Response Entropy Increases During Painful Stimulation

Abstract

Frontal electromyography (FEMG) may increase during painful stimulation and indicate patient arousal. The Datex-Ohmeda Entropy Module calculates state entropy (SE) of the electroencephalogram (EEG; 0.8-32 Hz) and response entropy (RE) of EEG and FEMG (0.8-47 Hz). We determined whether RE increases above SE (RE--SE), an indication of FEMG, increase during painful stimuli and if this is related to paralysis or level of anesthesia. With the unanesthetized baseline measurement, SE was 89 +/- 2 and RE was 98 +/- 2. During paralysis and anesthesia with either 0.8% (n = 10) or 1.4% (n = 10) isoflurane, SE decreased to 63 +/- 7 and 34 +/- 14, respectively, and the RE--SE difference decreased 90%. Before recovery from paralysis, arterial catheter or head pin placement increased RE--SE above unanesthetized levels in eight patients (five treated with 0.8% and three with 1.4% isoflurane), consistent with an increase in FEMG. The elevated RE--SE difference was related to a significant increase in SE, blood pressure, and heart rate. After recovery from paralysis, tetanic stimulation of the ulnar nerve increased the RE--SE difference above unanesthetized levels in 8 of 20 patients (6 treated with 0.8% and 2 with 1.4% isoflurane). In these patients, SE increased significantly. The remaining 12 patients did not show an increase in RE--SE during tetanic stimulation and SE did not increase. We conclude that increased RE during painful stimulation was not dependent on recovery from paralysis but was seen more often in patients anesthetized with 0.8% compared with 1.4% isoflurane. This suggests that RE reflects FEMG and may be useful to identify inadequate anesthesia and patient arousal during painful stimuli.

Electroencephalographic Response to Procedural Pain in Healthy Term Newborn Infants

“…It has been reported that the frontal EMG may be of value even in assessing adequacy of anesthesia (22). A recent publication also demonstrates graded responses to pain stimulation associated with different depth of anesthesia (23). Further studies may clarify whether recording of facial or scalp muscle EMG activity is a useful adjunct also for neonatal pain monitoring.…”

Spectral Entropy Parameters during Rapid Ventricular Pacing for Transcatheter Aortic Valve Implantation

“…In the study regarding RE responsiveness to pain stimulation, RE increased after surgical stimulation and was not dependent on recovery from muscle relaxation [14]. The authors suggest that RE reflects EMG and may be useful to identify inadequate anesthesia and patient arousal during painful stimuli.…”

“…RE and SE distinguished very well between conscious and unconscious states and exhibited high sensitivity and specificity in the detection of loss of consciousness. In studies regarding RE responsiveness to pain stimulation [14], RE increased after surgical stimulation and it was shown to predict movement in a patient after stimulation; it was also a better predictor of stimulation than the BIS index combined with hemodynamic responses [15].…”

To Compare the Dose of Propofol for Induction of Anaesthesia by Entropy Monitoring against Standard Induction dose in Elderly Patients

“…Wheeler and colleagues demonstrated that Response Entropy, RE-SE difference, Heart Rate and Blood Pressure were significantly increased during painful stimulation. (17) It has been reported that excitability of subcortical structures evoked by noxious stimuli will increase the difference between RE and SE. Takamastu and colleagues also reported that frontal Electromyogram may be of value in assessing adequacy of anaesthesia and also reflects nociception, but it did not correlate with the intensity of the stimulation (18) .…”