A recent investigation into how common anaesthetic and sedative drugs affect the flow and volume of cerebrospinal fluid has revealed important insights related to the brain’s essential glymphatic system. These insights could have implications for neuroanaesthesia practices.
A recent investigation into how common anaesthetic and sedative drugs affect the flow and volume of cerebrospinal fluid has revealed important insights related to the brain’s essential glymphatic system. These insights could have implications for neuroanaesthesia practices.
Researchers from the University of Helsinki, University of Copenhagen, and University of Rochester discovered that two frequently used anaesthetic protocols exert a greater influence on cerebrospinal fluid flow and cerebral blood volume than the levels of carbon dioxide in the blood. This discovery could alter neuroanaesthesia methods in clinical environments, especially in treating neurological conditions, brain injuries, and in neurosurgery, where adjusting carbon dioxide levels is typically a part of managing cerebral blood flow, oxygenation, and intracranial pressure in patients who are intubated.
“The outcomes of this study indicate that the anaesthetics evaluated reduce the blood vessel responses and cerebrospinal fluid flow effects of carbon dioxide, which could guide the selection of anaesthetics in diverse clinical situations, potentially enhancing clinical methods. It is crucial to understand how these anaesthetics affect the brain’s fluid systems. More research in human subjects is essential,” says Associate Professor Tuomas Lilius, MD, from the University of Helsinki and Helsinki University Hospital.
What was done and how?
Employing a rat model, the researchers found that anaesthesia with ketamine and dexmedetomidine expanded the size of perivascular space, thereby increasing the flow of cerebrospinal fluid. This effect was not altered by additional inhaled carbon dioxide, known to dilate cerebral blood vessels. These results suggest that cerebrospinal fluid movement in the brain could be preserved, facilitating the brain’s clearance system, known as the glymphatic system. Conversely, using the inhaled anaesthetic isoflurane caused an increase in the diameter of cerebral blood vessels, leading to a decrease in both cerebrospinal fluid flow and volume.
If these findings are applicable to humans, they could influence the selection of anaesthesia for neurosurgical or neurological patients. The research suggests that dexmedetomidine might help counteract the effects of rising carbon dioxide levels on cerebrospinal fluid flow and blood volume in conditions where carbon dioxide builds up. This is important as high carbon dioxide levels can adversely affect patients with increased intracranial pressure,” states Terhi Lohela, a researcher and anaesthesiologist from the University of Helsinki and Helsinki University Hospital.
“The impact of the anaesthetics was so significant that it surpassed the effects of carbon dioxide, which is quite unexpected,” concludes Daniel Persson, the lead author and PhD researcher.
