State Entropy Research Articles

Decrease in spectral entropy by low tidal volume ventilation-associated severe hypercapnia: a case report.

Severe hypercapnia can be predicted by a decrease in cerebral electrical activity. The authors describe a sudden decrease in spectral entropy due to severe hypercapnia-induced respiratory acidosis in a patient with chronic pulmonary obstructive disease during lung resection. After two and a half hours of low tidal volume ventilation in the lateral position, the state entropy suddenly dropped from 45 to 7, without any changes in the effect-site concentration of propofol, end-tidal carbon dioxide (CO2) tension, oxygen saturation, or arterial pressure. However, arterial blood gas analysis showed severe respiratory acidosis (pH 7.01, PaCO2 115 mmHg and PaO2 246 mmHg with FIO2 of 0.5). Immediate hyperventilation improved the state entropy and acid-base balance. Electroencephalography-based spectral entropy can detect severe hypercapnia in chronic pulmonary obstructive disease patients with a large arterial to end-tidal CO2 difference due to prolonged hypoventilation during thoracic surgery.

The Constant Information Radar

The constant information radar, or CIR, is a tracking radar that modulates target revisit time by maintaining a fixed mutual information measure. For highly dynamic targets that deviate significantly from the path predicted by the tracking motion model, the CIR adjusts by illuminating the target more frequently than it would for well-modeled targets. If SNR is low, the radar delays revisit to the target until the state entropy overcomes noise uncertainty. As a result, we show that the information measure is highly dependent on target entropy and target measurement covariance. A constant information measure maintains a fixed spectral efficiency to support the RF convergence of radar and communications. The result is a radar implementing a novel target scheduling algorithm based on information instead of heuristic or ad hoc methods. The CIR mathematically ensures that spectral use is justified.

Connecting electronic entropy to empirically accessible electronic properties in high temperature systems

A quantitative theoretical model connecting the thermopower and electronic entropy of molten systems is proposed, the validity of which is tested for semiconductors and metallic materials. The model accurately provides the entropy of mixing for molten semiconductors, as shown for the representative system Te–Tl. Predictions of the electronic entropy of fusion for compounds are in agreement with available data and offer a novel means to identify the correct electrical conductivity model when Hall measurements are not available. Electronic entropy for molten semiconductor and metallic systems is shown to reflect order in the molten and solid state. The model proves accurate at predicting the electronic state entropy contribution to the electronic entropy of mixing.

Surgical pleth index: prediction of postoperative pain and influence of arousal

BackgroundThere are conflicting reports concerning the outcome after anaesthesia guided by the surgical pleth index (SPI; GE Healthcare, Helsinki, Finland). One potential explanation may be the lack of evidence for the selection of SPI cut-off values. The aim of this trial was to investigate the correlation between SPI, arousal, and postoperative pain and to define a cut-off value for SPI to predict moderate-to-severe pain. MethodsAfter obtaining ethical approval and written informed consent, 70 patients undergoing non-emergency surgery were enrolled. Data relating to SPI, heart rate, mean arterial pressure, and state entropy were recorded every 10 s for the last 10 min of surgery (state entropy <60 at all times). Subsequently, recordings continued during the phase of arousal. After recovery room admission, pain scores (numerical rating scale 0–10) were obtained every 3 min for 15 min. ResultsData from 65 patients were analysed. Receiver-operating characteristic curve analysis revealed an optimal intraoperative cut-off SPI value of 30 to discriminate between numerical rating scale scores 0–3 and 4–10. For this value, the negative and positive predictive values to discriminate between numerical rating scale scores 0–3 and 4–10 were 50 and 89.7%, respectively. The SPI was significantly affected by arousal, and SPI scores obtained during this phase were not predictive of postoperative pain. ConclusionsSurgical pleth index values are predictive of postoperative pain only if obtained before patient arousal. In contrast to previous studies, a relatively low SPI, >30, appears to predict pain with a high positive predictive value and may therefore be suggested for future studies of SPI-guided anaesthesia. Clinical trial registrationAustralian New Zealand Clinical Trials Registry: ACTRN12615000804583.

Thermodynamically controlled crystallization of glucose pentaacetates from amorphous phase

The α and β glucose pentaacetates are known sugar derivatives, which can be potentially used as stabilizers of amorphous phase of active ingredients of drugs (API). In the present work, crystallization behavior of equimolar mixture of α and β form in comparison to both pure anomers is revealed. It was shown that despite the same molecular interactions and similar molecular dynamics, crystallization from amorphous phase is significantly suppressed in equimolar mixture. Time dependent X-ray diffraction studies confirmed higher stability of the quenched amorphous equimolar mixture. Its tendency to crystallization is about 10 times lower than for pure anomers. Calorimetric studies revealed that the α and β anomers don’t form solid solutions and have eutectic point for xα = 0.625. Suppressed crystallization tendency in the mixture is probably caused by the altered thermodynamics of the system. The factors such as difference of free energy between crystalline and amorphous state or altered configurational entropy are probably responsible for the inhibitory effect.

Entropy Monitoring Effect in Hepatic Cirrhotic Patients Undergoing Major Liver Resection on Sevoflurane Consumption and Hemodynamics. A Randomized Controlled Study

Background and Goal of study: Inappropriate titration of the anesthetic agents can lead to an under or excessive depth of anesthesia. Aim is to study effect of introducing Entropy monitoring during major liver resection among cirrhotic patients with chronic hepatitis C (Child A) undergoing major liver resection on general anesthetic requirements and hemodynamics. Methods: 60 consecutive patients were randomly divided into two groups in a prospective hospital based comparative study registered in Menoufiya University, Egypt. Group I guided with Entropy, Group II also guided with standard practice but obscured from Anaethesist. Sevoflurane with O2 /Air 50% at 2 l/min adjusted to achieve a State (SE) and Response (RE) Entropy (40-60 with a gradient of 5-10. Boluses of Fentanyl (1 - 2 μg/kg) were given if the difference between SE and RE was more than 10 for more than two minutes. Sevoflurane (ml) consumed were monitored by GE Datex-Ohemda S/5 Anesthetic Delivery Unit System. Results: Age, weight and fentanyl consumption were comparable between both groups (P >0.05). Mean (SD) Sevoflourane consumption (ml) after 2hr, 4hr, and 6hr in GI (Entropy) versus II (Standard) were 16(2.19) vs 20.8(1.88), 10.7(1.94) vs 17.4(1.92), and 9(1.22) vs 14.1(2.19), P 0.05. Anaesthesia time was comparable between both groups with the same surgical and an aesthetic team. Conclusion: Entropy monitoring for hepatic patients reduced general anaesthetic agent consumption during induction and surgery and enhanced recovery with favourable haemodynamic consequences. Encouraging the use of Anaesthesia depth monitors can have an important economic impact when applied on a larger scale.

Ensayo clínico cruzado y aleatorizado para comparar 2 modelos farmacocinéticos de propofol usando índices de entropía

IntroductionThere are two different pharmacokinetic models (Marsh and Schnider) for the administration of total intravenous anesthesia with propofol, the parameter differences could have some impact over the depth of anesthesia. Objectiveto determine if there is a significant difference in the variability of depth of anesthesia suggesting that one model is superior in achieving a more stable and predictable depth of anesthesia during surgery. Methodsa cross-over clinical trial was conducted on 16 healthy patients programmed for upper or lower limb ambulatory orthopedic surgery. Patients were randomly assigned to i) effect site target controlled infusion of propofol with Marsh model at a target concentration of 2,5μg/ml for 20minutes, a 20minute washout, then propofol was administered with Schnider model at the same effect site target for the reminder of the surgery, or ii) the reverse sequence. Differences in variability of depth of anesthesia, were assessed by comparing records of spectral entropy indices during surgery through an unpaired t-test. Resultsthere was no evidence of significant difference in the mean variances of either spectral entropy indices between the two models (P-value: 0.57 for State Entropy, P-value: 0.51 for Response Entropy). Conclusionthe study suggests that both pharmacokinetic models are equivalent in terms of stability of depth of anesthesia. It is important to keep testing determinants of the efficacy of the models in different types of population because their behavior according to individual characteristics of patients or variables such as cost-effectiveness could end up tilting the scale.

Randomized cross-over clinical trial comparing two pharmacokinetic models of propofol using entropy indices

IntroductionThere are two different pharmacokinetic models (Marsh and Schnider) for the administration of total intravenous anesthesia with propofol, the parameter differences could have some impact over the depth of anesthesia. ObjectiveTo determine if there is a significant difference in the variability of depth of anesthesia suggesting that one model is superior in achieving a more stable and predictable depth of anesthesia during surgery. MethodsA cross-over clinical trial was conducted on 16 healthy patients programmed for upper or lower limb ambulatory orthopedic surgery. Patients were randomly assigned to (i) effect site target controlled infusion of propofol with Marsh model at a target concentration of 2.5μg/ml for 20min, a 20min washout, then propofol was administered with Schnider model at the same effect site target for the reminder of the surgery, or (ii) the reverse sequence. Differences in variability of depth of anesthesia, were assessed by comparing records of spectral entropy indices during surgery through an unpaired t-test. ResultsThere was no evidence of significant difference in the mean variances of either spectral entropy indices between the two models (p-value: 0.57 for State Entropy, p-value: 0.51 for Response Entropy). ConclusionThe study suggests that both pharmacokinetic models are equivalent in terms of stability of depth of anesthesia. It is important to keep testing determinants of the efficacy of the models in different types of population because their behavior according to individual characteristics of patients or variables such as cost-effectiveness could end up tilting the scale.

Robust topological degeneracy of classical theories

We challenge the hypothesis that the ground states of a physical system whose degeneracy depends on topology must necessarily realize topological quantum order and display non-local entanglement. To this end, we introduce and study a classical rendition of the Toric Code model embedded on Riemann surfaces of different genus numbers. We find that the minimal ground state degeneracy (and those of all levels) depends on the topology of the embedding surface alone. As the ground states of this classical system may be distinguished by local measurements, a characteristic of Landau orders, this example illustrates that topological degeneracy is not a sufficient condition for topological quantum order. This conclusion is generic and, as shown, it applies to many other models. We also demonstrate that certain lattice realizations of these models, and other theories, display a ground state entropy (and those of all levels) that is "holographic", i.e., extensive in the system boundary. We find that clock and $U(1)$ gauge theories display topological (in addition to gauge) degeneracies.

Entropy vs standard clinical monitoring using total intravenous anesthesia during transvaginal oocyte retrieval in patients for in vitro fertilization

Study objectiveDay care surgery is an important arena for monitors of anesthetic depth where minimizing drug use is essential for rapid turnover. Underdosage, on the other hand, carries the risks of intraoperative awareness and pain. Transvaginal oocyte retrieval (TVOR), often performed under total intravenous anesthesia using propofol and fentanyl in Indian patients, is a procedure of special interest because, in addition to the above concerns, toxic effects of propofol on oocytes have been described. We have studied the role of entropy monitor, a depth of anesthesia monitor, in optomising drug titration and facilitating distinction between analgesic and hypnotic components of anesthesia. DesignProspective randomized controlled study. SettingOperating theater and postoperative recovery area. PatientsOne hundred twenty American Society of Anesthesiologists class I and II female patients coming to the IVF centre for TVOR under total intravenous anesthesia using propofol and fentanyl. They were randomly allocated into 2 groups: Group EM (drugs titrated as per entropy values: state entropy and response entropy) and group CM (drugs titrated as per standard clinical monitoring). InterventionNone. MeasurementsTotal propofol consumption (TP), total fentanyl consumption (TF), on-table recovery time (T1), time to discharge (T2), intraoperative awareness (A). Main resultsPatients in group EM demonstrated 6.7% lesser consumption of propofol (P= .01), 10.9% more consumption of fentanyl (P= .007) and 1 minute faster recovery on-table (P= .009) as compared to group CM. In the PACU, only 10% patients of group EM required supplemental analgesia as opposed to 28.3% in CM group (P= .01). Time to discharge was similar in both groups and no intraoperative awareness was noted. ConclusionEntropy monitor is a useful tool allowing distinction between analgesic and hypnotic components of general anesthesia in patients undergoing TVOR and facilitating drug titration accordingly. Its impact on intraoperative awareness needs to be further evaluated.

Theoretical investigation on the magnetocaloric effect in amorphous [formula omitted] system

In this work, we investigated the magnetic and magnetocaloric properties of the amorphous system Eu80Au20. The magnetic state equation and entropy were considered in the framework of Handrich–Kaneyoshi model, which takes into account the amorphization through the symmetric exchange fluctuation in the mean field approximation. The exchange and structural fluctuations parameters were chosen based on the experimental data of Eu80Au20. The isothermal entropy change was calculated for several variations of external magnetic field. Furthermore, the adiabatic temperature change and the refrigerant capacity were calculated for a magnetic field change from 0 to 5T.

Exact Nonmagnetic Ground State and Residual Entropy of S = 1/2 Heisenberg Diamond Spin Lattices

Exactly solvable frustrated quantum spin models consisting of a diamond unit structure are presented. The ground states are characterized by tetramer-dimer states with a macroscopic degeneracy in a certain range of isotropic exchange interaction. The lower bound of the excitation gap is exactly calculated to be finite and the bulk entropy in the limit of zero temperature remains finite depending on the shape of the boundary of system. Residual entropy is in a range of 0~6.1% of the entropy at high temperature for hexagonal diamond lattice and 0~8.4% for square diamond lattice. These diamond lattices are generalized to any dimensions and it is likely to be synthesized experimentally.

Comparison of intravenous labetalol and bupivacaine scalp block on the hemodynamic and entropy changes following skull pin application: A randomized, open label clinical trial.

Background:The application of skull pins in neurosurgical procedures is a highly noxious stimulus that causes hemodynamic changes and a rise in spectral entropy levels. We designed a study to compare intravenous (IV) labetalol and bupivacaine scalp block in blunting these changes.Patients and Methods:Sixty-six patients undergoing elective neurosurgical procedures were randomized into two groups, L (labetalol) and B (bupivacaine) of 33 each. After a standard induction sequence using fentanyl, propofol and vecuronium, patients were intubated. Baseline hemodynamic parameters and entropy levels were noted. Five minutes before, application of the pins, group L patients received IV labetalol 0.25 mg/kg and group B patients received scalp block with 30 ml of 0.25% bupivacaine. Following application of the pins, heart rate (HR), systolic arterial pressure (SAP), diastolic arterial pressure (DAP), mean arterial pressure (MAP), and response entropy (RE)/state entropy (SE) were noted at regular time points up to 5 min.Results:The two groups were comparable with respect to their demographic characteristics. Baseline hemodynamic parameters and entropy levels were also similar. After pinning, the HR, SAP, DAP, MAP, and RE/SE all increased in both groups but were lower in the scalp block group patients. HR increased by 19.8% in group L and by 11% in group B. SAP increased by 11.9% in group L and remained unchanged in group B. DAP increased by 19.7% in group L and by 9.9% in group B, MAP increased by 15.6% in group L and 5% in group B (P < 0.05). No adverse effects were noted.Conclusion:Scalp block with bupivacaine is more effective than IV labetalol in attenuating the rise in hemodynamic parameters and entropy changes following skull pin application.

Sugammadex at both high and low doses does not affect the depth of anesthesia or hemodynamics: a randomized double blind trial.

Previous studies have shown that sugammadex decreases the anesthetic depth when administered to reverse the neuromuscular blockade produced by rocuronium/vecuronium. The aim of the present study was to investigate the effect of sugammadex alone on anesthetic depth and hemodynamics. Sixty patients scheduled for abdominal surgery participated in the study. Anesthesia was induced with thiopental/fentanyl and maintained with N2O/oxygen and sevoflurane concentrations adjusted to maintain Entropy and Bispectral Index (BIS) values between 40 and 50. Cis-atracurium 0.2mg/kg was administered for neuromuscular blockade which was monitored with a TOF-Watch® SX acceleromyograph. State entropy (SE), response entropy (RE), Bispectral Index (BIS), systolic (SAP) and diastolic blood pressure (DAP), heart rate (HR), SpO2, end-tidal CO2 and sevoflurane concentrations were recorded every 3min intraoperatively. Sugammadex 2mg/kg (Group-2), 4mg/kg (Group-4) or 16mg/kg (Group-16) was given intravenously when a count of two responses of the train-of-four (TOF) or a post-tetanic count (PTC) 1-3 appeared or when no response at all (PTC=0) was observed, respectively. The overall SE values, thus the primary outcome of the study, were 44±11, 43±10 and 43±11 for Group-2, Group-4 and Group-16, respectively (p=0.812). Also, the secondary endpoints, namely RE, BIS, SAP and DAP, HR and SpO2 did not differ between the three groups. Comparisons between Group-2 versus Group-4, Group-2 versus Group-16 and Group-4 versus Group-16 showed no differences (p>0.05) for all the studied variables. Sugammadex alone at low, medium or high clinical doses has no effect on anesthetic depth as assessed by Entropy and BIS or on hemodynamics.

Comparison of bispectral index and entropy monitoring in patients undergoing internalisation of deep brain stimulators

Abstract Introduction: Depth of anaesthesia (DOA) monitors are shown to reduce the intra-operative dose of anaesthetic agents, provide haemodynamic stability and shorten emergence times. Electroencephalography (EEG) based DOA monitors such as bispectral index (BIS) and entropy have been calibrated and validated in healthy subjects. Hence the clinical effectiveness of these monitors may be affected when monitoring patients with neurological disorders (e.g., epilepsy, dystonia, dementia and Parkinson’s disease). The aim of this study was to determine whether BIS and entropy correlate with each other and with clinical indices of DOA in patients with movement disorders under general anaesthesia (GA). Materials and Methods: We conducted a prospective, observational study in patients with movement disorders undergoing internalization of deep brain stimulators. All patients received standard GA with age-adjusted mean alveolar concentration (aaMAC) of an inhalational agent between 0.7 and 1.1. BIS and entropy sensors were applied on the patient’s left forehead. Data collected included clinical parameters and EEG-based DOA indices. Correlation analysis was performed between entropy, BIS and the clinical indices of DOA. Bland Altman analysis was performed to determine the agreement between BIS and entropy. Results: Thirty patients were studied (mean age was 58.4 ± 11 years, male: female 18:12 and weight 79.2 ± 17 kg). Indications for deep brain stimulation were Parkinson’s disease (n = 25), essential tremors (n = 2) and dystonia (n = 3). There was a very strong positive correlation between BIS and response entropy (RE) (r = 0.932) and BIS and state entropy (SE) (r = 0.950) and a strong negative correlation among aaMAC and BIS, RE and SE with r values of −0.686, −0.788 and −0.732, respectively. However, there was no correlation between BIS, RE, SE and haemodynamic values. Conclusion: Our study showed that BIS and entropy perform well in patients with movement disorders. There was a good correlation between the BIS and entropy devices. Haemodynamic parameters were not reliable indicators of DOA in these patients.

Effect of breastfeeding on haemodynamics and consumption of propofol and sevoflurane: A state entropy guided comparative study.

Background and Aims:Unique post-partum endocrine hormone oxytocin secreted during breastfeeding (BF) has amnestic, sedative properties and down-regulates stress responses. This study was done to assess the effect of BF on consumption of propofol, sevoflurane and haemodynamic stability in women.Methods:Study was conducted on 120 women aged 20–30 years of American Society of Anesthesiologists I and II physical status scheduled for tubectomy under general anaesthesia who were randomly allocated to three groups 40 of each; BF, withhold feeding (WF), and non-feeding (NF) groups. All received standard premedication. Heart rate (HR), mean arterial pressure (MAP) and state entropy (SE) values were recorded at regular intervals. All patients were induced with intravenous propofol until the SE levels dropped to 45, and dose of propofol recorded. Airway was secured with laryngeal mask airway and anaesthesia was maintained with sevoflurane in 60% N2O and O2. Sevoflurane concentration was adjusted to maintain SE between 40 and 60. End tidal concentration of sevoflurane and consumption of sevoflurane (ml) was recorded by GE Datex-Ohmeda S/5™ System. Results were analysed by analysis of variance and Chi-square test.Results:Demographic parameters were comparable. Dose of propofol and sevoflurane consumption in group BF was significantly reduced by 20% and 35%, respectively (P < 0.05) compared to group NF. Intra-operative HR and MAP were persistently low in group BF and elevated in group WF (P < 0.05).Conclusion:BF before induction of anaesthesia decreases the consumption of propofol, sevoflurane and maintains the intra-operative haemodynamic stability, whereas withholding BF increases propofol and sevoflurane consumption with intra-operative higher HR and MAP, compared to control group.

Effect of neuromuscular blockade reversal by pyridostigmine on spectral entropy values during recovery from desflurane anesthesia: a prospective, randomized, double-blind, controlled trial.

BackgroundAccording to several studies investigating the relationship between muscle activity and electroencephalogram results, reversal of neuromuscular blockade (NMB) may affect depth of anesthesia indices. Therefore, we investigated the effect of pyridostigmine on these indices via spectral entropy.MethodsFifty-six patients scheduled for thyroidectomy or parotidectomy were included in this study and randomized into two groups. At the start of skin suturing, the desflurane concentration was adjusted to 4.2 vol% in both groups. Following this, the pyridostigmine group (group P, n = 28) was administered pyridostigmine 0.2 mg/kg mixed with glycopyrrolate 0.04 mg/kg, while the control group (group C, n = 28) received normal saline. Entropy values (response entropy [RE] and state entropy [SE]), train of four (TOF) ratio, and end-tidal desflurane concentration were recorded from point of drug administration to 15 minutes post-drug administration.ResultsMean RE values at 15 minutes, when the maximum effect of pyridostigmine was anticipated, showed a statistically significant difference between groups (53.8 ± 10.5 in group P and 48.0 ± 8.8 in group C; P = 0.030). However, mean SE at 15 minutes showed no significant difference between the two groups (P = 0.066). At 15 minutes, there were significant differences in the TOF ratio between the two groups (P < 0.001).ConclusionsNMB reversal by pyridostigmine significantly increased RE values but not SE values. This finding suggests that spectral entropy may be a useful alternative tool for monitoring anesthetic depth during recovery from anesthesia in the presence of electromyogram activity.

Decision Making in the Arrow of Time

We show that the steady-state entropy production rate of a stochastic process is inversely proportional to the minimal time needed to decide on the direction of the arrow of time. Here we apply Wald's sequential probability ratio test to optimally decide on the direction of time's arrow in stationary Markov processes. Furthermore, the steady-state entropy production rate can be estimated using mean first-passage times of suitable physical variables. We derive a first-passage time fluctuation theorem which implies that the decision time distributions for correct and wrong decisions are equal. Our results are illustrated by numerical simulations of two simple examples of nonequilibrium processes.

Transient Velocity And Steady State Entropy Generation In A Microfluidic Couette Flow Containing Charged Nano Particles

An analysis has been provided to determine the transient velocity and steady state entropy generation in a microfluidic Couette flow influenced by electro-kinetic effect of charged nanoparticles. The equation for calculating the Couette flow velocity profile is derived for transient flow. The solutions for momentum and energy equations are used to get the exact solution for the dimensionless velocity ratio and dimensionless entropy generation number. The effects of the dimensionless entropy generation number, Bejan number, irreversibility ratio, entropy generation due to fluid friction and due to heat transfer on dimensionless time, relative channel height, Brinkman number, dimensionless temperature ratio, nanoparticle volume fraction are analyzed.

Signature of a continuous quantum phase transition in non-equilibrium energy absorption: Footprints of criticality on higher excited states.

Understanding phase transitions in quantum matters constitutes a significant part of present day condensed matter physics. Quantum phase transitions concern ground state properties of many-body systems, and hence their signatures are expected to be pronounced in low-energy states. Here we report signature of a quantum critical point manifested in strongly out-of-equilibrium states with finite energy density with respect to the ground state and extensive (subsystem) entanglement entropy, generated by an external pulse. These non-equilibrium states are evidently completely disordered (e.g., paramagnetic in case of a magnetic ordering transition). The pulse is applied by switching a coupling of the Hamiltonian from an initial value (λI) to a final value (λF) for sufficiently long time and back again. The signature appears as non-analyticities (kinks) in the energy absorbed by the system from the pulse as a function of λF at critical-points (i.e., at values of λF corresponding to static critical-points of the system). As one excites higher and higher eigenstates of the final Hamiltonian H(λF) by increasing the pulse height , the non-analyticity grows stronger monotonically with it. This implies adding contributions from higher eigenstates help magnifying the non-analyticity, indicating strong imprint of the critical-point on them. Our findings are grounded on exact analytical results derived for Ising and XY chains in transverse field.