Rogean Rodrigues Nunes

Avaliação dos parâmetros derivados do eletroencefalograma durante administração de diferentes concentrações de óxido nitroso

BACKGROUND AND OBJECTIVES Spectral electroencephalography has been used to measure anesthetic depth, hypnosis and sedation levels induced by different anesthetic agents. This study aimed at evaluating the effects of N2O on electroencephalographic (EEG) variables and sedation levels according to Observer Assessment of Alertness/Sedation (OAA/S) scale, as well as on hemodynamic and respiratory parameters. METHODS Thirty adult patients from both genders, physical status ASA I, aged 20 and 40 years, were submitted to the following protocol: after 10 minutes of relaxation, spontaneously breathing with eyes close, patients were given 30% and 50% N2O concentrations under face mask. Data were collected in three moments: M1- before N2O administration; M2 - 30% N2O in O2; M3 - 50% N2O in O2. Data for M2 and M3 were collected 15 minutes after stabilization of 30% and 50% N2O expired fractions (FeN2O), respectively, with a 5-minute interval between fractions. The following parameters were evaluated: electroencephalographic: BIS, SEF1, SEF2, power energy (PE) and burst suppression (BS); hemodynamic: heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP); respiratory: oxygen hemoglobin saturation (SpO2), carbon dioxide expired pressure (P ET CO2), minute ventilation and respiratory rate; clinical: patients were rated in a descending order (5, 4, 3, 2 and 1) according to OAA/S scale. RESULTS N2O administrated at 30% and 50% concentrations has statistically changed BIS, SEF1, SEF2, PE and OAA/S level of sedation in the studied moments. No clinically important changes were observed, as all patients were cooperative and slightly sedated, though SEF1 and SEF2 indications of deep hypnosis. Hemodynamic and respiratory parameters changes were not statistically significant. CONCLUSIONS N2O at 30% and 50% concentrations in non-premedicated patients has induced mild sedation according to OAA/S scale. There has been correspondence with BIS, but not with SEF1 and SEF2.

Bispectral index and other processed parameters of electroencephalogram: an update

BACKGROUND AND OBJECTIVES The processed analysis of electroencephalogram became extremely important to monitor nervous system, being used to obtain a better anesthetic adequacy. The objective was to conduct a review about each processed parameter, defining its real importance. CONTENT A review was conducted showing mathematical, physical and clinical aspects as well as their correlations and updates, presenting new integrated parameters. CONCLUSIONS An adequate analysis of processed parameters of electroencephalogram may provide more intraoperative safety as well as result in a better outcome for the patient.

Entropia espectral: um novo método para adequação anestésica

BACKGROUND AND OBJECTIVES Though universally employed, clinical signs to evaluate anesthetic adequacy are not reliable. Over the past years several pieces of equipment have been devised to improve intraoperative handling of anesthetic drugs, some of them directly measuring cerebral cortical activity (hypnosis). None of them, however, has offered the possibility of directly evaluating sub-cortical activity (motor response). CONTENTS Spectral entropy measures irregularity, complexity or amount of EEG disorders and has been proposed as indicator of anesthetic depth. Signal is collected from the fronto-temporal region and processed according to Shannons equation (H = - Sp k log p k, where p k represents the probability of a discrete k event), resulting in two types of analyses: 1) state entropy (SE), which evaluates cerebral cortex electrical activity (0.8 - 32Hz) and 2) response entropy (RE), containing both subcortical electromyographic and cortical electroence- phalographic components and analyzes frequencies in the range 0.8 - 47Hz. CONCLUSIONS Frontal muscles activation may indicate inadequacy of the subcortical component (nociception). Such activation appears as a gap between SE and RE. This, it is possible to directly evaluate both cortical (SE) and subcortical (RE) components providing better anesthetic adequacy.

Risk Factor for Intraoperative Awareness

BACKGROUND AND OBJECTIVES The intraoperative awareness is an adverse event in the general anesthesia, and may occur in approximately 20,000 cases per year, which justifies the study of the risk factors for this event. The objective of this study was to review this subject in order to reduce the incidence of intraoperative awareness and psychological sequelae incurring from this incident, which may result in post-traumatic stress disorder with negative repercussions on the surgical patient social, psychic and functional development. CONTENT It was conducted a review of the intraoperative awareness assessing its different phases during general anesthesia such as dreaming, wakefulness, explicit and implicit memory, as well as the analysis, consequences and prevention of its main related factors. CONCLUSIONS The reduction of awareness incidence during anesthesia is related to the anesthesiologist improved scientific and technical performance, involving issues such as monitoring, comprehension of the anesthesia activity components, hypnotic and analgesic drugs, neuromuscular blocking agents, autonomic and motor reflex control, in addition to the risk factors involved in this event.

Anesthetics, cerebral protection and preconditioning.

BACKGROUND AND OBJECTIVES Several studies demonstrate that cerebral preconditioning is a protective mechanism against a stressful situation. Preconditioning determinants are described, as well as the neuroprotection provided by anesthetic and non-anesthetics agents. CONTENT Review based on the main articles addressing the pathophysiology of ischemia-reperfusion and neuronal injury and pharmacological and non-pharmacological factors (inflammation, glycemia, and temperature) related to the change in response to ischemia-reperfusion, in addition to neuroprotection induced by anesthetic use. CONCLUSIONS The brain has the ability to protect itself against ischemia when stimulated. The elucidation of this mechanism enables the application of preconditioning inducing substances (some anesthetics), other drugs, and non-pharmacological measures, such as hypothermia, aimed at inducing tolerance to ischemic lesions.

Spectral entropy: a new method for anesthetic adequacy

BACKGROUND AND OBJECTIVES Though universally employed, clinical signs to evaluate anesthetic adequacy are not reliable. Over the past years several pieces of equipment have been devised to improve intraoperative handling of anesthetic drugs, some of them directly measuring cerebral cortical activity (hypnosis). None of them, however, has offered the possibility of directly evaluating sub-cortical activity (motor response). CONTENTS Spectral entropy measures irregularity, complexity or amount of EEG disorders and has been proposed as indicator of anesthetic depth. Signal is collected from the fronto-temporal region and processed according to Shannons equation (H = - Sp k log p k, where p k represents the probability of a discrete k event), resulting in two types of analyses: 1) state entropy (SE), which evaluates cerebral cortex electrical activity (0.8 - 32Hz) and 2) response entropy (RE), containing both subcortical electromyographic and cortical electroence- phalographic components and analyzes frequencies in the range 0.8 - 47Hz. CONCLUSIONS Frontal muscles activation may indicate inadequacy of the subcortical component (nociception). Such activation appears as a gap between SE and RE. This, it is possible to directly evaluate both cortical (SE) and subcortical (RE) components providing better anesthetic adequacy.

[Entropy: a new method of measuring depth of anesthesia. Comparative study with bispectral index during clinical evaluation in tracheal intubation of patients anesthetized with sevoflurane.].

BACKGROUND AND OBJECTIVES: Spectral entropy, a new EEG analysis method based on the quantification of EEG chaos, was developed to monitor anesthetic depth. The spectral entropy involves two distinct types of analysis: state entropy (SE), which includes low frequency signals (< 32 Hz), and response entropy (RE), which includes signals up to 47 Hz. This study aimed at comparing entropy-derived values to BIS-derived values and sub-cortical (autonomic and somatic) responses recorded during tracheal intubation in patients submitted to general anesthesia with sevoflurane. METHODS: Participated in this study 36 patients ASA I, aged 20 to 44 years, assigned to four groups (G1-G4) of nine patients submitted to tracheal intubation (TI). In all groups anesthesia was induced with sevoflurane, associated or not to fentanyl, according to the following regimens: G1 = sevoflurane plus 2.5 µg.kg-1 fentanyl; G2 = sevoflurane plus 5 µg.kg-1 fentanyl; G3 = sevoflurane plus 7.5 µg.kg-1 fentanyl; and G4 = sevoflurane plus saline solution. The following parameters were monitored: SBP, DBP, HR, BIS, SE, RE, sevoflurane expired concentration (EC) and motor response to TI at three moments: M1 = immediately before induction; M2 = immediately before tracheal intubation and M3 = one minute after tracheal intubation. RESULTS: BIS and SE values have linearly varied in all groups, with significant differences between M2 and M3 for Groups 1 and 4. At M3, BIS and SE values in G4 were above those for the threshold between consciousness and unconsciousness. Hemodynamic changes were not clinically significant, with the exception of HR increase between M1 and M3 for G4 (p < 0.05%). In G1, 66% of patients have reacted to TI maneuvers as compared to 100% in G4. CONCLUSIONS: Our findings suggest that sevoflurane alone or in association with 2.5 µg.kg-1 or 5 µg.kg-1 fentanyl does not effectively block CNS cortical and subcortical components responses during tracheal intubation, being sevoflurane plus 7.5 µg.kg-1 fentanyl the best association to control anesthetic components.BACKGROUND AND OBJECTIVES Spectral entropy, a new EEG analysis method based on the quantification of EEG chaos, was developed to monitor anesthetic depth. The spectral entropy involves two distinct types of analysis: state entropy (SE), which includes low frequency signals (< 32 Hz), and response entropy (RE), which includes signals up to 47 Hz. This study aimed at comparing entropy-derived values to BIS-derived values and sub-cortical (autonomic and somatic) responses recorded during tracheal intubation in patients submitted to general anesthesia with sevoflurane. METHODS Participated in this study 36 patients ASA I, aged 20 to 44 years, assigned to four groups (G1-G4) of nine patients submitted to tracheal intubation (TI). In all groups anesthesia was induced with sevoflurane, associated or not to fentanyl, according to the following regimens: G1 = sevoflurane plus 2.5 microg.kg-1 fentanyl; G2 = sevoflurane plus 5 microg.kg-1 fentanyl; G3 = sevoflurane plus 7.5 microg.kg-1 fentanyl; and G4 = sevoflurane plus saline solution. The following parameters were monitored: SBP, DBP, HR, BIS, SE, RE, sevoflurane expired concentration (EC) and motor response to TI at three moments: M1 = immediately before induction; M2 = immediately before tracheal intubation and M3 = one minute after tracheal intubation. RESULTS BIS and SE values have linearly varied in all groups, with significant differences between M2 and M3 for Groups 1 and 4. At M3, BIS and SE values in G4 were above those for the threshold between consciousness and unconsciousness. Hemodynamic changes were not clinically significant, with the exception of HR increase between M1 and M3 for G4 (p < 0.05%). In G1, 66% of patients have reacted to TI maneuvers as compared to 100% in G4. CONCLUSIONS Our findings suggest that sevoflurane alone or in association with 2.5 microg.kg-1 or 5 microg.kg-1 fentanyl does not effectively block CNS cortical and subcortical components responses during tracheal intubation, being sevoflurane plus 7.5 microg.kg-1 fentanyl the best association to control anesthetic components.

Influence of Total Intravenous Anesthesia, Entropy and Laparoscopy on Oxidative Stress

BACKGROUND AND OBJECTIVES Recent studies have correlated postoperative mortality with anesthetic mortality, especially with the depth of anesthesia and systolic blood pressure (SBP). The aim of this study is to evaluate the effects of the depth of total intravenous anesthesia (TIVA) using remifentanil and propofol, performed with monitoring of response entropy (RE) on blood concentrations of oxidative stress markers (TBARS and glutathione) during laparoscopic operations. METHOD Twenty adult patients, ASA I, BMI 20-26 kg.m(-2), aged 20 to 40 years, were randomly distributed into two groups: Group I underwent anesthetic-surgical procedure with RE maintained between 45 and 59, and Group II underwent anesthetic-surgical procedure with RE between 30 and 44. In both groups, the remifentanil and propofol infusion was controlled by the effector site (Es), adjusted to maintain RE desired values (Groups I and II) and always assessing the suppression rate (SR). Patients were evaluated in six periods: M1 (immediately before anesthesia), M2 (before tracheal intubation [TI]), M3 (5-minutes after TI), M4 (immediately before pneumoperitoneum [PPT]), M5 (1-minute after PPT), and M6 (1-hour after the operation). The following parameters were assessed at all times: SBP, DBP, HR, RE, SR, TBARS, and glutathione. RESULTS We found increases in TBARS and glutathione in M5, both in Group I and Group II (p<0.05), with higher values in Group II, and SR in three patients in Group II, immediately after PPT. CONCLUSIONS Increased markers in Group I (M5) suggests an increase in anaerobic metabolism (AM) in the splanchnic circulation while the highest values seen in Group II (GII > GI in M5, p<0.05%) suggest interference of another factor (deep anesthesia) responsible for the increase in AM, probably as a result of increased autonomic nervous system depression and minor splanchnic self-regulation.

Influência da dexmedetomidina na concentração expirada do sevoflurano: avaliação pelo índice bispectral, taxa de supressão e análise espectral da potência do eletroencefalograma

JUSTIFICATIVA Y OBJETIVOS: La dexmedetomidina, un a2-agonista adrenergico, ha sido descrita como capaz de reducir el consumo tanto de agentes venosos como inhalatorios. El objetivo de este estudio fue evaluar la influencia de la dexmedetomidina en la concentracion expirada (CE) de sevoflurano, con monitorizacion de la profundidad de la anestesia. METODO: Participaron del estudio 40 pacientes del sexo femenino, estado fisico ASA I, sometidas a laparoscopia ginecologica bajo anestesia general mantenida con sevoflurano, divididas aleatoriamente en dos grupos: Grupo I (20): sin dexmedetomidina, y Grupo II (20): con dexmedetomidina en infusion continua en el siguiente esquema: Fase rapida (1 µg.kg-1 en 10 minutos), 10 minutos antes de la induccion de la anestesia, seguida por un periodo de manutencion (0,4 µg.kg-1.h-1) hasta el final de la cirugia. Fueron analizados los siguientes parametros: PA, FC, BIS, SEF 95%, amplitud relativa en la frecuencia de banda delta (d%), tasa de supresion (TS), rSO2, CE, SpO2 yPETCO2, en los siguientes momentos: M1 - antes de la infusion de la dexmedetomidina o solucion fisiologica a 0,9%, M2: antes de la intubacion traqueal (IT), M3: despues a IT, M4: antes de la incision, M5: despues de la incision, M6: antes de la insuflacion de CO2, M7: despues de la insuflacion de CO2, M8: 10 minutos despues de la insuflacion de CO2, M9: 10 min. despues M8, M10: 20 min despues M8, M11: 30 min despues M8, M12: 40 min despues M8 y M13: al despertar. Anotamos tambien el tiempo de despertar y de alta hospitalar. RESULTADOS: La dexmedetomidina reducio la concentracion expirada de sevoflurano de M4 hasta M13 (p < 0,05), comparandose GI y GII. No fueron observados cambios clinicamente significativos en los parametros hemodinamicos. El tiempo de despertar en el GI fue 11 ± 0,91 minutos y en el GII fue 6,35 ± 0,93 minutos (p < 0,05). El tiempo de alta hospitalar en el GI fue 7,45 ± 0,69 horas y en el GII fue 8,37 ± 0,88 horas (p < 0,05). CONCLUSIONES: La dexmedetomidina es efectiva en reducir la concentracion expirada del sevoflurano, manteniendo estabilidad hemodinamica, sin comprometer el tiempo de alta hospitalar, ademas de promover un despertar mas precoz.BACKGROUND AND OBJECTIVES Dexmedetomidine, an alpha2-adrenergic agonist, has been described as being able to decrease the demand for both venous and inhalational agents. This study aimed at evaluating the influence of Dexmedetomidine upon sevoflurane end-expiratory concentration (EC) with monitoring the depth of anesthesia. METHODS Participated in this study 40 female adult patients, physical status ASA I, submitted to gynecological laparoscopy under general anesthesia maintained with sevoflurane, who were randomly divided in two groups: Group I (n=20), without dexmedetomidine; and Group II (n=20), with dexmedetomidine, in continuous infusion, as follows: Rapid phase (1 microg kg(-1) in 10 min(-1)) 10 minutes before anesthesia induction, followed by a maintenance phase (0.4 microg kg(-1) h(-1)) throughout the surgery. The following parameters were analyzed: BP, HR, BIS, SEF 95%, delta%, suppression rate (SR), rSO2, CE, SpO2 and P(ET)CO2, in the following moments: M1 - before dexmedetomidine or 0.9% saline infusion; M2 - prior to intubation; M3 - following intubation; M4 - before incision; M5 - following incision; M6 - before CO2 inflation; M7 - following CO2 inflation; M8 - 10 min after CO2 inflation; M9 - 10 min after M8; M10 - 20 min after M8; M11 - 30 min after M8; M12 - 40 min after M8; and M13 - at emergence. Time for emergence and hospital discharge were also recorded. RESULTS Dexmedetomidine has decreased sevoflurane end-expiratory concentration from M4 to M13 (p<0.05) when comparing Group I and Group II. No clinically significant changes were observed in hemodynamic parameters. Time for emergence in Groups I and II was 11 +/- 0.91 min. and 6.35 +/- 0.93 min., respectively (p < 0.05). Time for hospital discharge was 7.45 +/- 0.69 h in Group I and 8.37 +/- 0.88 h in Group II (p < 0.05). CONCLUSIONS Dexmedetomidine was effective in decreasing sevoflurane end-expiratory concentration while maintaining hemodynamic stability without impairing time for hospital discharge, in addition to promoting an earlier emergence.

Índice bispectral e outros parâmetros processados do eletroencefalograma: uma atualização

JUSTIFICATIVA Y OBJETIVOS: El analisis procesado del electroencefalograma se convirtio en algo extremadamente importante en el monitoreo del sistema nervioso, siendo utilizado para lograr una mejor adecuacion anestesica. El objetivo fue realizar una revision sobre cada uno de los parametros procesados, definiendo su real importancia. CONTENIDO: Se realizo una revision mostrando los aspectos matematicos, fisicos y clinicos, como tambien sus correlaciones y actualizaciones, y presentando nuevos parametros integrados. CONCLUSIONES: El analisis adecuado de los parametros procesados del electroencefalograma, puede proporcionar una mayor seguridad intraoperatoria como tambien un mejor resultado para el paciente