The use and the hemodynamic effects of propofol and midazolam were studied during titrated continuous infusions to deep sedation (sedation level 5: asleep, sluggish response to light glabellar tap or loud auditory stimulus) following coronary artery surgery. The drugs were compared in 30 ventilated patients in an open randomized study. The duration of infusion was approximately 570 minutes in both groups. After a loading dose of propofol (1 mg/kg) or midazolam (0.07 mg/kg), the infusion rates were 2.71 +/- 1.13 mg/kg/h and 0.092 +/- 0.028 mg/kg/h, respectively. An analgesic infusion of sufentanil was also given in both groups. In the midazolam group, to maintain the predetermined level of sedation, more frequent additional bolus doses (4.7 +/- 1.8; P < 0.001) and infusion rate adjustments (5.3 +/- 1.6; P < 0.001) were required than for similar sedation in the propofol group (2.3 +/- 1.0 bolus doses and 3.3 +/- 1.2 adjustments). The time from stopping sedation to patient responsiveness was 11 +/- 8 minutes in the propofol group and 72 +/- 70 minutes in the midazolam group (P < 0.001), and the time from stopping sedation to extubation was 250 +/- 135 minutes and 391 +/- 128 minutes (P < 0.014), respectively. Following the loading dose of propofol, there was a fall in blood pressure (BP) (mean from 80 +/- 11 mmHg to 67.5 +/- 10 mmHg; P < 0.05). After approximately 15 minutes, BP started to rise but remained below pretreatment level throughout sedation.(ABSTRACT TRUNCATED AT 250 WORDS)