RESUMO
PURPOSE OF REVIEW: Self-awareness can be defined as the capacity of becoming the object of one's own awareness and, increasingly, it has been the target of scientific inquiry. Self-awareness has important clinical implications, and a better understanding of the neurochemical basis of self-awareness may help clarifying causes and developing interventions for different psychopathological conditions. The current article explores the relationship between neurochemistry and self-awareness, with special attention to the effects of psychedelics. RECENT FINDINGS: The functioning of self-related networks, such as the default-mode network and the salience network, and how these are influenced by different neurotransmitters is discussed. The impact of psychedelics on self-awareness is reviewed in relation to specific processes, such as interoception, body ownership, agency, metacognition, emotional regulation and autobiographical memory, within a framework based on predictive coding. Improved outcomes in emotional regulation and autobiographical memory have been observed in association with the use of psychedelics, suggesting higher-order self-awareness changes, which can be modulated by relaxation of priors and improved coping mechanisms linked to cognitive flexibility. Alterations in bodily self-awareness are less consistent, being potentially impacted by doses employed, differences in acute/long-term effects and the presence of clinical conditions. Future studies investigating the effects of different molecules in rebalancing connectivity between resting-state networks may lead to novel therapeutic approaches and the refinement of existing treatments.
Assuntos
Conscientização , Encéfalo , Alucinógenos , Neurotransmissores , Humanos , Alucinógenos/farmacologia , Neurotransmissores/metabolismo , Encéfalo/efeitos dos fármacos , Encéfalo/metabolismo , Conscientização/fisiologia , Conscientização/efeitos dos fármacos , Rede Nervosa/efeitos dos fármacos , Rede Nervosa/metabolismoRESUMO
INTRODUCTION: Continuous palliative sedation (PS) is currently titrated based on clinical observation; however, it is often unclear if patients are still aware of their suffering. The aim of this prospective study is to characterize the level of consciousness in patients undergoing PS using Bispectral Index (BIS) monitoring. PATIENTS AND METHODS: We enrolled consecutive patients with refractory symptoms requiring PS. We documented the level of sedation using Ramsay Sedation Scale (RSS) and BIS at 0, 2, 4, 6, 12, and 24 h during the first day of PS and examined their degree of association. Intravenous midazolam or propofol was titrated according to the sedation level. RESULTS: Twenty patients on PS were recruited and had BIS continuous monitoring. Delirium was the most frequent reason for PS (n = 15, 75%). The median time of sedation was 24.5 h (interquartile range 6-46). The average time to achieve the desired sedation level was 6 h, and dose titration was required in 80% of the cases. At baseline, 14 (70%) patients were considered to be awake according to RSS (i.e., 1-3) and 19 (95%) were awake according to BIS (i.e., >60%). This proportion decreased to 31 and 56% at 4 h, 27% and 53 at 6 h, and 22 and 33% at 24 h. RS and BIS had moderate correlation (rho = -0.58 to -0.65); however, a small proportion of patients were found to be awake by BIS (i.e., ≥60%) despite clinical observation (i.e., RSS 4-6) indicating otherwise. CONCLUSIONS: The BIS is a noninvasive, bedside, real-time continuous monitoring method that may facilitate the objective assessment of level of consciousness and dose titration in patients undergoing PS.
Assuntos
Dor do Câncer/terapia , Sedação Consciente/métodos , Eletroencefalografia/métodos , Monitorização Fisiológica/métodos , Neoplasias/terapia , Cuidados Paliativos/métodos , Adulto , Idoso , Conscientização/efeitos dos fármacos , Estado de Consciência/efeitos dos fármacos , Delírio/induzido quimicamente , Feminino , Humanos , Hipnóticos e Sedativos/administração & dosagem , Hipnóticos e Sedativos/efeitos adversos , Masculino , Midazolam/administração & dosagem , Midazolam/efeitos adversos , Pessoa de Meia-Idade , Neoplasias/patologia , Projetos Piloto , Propofol/administração & dosagem , Propofol/efeitos adversos , Estudos ProspectivosRESUMO
RATIONALE: Ketamine is an NMDA receptor antagonist with psychotogenic and cognitive effects in healthy volunteers and schizophrenic patients which has been proposed to be a useful tool to investigate neurobiological basis of schizophrenia. OBJECTIVE: The present study characterized the effects of a subanesthetic dose of ketamine on memory and related subjective states of awareness in healthy volunteers. METHODS: Twenty-six subjects were given either a 60-min ketamine (0.5 mg/kg per hour) or a placebo infusion. To obtain constant plasma ketamine throughout the experiment, ketamine was administered using a computer-controlled infusion system. Subjects carried out episodic memory tasks involving words presented before and during infusion. Memory performance was assessed with recognition and free recall tasks. Subjective states of awareness were assessed using an experiential approach. Levels of psychopathology were evaluated with BPRS. RESULTS: Ketamine impaired performance in free recall and recognition of words presented during, but not before, infusion. There were no differences between groups concerning states of awareness associated with recognition memory. Subjects under ketamine had higher BPRS total scores as well as BPRS negative and positive cluster scores than control subjects. CONCLUSIONS: Ketamine decreases episodic memory performance by impairing encoding, but not retrieval processes. It does not selectively impair subjective states of awareness associated with recognition memory as it has been seen in patients with schizophrenia. Ketamine might mimic the memory impairment associated with acute, but not chronic, forms of schizophrenia.
Assuntos
Conscientização/efeitos dos fármacos , Antagonistas de Aminoácidos Excitatórios/farmacologia , Ketamina/farmacologia , Memória/efeitos dos fármacos , Receptores de N-Metil-D-Aspartato/antagonistas & inibidores , Adulto , Atenção/efeitos dos fármacos , Feminino , Humanos , Ketamina/sangue , Masculino , Rememoração Mental/efeitos dos fármacosRESUMO
A 17-year-old boy with type 1 diabetes mellitus developed new loss of hypoglycemia awareness while being treated with fluoxetine hydrochloride for depression. Hypoglycemia unawareness resolved after this medication was discontinued.