Does anesthesia kill brain cells?

In this post we are going to answer the question ‘’Does anesthesia kill brain cells?’’ We will explain to you how general anesthesia works in the body, in the brain and what negative effects it has on it.

Does anesthesia kill brain cells?

Yes, anesthesia kills brain cells, but only those that have not fully matured.

Anesthesia is a drug used in surgeries to reduce or avoid pain in patients.

There is local anesthesia, which is administered to a part of the body while the person is awake; the regional one, in charge of blocking pain in a specific area; and the general one, which puts individuals in a deep sleep.

The first procedure where anesthesia was used was performed in 1846 by a dentist; since then other general anesthetic drugs have appeared. However, until now it was not clear how these substances lead to loss of consciousness; it is also not known whether anesthetic drugs and sleep share any neural pathways.

For years, it was thought that general anesthesia inhibited brain activity to the point of leaving a person without movement or the ability to feel pain.

In more recent times, specialists have noticed that certain brain circuits are very active during sleep and that, in the same way, anesthesia could work.

Effects of anesthesia: the unknown and dangerous consequence of operations

Every surgical operation forces the patient’s body to face a series of challenges, more or less traumatic, whose consequences are unforeseeable.

Among them are not only the surgical ones themselves but also anesthesia, the process that allows blocking the tactile and painful sensitivity of the patient to be able to perform surgery, universally extended and whose effects are still under discussion in the medical community.

Among all of them, during the last decades the so-called postoperative delirium, conceptualized for the first time in the late eighties, has gained special importance.

Although at first not enough evidence was found to relate it to anesthesia itself, more and more research shows that this state of confusion is caused by the amount of anaesthesia-induced in the patient’s body.

According to a study published last summer in Anesthesia & Analgesia, the official journal of the International Society for Research on Anesthesia (IARS), 45% of patients suffered from this delirium after the operation.

Sometimes, it can be a simple restlessness, sometimes accompanied by memory loss; in others, terrifying hallucinations or even states of violence can occur when the patient wakes up from anesthesia, which can endanger the physical integrity of the patient or the doctors.

Most of the effects usually wear off in a day or two, but this is not always the case.

A rude awakening

Concern about this delusion has increased after some studies have identified that the cognitive consequences of surgery can last for more than a few months.

This is what the research is known as “Cognitive trajectories after postoperative delirium” exposed, which identified that those patients older than 60 years who had undergone a cardiac operation took between six months and a year to fully recover their mental capacity.

Those who spent more than three days suffering from delirium dragged on the process for more than a year.

It was the first time that a study showed that delirium, which until then had been considered a temporary difficulty, could have an effect in the long term. With the aim of recapitulating everything published to date, Scientific American has dedicated an article to remembering where we are.

In it, although a consensus has not yet been reached, three researchers from John Hopkins University identified that, before a hip replacement operation, the amount of anesthesia received had a significant influence on the chances of suffering postoperative delirium.

As the researchers pointed out, more than twice the patients who were operated on under general anesthesia suffered confusion upon awakening.

This study concluded that “brief postoperative delirium (less than six weeks) is a decisive factor for long-term functioning after hip fracture repair, because it impacts the ability to live independently.” That is, it can be a serious obstacle in the recovery of the patient’s self-sufficiency.

Two other important factors

It is very difficult to know the specific effects of anesthesia and its responsibility in the appearance of delirium, since the operating room gives rise to a large number of stressors that cannot be isolated.

The nervousness, anxiety, medical treatment, or restricted patient movements associated with a hospital stay can themselves trigger confusion in certain patients.

On the other hand, science has not yet been able to find out which drug compound injected in the form of anesthesia is the one that causes these side effects, as the professor of anesthesiology at the University of Pennsylvania Roderic G. Eckenhoff points out in the previously cited article:

“No anesthetic has been exonerated by the patients,” he explained. “There is no one in particular that we should discourage.”

However, there are certain drugs that have been identified as possible causes of this agitation: as an investigation published in the Mexican Journal of Anesthesiology recalls, midazolam, ketamine, thiopental or propofol can cause hallucinations, disinhibition or other effects both in children as well as adults.

Two other factors have been pointed out that can give rise to this cognitive dysfunction: on the one hand, the age of the patients – it usually affects especially those over 70 years of age -; on the other hand, the previous existence of some symptoms of cognitive decline, such as frequent forgetfulness or disorientation.

The severity of the operation also determines the chances of delirium, so while more than 50% of heart surgery patients show confusion, this percentage drops to 15% in the case of hip operations.

How to avoid it?

Given the uncertainty that still exists about the causes and possible consequences of this delusion, various measures have been tried to prevent this cognitive problem from affecting the elderly.

Leaving aside drugs such as ondansetron, a 5HT3 antagonist that is used frequently, it is important to detect the problem early (in some children, preoperative anxiety favored the appearance of delirium) or to avoid clinical conditions such as sustained hypotension, hypercapnia or hypoxia.

Another possible solution pointed out by medical experts is to use only general anesthesia for those cases in which there is no alternative, since local anesthesia limits the chances of suffering from dementia, as well as the use of total intravenous anesthesia based on propofol, which reports a low postoperative agitation index.

Good hydration and feeding of the patient during the days prior to hospital admission, as well as a good rest, can also improve blood flow to the brain and, thereby, alleviate the possible negative consequences of surgery.

In addition, the help of family and friends is vitally important. The mental activity that the patient performs during a conversation with those close to him will improve his cognitive recovery.

Anesthesia affects neural connections

New research has found that anesthesia not only temporarily suspends awareness and sensitivity to pain, but also disrupts communication between neurons and makes surgery possible.

It especially affects vulnerable people such as children, people with Alzheimer’s or Parkinson’s.

Anesthesia is a controlled medical act in which drugs are used to block the tactile and painful sensitivity of a patient, whether in all or part of her body, whether with or without consciousness.

General anesthesia is characterized by hypnosis, amnesia, analgesia, muscle relaxation, and the abolition of reflexes.

Although anesthesia is a medical practice that dates back to the 19th century, science does not yet know very well how the brain mechanism that achieves the anesthetic effect works. The new research sheds light on these processes. Their results are published in the journal Cell Reports.

In that article, the scientists explain that the hypnotic drugs used for general anesthesia have an effect that goes far beyond what is known as activating the inhibitory neurotransmitters of the central nervous system and, as a consequence, triggers of artificial sleep.

Medications such as Propofol (discovered in 1977), a short-acting intravenous anesthetic agent, or Etomidate, a short-acting hypnotic, with anesthetic and amnesic effect, but without analgesic effect (injected), also disturb the communication between neurons.

According to this research, Propofol alters even presynaptic mechanisms, affecting communication between neurons throughout the brain in a systematic way.

The discovery has been produced by manipulating the protein Syntaxin 1A (STX1A), present in each of the synapses (neuronal connections) of the brain. This protein regulates the release of neurotransmitters in the central nervous system.

According to this research, the action of this protein is much more important than turning the sleep switch on or off, as its action spans billions of synapses in the human brain.

We believe that the widespread disruption of synaptic connectivity, the brain’s communication pathways, is what makes surgery possible, although effective anesthetics like Propofol put you to sleep first, explains lead author of the research, Bruno van Swinderen, in a release.

Better understood anesthesia

The discovery sheds new light on how general anesthetics work in the brain and also allows us to understand why some patients develop temporary cognitive disorders after general anesthesia, as it is due to the impairment of communication between neurons caused by anesthetic drugs.

The discovery has implications for people whose brain connectivity is vulnerable – for example, in children, whose brains are still developing, or in people with Alzheimer’s or Parkinson’s disease, the researchers note.

It has never been understood why general anesthesia is sometimes problematic for the very young and old. This mechanism may be an explanation, they point out.

Scientists now want to determine to what extent the effectiveness of anesthetic drugs is based on loss of consciousness or blockage of synapses, in order to discover whether these anesthetics have long-lasting effects in vulnerable people, as well as to allow the development of a new generation of anesthetic drugs.

Swinderen concludes that more research will be needed to determine whether general anesthetics have any lasting effects on these vulnerable groups of people.

FAQS: Does anesthesia kill brain cells?

Is anesthesia bad for your brain?

Operations under general anesthesia damage the brain more than previously thought. They can cause long-term memory and concentration problems.

How Long Does anesthesia affect the brain?

Three months later, one-tenth of patients also suffer from cognitive disability. Anesthetics stimulate receptors for memory loss in the brain, meaning that painful experiences during surgery are not recalled by patients.

Can anesthesia cause neurological problems?

Animal studies have shown that high pressures at the start of injection are associated with intraneural needle positioning and therefore can lead to severe fascicular damage and neurological deficits.

What part of the brain does anesthesia affect?

While propofol and other general anesthetics make us sleepy, it is their widespread disruption of synaptic connectivity or communication pathways throughout the brain that makes surgery possible.

Does Anesthesia shorten your life?

A recent clinical study found that deep anesthesia was associated with increased 1-year mortality among middle-aged and elderly surgical patients, as calculated by Bispectral index monitoring.

In this post we answered the question ‘’Does anesthesia kill brain cells?’’ We explained to you how general anesthesia works in the body, in the brain and what negative effects it has on it.

If you have any questions or comments please let us know!


Saczynski, J. S., Marcantonio, E. R., Quach, L., Fong, T. G., Gross, A., Inouye, S. K., & Jones, R. N. (2012). Cognitive trajectories after postoperative delirium. The New England Journal of Medicine, 367(1), 30–39.

‌Storrs, C. (2014). Hidden Dangers of Going Under. Scientific American, 310(4), 34–35.

‌Zakriya, K., Sieber, F. E., Christmas, C., Wenz, J. F., & Franckowiak, S. (2004). Brief Postoperative Delirium in Hip Fracture Patients Affects Functional Outcome at Three Months. Anesthesia & Analgesia, 1798–1802.