A multifunction adaptor for an open-ended catheter that allows placement of the catheter while minimizing the risk of air embolism or blood loss through the open (proximal) end of the catheter body. In one variation, the design allows passage of a standard guidewire for "over-the-guidewire" placement techniques and a connection for catheter flushing using a standard syringe. In another variation, the multifunction adaptor is configured for coupling a tunneler to the proximal end of a catheter.