A device used for access and bloodless exchange of guide wires and catheters. They also serve as a protection of the vessel or a drainage tract during manipulation and thereby also reduce pain for the patient. Sheaths are available with and without a sealing diaphragm (check-flow valve) (Fig.1). The advantage of a diaphragm is that there is no blood loss once the catheter has been removed so easy catheter exchange and insertion of balloon catheters etc. without blood loss is made possible. Introducer sheaths may allow easy retrieval of foreign bodies without trauma to the vessel wall. Long sheaths may be used to protect the vessel wall against trauma by catheter and guide wire manipulation. Standard sheaths have a length of 10 cm and come in sizes of 4F to 9F, but lengths up to 50 cm and sizes up to 24F are also available. So-called crossover sheaths are used for crossover approaches across the aortic or vena cava bifurcation.
"Peel-away"-sheaths are mainly used for introduction of drainage catheters. The sheath can be "peeled" off the drainage catheter after its insertion.




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Note added at 7 mins (2004-10-25 01:56:24 GMT)
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Ref: http://www.amershamhealth.com/medcyclopaedia/medical/volume ...

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Note added at 16 mins (2004-10-25 02:05:00 GMT)
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Another Simple definition for Catheter sheath (Introducer sheath):

A catheter-like tube that is placed inside a patient\'s vessel during an interventional procedure to help the doctor with insertion and proper placement of the actual catheter. Also called a sheath.

Ref: http://www.tmc.edu/thi/glossary.html