A large pneumatic (i.e., gas-operated) tourniquets is then placed around the upper arm. A rubber strip is wound around the arm in order to express as much blood as possible out of the veins of the arm, the tourniquet is inflated, and then a dilute solution of a local anesthetic drug is injected through the previously placed IV catheter which is subsequently removed. The anesthetic solution seems to work by traveling through the veins to reach the nerves of the arm, which are thus anesthetized, producing numbness of the arm. The numbness continues until the tourniquet is deflated, at which blood flow to the arm is restored and "washes out" the anesthetic with a return of sensation. The primary limitation of the technique stems from the fact that after a period of time the tightness of the tourniquet begins to become difficult to bear. In our practice, we often use a double tourniquet so that when the first one (closest to the shoulder) becomes tiresome, we inflate the second one (closer to the elbow) which lies over a part of the arm that has been numbed. Between this maneuver and supplementation with narcotics and sedatives through the other IV, most patients can be kept comfortable throughout the procedure. If the tourniquet becomes the source of too much discomfort or restlessness, the patient may be given a general anesthetic to carry them through the operation, but this is infrequently required. Complications of the technique are relatively rare; seizures have been reported as a result of too great an amount of local anesthetic solution reaching the body because of tourniquet failure or after deflating the tourniquet following too short an inflation time.