When to escalate
- Define "difficult access" early — two failed attempts by a competent operator, or a patient with a known history of difficult cannulation (IVDU, chemotherapy, obesity, chronic illness, oedema).
- Escalation ladder: visual/palpation attempt → near-infrared or tourniquet aids → ultrasound-guided peripheral cannulation (deep basilic/brachial/cephalic veins) → alternative routes (intraosseous, external jugular, ultrasound-guided central access) depending on urgency.
- Do not persist with repeated blind attempts — each failed attempt reduces success of subsequent ones and damages veins needed for later access.
- Consider the clinical urgency: in a peri-arrest patient, move to intraosseous access rather than prolonging attempts at difficult IV access.
Vein selection
Preferred deep veins
- Basilic vein — medial upper arm, usually the largest and straightest deep vein; first choice for ultrasound-guided access.
- Brachial vein(s) — paired veins running with the brachial artery; more central, but closer to the neurovascular bundle.
- Cephalic vein — lateral upper arm; smaller and more mobile, technically harder.
Avoid or use with caution
- Veins directly overlying an artery or nerve without a clear ultrasound window.
- Areas of infection, cellulitis, or lymphoedema (e.g. post-mastectomy arm).
- Antecubital fossa veins if a longer indwelling line is anticipated — position affects flow and comfort.
Equipment
Probe orientation — short-axis view
A short-axis (transverse) view shows the vein and artery as circles in cross-section and is the easiest orientation to learn; long-axis (longitudinal) tracks the needle tip along its length once confident. Many operators start short-axis to find the vein, then rotate to long-axis to advance.
Step-by-step technique
Prepare and position
Tourniquet on, arm abducted and externally rotated to expose the medial upper arm. Survey with the probe to identify a straight vessel segment away from bifurcations, valves and the neurovascular bundle.
Confirm the vessel is venous
Compress gently — a vein collapses, an artery does not. Check the vein is not directly superficial to the artery (risk of through-and-through puncture).
Sterile technique
Sterile gel, sterile (or clean single-use) probe cover, skin antisepsis. Use a longer cannula (typically 45–50 mm) — standard-length cannulas often fail to reach deep veins or to keep enough length intraluminal once venous depth is accounted for.
Needle insertion — short-axis
Centre the vein in the image, insert the needle at the midpoint of the probe at roughly 45°, and track the needle tip (a bright dot) as it advances — walk the probe distally in small steps, keeping the tip visualised at all times ("tip-tracking") rather than the shaft.
Confirm entry
Look for the needle tip indenting, then piercing, the anterior vein wall; flashback in the cannula confirms intraluminal position.
Advance and thread
Once flashback is seen, flatten the angle slightly and advance a few millimetres to ensure the plastic cannula (not just the needle tip) is intraluminal before threading it off the needle. Confirm on ultrasound if uncertain.
Secure and confirm patency
Withdraw the needle, connect, flush, and confirm free flow without extravasation. Secure well — deep-vein cannulas dislodge more easily than superficial ones with arm movement.
Complications & troubleshooting
Complications
- Arterial puncture — deep veins run alongside arteries; withdraw and apply firm pressure.
- Extravasation — less visible than with superficial cannulas as the site is deeper; check flow and swelling actively, especially before vesicant or irritant infusions.
- Nerve irritation from repeated attempts near the neurovascular bundle.
- Higher dislodgement rate than superficial cannulas — secure meticulously.
Troubleshooting
- Losing the needle tip on screen — stop advancing, re-locate the tip before continuing.
- No flashback despite apparent wall puncture — the cannula tip may still be extraluminal; confirm position on ultrasound before threading.
- Vein rolls away from the needle — reduce needle angle and re-approach more centrally.
Confirming and documenting
- Confirm the cannula tip lies within the vein lumen (free flush, no resistance, no swelling) before relying on it for irritant drugs or vasopressors.
- Document: vein used, depth, cannula length/gauge, number of attempts, and complications.
- Flag deep-vein cannulas clearly for nursing staff — they are less visible and need more frequent site checks than standard peripheral lines.
Alternatives if this fails
- Intraosseous access — the fastest option in an urgent or arrested patient; see the intraosseous access page.
- External jugular vein — visible with a head-down tilt and Valsalva; a reasonable peripheral option in the deteriorating patient.
- Ultrasound-guided central access (internal jugular or femoral) — for patients needing invasive monitoring, vasopressors, or in whom no peripheral option exists; see the CVC and femoral access pages.
- Escalate early to seniors or vascular access teams for repeatedly difficult access rather than exhausting all sites alone.
Pitfalls & pearls
- Two failed blind attempts is the trigger to switch to ultrasound, not the fifth.
- Track the needle tip, not the shaft — losing tip visualisation is the commonest cause of arterial puncture.
- A standard-length cannula in a deep vein often leaves too little plastic intraluminal — use a longer catheter designed for the purpose.
- Deep-vein cannulas are more prone to silent extravasation — check actively before pushing irritant drugs.
DOPS pointers
RCEM curriculum: point-of-care ultrasound-guided vascular access. What assessors look for at each entrustment level:
| 1 | Observed only — can identify vein vs artery on ultrasound and describe probe orientation. |
| 2a | Performs with direct supervision: correctly identifies the target vessel, maintains needle-tip visualisation, achieves flashback. |
| 2b | Performs with supervisor in the department: manages the whole sequence including securing and confirming patency. |
| 3 | Indirect supervision: troubleshoots lost tip visualisation, arterial proximity, and escalates appropriately when access remains impossible. |
| 4 | Independent; teaches probe orientation and tip-tracking technique to others. |
References
- Moore CL. Ultrasound-guided peripheral venous cannulation in critically ill patients: a practical guideline. Ultrasound J 2019;11:9.
- RCEM Curriculum 2021 — Emergency Medicine Specialty Learning Outcomes: point-of-care ultrasound-guided vascular access.
- Costantino TG, et al. Ultrasonography-guided peripheral intravenous access versus traditional approaches in patients with difficult intravenous access. Ann Emerg Med 2005;46(5):456–461.