Before any guidewire, catheter, balloon, or stent enters a patient's vascular system, an introducer sheath is placed first. It is easy to overlook this component in discussions of more dramatic technologies like atherectomy or stent grafts, but the sheath is the literal gateway through which every other endovascular device must pass — and its design directly affects how smoothly, and how safely, an entire peripheral intervention proceeds.
What Does an Introducer Sheath Actually Do?
An introducer sheath is inserted into the femoral, radial, or other access artery over a guidewire, typically after a small skin incision and initial needle puncture. Once seated, it creates a stable, sealed conduit through the skin and vessel wall, allowing subsequent devices to be exchanged in and out without repeated vessel puncture and with minimal blood loss. The sheath's outer dilator smooths the initial insertion, while the sheath body itself remains in place for the duration of the procedure, anchoring the access site.
The Role of the Hemostasis Valve
A hemostasis valve sits at the proximal end of the sheath and is one of its most important functional components. This valve seals around whatever device is currently passing through it — whether that is a guidewire, catheter, or nothing at all between exchanges — preventing backflow of blood out of the sheath while still allowing devices to slide through with minimal friction. Many sheaths also include a side port near the hub, which allows for continuous flushing with heparinized saline or contrast injection without needing to remove the valve.
Understanding French Sizing
Sheath size is expressed in French (F) units, where each French unit equals approximately 0.33 millimeters of outer diameter. French sizing determines which devices — catheters, balloons, stent delivery systems — can pass through a given sheath, since each of those devices has its own compatible sheath-size requirement listed in its Instructions for Use. Smaller sheaths, such as 4F–6F, are typical for routine diagnostic and standard peripheral interventional work, while larger-bore sheaths, sometimes 7F to well beyond, are required for devices like large-bore aspiration thrombectomy catheters or certain stent graft delivery systems.
Why Sheath Selection Matters Clinically
Selecting the correct sheath size and length is not a trivial step. A sheath that is too small will not accommodate the intended therapeutic device, forcing an exchange mid-procedure. A sheath that is unnecessarily large increases the caliber of the arteriotomy, which can raise the risk of access-site complications such as bleeding, hematoma, or pseudoaneurysm, particularly in smaller-caliber vessels or in patients with significant peripheral arterial disease affecting the access vessel itself. Sheath length also matters in tortuous anatomy, where a longer sheath can provide more stable support further into the vascular tree.
INVAMED's Invaducer Introducer System
INVAMED manufactures the Invaducer Intraducer, an introducer sheath set designed for percutaneous catheter introduction with an emphasis on minimal blood loss during device exchange. According to the manufacturer, the set is intended to include a dilator, guidewire, syringe, and sheath, with the sheath itself incorporating a hemostasis valve and a proximal side port for flushing or contrast delivery. Full specifications, available French sizes, and country-specific availability should be confirmed via the Invaducer Intraducer product page and the applicable Instructions for Use (IFU). The broader peripheral arterial disease device category includes the guidewires, balloons, and stents that pass through sheaths like this one during a typical procedure.
Access Site Care After Sheath Removal
Once the procedure concludes, the sheath is removed and hemostasis is achieved through manual compression, a closure device, or, in some settings, a compression band or dressing. The choice of closure method depends on the sheath size used, the specific artery accessed, and the patient's individual bleeding risk profile, all of which a qualified physician assesses on a case-by-case basis.
Can the same sheath be used for both radial and femoral access?
Sheaths are generally designed with access-site-specific considerations such as length and profile, and radial-specific sheaths are typically shorter and lower-profile than femoral sheaths. The treating physician selects a sheath appropriate to the planned access site and the devices intended for use during the procedure.
Device availability and regulatory status vary by country. Please contact INVAMED or your authorized local distributor for current regulatory information applicable to your region.