Arterial Line
Insertion
Continuous, accurate blood-pressure monitoring & repeated arterial blood-gas sampling in the unstable patient — the radial, ultrasound-guided approach.
🔴 Before you start
Arterial lines are never for drug administration. Avoid an end-artery (brachial), an infected or burnt site, a limb with poor collateral flow or an AV fistula. Insert under sterile technique, label the line clearly, and watch the distal limb for ischaemia.
- Haemodynamic instability / shock
- Vasopressor or inotrope titration
- Frequent ABG / blood sampling
- Major trauma · sepsis
- Post-cardiac-arrest care
- Severe respiratory failure
- Labile BP / unreliable NIBP
- Anticipated clinical instability
- Local infection · burns · cellulitis
- Severe peripheral vascular disease
- Inadequate collateral circulation
- AV fistula in the limb
- Proximal traumatic / vascular injury
- Coagulopathy / thrombolysis (relative)
- Raynaud's · Buerger's · scleroderma
- Small or vasospastic artery
- Femoral — larger; higher infection risk
- Dorsalis pedis · posterior tibial
- Axillary (specialist / ICU)
- Sterile gloves, gown, mask & drape
- Chlorhexidine 2% in alcohol
- Linear US probe + sterile sheath & gel
- Arterial line kit — Seldinger (catheter, needle, guidewire)
- 1% lignocaine + syringe
- Pressure tubing + transducer set
- 0.9% saline flush bag in pressure cuff
- Suture / securement device
- Transparent occlusive dressing
Ultrasound by default
Higher first-pass success & fewer complications in adults and children. Shallow angle, bevel-up; in-plane in experienced hands.
🟢 LITFL · Cochrane · Gibbons 2020
Allen's test — not routine
Now considered unreliable & "of historical interest." An abnormal test does not predict ischaemia or contraindicate radial access.
🟢 AHA · RADAR trial · Slogoff 1983
Pressurise to 300 mmHg
Inflate the flush cuff to 300 mmHg for a continuous ~3 mL/h flush — prevents clotting & backflow, keeps the trace crisp.
⚪ Standard transducer set-up
Zero & level the transducer
Level the transducer to the phlebostatic axis (mid-axillary, heart level) and zero to atmosphere — or your numbers lie.
⚪ Deranged Physiology
Prepare & consent
- Explain & consent
- Wrist extended on a roll
- Sterile prep & drape
Prime equipment
- Prime tubing — remove bubbles
- Pressurise bag to 300 mmHg
Zero & level
- Transducer at phlebostatic axis
- Zero to atmosphere
US assessment
- Identify artery — pulsatile, non-compressible
- Assess depth, calibre, path
Local anaesthetic
- Infiltrate 1% lignocaine
- Raise a small wheal at entry
Needle insertion
- Shallow angle, bevel-up
- Aim for the anterior wall
Cannulate
- Pulsatile flashback → flatten angle
- Integral wire or Seldinger — never force
Connect & confirm
- Connect to transducer tubing
- Confirm a true arterial waveform
Secure & dress
- Suture / securement device
- Transparent dressing; label + date
Document & check
- Indication, site, attempts
- Check distal colour, warmth, cap refill
External educational video — tap to play an embedded YouTube clip by Dr Ki-Jinn Chin (not produced by ED AI Tutor). Watch on YouTube ↗ · always confirm technique against your local protocols.
Waveform check
Causes: air bubble, clot, kinked tubing, loose connection, catheter against wall, low pressure-bag, vasospasm or true hypotension.
Transducer setup
Post-procedure
- Confirm waveform & correlate with a cuff BP
- Check distal perfusion hourly — colour, warmth, cap refill
- Keep the flush bag at 300 mmHg & lines visible
- Inspect site for bleeding, swelling, signs of infection
- Remove as soon as no longer needed
- Thrombosis / occlusion most common
- Vasospasm
- Distal ischaemia (rare)
- Haematoma / bleeding
- Infection / CRBSI
- Pseudoaneurysm
- Nerve injury · inaccurate readings
- Use ultrasound as the default
- Choose the best site, not the easiest
- Small needle, shallow angle, anterior-wall puncture
- Never force the wire or catheter
- Strict sterile technique
- Confirm a true waveform before trusting numbers
- Secure well — dislodgement = arterial bleed
- Reassess distal perfusion regularly
- Radial preferred — good collateral, easily palpated
- Ultrasound-guided preferred over landmark
- Use the smallest catheter that does the job
- Avoid Seldinger for radial in small children — vessel may be too small for a wire
- Brachial & femoral are end/large arteries — extra caution
| Age / weight | Catheter |
|---|---|
| Neonate / < 5 kg | 24 G |
| 5 – 20 kg | 22 – 24 G |
| > 20 kg / adult | 20 – 22 G |
Guide only — match to vessel size on ultrasound & clinical judgment.
ED AI Tutor — ED Procedures Series · v0.2 · For clinician education only. Not a substitute for clinical judgment, local guidelines or senior oversight. Always verify drug doses, catheter sizes and contraindications against current institutional protocols.
