Setting targets for sedation with a target-controlled propofol infusion

We studied 30 unpremedicated patients undergoing muscle biopsy under femora l nerve block to determine sedation levels reached with a Diprifusor(R) tar get-controlled propofol infusion, in order to establish the equivalent of t he ED50 for different levels of depth of sedation. Infusion was started at 0.8 mu g.ml(-1) and altered by increments of 0.1 mu g.ml(-1) after equilibr ium between target and calculated concentrations, until the desired level o f sedation was reached. The ED50 target propofol concentrations for sedatio n at sedation levels 2 (drowsy), 3 (drowsy, responds to verbal stimulation) and 4 (responsive to physical stimulation only) were 1.0 mu g.ml(-1), 1.6 mu g.ml(-1) and 2.1 mu g.ml(-1), respectively. At sedation level 3, several patients exhibited spontaneous movement, hindering surgery. Oxygen supplem entation is recommended for sedation at level 4.