Clinical Study Of Spectral Entropy As An Electroencephalographic Measure During General Anaesthesia

Objective: To explore the application of Spectral Entropy (including response entropy and state entropy) as a new electroencephalographic measure during recovering period of general anaesthesia and compare it with BIS. Methods: Fifteen ASA II patients (male, 6 cases; female, 9 cases) aged 20-55yrs undergoing elective abdominal surgery were studied. Anaesthesia was induced with propofol 2 mg .kg^-1 , vecuronium 0. 1 mg .kg^-1 and fentanyl 4μg .kg^-1 iv. After intubation anaesthesia was maintained with isoflurane inhalation combined with intermittent injection of vecuronium and fentany.Applying self-control design, per case was monitered with Spectral Entropy and BIS at the same time.We defined the response to verbal commands as the time point of regaining consciousness, then recorded the data at following times: baseline values 60sec before regaining of consciousness 45sec before 30sec before,regaining of consciousness 30sec after regaining of consciousness 45sec after 60sec after. Results: Prediction probabilities of response entropy (RE), state entropy (SE) and BIS for regaining consciousness were 0.9376 0.9252 and 0.9019 respectively, and no statistic differences between them (P>0.05); Furthermore, Logistic regressive equations of prediction probability and RE, SE or BIS were calculated out as ln P_k/(1- P_k)= -19.825 + 0.243x ln P_k/(1- P_k)= -18.012 + 0.236x and ln P_k/(1- P_k)= -21.780 + 0.316x respectively. Then from the perspective of sensitivity /specificity, entropy index (RE SE)and BIS had threshold values for regaining consciousness of 83 76 and 71 with sensitivity/ specificity of 0.90/0.85 0.89/0.80 and 0.88/0.78 respectively. RE was 30s earlier than BIS in predicting regaining consciousness. And last RE SE and BIS had different baseline variabilities of 0.8% 1.9% 3.0%.Conclusion: Both entropy index and BIS can monitor regaining of consciousness accurately and sensitively but response entropy is 30s earlier than BIS in predicting regaining of consciousness, so response entropy has promising application in clinic.Objective: To evaluate the application of Spectral Entropy (including response entropy and state entropy ) as a new electroencephalographic measure during inducing period of general anaesthesia and compare it with BIS. Methods: Twenty ASA II patients (male, 11 cases; female, 9 cases) aged 20-55yrs undergoing elective abdominal surgery were studied. Anaesthesia was induced with propofol 2 mg .kg^-1 , vecuronium 0. 1 mg .kg^-1 and fentanyl 4μg .kg^-1 iv. After intubation anaesthesia was maintained with propofol at 8 mg .kg^-1 .h^-1 infusion rate with intermittent injection of vecuronium and fentany. Applying self-control design, every patient was monitered with Spectral Entropy and BIS simutaneously. Loss of eyelash reflex together with no responses to verbal commands and slight prodding or shaking were considered to be unconscious, then we recorded the data at following times: baseline values 60sec before loss of eyelash reflex 45secbefore 30secbefore loss of eyelash reflex 30sec after loss of eyelash reflex 45sec after 60sec after. Results: Prediction probabilities of response entropy (RE) state entropy (SE) and BIS for loss of consciousness were 0.9386 0.9312 and 0.9149 respectively, and no statistic differences between them (P>0.05); Furthermore, Logistic regressive equations of prediction probability and RE SE or BIS were calculated out as ln P_k /(1- P_k)= 20.724 - 0.267x ln P_k /(1- P_k)= 19.278 - 0.26x and ln P_k /(1- P_k)= 23.865 - 0.348x respectively. Then from the perspective of sensitivity /specificity, entropy index (RE SE)and BIS had threshold values for loss of consciousness of 76 73 and 68 with sensitivity/ specificity of 0.84/0.77 0.71/0.84 and 0.68/0.71 respectively. After loss of consciousness, RE and SE kept going down to 23.4±6.5 and 23.9±6.4 and reached the lowest values of 11-18, meanwhile EEG waveform showed suppressed pattern, that meant burstsuppression happened. But we couldn't see the similar changes on BIS. Conclusions: Entropy index seems to be better than BIS in predicting loss of consciousness, moreover it can indicate burst suppression but BIS can't.Objective: To study if the Spectral Entropy (including response entropy and state entropy) can predict movement at skin incision during propofol anaesthesia and compare it with BIS.Methods: Twenty ASA II patients aged 20-55 yrs undergoing elective abdominal surgery were studied. They were allocated into two groups of Mover and Non-mover by whether they had response to skin incision or not. Anaesthesia was induced with propofol 2.5 mg .kg^-1 , succinylcholine 1.5 mg .kg^-1 and fentanyl 2μg .kg^-1 iv. After intubation anaesthesia was maintained with propofol at 20mg.kg^-1.h^-1 infusion rate, then 15min later, operation began without neuromuscular blockers. The propofol infusion rate was increased by 10 percent for the next patient if movement was detected or decreased by 10 percent if movement was not detected. Per case was monitered with Spectral Entropy and BIS at the same times. Data was recorded at following times: baseline values 60 and 30s before skin incision 45 and 120s after skin incision. Results: BIS index had no significant difference between Mover and Non-mover (P>0.05) but response entropy (RE) and state entropy (SE) had significant differences between Mover and Non-mover (P<0.05) ; RE and SE could predict movement at skin incision with P_k of 0.8935 and 0.8872 respectively but BIS couldn't with P_k of 0.5719; Furthermore, Logistic regressive equations of prediction probability and RE or SE were calculated out as ln P_k /(1- P_k)= 26.505 - 0.394x and ln P_k /(1- P_k)= 28.553 - 0.435x respectively.Conclusion: Entropy index can predict movement at skin incision during propofol anaesthesia, so it can reflect analgesic depth of anesthesia. But BIS can't.Objective: To investigate if the Spectral Entropy (including response entropy and state entropy) can predict movement at skin incision during isoflurane anaesthesia and compare it with BIS.Methods: Twenty ASA II patients aged 20-55 yrs undergoing elective abdominal surgery were studied. They were allocated into two groups of Mover and Non-mover by whether they had response to skin incision or not. Anaesthesia was induced with propofol 2.5 mg .kg^-1 , succinylcholine 1.5 mg .kg^-1 and fentanyl 2 μg .kg^-1 iv. After intubation isoflurane was inhaled and end-tidal concentration was maintained at 1.3MAC for 30min, then operation began without neuromuscular blockers. The isoflurane end-tidal concentration was increased by 10 percent for the next patient if movement was detected or decreased by 10 percent if movement was not detected. Every patient was monitered with Spectral Entropy and BIS simutaneously. Data was recorded at following times: baseline values 60 and 30s before skin incision 45 and 120s after skin incision. Results: BIS index had no significant difference between Mover and Non-mover (P>0.05) but response entropy (RE) and state entropy (SE) had significant differences between Mover and Non-mover (P<0.05 ); RE and SE could predict movement at skin incision with P_k of 0.8937 and 0.8852 respectively but BIS couldn't with P_k of 0.5919; Furthermore, Logistic regressive equations of prediction probability and RE SE were calculated out as ln P_k /(1- P_k)= 32.517 - 0.481x and ln P_k /(l-P_k)= 28.728 - 0.438x respectively.Conclusion: Entropy index can predict movement at skin incision during isoflurane anaesthesia but BIS can't, so it deserves prevalence in clinic.