Mapping the neural systems driving breathing at the transition to unconsciousness.

After falling asleep, the brain needs to detach from waking activity and reorganize into a functionally distinct state. A functional MRI (fMRI) study has recently revealed that the transition to unconsciousness induced by propofol involves a global decline of brain activity followed by a transient reduction in cortico-subcortical coupling. We have analyzed the relationships between transitional brain activity and breathing changes as one example of a vital function that needs the brain to readapt. Thirty healthy participants were originally examined. The analysis involved the correlation between breathing and fMRI signal upon loss of consciousness. We proposed that a decrease in ventilation would be coupled to the initial decline in fMRI signal in brain areas relevant for modulating breathing in the awake state, and that the subsequent recovery would be coupled to fMRI signal in structures relevant for controlling breathing during the unconscious state. Results showed that a slight reduction in breathing from wakefulness to unconsciousness was distinctively associated with decreased activity in brain systems underlying different aspects of consciousness including the prefrontal cortex, the default mode network and somatosensory areas. Breathing recovery was distinctively coupled to activity in deep brain structures controlling basic behaviors such as the hypothalamus and amygdala. Activity in the brainstem, cerebellum and hippocampus was associated with breathing variations in both states. Therefore, our brain maps illustrate potential drives to breathe, unique to wakefulness, in the form of brain systems underlying cognitive awareness, self-awareness and sensory awareness, and to unconsciousness involving structures controlling instinctive and homeostatic behaviors.

Evaluation of the density spectral array in the Wada test: report of six cases.

Wada test is an invasive procedure used in the preoperative evaluation for epilepsy surgery to determine language lateralization, postoperative risk of amnesia syndrome, and to assess the risk of memory deficits. It involves injection of amobarbital into internal carotid artery of the affected hemisphere followed by the healthy hemisphere to shut down brain function. We performed an observational study evaluating the density spectral array (DSA) of the bilateral bispectral index VISTA™ Monitoring System (BVMS) in 6 patients with drug-resistant epilepsy undergoing Wada test. DSA revealed the presence of bifrontal alpha waves in absence of loss of consciousness in all patients.

Effect of dexmedetomidine on evoked-potential monitoring in patients undergoing brain stem and supratentorial cranial surgery.

BACKGROUND: Dexmedetomidine is used as adjuvant in total intravenous anaesthesia (TIVA), but there have been few studies concerning its effect on intraoperative neurophysiological monitoring (IONM) during cranial surgery. Our aim was to study the effect of dexmedetomidine on IONM in patients undergoing brain stem and supratentorial cranial surgery. METHODS: Two prospective, randomized, double-blind substudies were conducted. In substudy 1, during TIVA with an infusion of propofol and remifentanil, 10 patients received saline solution (SS) (PR group) and another 10 (PRD group) received dexmedetomidine (0.5 mcg/kg/h). Total dosage of propofol and remifentanil, intensity, latency and amplitude of motor-evoked potentials following transcranial electrical stimulation (tcMEPs) as well as somatosensory-evoked potentials (SSEP) were recorded at baseline, 15, 30, 45 minutes, and at the end of surgery. In order to identify differences in the same patient after dexmedetomidine administration, we designed substudy 2 with 20 new patients randomized to two groups. After 30 minutes with TIVA, 10 patients received dexmedetomidine (0.5 mcg/kg/h) and 10 patients SS. The same variables were recorded. RESULTS: In substudy 1, propofol requirements were significantly lower (P = .004) and tcMEP intensity at the end of surgery was significantly higher in PRD group, but no statistically significant differences were observed for remifentanil requirements, SSEP and tcMEP latency or amplitude. In substudy 2, no differences in any of the variables were identified. CONCLUSIONS: The administration of dexmedetomidine at a dosage of 0.5 mg/kg/h may reduce propofol requirements and adversely affect some neuromonitoring variables. However, it can be an alternative on IONM during cranial surgeries. REDEX EudraCT: 2014-000962-23.

Largest scale dissociation of brain activity at propofol-induced loss of consciousness.

The brain is a functional unit made up of multilevel connected elements showing a pattern of synchronized activity that varies in different states. The wake-sleep cycle is a major variation of brain functional condition that is ultimately regulated by subcortical arousal- and sleep-promoting cell groups. We analyzed the evolution of functional MRI (fMRI) signal in the whole cortex and in a deep region including most sleep- and wake-regulating subcortical nuclei at loss of consciousness induced by the hypnotic agent propofol. Optimal data were obtained in 21 of the 30 healthy participants examined. A dynamic analysis of fMRI time courses on a time-scale of seconds was conducted to characterize consciousness transition, and functional connectivity maps were generated to detail the anatomy of structures showing different dynamics. Inside the magnet, loss of consciousness was marked by the participants ceasing to move their hands. We observed activity synchronization after loss of consciousness within both the cerebral cortex and subcortical structures. However, the evolution of fMRI signal was dissociated, showing a transient reduction of global cortico-subcortical coupling that was restored during the unconscious state. An exception to cortico-subcortical decoupling was a brain network related to self-awareness (i.e. the default mode network) that remained connected to subcortical brain structures. Propofol-induced unconsciousness is thus characterized by an initial, transitory dissociated synchronization at the largest scale of brain activity. Such cortico-subcortical decoupling and subsequent recoupling may allow the brain to detach from waking activity and reorganize into a functionally distinct state.

Density spectral array during the intra and postoperative of a left frontal craniotomy / Matriz de Densidad Espectral durante el intra y el posoperatorio de una craneotomía frontal izquierda

Abstract We present the case of an adult with an extensive left frontal meningioma. He was scheduled for resection by craniotomy. During the surgery we used the density spectral array (DSA) and asymmetry obtained from Bispectral Index VISTA Monitoring System Bilateral. We observed a power increase in low frequency (0.1-1 Hz) and alpha bands (8-12 Hz) in the left hemisphere, where the meningioma was located. In this case, DSA was useful during and after the surgery because it provided information about the hemisphere with maximum brain activity and its subsequent normalization, which may reflect the effectiveness of the surgery.

Resumen Presentamos el caso de un paciente adulto con diagnóstico de un meningioma extenso a nivel frontal izquierdo, que fue programado para exéresis mediante craneotomía. Durante la cirugía se utilizó la Matriz de Densidad Espectral (MDE) y la asimetría obtenida del Sistema de Monitorización VISTATM del Índice Biespectral Bilateral (BVMS). Se observó un aumento de potencia en las bandas de baja frecuencia (0.1-1Hz) y en las bandas alfa (812 Hz) del hemisferio cerebral izquierdo, donde se encontraba el meningioma. En este caso la MDE demostró su utilidad durante y después de la cirugía, al proporcionar información sobre el hemisferio con registro de máxima actividad cerebral y su posterior normalización, reflejando así la efectividad de la cirugía.

Sedación con propofol y remifentanilo para la ultrasonografía endobronquial con punción-aspiración en tiempo real / Sedation with propofol and remifentanil for real-time endobronchial ultrasound needle aspiration

Introducción: Para la óptima realización de la ultrasonografía endobronquial (USEB) lineal es imprescindible que el paciente esté sedado para que se mantenga tranquilo, no tosa ni se mueva y el endoscopista trabaje cómodamente con un buen rendimiento de la exploración. Actualmente la técnica anestésica no está estandarizada y varía desde una anestesia general a una sedación. El objetivo del presente trabajo es conocer la dosificación, la seguridad y la satisfacción de la sedación endovenosa con propofol y remifentanilo e identificar los posibles factores predictivos de tos durante el procedimiento. Pacientes y métodos: Se estudió prospectivamente a los pacientes a quienes se realizó la USEB bajo sedación en un hospital de tercer nivel. Resultados: Se realizó la USEB a 90pacientes bajo sedación con remifentanilo y propofol, a una velocidad de infusión de 0,13 (0,09-0,17) ixgkg-¹ min^¹ y 2,34 (1,5-3,6) mgkg-¹ h_1, respectivamente. El 81% de los pacientes tosieron en algún momento de la exploración. En el 8% de los pacientes se interrumpió el procedimiento puntualmente por tos y desaturación. No se registraron complicaciones graves directamente relacionadas con la sedación. El nivel de satisfacción del neumólogo y del paciente con el procedimiento fue excelente o bueno en la mayoría de casos. No se observó relación estadísticamente significativa entre el número de episodios de tos durante la ecobroncoscopia y las variables test de la tos, ser tosedor habitual, hábito tabáquico o grado de severidad de la EPOC. Conclusiones: La sedación con remifentanilo y propofol realizada por un anestesiólogo permite realizar la USEB lineal en ventilación espontánea aunque con una elevada incidencia de tos y desaturación, siendo esta última la complicación más frecuente. No se encontraron factores predictivos de la tos durante el procedimiento.

Introduction: Optimal linear endobronchial ultrasound (EBUS) outcomes require sedation to ensure that the patient remains calm, immobile, and does not cough, and so that the bronchoscopist can work comfortably. The choice of anesthesia techniques, on a spectrum ranging from general anesthesia to sedation, is not standardized. The aims of this study were to determine doses, safety and satisfaction for intravenous sedation with propofol and remifentanil, and identify potential predictors of coughing during the procedure, and determine patient and bronchoscopist satisfaction with the procedure. Patients and methods: The prospective study included patients undergoing EBUS under sedation in a tertiary hospital. Results: A total of 90 patients underwent EBUS under sedation with remifentanil and propofol, at infusion rates of 0,13 (0,09-0,17) g kg-¹ min^¹ and 2.34 (1.5-3.6) mg kg-¹ Lr¹, respectively. Just over four fifths of the patients (81%) coughed at some point during the ultrasound procedure. In 8% of patients the procedure was promptly discontinued due to coughing and desaturation. There were no major complications directly related to sedation. Bronchoscopists and patients rated their satisfaction with the procedure as excellent or good in most cases. There was no statistically significant relationship between the number of coughing episodes during the procedure and any of the following variables: positive cough test, a habitual cough, tobacco dependence, or severity of chronic obstructive pulmonary disease. Conclusions: Remifentanil and propofol administered by an anesthesiologist enabled spontaneously breathing patients to undergo linear EBUS, although with a high incidence of coughing and particularly desaturation. No predictors for coughing during EBUS were identified.

[Anesthesia in thoracic surgery in Catalonia: results of a survey carried out in 2003]. / Actividad anestésica en cirugía torácica en Cataluña. Resultados de una encuesta realizada durante 2003.

OBJECTIVE: To determine the anesthetic, surgical, and postoperative characteristics of patients who underwent thoracic surgery in Catalonia, Spain, in 2003. MATERIAL AND METHODS: A prospective, cross-sectional survey was carried out on 14 randomly chosen days in 2003. All hospitals performing thoracic surgery in Catalonia took part. Data were collected on patient characteristics, anesthetic techniques, procedures, analgesia, and postoperative care. RESULTS: Data on 171 anesthetic procedures in thoracic surgery were collected from 27 hospitals; these procedures represented 0.7% of the total anesthetic workload. Extrapolation from the collected data indicated that 4458 anesthetic procedures were performed in thoracic surgery in 2003 (95% confidence interval, 3624-4823 procedures). Of these procedures, 75.4% were performed in public hospitals and 24.6% in private hospitals. The median age of patients was 55 years (10th-90th percentiles, 22.4-73 years) and 63.9% were men. Surgical procedures were scheduled in 92.8% of the cases. The most common interventions were lung and bronchial surgery other than resection (36.8%), lung and/or bronchial resection (24.6%), and thoracoscopy and mediastinoscopy (20.5%). The median duration of pneumonectomies and lobectomies was 180 minutes (10th-90th percentiles, 90-221 minutes). General anesthesia was the most commonly used procedure (74.3%). Postoperative recovery took place in a conventional recovery room in 54.4% of cases, in a postanesthetic intensive care unit in 33.3% of cases, and in an intensive care unit in 12.3% of cases. CONCLUSIONS: This survey provided information on anesthesia in thoracic surgery, which represented 0.7% of all anesthesia procedures in an area with a population of 7 million.