UUCI Health · Department of Neurology
APP Class II · Procedural Competency Series · 2026
●  Procedure 05·Neurocritical Care·Moderate-risk tier
05.

Arterial Line

Radial.

Continuous MAP monitoring under POCUS guidance — the default arterial site for aSAH, ICH, TTM, and status epilepticus.
Chadwycke R. Smith, MSN, NP, AGACNP-BC
APP Education · Department of Neurology
Approving authority: Claire Henchcliffe, MD, DPhil · Chair, Department of Neurology
Version 2.0 · 2026-05-11
Source-of-truth: 01_Procedures/05_Arterial_Line_Radial/
A-line Radial · UCI Neurology APP Class II
01 / 22
UUCI · APP Class II
Procedure 05 · A-line Radial
02 · Why this matters
Asymptomatic transient radial thrombosis
~20%
of placements — usually silent and self-resolving. Symptomatic hand ischemia is < 1%, but is the principal serious complication specific to the radial site.
  • Default arterial site — continuous MAP in aSAH, ICH, TTM, status epilepticus.
  • Lower complication profile than femoral in most patients.
  • Reliable ulnar collateral via the deep + superficial palmar arches.
  • Frequent ABG sampling without repeated arterial puncture.
  • Femoral fallback when shock, weak pulse, or failed radial attempts dictate.
Scheer B, Perel A, Pfeiffer UJ. Crit Care. 2002;6(3):199–204 · PMID 12133178
Brzezinski M, Luisetti T, London MJ. Anesth Analg. 2009;109(6):1763–81 · PMID 19923502
A-line Radial · Why this matters
02 / 22
UUCI · APP Class II
Procedure 05 · A-line Radial
03 · Course objectives

What you'll leave with — six competencies.

01 · Cognitive

Indications & contraindications.

Pressor titration, hypertensive emergency, frequent ABGs, beat-to-beat MAP monitoring; absolute and relative contraindications.

02 · Cognitive

Anatomy & collateral flow.

Radial artery course at the wrist; ulnar collateral via the deep + superficial palmar arch; documentation as the standard.

03 · Psychomotor

US-first technique.

Short-axis at the wrist; long-axis in-plane for real-time needle-tip tracking; preferred over modified Allen alone.

04 · Psychomotor

Transducer setup.

Level to the phlebostatic axis · zero to atmosphere · square-wave damping check before any titration.

05 · Cognitive

Waveform interpretation.

Recognize over- and under-damped tracings; correlate with cuff pressure on discordance; do not treat artifact.

06 · Affective

Complication recognition.

Occlusion, distal ischemia, hematoma, nerve injury — hourly perfusion check, remove early, escalate cleanly.

A-line Radial · Course objectives
03 / 22
UUCI · APP Class II
Section I of III
I.
Section one

Anatomy & collateral flow.

Distal ventral wrist — radial artery between FCR tendon and radius, with the ulnar artery as the collateral safety net. Document the assessment before you puncture.
Objectives C-1 · C-2 · C-3 · C-6 — slides 5–7
A-line Radial · Section I
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UUCI · APP Class II
Procedure 05 · A-line Radial
04 · Anatomy

The radial artery at the wrist.

Classical anatomical engraving of the radial artery at the pulse groove at the distal wrist, between the flexor carpi radialis tendon medially and the distal radius laterally, with adjacent musculature
Hughes AW · Wikimedia · Radial Artery at Gouttière du PoulsPublic domain
Landmark stack — distal ventral wrist
  • Artery courses between FCR tendon (medial) and the distal radius (lateral)
  • Palmar to the radial styloid process
  • Paired venae comitantes flank the artery
  • Superficial branch of the radial nerve runs deep and lateral
  • Deep palmar arch supplies ulnar collateral to the hand
  • Most superficial and accessible at the distal ventral wrist
Brzezinski M, Luisetti T, London MJ. Radial artery cannulation: a comprehensive review. Anesth Analg. 2009;109(6):1763–81 · PMID 19923502
A-line Radial · Anatomy at the wrist
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UUCI · APP Class II
Procedure 05 · A-line Radial
05 · Ultrasound

Short-axis at the wrist — identify before you puncture.

Sonographic signatures
  • Radial artery — pulsatile, round, thick-walled, non-compressible
  • Venae comitantes — paired, thin-walled, compressible under probe pressure
  • FCR tendon — echogenic fibrillar structure medial to the artery
  • Distal radius — posterior acoustic shadow as deep landmark
  • Color Doppler confirms arterial pulsatility in weak-pulse or hypotensive patients
When US is indicated over palpation

Weak or impalpable pulse · obesity · vasopressor-dependent shock · edema · prior failed landmark attempts. Long-axis in-plane once short-axis localization is established — real-time needle-tip tracking reduces posterior-wall transfixion.

Brzezinski M et al. Anesth Analg. 2009;109(6):1763–81 · PMID 19923502
Sonographic schematic — pool gap
Short-axis: pulsatile artery, paired compressible veins, FCR tendon medial, radius shadow deep.
No PD/CC sonogram in poolGenerative top-up flagged
A-line Radial · Ultrasound
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UUCI · APP Class II
Procedure 05 · A-line Radial
06 · Collateral flow assessment

Document the assessment — not a pass/fail.

Three accepted methods
  • 01
    Modified Allen test. Compress radial + ulnar · clench & blanch palm · release ulnar · flush in < 6 s = adequate collateral. Sensitivity is poor — used alone it does not exclude ischemia risk.
  • 02
    POCUS ulnar Doppler. Color Doppler over the deep palmar arch with radial compression confirms ulnar inflow. Modern standard for collateral assessment per Shiloh 2011.
  • 03
    Clinical-judgment note. When neither is feasible, an explicit clinical judgment note in the pre-procedure record satisfies the documentation requirement.
Shiloh AL et al. Chest. 2011;139(3):524–9 · PMID 20724734 · Brzezinski M et al. Anesth Analg. 2009;109(6):1763–81
Anatomical plate showing the radial and ulnar arteries at the wrist and hand with deep and superficial palmar arches forming the collateral circulation
Piersol GA · Wikimedia · Radial & Ulnar Arteries at Wrist & HandPublic domain
UCI standard

Documentation of a collateral flow assessment — by Allen, POCUS, or clinical-judgment note — is the standard. Pass/fail of the Allen test alone is not.

A-line Radial · Collateral flow
07 / 22
UUCI · APP Class II
Procedure 05 · A-line Radial
07 · Indications · contraindications

When radial wins — and when it doesn't.

Indications
  • Tight MAP control — aSAH, ICH, hypertensive emergency
  • TTM and post-arrest neuroprognostication
  • Status epilepticus on continuous infusions / pressors
  • Frequent ABG sampling — pressor or vent titration
  • Default first site when collateral is intact and wrist accessible
Scheer B et al. Crit Care. 2002;6(3):199–204 · PMID 12133178
Brzezinski M et al. Anesth Analg. 2009;109(6):1763–81 · PMID 19923502
Contraindications & ASRA holds
  • Absolute: inadequate ulnar collateral · active infection at site
  • Absolute: Raynaud · Buerger · vasculitis
  • Absolute: ipsilateral AV fistula or planned dialysis access
  • Absolute: prior ipsilateral radial harvest (CABG)
  • Relative: severe vasoconstriction on high-dose pressors · severe coagulopathy
  • ASRA holds: ASA continue · clopidogrel 7d · UFH 4–6h · LMWH prophy 12h / Tx 24h · DOACs 48–72h · INR ≤ 1.4 elective
Kopp SL, Horlocker TT, Vandermeulen E, et al. Reg Anesth Pain Med. 2025 · PMID 39880411
A-line Radial · Indications & contraindications
08 / 22
UUCI · APP Class II
Procedure 05 · A-line Radial
08 · Pre-procedure · time-out

Laterality is the safety focus.

  • 01
    Informed consent. Indication · femoral-fallback alternative · material risks (thrombosis, hematoma, ischemia, nerve injury) · refusal pathway acknowledged. Surrogate when patient lacks capacity.
  • 02
    Labs reviewed. Platelets · INR · PTT. Apply ASRA holds for antithrombotics.
  • 03
    Collateral flow documented. Allen, POCUS, or clinical-judgment note — recorded in pre-procedure note.
  • 04
    Laterality confirmed. Left wrist vs right wrist — stated aloud. This is the named safety focus for the lateralized procedure.
  • 05
    Team time-out. Per TJC UP.01.03.01 — correct patient, procedure, side, equipment, consent. Transducer primed · flush bag pressurized to 300 mmHg.
TJC standard

UP.01.03.01

Pre-procedure verification, site marking, formal time-out — and for radial, laterality is the verification that matters most.
The Joint Commission. Universal Protocol UP.01.03.01.
TJC Hospital Accreditation Standards · 2024.
If a complication occurs — bedside disclosure to patient + family within 24 h per UCI policy.
A-line Radial · Pre-procedure verification
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UUCI · APP Class II
Key fact · POCUS-first
Shiloh meta-analysis · Chest · 2011
62%
first-pass success with ultrasound-guided radial cannulation versus 34% with palpation alone. POCUS-first is the institutional default.
Weak pulse
US mandatory
Hypotension
US mandatory
Obesity / edema
US mandatory
2 failed landmark
Escalate to US
Shiloh AL et al. Chest. 2011;139(3):524–9 · PMID 20724734 · update: Wu G et al. J Clin Med. 2022;11(21):6539 · PMID 36362767
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UUCI · APP Class II
Procedure 05 · A-line Radial
09 · Kit · ultrasound pre-scan

What's on the table — before you scrub.

Kit checklist
  • Integrated radial a-line kit (Seldinger)
  • Or over-the-needle cannula (transfixion)
  • Chlorhexidine-alcohol prep stick
  • Sterile fenestrated drape
  • 1% lidocaine · 25g needle · 3 mL syringe
  • Pressurized flush transducer set (primed)
  • Pressure bag at 300 mmHg · ~3 mL/hr
  • Suture or StatLock securement
  • Transparent occlusive dressing (CHG-impregnated)
  • Linear high-frequency US probe · sterile sleeve · gel
Pre-scan rules
  • Linear high-frequency probe (vascular preset)
  • Short-axis confirms pulsatility + non-compressibility (artery) vs paired compressible veins
  • Identify FCR tendon medial · distal radius shadow deep
  • Map artery depth, diameter, anatomic variants
  • Color Doppler for weak-pulse / hypotensive cases
  • Mark skin entry under probe footprint
Brzezinski M et al. Anesth Analg. 2009;109(6):1763–81 · Shiloh AL et al. Chest. 2011;139(3):524–9
A-line Radial · Kit & ultrasound
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UUCI · APP Class II
Section II of III
II.
Section two

Cannulation &
waveform.

Eight numbered steps. Integrated Seldinger or transfixion — both accepted. Every step a gate. The waveform is the last verification.
Objectives P-1 · P-2 · P-4 · P-5 · P-6 · P-7 · P-8 · C-7 — slides 13–16
A-line Radial · Section II
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UUCI · APP Class II
Procedure 05 · A-line Radial
10 · Steps 1–3

Position, prep, anesthetize.

01

Position ·
wrist on a roll.

  • Arm supinated on flat surface
  • Wrist extended 30–45° over a folded towel roll
  • Forearm secured to armboard / bed
  • Fingers exposed for distal perfusion checks
  • Identify radial pulse at maximum impulse
02

Prep & drape ·
sterile field.

  • Hand hygiene · sterile gloves · mask · eye protection
  • CHG-alcohol prep — scrub 30 s · dry 2 min
  • Sterile fenestrated drape over wrist
  • Sterile probe cover when US is used
  • Maintain sterile field throughout
03

Local anesthesia ·
shallow wheal.

  • 1–2 mL of 1% lidocaine in a 3 mL syringe
  • 25g needle for the skin wheal
  • Infiltrate over the palpated pulse
  • Small subcutaneous only — avoid deep injection
  • Wait 60 s for anesthetic onset
O'Grady NP et al. Clin Infect Dis. 2011;52(9):e162–e193 · PMID 21460264 · TJC IC.02.02.01
A-line Radial · Steps 1–3
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UUCI · APP Class II
Procedure 05 · A-line Radial
11 · Steps 4–6

Localize, enter, flashback.

Anatomical plate of the forearm showing the course of the radial artery from the cubital fossa to the wrist, with the parallel ulnar artery
Gerrish F · Wikimedia · Radial & Ulnar ArteriesPublic domain
04

Pulse · US
localization.

  • Palpate point of maximum impulse
  • Pre-scan short-axis to confirm artery
  • Doppler for weak-pulse / shock
  • Mark position + depth
  • Long-axis in-plane for needle-tip tracking
05

Needle entry ·
30–45°.

  • 30–45° angle to skin
  • Steeper under US short-axis
  • Shallower for landmark / palpation
  • Advance slowly
  • Two approaches: Seldinger vs transfixion
06

Pulsatile
return.

  • Bright-red, pulsatile flash at hub
  • Stabilize the needle — do not advance
  • Confirm: pulsatile + bright red
  • Differentiate from venous (dark, non-pulsatile)
  • WIRE-NEVER-LOST if Seldinger.
A-line Radial · Steps 4–6
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UUCI · APP Class II
Procedure 05 · A-line Radial · Critical checkpoint
Critical · level · zero · square-wave before you trust the number

Prove the waveform is real
before you titrate.

Optimally damped

Sharp systolic upstroke · dicrotic notch visible · 1–2 brisk undershoots after the square-wave release. Proceed.

Over-damped

Blunted upstroke · absent dicrotic notch · no oscillations. Underestimates systolic, overestimates diastolic. Check air in tubing, kinks, clots, loose connections, catheter against vessel wall.

Under-damped

Exaggerated upstroke with ringing · > 2 oscillations. Overestimates systolic. Shorten or stiffen tubing · remove stopcocks · re-prime. Do not treat the spuriously high systolic.

Phlebostatic axis
4th intercostal space · mid-axillary line.
Zero to atmosphere. Re-level on position change.
Bress AP, Anderson TS, Flack JM, et al. Hypertension. 2024;81(8):e94–e106 · PMID 38804130
Scheer B et al. Crit Care. 2002;6(3):199–204 · PMID 12133178
A-line Radial · Critical waveform checkpoint
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UUCI · APP Class II
Procedure 05 · A-line Radial
12 · Steps 7–8

Cannulate, secure, perfusion check.

Cadaveric dissection at the distal forearm showing the radial artery and its relationship to surrounding structures at the planned cannulation depth
Anatomist90 · Wikimedia · Radial arteryCC BY-SA 3.0
Cadaveric close-up at the wrist showing the radial artery cannulation target between the flexor carpi radialis tendon and the radius
Anatomist90 · Wikimedia · Wrist · radial detailCC BY-SA 3.0
Step 07 — wire or cannula advance
  • Seldinger: advance J-tip wire smoothly · no force on resistance · wire-never-lost
  • Thread catheter over wire into the artery · withdraw wire in one motion
  • Transfixion: deliberately through both walls · remove stylet · slowly withdraw catheter until pulsatile flashback returns
  • Advance catheter into the lumen · confirm pulsatile blood return
Step 08 — secure · dress · perfusion check
  • Suture or StatLock securement at the hub
  • Transparent occlusive dressing over insertion site
  • Fingers exposed · wrist immobilizer optional for restless patients
  • Immediate distal perfusion check — pulse · color · temperature · capillary refill at thumb and index
  • Order set: continuous pressurized flush · q1h perfusion checks × 4h · escalation parameters
A-line Radial · Steps 7–8
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UUCI · APP Class II
Section III of III
III.
Section three

Recognize.
Remove.

The catastrophe is not the cannulation — it is the delay in removing the line when the hand goes cool. The catheter is replaceable. The hand is not.
Objectives C-8 · A-3 · A-4 — slides 18–19
A-line Radial · Section III
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UUCI · APP Class II
Procedure 05 · A-line Radial
13 · Complications

Five events you diagnose on sight.

ComplicationIncidenceRecognitionAction / escalation
Thrombosis · occlusion ~20% asymptomatic, transient Loss of waveform · loss of pulse on removal Smaller catheter + shorter dwell lower risk · usually silent + self-resolves.
Hand · digit ischemia < 1% symptomatic Pallor · pain · paresthesia · loss of pulse · delayed capillary refill at thumb / index Immediate removal · direct pressure · attending + vascular surgery consult if not resolving.
Hematoma Common · usually minor Swelling · bruising at site Direct pressure ≥ 5 min post-removal · longer if anticoagulated · mark and re-check.
Infection · CRBSI Rare · < 1 / 1,000 catheter-days target Site erythema · purulence · positive cultures Sterile technique + CHG-alcohol prep + daily review per CDC 2011.
Radial nerve injury Zero tolerance New radial-distribution sensory or motor deficit Remove line · document · neurology consult · triggers focused review.
Pseudoaneurysm · AV fistula Late vascular Pulsatile mass · bruit post-removal Vascular ultrasound · surgery consult.
Brzezinski M et al. Anesth Analg. 2009;109(6):1763–81 · PMID 19923502 · Scheer B et al. Crit Care. 2002;6(3):199–204 · PMID 12133178 · Mariano-Gomes PM et al. Enferm Intensiva. 2024;35(4):410–427 · PMID 39004562
A-line Radial · Complications
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UUCI · APP Class II
Procedure 05 · A-line Radial
14 · Pitfalls

Four errors we see — repeatedly.

01

Under-damped waveform missed.

A spuriously elevated systolic gets treated. Square-wave test on every connection and every shift. If the invasive reading disagrees with the cuff by > 20 mmHg, trust neither until you re-prove the system.

02

Failure to re-level the transducer.

Patient repositioned, bed lowered, transducer never moved — your MAP is wrong. Re-level to the phlebostatic axis after any position change.

03

Allen test alone for collateral.

The modified Allen test has poor sensitivity. Where POCUS is feasible, POCUS Doppler of the deep palmar arch is the modern standard. Documentation is the requirement — not a pass / fail score.

04

Late removal on distal ischemia.

Pallor, pain, paresthesia, loss of pulse — remove first, escalate second. The catheter is replaceable. The hand is not.

A-line Radial · Pitfalls
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UUCI · APP Class II
Procedure 05 · A-line Radial
15 · UCI FPPE · OPPE

Your competency pathway.

StageTriggerScope
FPPEBoard approval of radial A-line privilegeFirst 3 independent cases · concurrent review within 14 d · aggregate at 3-case completion · close within 6 mo
OPPEContinuous baseline · q6 mo (TJC MS.08.01.03)10% sample (min 2 · max 10) · 100% review on any complication flag
Triggered FPPEHand ischemia · nerve injury · CRBSI · ≥ 2 failed in 90 dAd-hoc focused review · 3 subsequent cases · a/b/c outcome
Reinstatement< 3 cases / rolling 24 moStream B + 1 proctored case rated Independent
Tracked OPPE indicators
  • First-attempt success ≥ 70% (radial baseline)
  • US used ≥ 80% overall · 100% in shock / weak-pulse / obesity / 2 failed landmark
  • Symptomatic thrombosis < 2% · hand ischemia < 0.5%
  • Radial nerve injury — zero tolerance
  • Optimal damping at 24 h ≥ 85%
  • CRBSI < 1 / 1,000 catheter-days
  • Documentation completeness 100%
Moderate-risk tier Departures require written justification.
A-line Radial · FPPE / OPPE pathway
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UUCI · APP Class II
Procedure 05 · A-line Radial
16 · References & acknowledgments

Sources of truth.

  1. 01Brzezinski M, Luisetti T, London MJ. Radial artery cannulation: a comprehensive review of recent anatomic and physiologic investigations. Anesth Analg. 2009;109(6):1763–81. PMID 19923502.
  2. 02Shiloh AL, Savel RH, Paulin LM, Eisen LA. Ultrasound-guided catheterization of the radial artery: a systematic review and meta-analysis. Chest. 2011;139(3):524–9. PMID 20724734.
  3. 03Scheer B, Perel A, Pfeiffer UJ. Clinical review: complications and risk factors of peripheral arterial catheters used for haemodynamic monitoring. Crit Care. 2002;6(3):199–204. PMID 12133178.
  4. 04Mariano-Gomes PM, Ouverney-Braz A, Oroski-Paes G. Adverse events with arterial catheters in intensive care units: a scoping review. Enferm Intensiva (Engl Ed). 2024;35(4):410–427. PMID 39004562.
  5. 05Kopp SL, Horlocker TT, Vandermeulen E, et al. Regional anesthesia in the patient receiving antithrombotic or thrombolytic therapy: American Society of Regional Anesthesia and Pain Medicine evidence-based guidelines (5th ed). Reg Anesth Pain Med. 2025. PMID 39880411.
  6. 06O'Grady NP, Alexander M, Burns LA, et al. Guidelines for the prevention of intravascular catheter-related infections. Clin Infect Dis. 2011;52(9):e162–e193. PMID 21460264.
  7. 07The Joint Commission. Universal Protocol UP.01.03.01. TJC Hospital Accreditation Standards; 2024.
  8. 07aThe Joint Commission. Universal Protocol UP.01.01.01 — preprocedure verification; use a standardized list (H&P, signed consent, nursing & preanesthesia assessment, labeled imaging, required equipment/devices). National Patient Safety Goals (HAP); effective January 2025.
  9. 07bThe Joint Commission. NPSG.01.01.01 EP 1 — use at least two patient identifiers (room number is not an identifier) before any treatment or procedure. National Patient Safety Goals (HAP); effective January 2025.
  10. 07cThe Joint Commission. NPSG.07.01.01 EP 1 — implement CDC and/or WHO hand-hygiene categories IA, IB, IC. National Patient Safety Goals (HAP); effective January 2025.
  11. 07dThe Joint Commission. Universal Protocol UP.01.02.01 — mark the procedure site; mark by the accountable licensed practitioner (APRN/PA delegation permitted per institutional policy); unambiguous, visible after prep & drape. National Patient Safety Goals (HAP); effective January 2025.
  12. 07eThe Joint Commission. NPSG.03.04.01 — label all medications, medication containers, and solutions on and off the sterile field (name, strength, amount, diluent, expiration). EP 4 requires two-individual verification when preparer ≠ administrator. National Patient Safety Goals (HAP); effective January 2025.
  13. 07fThe Joint Commission. NPSG.06.01.01 — clinical alarm safety; clinically appropriate settings, authority to change parameters, monitoring/response, and periodic accuracy checks for high-risk alarms. National Patient Safety Goals (HAP); effective January 2025.
  14. 07gThe Joint Commission. NPSG.02.03.01 EP 1 — report critical results of tests and diagnostic procedures within an established time frame; written procedures define which results are critical and to/from whom they are reported. National Patient Safety Goals (HAP); effective January 2025.
  15. 08The Joint Commission. IC.02.02.01 — implement evidence-based practices to prevent HAIs. 2024.
  16. 09The Joint Commission. HR.01.06.01 — competence verified before patient care. 2024.
  17. 10The Joint Commission. MS.08.01.01 / MS.08.01.03 — FPPE and OPPE for privileged practitioners. 2024.
  18. 11Bress AP, Anderson TS, Flack JM, et al. The management of elevated blood pressure in the acute care setting: a scientific statement from the American Heart Association. Hypertension. 2024;81(8):e94–e106. PMID 38804130.
  19. 12Wu G, Chen C, Gu X, et al. Ultrasound-Guided Dynamic Needle-Tip Positioning Method Is Superior to Conventional Palpation and Ultrasound Method in Arterial Catheterization: a systematic review and meta-analysis. J Clin Med. 2022;11(21):6539. PMID 36362767.
  20. 13UCI APP Class 2 Training Plan Process. Department of Neurology, University of California, Irvine. April 2026.
A-line Radial · References
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UUCI · APP Class II
Procedure 05 · A-line Radial
End of module · Procedure 05

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UCI Health · APP Education
Version 2.0 · 2026-05-11
A-line Radial · End
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