Evaluation of entropy for monitoring the depth of anesthesia compared with bispectral index: a multicenter clinical trial / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>As a new electroencephalogram (EEG) signal processing technique for monitoring the depth of anesthesia, entropy consists of two indices: reaction entropy (RE) and state entropy (SE). Our study compared entropy with classical bispectral index (BIS) in reduction of myoelectrical interference and noxious stimuli with EEG signals.</p><p><b>METHODS</b>Two hundred and eighty patients (ASA I-II, 18-60 years old) undergoing scheduled surgeries from seven medical centers were enrolled. Anesthesia induction was managed with propofol via the target-controlled infusion (TCI) system. The results of BIS, RE, SE, mean arterial pressure (MAP) and heart rate (HR) were recorded before anesthesia induction, at the moment of unconsciousness, before and 2 minutes after administration of muscle relaxant, and before and one and three minutes after the tracheal intubation.</p><p><b>RESULTS</b>The values of half maximum effective concentrations (EC50), 5% effective concentrations (EC05) and 95% effective concentrations (EC95) of propofol effect-site concentration at the onset of unconsciousness were 1.2 (1.1-1.3 µg/ml), 2.5 (2.4-2.5 µg/ml) and 3.7 (3.7-3.8 µg/ml), while those of the predicted plasma propofol concentration were 2.8 (2.7-2.9 µg/ml), 3.9 (3.8-3.9 µg/ml) and 4.9 (4.8-5.0 µg/ml), respectively. The values of BIS, SE and RE were 62, 59 and 63 when 50% of patients lost consciousness, and 79, 80, 85 and 42, 37, 44, respectively, when 5% and 95% of patients were unconscious. The values of BIS, RE and SE dropped two minutes after the injection of muscle relaxant, but there were no significant differences between RE and SE. MAP and HR increased visibly, which indicated a reaction to tracheal intubation; the values of BIS, RE and SE, however, did not display any significant changes.</p><p><b>CONCLUSIONS</b>This large-sample multicentric study confirmed the values of RE and SE as approximating BIS value, at the onset of unconsciousness during propofol TCI anesthesia. After elimination of myoelectrical activation, all values of RE, SE and BIS decreased significantly and the three indices were less sensitive to noxious stimuli than cardiovascular responses.</p>

Correlation between the results of photoplethysmography and modified Allen test in healthy volunteers of different ages / 南方医科大学学报

<p><b>OBJECTIVE</b>To evaluate the correlation between the results of photoplethysmography and modified Allen test in healthy volunteers of different ages.</p><p><b>METHODS</b>In 240 healthy volunteers of 3 different age groups, namely the young group (below 40 years of age, n=98), middle-aged group (between 40 and 60 years, n=74) and senior group (above 60 years, n=68), photoplethysmography and modified Allen test were performed to evaluate the recovery time of the hand circulation after relief of ulnar artery compression, and the correlation between the results of the two tests was analyzed.</p><p><b>RESULTS</b>The results of photoplethysmography and modified Allen test showed a positive linear correlation (P<0.01). The recovery time of hand circulation in the senior group was significantly longer than that in the young group and middle-aged group (P<0.01). In each group, the recovery time of the blood flow as defined by modified Allen test was significantly shorter than that determined by modified Allen test.</p><p><b>CONCLUSION</b>The results of photoplethysmography and modified Allen test show a good positive linear correlation in determining the recovery time of hand blood flow in healthy volunteers of different ages after relief of the ulnar artery compression, but the results of latter test can be more objective.</p>