General anesthesia consists of the induction of a reversible loss of consciousness that makes it possible to inhibit pain during medical tests and surgical operations. It is a very safe method and has been in use for decades, but any improvement in the procedure helps to avoid drug overdose and to ensure that the patient remains unconscious during the operation. In this study, which is published in the scientific journal Sleep , healthy volunteers underwent neuroimaging tests to see the reaction of the brain during the anesthetic procedure . Researchers have been able to determine the exact moment in which the cortex and the brainstem stop being synchronized, that is, when you reach the loss of consciousness.
The participants in the study were anesthetized with propofol, and during the process they had to squeeze a sensor every two seconds. The researchers, from the Anesthesiology Service of the Hospital del Mar (Barcelona), simultaneously monitored their vital signs and controlled brain activity by means of magnetic resonance imaging and an electroencephalogram.
What happens when you lose consciousness?
The scientists observed that the moment in which the volunteers stopped pressing the sensor coincided with the loss of connection between the cerebral cortex, responsible for the executive functions of the brain, and the subcortical part and the brainstem. This information on the threshold of consciousness of each patient is very valuable, as it helps to increase the safety and control of the entire process. “Until now we had devices that help us to roughly identify when the patient is unconscious, but not the exact moment when they lose consciousness,” explains Juan L. Fernández Candil, assistant physician at the Anesthesiology Service and signatory of the work. “If you have a monitor that allows you to adjust the doses of drugs to know if the patient is conscious or unconscious, the overdose and possible side effects of anesthetic drugs are limited”, adds Lluís Gallart, section chief of the Department of Anesthesiology and also signatory of the work.
A valid method in the operating room
The problem is that installing an MRI in each operating room is not feasible, so the next step of the research will be to validate a method to apply these discoveries during the general anesthesia process in real patients. “We cannot put an MRI in each operating room, but we could have a device that allows us to monitor the patient’s electroencephalogram , so that, if we correlate what has happened during the study in the clinic (when the patient stops squeezing with their hands) and the neuroimaging with the data from the electroencephalogram of the volunteers who have participated in our research, we would have a valid tool to know when the patient loses consciousness “, indicates Fernández Candil. ” This would help us to dose the drugs much better, to improve the safety of the procedure and to have more guarantees that the patient is totally unconscious during the surgical intervention,” he concludes.
Referencia: Pujol et al. 2021. Largest scale dissociation of brain activity at propofol-induced loss of consciousness. Sleep. 2021 Jan 21;44(1):zsaa152. doi: 10.1093/sleep/zsaa152. PMID: 32813022.
