Procedures

Arterial line insertion and troubleshooting

Reviewed Nov 2026·5 references
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Radial cannulation with ultrasound, transducer set-up, zeroing, and the square-wave test.

Definition
Arterial cannulation provides continuous blood pressure and frequent blood gas sampling. Indications: vasopressors, haemodynamic instability, frequent ABGs, unreliable NIBP. Radial is first choice; femoral and brachial are alternatives.

At the bedside

  1. 1

    Site

    Radial (first choice) > femoral > brachial (end artery, use with caution) > dorsalis pedis.

  2. 2

    Ultrasound

    Ultrasound guidance increases first-pass success and reduces haematoma.

  3. 3

    Technique

    Wrist extended; aseptic; 20 G catheter (radial) via direct puncture or Seldinger; secure and dress.

  4. 4

    Transducer

    Pressure bag at 300 mmHg giving ~3 mL/h flush of saline; no glucose-containing flush.

  5. 5

    Zero and level

    Level the transducer at the phlebostatic axis (4th intercostal space, mid-axillary line); zero to atmosphere; re-level after bed changes.

  6. 6

    Check damping

    Fast-flush (square-wave) test: 1-2 oscillations = optimal; none = overdamped (air, clot, kink); many = underdamped (stiff long tubing).

  7. 7

    Remove

    Remove when no longer needed; check hand perfusion daily.

Local anaesthetic

Lidocaine (lignocaine)

Infiltration
Dose
1-2% lidocaine; stay under 4.5 mg/kg plain
Worked example
70 kg: max ~300 mg plain = 30 mL of 1% (10 mg/mL) or 15 mL of 2%.

Arterial waveform troubleshooting

ProblemEffectFix
OverdampedFalsely low systolic, high diastolic; MAP roughly preservedRemove air bubbles, clot, kinks; check bag pressure
Underdamped (resonance)Overshoot: falsely high systolic, low diastolicShorten tubing; damping device
Transducer too lowAll pressures read highRe-level at phlebostatic axis
Transducer too highAll pressures read lowRe-level
Red flag · call your senior now
Pale, cold or painful hand after radial cannulation: remove the catheter and assess perfusion.
Red flag
Accidental drug injection into an arterial line: stop, leave catheter, seek vascular advice.
Pitfall
Trusting a systolic value from an overdamped trace - use MAP for decisions.
Pearl
The modified Allen test predicts ischaemia poorly; ultrasound of ulnar flow and clinical monitoring are more useful.

References

  1. 1

    Farkas J. The Internet Book of Critical Care (IBCC). EMCrit Project; continuously updated.

  2. 2

    Lamperti M, Biasucci DG, Disma N, et al. European Society of Anaesthesiology guidelines on peri-operative use of ultrasound-guided for vascular access (PERSEUS vascular access). Eur J Anaesthesiol 2020;37:344-76.

  3. 3

    Lamperti M, Bodenham AR, Pittiruti M, et al. International evidence-based recommendations on ultrasound-guided vascular access. Intensive Care Med 2012;38:1105-17.

  4. 4

    Buetti N, Marschall J, Drees M, et al. Strategies to prevent central line-associated bloodstream infections in acute-care hospitals: 2022 update. Infect Control Hosp Epidemiol 2022;43:553-69.

  5. 5

    Neal JM, Barrington MJ, Fettiplace MR, et al. The third American Society of Regional Anesthesia and Pain Medicine practice advisory on local anesthetic systemic toxicity: executive summary 2017. Reg Anesth Pain Med 2018;43:113-23.

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