Abstracts and Programme: EUROANAESTHESIA 2011: The European Anaesthesiology Congress: Perioperative Care of the Elderly
Background and Goal of Study: Quantitative relationship between BIS values and propofol doses has not been extensively studied. The generally recommended dose for induction has a wide range (1 to 2.5 mg/kg), which may cause too deep sedation in the elderly. The goal of the study was to quantitatively assess the effect of propofol on BIS during induction and compare its features between younger and older patients.
Materials and Methods: After obtaining informed consent, 72 patients (38 men and 34 women, ASA PS 1 or 2) undergoing elective non-cardiac surgery were assigned to either below/equal to 60 or above 60 years of age group (younger and older group). They were randomly allocated to one of three subgroups (12 subjects in each subgroup) depending on the dose of propofol: 1.5, 2.0 or 2.5 mg/kg (younger group) or 1.0, 1.5 or 2.0 mg/kg group (older group). Bolus doses of propofol were administered following 40 mg of intravenous lignocaine. Fentanyl (2 mg/kg) and rocuronium (0.9 mg/kg) were given at 1.5 and 2 minutes after injection of propofol, respectively.
The difference between the baseline and minimum BIS value (ΔBIS) during the first 5 minutes after propofol injection was compared between the two age groups.
Results and Discussion: The mean ages of younger and older patients were 41 and 69 years, respectively. The ΔBIS were normally distributed within the subgroups (Shapiro-Wilk test), and their means varied between the subgroups (one-way ANOVA; P =0.029 and P < 0.001 in younger and older group, respectively).
A linear regression analysis demonstrated a good fit correlation between ΔBIS values and doses of propofol in both age groups (adjusted R2 values of 0.97 and 0.93 for younger and older group, respectively).
Conclusion(s): A dose-dependent relationship between propofol dose and ΔBIS exists. Based on the change of BIS values during induction, 1.0 mg/kg of propofol is sufficient to provide adequate depth of anaesthesia in elderly patients.