Patient-controlled sedation for cataract surgery using peribulbar block.

Patients undergoing cataract surgery using peribulbar block were allocated randomly to self-administer doses of either midazolam 0.1 mg or propofol 3.3 mg without a lock-out facility; in the control group the syringe was charged with saline, not as a placebo, but to "blind" the surgeon and the nurse observer. For midazolam and propofol, median doses were 2.54 (0.1-6.0) mg and 87.4 (0-145) mg, respectively. Patient-controlled sedation significantly reduced the level of anxiety, with median visual analogue anxiety scores in the midazolam, propofol and saline groups of 5 (0-38) mm, 5 (0-25) mm and 15 (0-92) mm, respectively (P < 0.05). Some patients did not administer the sedative when available while others in the saline group would have benefited from anxiolytic drugs. While both drugs prevented an increase in heart rate, only midazolam prevented an increase in arterial pressure during surgery.