The ornamental design for a catheterholder, as shown and described.
FIG. 1 is a top plan view of a catheter holder;
FIG. 2 is a front elevational view, the rear being identical;
FIG. 3 is a left side elevational view, the right side being identical;
and,
FIG. 4 is a perspective view, the broken lines showing a leg and a catheter
are for illustrative purposes only, and form no part of the claimed design
.