[en] The purpose of this study was to compare effect of intravenous dex medetomidine with the intravenous propofol adjuvant to spinal intrathecal anesthesia on the duration of spinal anesthesia and hemodynamic parameters during total knee replacement surgery. Supplementation of spinal anesthesia with intravenous dexemedetomidine or propofol produces good sedation levels without significant clinical hemodynamic changes. Adding dex medetomidine produces significantly longer sensory and motor block than propofol . (authors).