A rational approach to the control of sedation in intensive care unit patients based on closed-loop control.

Optimal control of long-term sedation during therapy in the intensive care unit is difficult to achieve in a number of patients when based on commonly used clinical sedation scores alone. We therefore used the median frequency of the EEG power spectrum as a quantitative measure for closed-loop administration of propofol in 21 artificially ventilated patients (nine trauma, 12 non-trauma). The EEG setpoint was correlated with a clinical sedation score and defined such, that mechanical ventilation was tolerated. The sedative therapy was given for 31 +/- 30 h. Non-trauma patients required sedation with an EEG median frequency between 2 and 3 Hz (propofol consumption: 1.4 +/- 0.8 mg kg-1 h-1) and sedation seemed to follow some circadian patterns, whereas trauma patients needed significantly deeper sedation (EEG median frequency: 1-2 Hz; propofol consumption: 2.6 +/- 0.8 mg kg-1 h-1). We conclude that the EEG closed-loop system could safely and reliably administer propofol to maintain a predetermined level of sedation for patients in intensive care unit over a protracted time.