Ultrasound-guided vascular access

What it is

Ultrasound guidance means watching the vessel, and ideally the needle tip, on the screen while the needle is advanced. It is the standard of care for internal jugular lines, it lowers arterial puncture and failed attempts at other central sites, and it rescues patients with difficult peripheral veins (obesity, oedema, drug use, chemotherapy, repeated admissions). A high-frequency linear probe is used. Veins are thin-walled, oval, collapse with gentle probe pressure and often fill with a Valsalva or a tourniquet; arteries are round, thick-walled, pulsatile and do not compress, and colour or pulsed Doppler confirms the difference. There are two views. In the short-axis (out-of-plane) view the vessel is a circle and the needle a bright dot; it is quick to learn but the dot may be the shaft rather than the tip, so the operator walks the probe ahead of the tip step by step. In the long-axis (in-plane) view the whole needle is seen entering the vessel, which avoids going through the back wall but is harder to keep in line. For peripheral cannulas a longer catheter is chosen for deep veins so that most of its length lies inside the vessel; short catheters in deep veins fall out and infiltrate.

Indications

• Internal jugular central line: ultrasound is the standard of care, not an option.
• Subclavian, axillary and femoral central lines and arterial lines, to lower arterial puncture and repeat attempts.
• Difficult peripheral access: after failed attempts, or when no vein can be seen or felt.
• Patients with high bleeding risk, where one clean pass matters most.
• Checking a vein before puncture: patency, size, depth and thrombosis.

Contraindications and precautions

• Thrombosed or non-compressible vein on the scan: choose another vein; a clot is a contraindication at that site.
• Infection, burns or injury over the site: choose another site.
• A very deep, small or tortuous vein: success is low; consider another vein or a different line.
• Inexperience: practise on simulators and under supervision; poor technique turns the probe into false reassurance.
• Central lines need a sterile probe cover and sterile gel; peripheral access still needs a clean probe and skin prep.

Equipment

• Ultrasound machine with a high-frequency linear probe, set to vascular preset and correct depth.
• Sterile probe cover and sterile gel for central lines; clean gel and probe disinfection for peripheral lines.
• Tourniquet (for peripheral veins), skin antiseptic and gloves.
• Cannula of suitable length for the depth, or the central line pack.
• Saline flush, securing device and dressing.

Step by step (and why)

1. Place the screen in your line of sight beyond the site — you look at the needle and image without turning your head.
2. Scan both vessels in short axis and compress gently — the vein collapses, the artery does not.
3. Check depth, size and patency, and add Doppler if unsure — this chooses the vein and the catheter length.
4. Prepare the skin and probe as the line needs (sterile for central) — the probe touches the puncture site.
5. Centre the vein on screen and enter close to the probe at an angle matched to its depth — the tip meets the beam sooner.
6. Out of plane: slide the probe ahead of the tip, move the needle up to the beam, repeat — you follow the tip, not the shaft.
7. See the tip tent and enter the vein, then a flash of blood — seeing the tip inside avoids the back wall.
8. Advance the catheter or wire and confirm it in the vein in long axis — visual proof before dilating or securing.
9. Flush, secure and document the vein used and its depth — the next operator benefits, and infiltration is spotted early.

Vein or artery on the scan

Complications

• Arterial puncture or cannulation when the artery is mistaken for the vein, or the needle passes through the vein.
• Back-wall puncture and haematoma, usually from losing the needle tip in short axis.
• Nerve injury, for example to the median nerve beside the brachial artery when using the basilic or brachial veins.
• Infiltration and early failure of short catheters placed in deep veins.
• Infection if the probe, gel or technique is not clean, and catheter-related thrombosis.

Next step

• Check the cannula or line flushes freely without swelling, then label and document the vein and depth.
• For a central line, complete the central line checks (venous position, chest X-ray for neck and chest lines).
• Call a senior after two failed attempts, or if only the artery can be found.
• Inspect peripheral cannulas each shift for pain, swelling or redness, and remove them when no longer needed.
• Clean and disinfect the probe after each patient as the unit protocol sets.

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Elsewhere in DurgiPedia

• Inserting a peripheral IV catheter
• IV complications: phlebitis, infiltration and extravasation
• Clean and sterile technique: medical and surgical asepsis

Connections

← All clinical skills

Educational content; it does not replace supervised hands-on training, your institution's protocols or a prescriber's order. A procedure is learnt with a teacher and done only once you are trained to do it.

Sources: Ultrasound-Guided Intravenous Access (StatPearls (NCBI Bookshelf), 2025); Central Venous Catheter Insertion (StatPearls (NCBI Bookshelf), 2025).

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Representative model, for educational purposes only.