Читать книгу Veterinary Surgical Oncology - Группа авторов - Страница 64

The use of IV sheaths (Figure 3.1) is indicated when a procedure involves multiple exchanges into and out of a vessel. The sheath protects the vessel wall from damage and allows for easier passage of different catheter types. Additionally, sheaths protect the vessel from stiff IV devices, balloon catheters, and IV foreign bodies (Braun 1997; Valji 2006; Stavropoulos et al. 2006).

A dilator that tapers down to a guidewire is usually present within a sheath and allows expansion of the previously made hole in the blood vessel. Sheaths contain a valve that prevents blood leakage while allowing entrance of specialized catheters, wires, stents, snares, and biopsy forceps (Snow and O’Connell 2000; Stavropoulos et al. 2006). Additionally, sheaths contain a sidearm that allows for injection of contrast, which can pass around wires and nonocclusive catheters (Snow and O’Connell 2000; Valji 2006). The French gauge of a sheath is determined by the largest gauge catheter that can fit through the sheath and represents the inner diameter of the sheath (Braun 1997; Snow and O’Connell 2000). The French size of a sheath is generally considered to be 2 French gauges smaller than the outer diameter (Valji 2006).

In human medicine, sheaths have also been used for nonvascular procedures such as antegrade ureteric stenting, percutaneous transhepatic biliary drainage, and colonic stenting (Braun 1997; Snow and O’Connell 2000). The use of sheaths in urethral stenting has been described in veterinary medicine (Weisse et al. 2006; Newman et al. 2009). Some sheaths are designed with a peel‐away component that is used during the placement of venous access devices and drainage catheters (Braun 1997). The peel‐away component allows a device to be inserted through the sheath, and the sheath can then be removed while leaving the device in place.