Individual effect-site concentrations of propofol at return of consciousness are related to the concentrations at loss of consciousness and age in neurosurgical patients.

Study Objective: To investigate whether a patient's propofol effect-site concentration at return to consciousness (ROC) was related to the propofol effect-site concentration at loss of consciousness (LOC) and to patients' individual demographic parameters.

Design: Prospective study.

Setting: Operating room.

Patients: 31 ASA physical status I and II neurosurgical patients with Glasgow Coma Score > 15, and scheduled to receive total intravenous anesthesia with effect-site target controlled infusion (TCI) of propofol and remifentanil.

Interventions: A constant propofol infusion was administered until LOC. At LOC, remifentanil started with a plasma concentration target of 2.5 ng mL(-1).

Main Results: Propofol concentration at LOC was 4.9 +/- 1 microg mL(-1). At ROC, propofol and remifentanil concentrations were 1.16 +/- 0.3 microg mL(-1) and 3.41 +/- 1.5 ng mL(-1). Significant correlation was observed between propofol concentrations at ROC and LOC, between propofol concentration at ROC and patient age (48.7 +/- 15 yrs), and between propofol concentrations at ROC and LOC, divided by patient's age.

Conclusions: The correlation between propofol concentrations at ROC and LOC was improved by inclusion of patient age data.