New research has shown that there may be neurological consequences after long-term anaesthesia.
Prolonged anesthesia, also known as medically induced coma, takes the brain to a state of deep unconsciousness beyond short-term anaesthesia for surgical procedures. It is used to treat refractory intracranial hypertension and status epilepticus.
Though they are life-saving practices performed in ICUs the world over, they are not without cognitive side effects. Family members often report that their loved ones are not quite the same when they are discharged from hospital following prolonged anaesthesia.
“It is long known that ICU survivors suffer lasting cognitive impairment, such as confusion and memory loss, that can languish for months and, in some cases, years,” said lead author Michael Wenzel, MD, a former postdoctoral researcher at Columbia University with experience as a physician in neuro-intensive care in Germany.
Dr Wenzel said cognitive dysfunction after hospitalisation will likely become more widespread in the wake of COVID, with large numbers of ventilated patients awakening from days to weeks of unconsciousness.
Senior author Rafael Yuste, a professor of Biological Sciences at Columbia and senior author of the paper said that to date there had been no research on the direct effects of anaesthesia on neural connections.
“This is because it is difficult to examine the brains of patients at a resolution high enough to monitor connections between individual neurons,” Yuste said.
Yuste and Wenzel sought to investigate the connections between neurons, or synapses, and related cognitive effects of prolonged anaesthesia, using mice. With a specially built miniature ‘ICU’ for mice, they performed continuous anaesthesia for up to 40 hours, much longer than the longest animal study so far.
The researchers used in vivo two-photon microscopy to observe cortical synapses in the sensory cortex, combined with repeated assessment of behaviour in the cortex.
They found that, contrary to the view that neural connections in adult brains are stable in short-term anaesthesia, in long-term anaesthesia there are significant changes in synaptic architecture at any age.
“Our results should ring an alarm bell in the medical community, as they document a physical link between cognitive impairment and prolonged medically induced coma,” Wenzel said.
Further study is needed, the researchers said, adding that it will be important to test a range of anesthetics, as well as the combination of anesthetics administered to patients. Anaesthetics are not tailored to patients in any systematic fashion.
“We are well aware that anaesthesia is a life-saving procedure,” Wenzel said. “Refining treatment plans for patients and developing supportive therapies that keep the brain in shape during prolonged anaesthesia would substantially improve clinical outcomes for those whose lives are saved, but whose quality of life has been compromised.”
Source: Medical Xpress
Journal information: Michael Wenzel et al, Prolonged anesthesia alters brain synaptic architecture, Proceedings of the National Academy of Sciences (2021). DOI: 10.1073/pnas.2023676118
