Ultrasound-guided peripheral IV: when to use it and step-by-step technique

When no vein can be seen or felt, ultrasound turns a blind stick into a guided one. This guide explains which patients it helps and which it does not, how to choose the vein and the catheter length, how to track the tip in short and long axis, the most common mistakes, and why, in kidney disease, peripheral IV access is also about preserving veins for a future fistula.

For professionals · Updated November 13, 2026 · 10-minute read

Key points

It is not for everyone. In patients with difficult venous access, ultrasound may raise success. In patients with easy veins, a Cochrane review found lower first-pass success and about 95 seconds of extra procedure time [1].
In a meta-analysis of 8 studies (1,660 patients), success was 81% with ultrasound versus 70% without, with fewer punctures and less time, but no fewer complications [2].
The vein: success was higher in veins of 4 mm or more and 0.3–1.5 cm deep [4]. Beyond about 1.6 cm, no vein was cannulated successfully [5].
The catheter: enough of it has to sit inside the vein. With 65% or more of the catheter in the lumen no IV failed; with less than 30%, all of them did [6].
In kidney disease, preserve the arm veins for a future fistula: the Spanish GEMAV guideline recommends the back of the hand for IV lines and blood draws [9].

When to use ultrasound

Difficult intravenous access usually means two or more failed attempts, or no suitable vein that can be seen or felt. For these patients, the US Society of Hospital Medicine recommends real-time ultrasound to reduce procedure time, attempts and needle redirections [3]. Typical situations: obesity, edema, veins damaged by previous treatments or many previous cannulations.

The 2022 Cochrane review (14 trials and 2 quasi-randomized trials, 2,267 participants) tempers the enthusiasm. The effect of ultrasound depends on how difficult the patient is with the landmark technique [1]:

Difficult: it may increase first-pass and overall success (low- or very low-certainty evidence).
Moderately difficult: it probably increases first-pass success.
Easy: it reduced first-pass success (risk ratio 0.89) and lengthened the procedure by about 95 seconds (high-certainty evidence).

So use it where it adds value: after the usual technique has failed, or when you already know the patient is difficult. Many infusion therapy guidelines limit attempts to two per clinician before escalating to someone more experienced or to ultrasound [10].

Equipment

A high-frequency linear probe. A portable or handheld scanner is fine.
Asepsis: a sterile probe cover and gel, or a no-touch technique in which the probe never touches the insertion site, per your facility's protocol.
A catheter long enough for the depth of the vein (how to work it out is below).
A tourniquet and a securement dressing.

Choosing the vein

Criterion	What to look for
Diameter	The strongest factor. In one study, success was higher in veins of 4 mm or more [4]; in another, every extra millimeter of diameter increased the odds of success [5].
Depth	Best between 0.3 and 1.5 cm [4]. Beyond about 1.6 cm no vein was cannulated; below that, a larger, slightly deeper vein is a better target than a thin, superficial one [5].
Course	A straight segment you can follow in long axis, with no bifurcation or valve at the entry point.
That it is a vein	It collapses with light pressure, does not pulsate and Doppler shows continuous or phasic flow. The artery stays round and pulsatile.
That it is healthy	No thrombus (it does not collapse fully, echogenic content) and no thickened walls.
Neighbors	At the elbow and in the upper arm, the basilic and brachial veins run next to the brachial artery and the median nerve: identify them before you needle.

Choosing the catheter: how much ends up in the vein

An ultrasound-guided IV that works when placed can fail within hours if barely any catheter sits inside the vein. In a prospective study of 86 ultrasound-guided IVs in the emergency department [6]:

with less than 30% of the catheter inside the vein, all failed;
with 30–64%, 32% failed;
with 65% or more, none failed.

It is a small observational study, but the geometry explains it. The needle travels roughly depth ÷ sine of the angle before entering the vein. Approximate straight-line calculation:

Vein depth	Path at 30°	Path at 45°	32 mm catheter at 30°: inside the vein
0.5 cm	≈ 10 mm	≈ 7 mm	≈ 22 mm (≈ 70%)
1 cm	≈ 20 mm	≈ 14 mm	≈ 12 mm (≈ 38%)
1.5 cm	≈ 30 mm	≈ 21 mm	≈ 2 mm: it does not reach

In veins 1 cm deep or more, a standard catheter falls short: use a longer one and measure depth at the exact entry point. The same geometry decides the length of fistula needles (see dialysis needle size, length and angle).

Step-by-step technique

Short axis (out of plane) with dynamic needle tip positioning

This is the most widely used approach for peripheral IVs: the vein appears as a circle and is easy to keep centered. In a phantom study, ultrasound novices were more successful tracking the tip in short axis than in long axis (97% vs 81%) [7].

Apply the tourniquet, find the vein in short axis and center it on screen, under the middle of the probe. Measure its depth without pressing.
Puncture at the midline of the probe, at a distance similar to the vein's depth, at an angle of about 30–45°.
Advance until you see the bright dot of the needle. Slide the probe away until it disappears and back just enough to recover it: that last visible dot is the tip.
Advance the needle 1–2 mm, slide the probe again and repeat until you see the tip indent the wall (tenting) and enter the center of the lumen.
At flashback, lower the angle and advance the tip a few millimeters further inside the lumen, tracking it with the probe. The catheter tip sits slightly behind the bevel: if you advance the catheter as soon as you see flashback, it may end up outside.
Advance the catheter over the needle, remove the needle and check in long axis that the catheter is inside the vein.
Flush with saline: with the probe on, you will see microbubbles travel down the vein, with no collection around it. Secure the catheter.

Long axis (in plane)

You see the whole needle, tip included, and can judge how much catheter goes in, but you have to keep the needle inside a beam only a few millimeters thick. It is useful in large, straight veins and to confirm the final catheter position. Both approaches are compared in the guide to ultrasound-guided fistula cannulation: the technique is the same.

Common mistakes

Mistaking the needle shaft for the tip in short axis. In a phantom study, 64% of residents went through the back wall of the jugular vein while feeling confident [8]. Do not advance until you have found the tip.
Advancing the catheter too early, with the bevel in the lumen but the catheter tip still in the wall.
A catheter too short for the depth: it works at first and fails within hours.
Pressing with the probe: the vein collapses and disappears from the screen.
Hitting the artery: check compressibility, pulsation and Doppler first (see artery vs vein).
Choosing a vein that is too deep because it looks good: beyond 1.5 cm, success falls [4,5].

In kidney disease: preserve the veins

In a person with advanced chronic kidney disease, the forearm and upper-arm veins are the raw material for a future arteriovenous fistula. Every IV, blood draw and phlebitis can damage them. The Spanish GEMAV guideline recommends preserving these patients' venous network and using the veins on the back of the hand for IV lines and blood draws [9].

Ask whether the patient has advanced kidney disease or will need dialysis before choosing the vein.
Never place an IV or draw blood in an arm with an arteriovenous fistula.
If you need ultrasound to find a vein, avoid forearm and upper-arm veins, above all the cephalic vein of the non-dominant arm [9]. If there is no alternative, choose the one of least value for a future access, agree it with nephrology and record it in the chart.

Practice it in the simulator. The "Difficult peripheral IV" case reproduces difficult venous access: a thin, deep basilic vein above the elbow, with the brachial artery and the median nerve beneath it. You cannulate it with an over-the-needle catheter: flashback, advance 1–2 mm further, slide the catheter while holding the needle still, remove the needle and flush with saline. It has its own list of steps and its own assessment, which measures how much catheter ends up inside the vein, and lesson 9 walks you through it step by step. The patient in the case does not have kidney disease: in advanced kidney disease, that vein is precisely one of those to preserve.

Guided lesson: ultrasound-guided peripheral IV Open the case: difficult peripheral IV Guided lesson: artery or vein? Guided lesson: short axis (DNTP)

Frequently asked questions

Which patients benefit from an ultrasound-guided IV?

Those with difficult venous access: two or more failed attempts, or no vein that can be seen or felt. In patients with easy veins it does not help: a Cochrane review found lower first-pass success and a longer procedure with ultrasound.

In plane or out of plane for a peripheral IV?

Short axis (out of plane) with dynamic tip positioning is the most widely used and worked best for novices in a phantom study. Long axis shows the whole needle and helps confirm the catheter. In practice, learn both.

What catheter length should I use?

Long enough for at least two thirds to sit inside the vein. In veins 1 cm deep or more, a standard catheter falls short and a longer one is better. Measure depth at the entry point.

How many attempts are acceptable?

Many guidelines limit attempts to two per clinician before escalating to someone more experienced or to ultrasound. Every extra attempt damages veins and adds discomfort.

How do you tell a vein from an artery on ultrasound?

The vein flattens with light probe pressure and does not pulsate; the artery stays round and pulsatile. Color or pulsed-wave Doppler confirms it: continuous or phasic flow in the vein, pulsatile flow in the artery.

Can an IV be placed in a fistula arm?

No. The arm with an arteriovenous fistula is not used for IVs, blood draws or blood pressure measurement. In advanced kidney disease, it is also wise to preserve the veins of both arms and use the back of the hand.

Educational content. It does not replace supervised hands-on training or your facility's protocols.

References

Tada M, Yamada N, Matsumoto T, Takeda C, Furukawa TA, Watanabe N. Ultrasound guidance versus landmark method for peripheral venous cannulation in adults. Cochrane Database Syst Rev. 2022;12(12):CD013434. doi.org
van Loon FHJ, Buise MP, Claassen JJF, et al. Comparison of ultrasound guidance with palpation and direct visualisation for peripheral vein cannulation in adult patients: a systematic review and meta-analysis. Br J Anaesth. 2018;121(2):358-366. doi.org
Franco-Sadud R, Schnobrich D, Mathews BK, et al. Recommendations on the use of ultrasound guidance for central and peripheral vascular access in adults: a position statement of the Society of Hospital Medicine. J Hosp Med. 2019;14:E1-E22. doi.org
Witting MD, Schenkel SM, Lawner BJ, Euerle BD. Effects of vein width and depth on ultrasound-guided peripheral intravenous success rates. J Emerg Med. 2010;39(1):70-75. pubmed.ncbi.nlm.nih.gov
Panebianco NL, Fredette JM, Szyld D, et al. What you see (sonographically) is what you get: vein and patient characteristics associated with successful ultrasound-guided peripheral intravenous placement in patients with difficult access. Acad Emerg Med. 2009;16(12):1298-1303. pubmed.ncbi.nlm.nih.gov
Pandurangadu AV, Tucker J, Brackney AR, Bahl A. Ultrasound-guided intravenous catheter survival impacted by amount of catheter residing in the vein. Emerg Med J. 2018;35(9):550-555. doi.org
Clemmesen L, Knudsen L, Sloth E, Bendtsen T. Dynamic needle tip positioning: ultrasound guidance for peripheral vascular access. A randomized, controlled and blinded study in phantoms performed by ultrasound novices. Ultraschall Med. 2012;33(7):E321-E325. doi.org
Blaivas M, Adhikari S. An unseen danger: frequency of posterior vessel wall penetration by needles during attempts to place internal jugular vein central catheters using ultrasound guidance. Crit Care Med. 2009;37(8):2345-2349. doi.org
Ibeas J, Roca-Tey R, Vallespín J, Moreno T, et al. Spanish Clinical Guidelines on Vascular Access for Haemodialysis (GEMAV). Nefrología. 2017;37(Suppl 1):1-191. doi.org
Cancer Nurses Society of Australia. Patients with difficult intravenous access. In: Vascular access devices, section 2: vessel health and preservation. cnsa.org.au