The impact of anaesthesia on the human brain

The impact of anaesthesia on the human brain

Sunday 2 June, 0800-0900H – Piano Hall

There is a large body of pre-clinical and clinical evidence that exposure to anaesthetic drugs, and the trauma of surgery, might lead to long-term problems in the brain, particularly in very young and elderly patients. This three-part session will analyse this evidence in detail.

The first talk addresses central nervous system (CNS) immune activation and long-term cognitive changes in the human brain following surgery, and will be presented by Professor Lars Eriksson, Professor of Anesthesiology and Intensive Care at the Department of Physiology and Pharmacology, and Physician at the Section for Trauma and Acute Anesthesiology at Karolinska University Hospital, Stockholm, Sweden.

He will discuss how surgery triggers the innate immune system to launch a systemic inflammatory response that spreads by blood-born cellular and molecular signalling and rapidly reaches the brain via a transient disintegrated blood-brain-barrier, to activate the intrinsic brain immune system. This neuroinflammatory response is associated with impaired neuronal function and damage in areas of relevance for cognitive processing with cognitive decline post-surgery.

He explains: “This lecture will discuss the mechanism and regulatory pathways behind surgery-induced neuroinflammation and later cognitive decline on the basis of preclinical surgical models and series of clinical studies on surgical patients using novel CSF biochemical and imaging techniques.”

In the second talk, Professor Liz Evered of St Vincent’s Hospital, Melbourne, will ask if the neurological sequelae of anaesthesia and surgery are equivalent to traumatic brain injury.“Since 1846 it has been believed that general anaesthesia is reversible and does not damage the central nervous system (CNS). However, at a clinical level, changes in cognition following anaesthesia and surgery have been observed for more than 100 years,” she explains.

Thanks to recent advances in single molecule assay techniques (Simoa) two markers of neuronal damage, neurofilament light (NFL) and tau, can be assayed in blood. NFL is a specific marker of axonal injury and tau an integral component of axonal integrity. Prof Evered says: “This talk will discuss recent evidence demonstrating that both these markers are elevated in response to surgery and anaesthesia, suggesting neuronal damage has occurred. Furthermore, preliminary data will be presented which shows that these increases are associated with postoperative delirium (POD) and postoperative neurocognitive disorder (NCD) at 3 months. Specific domains of decline observed in the diagnosis of postoperative NCD will be discussed.”

The final part of this session addresses the new nomenclature for perioperative cognitive disorders and the first 18 months of their use in the literature. This talk will be given by Dr Roderic G. Eckenhoff, Austin Lamont Professor of Anesthesia, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, USA.

He says: “Cognitive impairments after anaesthesia and surgery have been recognised clinically for over 100 years, but only studied carefully for the last two decades. The initial moniker attached was Post Operative Cognitive Dysfunction (POCD).”

This largely research “diagnosis” has been variously defined, making systematic reviews and meta-analyses futile. POCD is also poorly recognised beyond anaesthesiology.  A new clinical nomenclature, developed by an international, interdisciplinary group, was published in late 2018. Founded in the DSM-5, the new umbrella term, Perioperative Neurocognitive Disorder (PND), contains several subcategories. Prof Eckenhoff concludes: “The goal of this presentation is to review the nomenclature, its penetrance into the literature and grants, the issues it has raised, and steps for moving forward.”