Relationship between bispectral index(BIS) and propofol blood concentration in patients with different age during target controlled infusion(TCI) of propofol

Objective To study the relationship between BIS value and propofol blood concentration in patients with different age during TCI of propofol.Methods Sixty patients of ASA class Ⅰ or Ⅱ,admitted upper abdominal surgey,were divided into adult group(n=30) and elderly group(n=30).Anesthesia was induced with TCI of remifentanil and propofol in two groups.Blood target concentration of remifentanil was set at 7 μg/L and propofol 3 mg/L.When lost consciousness,the patients were given vencuroium 0.1 mg/kg and intubated. Mechanical ventilation was maintained in all patients.After intubation,the blood target concentration of remifentanil was kept unchanged and of propofol reduced to 2.5 mg/L.The propofol infusion rate was adjusted to maintain a BIS value between 45 and 55 during surgery.Two millilitres of arterial blood samples were drawn for detecting propofol plasma concentration after TCI propofol for 5 min.Results There was no correlation between plasma propofol concentration and BIS values in adult group,but there was a high inverse correlation between the measured propofol concentration and BIS value in elderly group(r=-0.64816).Conclusion There is a good correlation between blood concentration of propofol and BIS value in elderly patients,which is not in adult paients.Therefore blood concentration of propofol in elderly patients can be applied to sedation assessment.