SKIM CONDUCTANCE RESPONSES IN PATIENTS SEDATED WITH MIDAZOLAM OR PROPOFOL

We have measured the skin conductance response under resting condition s and to innocuous auditory stimuli in 45 patients receiving midazolam (group M), propofol (group P) or no sedative drug (group ND) before m inor hand surgery under local anaesthesia. Administration of the sedat ive drugs was titrated to the end-point of slurring of speech and ptos is. The mean dose of midazolam was 0.06 (SD 0.01) mg kg(-1) and the me an infusion rate of propofol was 2.2 (0.39) mg kg(-1) h(-1) Subjective ratings of anxiety and sedation were measured using visual analogue s cales. These were similar in groups M and P and significantly differen t from those reported by group ND (P = 0.001-0.005). However, measures of skin conductance in group M were significantly lower than in group P (P = 0.002-0.013) and group ND (P = 0.004-0.016). These measures we re similar in groups P and ND. Skin conductance measures were related significantly to anxiety scores only in groups M and ND (P < 0.05). We conclude that skin conductance is not a non-specific index of sedativ e-anxiolytic action and therefore is not useful in comparative studies of anxiolytic drugs that exert their effects by different pharmacolog ical mechanisms.