Spectral Entropy (SpEn) is an alternative tool to the bispectral index (BIS) for monitoring depth of hypnosis. SpEn measures response entropy (RE) and state entropy (SE). This open-label prospective study was designed to evaluate SpEn and BIS in 20 patients undergoing elective supratentorial neurosurgery with craniotomy and resection of brain tumors. SpEn and BIS were obtained continuously by Datex Ohmeda M-entropy module S/5 (Helsinki, Finland) and Aspect Medical System BIS (Newton), respectively. Total intravenous anesthesia was performed in all patients by Fresenius Vial infusion system (Brezins, France) to maintain a plasma concentration of propofol of 2.5 to 5 μg mL−1 and sufentanil of 0.2 to 0.4 ηg mL−1. SpEn, BIS, the estimated propofol effect-site concentrations (Ce), the mean arterial pressure (MAP), and the heart rate (HR) were recorded during 12 specific events: induction of anesthesia, patient stop counting, loss of blinking reflex, intubation, mayfield pinning, craniotomy, termination of propofol infusion, recovery of blinking reflex, coughing, limb movement, order execution, and extubation. Stated that prediction probability or PK represents an indicator probability to predict correctly the rank order of an arbitrary pair of distinct observed indices of depth of hypnosis (ie, clinical settings and SpEn indices, or BIS, Ce, MAP, HR), PK of BIS, SE, RE, and Ce provided a better depth of hypnosis than MAP and HR; RE being the best for rapidity, SE for sensitivity, and BIS for specificity. There is good correlation between the 3 hypnosis indices and Ce. This study demonstrates that SpEn provides a reproducible hypnosis index for patients undergoing supratentorial neurosurgical procedures.
Department of Neurosciences, Section of Anesthesia and Intensive Care, Azienda Ospedaliero, Universitaria Ospedali Riuniti Umberto I—G Salesi, GM Lancisi, Ancona, Italy
Reprints: Pietro Paolo Martorano, MD, Institute of Medical and Surgical Emergencies, Università Politecnica delle Marche, AO Ospedali Riuniti Umberto I—G Salesi, GM Lancisi, Via Conca 1, 60020 Torrette di Ancona, Italy (e-mail: firstname.lastname@example.org)
Received for publication August 12, 2005; accepted December 29, 2005