Generally IV's are started at the most peripheral site that is available and appropriate for the situation. This allows cannulation of a more proximal site if your attempt fails. If you puncture a proximal vein first, and then try to start an IV distal to the site, the fluid may leak from the injured proximal vessel. The veins on the dorsum of the hand are used most commonly because they are easily accessible. If unable to start an IV on the dorsum of the hand the next preferred site is the veins of the forearm and then the median cubital vein that crosses the antecubital fossa. In trauma patients it is common to go directly to the median cubital vein as the first choice because it will accommodate a large bore IV and it is generally easy to catheterize. In circumstances where the veins of the upper extremities are inaccessible the veins of the dorsum of the foot or the saphenous vein of the lower leg can be used. In circumstances where no peripheral IV access is possible a central IV can be started. Central IV's are beyond the scope of this module and so will not be discussed further.