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 ObjectiveTo 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.DesignProspective study.SettingOperating room.Patients31 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.InterventionsA constant propofol infusion was administered until LOC. At LOC, remifentanil started with a plasma concentration target of 2.5 ng mL−1.Main ResultsPropofol concentration at LOC was 4.9 ± 1 μg mL−1. At ROC, propofol and remifentanil concentrations were 1.16 ± 0.3 μg mL−1 and 3.41 ± 1.5 ng mL−1. Significant correlation was observed between propofol concentrationa 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.ConclusionsThe correlation between propofol concentrations at ROC and LOC was improved by inclusion of patient age data.