A medical system for connecting a multiple lumen medical catheter to associated medical instrumentation includes a connector member defining a longitudinal axis and having a first end for releasable coupling to the medical catheter and a second end for coupling to medical instrumentation. A mounting segment is adjacent the first end of the connector member. The mounting segment includes first and second mounting elements extending in a general longitudinal direction and arranged in spaced relation, and being adapted for reception within respective lumens of the catheter. The first and second mounting elements define inner opposing surfaces. At least one of the opposing surfaces may have an irregular surface portion dimensioned to engage the septum wall of the catheter to facilitate gripping engagement with the septum wall to assist in coupling of the connector member with the catheter.