RESUMO
Enterochromaffin (EC) cells synthesize 95% of the body 5-HT and release 5-HT in response to mechanical or chemical stimulation. EC cell 5-HT has physiological effects on gut motility, secretion and visceral sensation. Abnormal regulation of 5-HT occurs in gastrointestinal disorders and Inflammatory Bowel Diseases (IBD) where 5-HT may represent a key player in the pathogenesis of intestinal inflammation. The focus of this review is on mechanism(s) involved in EC cell "mechanosensation" and critical gaps in our knowledge for future research. Much of our knowledge and concepts are from a human BON cell model of EC, although more recent work has included other cell lines, native EC cells from mouse and human and intact mucosa. EC cells are "mechanosensors" that respond to physical forces generated during peristaltic activity by translating the mechanical stimulus (MS) into an intracellular biochemical response leading to 5-HT and ATP release. The emerging picture of mechanosensation includes Piezo 2 channels, caveolin-rich microdomains, and tight regulation of 5-HT release by purines. The "purinergic hypothesis" is that MS releases purines to act in an autocrine/paracrine manner to activate excitatory (P2Y1, P2Y4, P2Y6, and A2A/A2B) or inhibitory (P2Y12, A1, and A3) receptors to regulate 5-HT release. MS activates a P2Y1/Gαq/PLC/IP3-IP3R/SERCA Ca2+signaling pathway, an A2A/A2B-Gs/AC/cAMP-PKA signaling pathway, an ATP-gated P2X3 channel, and an inhibitory P2Y12-Gi/o/AC-cAMP pathway. In human IBD, P2X3 is down regulated and A2B is up regulated in EC cells, but the pathophysiological consequences of abnormal mechanosensory or purinergic 5-HT signaling remain unknown. EC cell mechanosensation remains poorly understood.
RESUMO
Introduction: The way neurosurgery has evolved has led to increased emphasis on anaesthetic techniques aimed at improving patient well-being. In the United States alone, the number of neurosurgeries has increased significantly, with growth reflected in approximately 12,000 spine procedures per year and another 2700 different neurosurgical procedures per year. For anaesthetists, this means that they are faced more frequently with the need to select the most adequate neuroanaesthesia technique for each patient. Objectives: The purpose of this review is to analyze the role of inhaled and intravenous anaesthetics in neurosurgical procedures. Methodology: A search was conducted in PubMed using the terms TIVA, inhaled anaesthetics, neurosurgery and spine surgery. Results: The articles included in the review show that the adequate anaesthetic technique, besides ensuring a rapid onset of action, contributes to ease of titration with minimum effect on systemic and cerebral haemodynamics; it must enable intraoperative neurophysiological monitoring and rapid emergence, in order to allow early assessment of the patients neurological function and improved outcome. Conclusions: In recent years, the question regarding the use of inhaled vs. intravenous anaesthetics in neurosurgery has given rise to several research studies. Although TIVA is the technique used most frequently, inhaled anaesthetics have also been shown to be safe, titratable, and to provide for adequate intraoperative monitoring and cerebral haemodynamic stability. In patients with normal intracranial compliance, inhaled agents (IA) are a good alternative to TIVA, especially in places where hospital resources are limited.
Introducción: La evolución en neurocirugía ha fomentado las técnicas anestésicas en pro del bienestar del paciente. Solo en Estados Unidos el volumen de neurocirugías ha aumentado de forma significativa, mostrando un crecimiento aproximado de 12.000 procedimientos de columna al a no, y de otros procedimientos neuroquirúrgicos de 2.700/a no. Esto enfrenta con mayor frecuencia a los anestesiólogos a la elección de la técnica neuroanestésica adecuada para cada paciente. Objetivos: Esta revisión pretende realizar un análisis del rol de los anestésicos inhalados e intravenosos en procedimientos neuroquirúrgicos. Metodología: Se realizó una búsqueda en PubMed utilizando TIVA, anestésicos inhalados, neurocirugía y cirugía de columna como términos de búsqueda. Resultados: Los artículos revisados muestran que, la técnica anestésica adecuada, además de tener un rápido inicio de acción, ser fácilmente titulable, con mínimo efecto en la hemodinámia sistémica y cerebral; debe permitir monitorización neurofisiológica intraoperatoria, y un rápido despertar, con el fin de permitir una evaluación temprana de la función neurológica del paciente y mejorar su desenlace. Conclusiones: Durante los últimos a nos la disyuntiva del uso de anestésicos inhalados ver sus intravenosos en neurocirugía ha producido el desarrollo de diversas investigaciones. Aunque TIVA es la técnica usada con mayor frecuencia, los anestésicos inhalados, también han mostrado ser seguros, titulables, proveer una adecuada monitorización intraoperatoria, y estabilidad hemodinámica cerebral. En pacientes con complacía intracraneal normal los agentes inhalados, son una buena alternativa a la anestesia con TIVA, especialmente en lugares con recursos hospitalarios limitados.