Causes and Solutions of the Trampoline Effect.

A trampoline effect may occur mainly when a buttonhole tract and the vessel flap fail to form a straight line. Certain findings, however, suggest another cause is when the vessel flap is too small. The frequency of the trampoline effect, for example, is lower when a buttonhole tract is created by multiple punctures of the arteriovenous fistula (AVF) vessel than when it is done by one-time puncture of the vessel. Lower frequency of the trampoline effect with multiple punctures of the AVF vessel may be due to enlargement of the initial puncture hole on the vessel every time the vessel is punctured with a sharp needle. Even if aiming at exactly the same point on the AVF vessel every time, the actual puncture point shifts slightly at every puncture, which potentially results in enlargement of the initial hole on the AVF vessel. Moreover, in some patients, continued use of a buttonhole tract for an extended period of time increases the frequency of the trampoline effect. In such cases, reduction of the incidence of the trampoline effect can be achieved by one buttonhole cannulation using a new dull needle with sharp side edges that is used to enlarge the vessel flap. Such single buttonhole cannulation may suggest that the increased frequency of the trampoline effect also potentially occurs in association with gradually diminishing flap size. As a final observation, dull needle insertion into a vessel flap in the reverse direction has been more smoothly achieved than insertion into a vessel flap in the conventional direction. A vessel flap in the reverse direction can be adopted clinically.