title: Comparison of electroencephalogram entropy versus loss of verbal response to determine the requirement of propofol for induction of general anaesthesia.
abstract: OBJECTIVE
  Propofol causes dose-dependent reduction in blood pressure (BP). This study was done to evaluate the use of spectral entropy on the dose of propofol required and the haemodynamic stability during induction of general anaesthesia (GA).
  
  
  METHODS
  In this randomised controlled study, 72 American Society of Anesthesiologists' physical status I and II patients undergoing general and orthopaedic surgeries were divided into Group S (n-36) and Group C (n-36). Patients in Group C were induced with propofol till loss of response to verbal commands and in Group S until the state entropy was <50 and state and response entropy difference was <10. The induction dose of propofol, haemodynamic parameters and the entropy values were recorded. Numerical data were expressed as a mean ± standard deviation and analysed using unpaired, two-tailed t-test. Categorical data were compared using Chi-square test. P < 0.05 value was considered significant.
  
  
  RESULTS
  The dose of propofol per kg was significantly more in the entropy group (1.80 ± 0.23 mg/kg in the Group C and 1.98 ± 0.217 mg/kg in the Group S [P < 0.05]). After induction, at intubation and 1 min after intubation, entropy values were lower in Group S than Group C (P < 0.05). The BP decreased significantly after induction compared with the baseline (P < 0.05), but there was no difference between the groups.
  
  
  CONCLUSIONS
  Propofol required for induction of GA when guided by electroencephalogram entropy was significantly higher than the induction dose based on loss of verbal response. Both conventional induction and induction with entropy as the endpoint resulted in similar haemodynamic profile.
authors.affiliation: Department of Anaesthesiology, Rajiv Gandhi Institute of Medical Sciences, Srikakulam, Andhra Pradesh, India.
authors.forename: Akasapu Karunakara
authors.initials: AK
authors.lastname: Rao
authors.affiliation: Department of Anaesthesiology and Critical Care, Nizam's Institute of Medical Sciences, Hyderabad, Telangana, India.
authors.forename: Indira
authors.initials: I
authors.lastname: Gurajala
authors.affiliation: Department of Anaesthesiology and Critical Care, Nizam's Institute of Medical Sciences, Hyderabad, Telangana, India.
authors.forename: Ramachandran
authors.initials: R
authors.lastname: Gopinath
keywords: Electroencephalogram entropy; induction dose; propofol