- P R Janzen: Academic Unit of Anaesthesia, Leeds Teaching Hospitals, UK.
We studied 30 unpremedicated patients undergoing muscle biopsy under femoral nerve block to determine sedation levels reached with a Diprifusor target-controlled propofol infusion, in order to establish the equivalent of the ED50 for different levels of depth of sedation. Infusion was started at 0.8 microg x ml(-1) and altered by increments of 0.1 microg x ml(-1) after equilibrium between target and calculated concentrations, until the desired level of sedation was reached. The ED50 target propofol concentrations for sedation at sedation levels 2 (drowsy), 3 (drowsy, responds to verbal stimulation) and 4 (responsive to physical stimulation only) were 1.0 microg x ml(-1), 1.6 microg x ml(-1) and 2.1 microg x ml(-1), respectively. At sedation level 3, several patients exhibited spontaneous movement, hindering surgery. Oxygen supplementation is recommended for sedation at level 4.