Palpate pulse or locate with ultrasound

Local anaesthetic infiltration

Insert finding needle 30-45 degrees to skin

Obtain arterial flashback

Perform Seldinger technique or cannulate vessel

Pulsatile flow of blood confirms position in vessel

Sequence (set up)

Connect transducer set to giving set under pressure and prime with flush device to remove all air bubbles

Position transducer at phlebostatic axis (height of atria, fourth intercostal space mid-axillary line)

Connect transducer cable to monitor

Calibrate: set off to patient and open to air then press ‘Zero’ on monitor

Calibrate: when ‘0’ on screen, set open to patient and transducer, off to air

Secure line and dress insertion site (suture if difficulty access or difficult to secure)

Arm board to hold wrist in extension (radial site only)

Sequence (collection from arterial line)

Remove bung from sampling port and attach a 5ml syringe

Turn three-way tap so the arterial line is open from the patient to the sampling port

Attach 5ml syringe to the sampling port and aspirate 2-5ml to ensure the line is clear of saline

Turn the three-way tap so the arterial line is closed from the patient to the sampling port

Remove the 5ml syringe and discard into yellow bin

Attach blood gas syringe to the sampling port

Turn three-way tap so the arterial line is open from the patient to the sampling port and allow syringe to fill

Gentle aspirate if passive filling is slow

Turn three-way tap so the arterial line is closed from the patient to the sampling port

Remove the blood gas syringe from the sampling port

Turn the three-way tap so the arterial line is open from the patient to the flush device

Press the flush device together or pull the toggle to flush the line

Turn the three-way tap so the arterial line is open from the flush device to the sampling port

Flush again into sterile gauze swab to ensure all air is expelled from the system

Turn the three-way tap so it is open to the patient and the transducer

Check there is an arterial waveform on the monitor

Place a new red non-injectable bung on the sampling port

Post-procedure care

Limb neurovascular observations (pulse, colour, temperature, sensation and cap refill)

Document insertion site, attempts, guidewire removal (if used) and any immediate complications


The radial artery is the preferred site due to accessibility and collateral circulation

The second option is a femoral arterial line, with brachial as a third option

Lignocaine relieves pain and reduces vasospasm at time of puncture aiding placement

If a catheter fails to thread it has not entered the lumen and should not be forced to advance

Ultrasound can significantly improve first attempt success rate


We do not recommend Allen’s test or a modified version of Allen’s test prior to placing an arterial line. The evidence for this test is weak with case reports of ischaemic complications after normal test results, and case reports of no ischaemic complications after catheterising of patients with abnormal results.

Peer review

This guideline has been reviewed and approved by the following expert groups:

Emergency Care Institute

Please direct feedback for this procedure to


NSW Agency for Clinical Innovation. Arterial lines monitoring and management. Sydney: ACI; 2014. 13pp. ICU guide (2014). Report LH_ICU2014. Available from:

Roberts JR, Custalow CB, Thomsen TW. Roberts and Hedges’ clinical procedures in emergency medicine and acute care. 7th ed. Philadelphia, PA: Elsevier; 2019.

Dunn RJ, Borland M, O’Brien D (eds.). The emergency medicine manual. Online ed. Tennyson, SA: Venom Publishing; 2019.

Theordore AC, Clermost G, Dalton A. Indications, interpretation, and techniques for arterial catheterization for invasive monitoring. In UpToDate. Waltham (MA): UpToDate; 2019. Available from:

Melhuish TM, White LD. Optimal wrist positioning for radial arterial cannulation in adults: A systematic review and meta-analysis. Am J Emerg Med. 2016;34(12):2372-2378. doi:10.1016/j.ajem.2016.08.059

White L, Halpin A, Turner M, Wallace L. Ultrasound-guided radial artery cannulation in adult and paediatric populations: a systematic review and meta-analysis. Br J Anaesth. 2016;116(5):610-617. doi:10.1093/bja/aew097

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