Long-term continuous infusion of propofol as a means of sedation for patients in intensive care unit: relationship between dosage and serum concentration.
We studied the effect of long-term continuous propofol infusion in patients who were utilizing mechanical ventilation in intensive care unit. The purpose of our study was to identify the appropriate dosage of propofol and to monitor the relating serum level that would provide satisfactory sedative and hypnotic effects to the patients, i.e., to procure a Ramsay Sedation Scale (RSS) value between 2 and 3. Ten mechanically ventilated ICU patients were studied. The syringe pump was set to deliver propofol at a rate of 1 mg/kg/h without an initial loading dose. After continuous infusion of propofol for 24 h, in each patient 5 ml of whole blood was sampled daily for one week. All samples were analyzed for serum level of propofol by high performance liquid chromatography. When the Ramsay Sedation Scale (RSS) value was between 2 and 3, the mean dosage of infused propofol was 0.71 +/- 0.31 mg/kg/h (ranging from 0.58 to 1.27 mg/kg/h) and the mean plasma concentration was 0.58 +/- 0.22 microgram/ml (ranging from 0.20 to 0.86 microgram/ml). The lipid serum level was measured in three patients whose infusion duration was greater than 14 days. The respective level was 321 mg/dl, 139 mg/dl, and 99 mg/dl. The first patient died from multiple organ failure as a result of multiple trauma. Four patients simultaneously received infusion of propofol and muscle relaxant. We concluded that propofol infusion given at a rate of 0.71 +/- 0.31 mg/kg/h and a plasma concentration level of less than 1 microgram/ml would be sufficient to produce a sedation with RSS value between 2 and 3.