Clinical assessment of target-controlled infusion of propofol during monitored anesthesia care

Purpose: To determine the plasma concentrations of propofol required to ach ieve different levels of sedation during monitored anesthesia care. Methods: Sixty ASA I-II, 18-65 yr-old patients, received a target-controlle d continuous iv infusion of propofol. The target plasma concentration of pr opofol (Cp-t) was initially set at 0.4 mu g.ml(-1). Two minutes after calcu lated equilibrium between plasma and effect-site concentrations, the Cp-t o f propofol was increased by 0.2 mu g.ml(-1) steps until the patient showed no reaction to squeezing the trapezius. The level of sedation was assessed immediately before each increase in propofol Cp-t using the Observer's Asse ssment of Alertness/Sedation (OAA/S) scale. Results: The Cp-t of propofol required to induce lethargic response to name was 1.3 mu g.ml(-1) (5 degrees and 95 degrees percentiles: 1.0 - 1.8 mu g. ml(-1)), to obtain response after loud and repeated calling name was 1.7 mu g.ml(-1) (1,2 - 2.2 mu g.ml(-1)), to obtain response after prodding or sha king was 2.0 mu g.ml(-1) (1.6 - 2.6 mu g.ml(-1)), tc,obtain response after squeezing the trapezius was 2.4 mu g.ml(-1) (1.8 - 3.0 mu g.ml(-1)). Patien ts showed no response after squeezing the trapezius at 2.8 mu g.ml(-1) (2.0 - 3.6 mu g.ml(-1)). Correlation between Cp-t propofol and sedation scores were r = 0.76, P < 0.0001. Conclusions: Target-controlled infusion of propofol provided easy and safe management of intraoperative sedation, allowing fast and predictable deepen ing in the level of sedation, while minimizing systemic side effects of int ravenous sedation due to the minimal risk of overdosing the drug.