Comparison of entropy and bispectral index values during propofol induction

Objectives: To identify the entropy levels that wouldcorrespond to bispectral index (BIS) levels in generalanesthesia (GA) induction in patients who will undergoelective lumbar disc surgery (LDS).Methods: Thirty cases who underwent LDS under GAwere included in our study after obtaining patient consentand approval of the Ethics Committee of Afyon KocatepeUniversity Medical School, Afyonkarahisar, Turkey,between January 01, 2004 to December 31, 2005. Bispectralindex and entropy electrodes were applied at the same timeto 30 cases in the study group. In order to assess the levelof sedation during anesthesia and recovery, ‘Observer’sAssessment of Alertness/Sedation’ (OAA/S) scale was used.Bispectral index, state-entropy (SE), response-entropy(RE), and OAA/S values were recorded simultaneously.Results: Induction OAA/S scores were in correlation withBIS and entropy values (RE-SE) in 30 cases. A significantdifference was found between BIS and entropy inductionvalues (p=0.0398). Induction mean arterial pressure andheart rate values at 30, 60, 90, and 120 seconds werelower than the values of the control, which was statisticallysignificant (p=0.0412).Conclusion: During the induction of GA, we foundentropy values to be more sensitive and they demonstrateda more rapid increase than BIS. Therefore, it would besafer to monitor entropy while using agents of inductionthat might cause severe hypotension. Induction agentsthat might cause severe hypotension could be more safelyadministered under entropy monitoring.