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Selection of a particular guidewire (Figure 3.1) is dictated by the size of access needle that has been placed, the technique to be performed, and the vessel(s) to be selected. Most guidewires are available in three standard lengths: 150, 180, and 260 cm (Braun 1997). Alternative lengths of 60, 125, and 145 cm have been reported, but these are not readily available (Valji 2006; Kipling et al. 2009). The standard diameters of most guidewires are 0.035 and 0.038 inches. Smaller gauge wires generally ranging from 0.010 to 0.018 inches are used when microcatheters and smaller (micropuncture) vascular access needles are used (Braun 1997; Valji 2006; Kipling et al. 2009).

There are a few primary principles that must be adhered to when using guidewires. First, many guidewires contain a hydrophilic coating made of polytetrafluoroethylene that requires priming with saline to allow for smooth passage through the lumen that has been selected (Braun 1997; Kipling et al. 2009). When sufficiently wet, the guidewire should pass easily through a catheter and allow an increased ability to perform vascular selection (Braun 1997; Kipling et al. 2009). It is essential that the guidewire remains wet during the procedure to improve the function of the guidewire (Kipling et al. 2009). Second, the length of the selected guidewire should be at least twice the length of the catheter that is being used (Braun 1997). Third, if a guidewire is not passing easily through a vascular access needle, the needle may need to be repositioned. The wire should not be forced, as the needle may be subintimal or against a sidewall (Valji 2006). Lastly, a torque device can be placed on the end of a guidewire (approximately 5–10 cm from a catheter hub that has been introduced over the guidewire) to better manipulate and steer the guidewire (Kipling et al. 2009). These torque devices can be invaluable when passing a guidewire into vessels that are difficult to access and when crossing stenotic regions.

Guidewires are also used for nonvascular stenting procedures (Hume et al. 2006; Weisse et al. 2006; Culp et al. 2007; Kipling et al. 2009; Hansen et al. 2012). Stents that are placed through malignant obstructions are introduced over a guidewire, and the stent delivery system tapers down to the guidewire to allow for easier placement. In companion animals, 0.035‐inch hydrophilic guidewires have been used to facilitate stent placement for tracheal, urethral, esophageal, and colonic obstructions (Hume et al. 2006; Weisse et al. 2006; Culp et al. 2007, 2011; Hansen et al. 2012).