[Propofol infusion for sedation in regional anesthesia. A comparison with midazolam]

50 non-premedicated ASA class I or II patients were allocated randomly into two groups and received either a variable infusion of propofol or midazolam for sedation during orthopaedic surgery with regional blockade. To achieve a well-sedated patient with eyes closed and able to follow commands, the dose requirements for propofol were 1.25 mg/kg +/- 0.5 as a loading dose followed by a mean infusion rate of 3.17 mg kg-1 h-1 +/- 1.4 and for midazolam 0.073 mg/kg +/-0.02 and 0.074 mg kg-1 h-1 +/- 0.14. Steady-state plasma concentrations of propofol averaged 1.23 micrograms/kg +/- 0.75 and of midazolam 134 ng/ml +/- 62. Recovery was significantly shorter for propofol: 3.42 +/- 2.5 versus 8.05 min +/6.2 for midazolam. Perioperative cooperation was similar in both groups providing good or excellent conditions in 76% with propofol and in 52% with midazolam. 2h after discontinuation of the infusion 92% of the propofol patients were alert, while 36% of the midazolam were sleeping again. Cardiovascular effects of both drugs were minimal; however significant respiratory depression and/or airway obstruction developed in both groups (propofol 48%, midazolam 52%) requiring therapeutic intervention. Additional undesirable effects were: severe cough (propofol 40%, midazolam 20%), inadvertent movements (propofol 36%, midazolam 24%), confusion (propofol 24%, midazolam 20%), euphoria (propofol 44%), pain on injection (propofol 32%). The results of the study indicate that both drugs are useful and controllable sedative agents for surgery under regional anaesthesia, provided that measures for continuous monitoring of respiration and emergency care are guaranteed.