Neurotoxicity of anesthetic agents for developing and adult brain

Abstract

1. Neurotoxicity of anesthetic agents to the developing brain: The neurotoxicity of various anesthetic and sedative agents to the developing brain has been clearly established in various laboratory animals, including subhuman primates. According to recent reports, anesthetic agents which block N-methyl-D-aspartate-type glutamate receptors and/or activate gammaaminobutyric acid-A receptors have neurotoxic properties when used during synaptogenesis. Despite numerous reports, however, the precise mechanisms underlying this neurotoxicity remain unknown. Moreover, it is believed that these results cannot be easily extrapolated into human clinical practice. The results of clinical studies on the neurotoxicity of anesthesia in pediatric patients have been conflicting, and definitive epidemiological evidence remains to be established. Therefore, it would be inappropriate to suggest that anesthesiologists change their anesthetic practice based on these studies at the present time. 2. Neurotoxicity of anesthetic agents to the adult brain: Postoperative delirium (POD) and postoperative cognitive dysfunction (POCD) are cognitive complications occurring after surgery under anesthesia. POD is a transient disturbance of consciousness, attention, cognition, or perception or disorganized thinking and can lead to various complications. It is important to determine the preoperative and intraoperative risk factors for POD in tackling this problem. It is also crucial to recognize and manage its underlying causes in ensuring an appropriate environment for a POD-free recovery. POCD is usually defined as persistent cognitive deterioration, which is clinically diagnosed using various types of neuropsychological tests. POCD and POD are both associated with the aggravation of complications after surgery under anesthesia. Although various factors such as systemic neuroinflammation have been postulated as causes of POCD, its underlying pathogenic mechanism remains to be clearly elucidated. POCD is often observed following cardiac surgery. However, recent studies have revealed that it can occur regardless of type of surgery or anesthesia. Suggested risk factors for POCD include advanced age, prolonged duration of surgery, respiratory and infectious complications, and the need for a second operation.