When attempting IV insertion, avoid areas at or immediately below a venous valve, as they can complicate the insertion procedure for the following reasons:

• Difficult insertion: Valves can obstruct the passage of the cannula, making insertion more difficult. 
• Risk of damage: Damaging a valve can lead to complications such as thrombophlebitis.
• Inefficient flow: If a catheter tip is positioned near or against a valve, it can impede the flow of fluids or medications.
• Increased risk of occlusion: Catheters placed near valves have a higher tendency to become occluded.
• Patient discomfort: Cannulating a vein at a valve can be uncomfortable. 
• Potential for infiltration: If the catheter is not positioned correctly due to a valve, there is a risk of paravenous infusion into the surrounding tissues, which can cause swelling and pain. 
• Reduced catheter longevity: Catheters placed near valves may not last as long and require more frequent replacement, leading to more discomfort for the patient and additional procedures.
• Blood draw can be difficult: The valve may obstruct the catheter, and there is a high risk of vein rupture if it is punctured during insertion.

For these reasons, when performing venipuncture, palpate the vein carefully and choose a site that feels smooth and free of the palpable “bumps” or resistance that might indicate the presence of a valve. Identifying and avoiding valves can increase the chances of successful IV cannulation, reduce patient discomfort, and decrease the potential for complications.

Here’s how to identify valves:

Palpation

• Use your fingers to palpate the vein gently.
• Valves typically feel like slight “bumps” or “knots” alongside the course of the vein.
• If a noticeable “bump” followed by a depression or void is felt while palpating a vein segment, this may indicate the presence of a valve.

Tourniquet application

• Apply a tourniquet above the site being assessed.
• This causes veins to distend, making it easier to palpate and identify irregularities or bumps that could indicate valves.

Visual inspection

• Valves can sometimes cause a visible bifurcation or branching in the vein.
• Look for areas where the vein appears to split or has a noticeable widening.

A venous valve in a dorsal hand vein is palpable as a slight “bump” or “knot” within the vein.

Transillumination

• Use a transilluminator or “vein light” to illuminate the subcutaneous structures (See Chapter 11: Intravenous Access Training and Assistance Tools in NYSORA’s ‘Mastering difficult IV access’ Manual).
• This can highlight the path of the vein and show areas with potential valves.

Ultrasound

• An increasingly commonly used method for difficult IV placement.
• Ultrasound can visualize the vein’s anatomy, including valves, bifurcations, and diameter.
• It can show real-time blood flow, with valves appearing as echogenic (bright) structures interrupting the vein’s lumen.

Assess blood flow

• Press distal to the site being assessed and release. If the blood flow stops momentarily and resumes, it might indicate proximity to a valve.
• Note: This method is not foolproof but can provide an additional clue.

Experience and training

• As with many clinical skills, the ability to identify veins and their valves improves with experience and training. Over time, practitioners become more adept at distinguishing the feel of a valve from other structures or irregularities in the vein.