| Abstract | [Abstract only] Mean arterial blood pressure (MAP) has been automatically regulated by computer controlled infusion of sodium nitroprusside (NP) in 7 cases of hypertensive crisis. Intrarterial pressure and ECG were continuously monitored for each patient. Before treatment the mean arterial pressure varied from 138 to 182 mm Hg (200/148 to 290/130 mm Hg). The NP infusion rate was initially specified at a low value and allowed to titrate upward until the desired level of MAP was reached. The computer samples MAP each 2 minutes and compares it with the set point. The tolerance about the set point is +/- 10 mm Hg. For MAPs greater than 10 mm Hg above the set point the infusion rate increases by 5 percent. For MAPs between 10 and 12 mm Hg below the set point the infusion rate is decreased by 5 percent; for pressures between 13 and 24 mm Hg too low, the decrease is 10 percent. For MAPs low by 25 mm Hg or more, the rate decreases by 10 percent on the first sample and the infusion is stopped on the second consecutive sample. Messages are delivered by the system if the rate increases by 50 percent within 30 minues, if a designated maximum infusion rate is reached, or if the system is stopped due to low blood pressure. Bedside audible alarms are used to insure further safety. With duration of infusion ranging from 10 to 60 hours, the percentage of time MAP was maintained with the +/- 10 mm Hg limits averaged 82 percent (range 77 to 89 percent). Once the blood pressure was under control, oral medications were commenced resulting in an automatic reduction in the infusion rate as their effects became manifest. There have been no system-induced complications. Computer control has improved the use of NP with respect to: 1) effectiveness of control, 2) providing a smooth transition to oral medications, and 3) improved work efficiency of the attending staff. |