RESUMO
The refined multiscale entropy (RMSE) approach is commonly applied to assess complexity as a function of the time scale. RMSE is normally based on the computation of sample entropy (SampEn) estimating complexity as conditional entropy. However, SampEn is dependent on the length and standard deviation of the data. Recently, fuzzy entropy (FuzEn) has been proposed, including several refinements, as an alternative to counteract these limitations. In this work, FuzEn, translated FuzEn (TFuzEn), translated-reflected FuzEn (TRFuzEn), inherent FuzEn (IFuzEn), and inherent translated FuzEn (ITFuzEn) were exploited as entropy-based measures in the computation of RMSE and their performance was compared to that of SampEn. FuzEn metrics were applied to synthetic time series of different lengths to evaluate the consistency of the different approaches. In addition, electroencephalograms of patients under sedation-analgesia procedure were analyzed based on the patient's response after the application of painful stimulation, such as nail bed compression or endoscopy tube insertion. Significant differences in FuzEn metrics were observed over simulations and real data as a function of the data length and the pain responses. Findings indicated that FuzEn, when exploited in RMSE applications, showed similar behavior to SampEn in long series, but its consistency was better than that of SampEn in short series both over simulations and real data. Conversely, its variants should be utilized with more caution, especially whether processes exhibit an important deterministic component and/or in nociception prediction at long scales.
RESUMO
Anesthesiology is a medical specialty in which quantification-the capacity to measure-is of major importance. The basic principle of our interventions as anesthesiologists is based on the administration of drugs, the observation of the effect that these drugs have on the patient, and the adjustment of drug delivery depending on the response that is observed. The magnitude ofthis response depends on: 1. Factors directly related to the patient such as their age, physical state, and the medication he/she is taking and, 2. Contextual factors such as the type of surgical procedure, its urgency, the point of time within the procedure, and the complications that can appear (bleeding, hypothermia, state of shock) to cite just a few of the most relevant aspects. Observing, adjusting, and magnitude-they are concepts that imply the possibility of measuring to precisely evaluate how the patient reacts in each and every moment of anesthetic drug delivery process.
Assuntos
HumanosRESUMO
BACKGROUND: The onset and offset of action of anesthetic gases might be delayed by respiratory changes and gas exchange alterations present in obese patients. In this study, we assessed the influence of obesity on the hysteresis between sevoflurane and its effect as measured by the bispectral index (BIS). Because the use of positive end-expiratory pressure (PEEP) in obese patients has improved gas exchange, we also assessed the influence of PEEP on hysteresis. METHODS: Fifteen obese and 15 normal-weight patients, ASA physical status I and II, 20 to 50 years old, scheduled to undergo general anesthesia for elective laparoscopic surgery, were prospectively studied. Anesthesia was induced with propofol and maintained with sevoflurane and fentanyl. At the end of surgery and after stable BIS values of 60 to 65, the inspired concentration of sevoflurane was increased to 5 vol% for 5 minutes or until BIS was <40 and then decreased. Sevoflurane transitions were performed once in normal-weight subjects (without PEEP) and twice in obese patients (one without PEEP and one with a PEEP of 8 cm H(2)O). The hysteresis between sevoflurane end-tidal concentrations and BIS during these transition periods was modeled with an inhibitory Emax model using a population pharmacokinetic/ pharmacodynamic (PK/PD) approach with NONMEM VI. A descriptive analysis of sevoflurane inspired and expired concentrations, BIS values, and time to reach different BIS end points was also used to compare the PK and PD characteristics. RESULTS: All patients completed the study. The data were adequately fit with the PK/PD model. The hysteresis expressed as the effect-site elimination rate constant was not influenced by body mass index or PEEP (P > 0.05). Neither obesity nor PEEP showed any influence on the PK/PD descriptors. CONCLUSIONS: Our results do not support the hypothesis that obesity prolongs induction or recovery times when sevoflurane, a poorly soluble anesthetic, is used to maintain anesthesia from 90 to 120 minutes.
Assuntos
Eletroencefalografia/efeitos dos fármacos , Éteres Metílicos/administração & dosagem , Éteres Metílicos/farmacocinética , Obesidade/metabolismo , Obesidade/fisiopatologia , Respiração com Pressão Positiva , Adulto , Procedimentos Cirúrgicos Eletivos/métodos , Eletroencefalografia/métodos , Feminino , Humanos , Masculino , Respiração com Pressão Positiva/métodos , Estudos Prospectivos , Sevoflurano , Volume de Ventilação Pulmonar/efeitos dos fármacos , Volume de Ventilação Pulmonar/fisiologia , Adulto JovemRESUMO
BACKGROUND: Age is an important determinant of the pharmacokinetic profile of inhaled anesthetics. The influence of age on the dynamic profile of sevoflurane's effect has not been well described. We performed this study to characterize the influence of age and other covariates on the dynamic relationship between sevoflurane end-tidal concentration (C(ET)) and its effect measured by bispectral index (BIS). METHODS: Fifty patients, aged 3-71 yr, scheduled for minor surgery were prospectively studied. The BIS and sevoflurane C(ET) were continuously measured during the study period. During maintenance of anesthesia and after stable BIS values of 60-65 were obtained, the inspired concentration of sevoflurane was increased to 5 vol % for 5 min or until BIS <40 and then decreased. The dynamic relationship between sevoflurane C(ET) and its effect as measured by BIS during this transition period were modeled with an inhibitory E(max) model using a population pharmacokinetic-pharmacodynamic approach with NONMEM V. A predictive check method was used to validate the final model. RESULTS: The sensitivity to sevoflurane's effect as measured by BIS expressed in the C(50) [steady-state C(ET) eliciting half of maximum response (I(max))] increased with age. The speed of change of sevoflurane's effect, expressed as the effect-site equilibration half-life (t(1/2) k(e0)), increased at older ages. The predictive check analysis confirmed the adequacy of the model. CONCLUSIONS: Age significantly affects the dynamic relationship between sevoflurane C(ET) and its effect measured with BIS.