Slipping Into Unconsciousness: General Anesthesia in the Vulnerable, Concussed Brain

Most of the focus surrounding the outcomes and use of general anesthesia has been on two populations – pediatric patients and elderly patients. This is due to the vulnerability of the young, developing brain and the aging brain. In an article titled “The Hidden Dangers of Going Under,” it is posed that the negative effects of general anesthesia in older adults may be due to the binding targets of the drug to the surface proteins of neurons in the brain which decrease in abundance with age. Input from experts suggests that the brain in an older adult may have a difficult time lighting up the connections within the brain that may have broken down under general anesthesia. 

What does this mean for the vulnerable, concussed or post-concussed brain in which there is already poor circuitry and difficulty lighting up connections? The very anesthetics used do such a great job because they incapacitate the surface proteins of neurons that are responsible for regulating attention, memory, learning and sleep. 

“Although physicians have known about the possibility of such confusion since at least the 1980s, they had decided, based on the then available evidence, that the drugs used to anesthetize a patient in the first place were unlikely to be responsible. Instead, they concluded, the condition occurred more often because of the stress of surgery, which might in turn unmask an underlying brain defect or the early stages of dementia. Studies in the past four years have cast doubt on that assumption, however, and suggest that a high enough dose of anesthesia can in fact raise the risk of delirium after surgery. Recent studies also indicate that the condition may be more pernicious than previously realized: even if the confusion dissipates, attention and memory can languish for months and, in some cases, years.”1

Because of so many variables and factors that go into surgery, scientists have struggled to point out causality between anesthesia and poor outcomes and symptoms. Anesthesia is only a piece of the puzzle and with so many compounding factors, can it truly be the culprit for worsening of preoperative symptoms in the concussed patient? I am going to address some of these components.

Are the negative effects of anesthesia dose dependent?

As research continues to be published on this topic, the amount of anesthesia given is being evaluated and considered. Is there a greater risk the deeper someone slips into unconsciousness?

Using EEG, we finally have more information as to what happens to the brain under anesthesia. EEG (electroencephalography) is similar to an EKG of the heart but measures the electrical activity of the brain. Most anesthesiologists do not monitor brain activity during surgery, though one anesthesiologist holds a strong stance on this topic and believes every patient’s brain should be monitored during surgery. Neuroscientist and anesthesiologist, Emery Brown, monitors all of his patients in surgery via EEG and believes this should be common practice. This way, the dosing of anesthesia can be very individualized and adjusted precisely for each patient.2,3

You can imagine that your neurons are constantly firing and communicating with each other as you think, move, talk, assess your environment and surroundings. One of the most common anesthetics used today, propofol, shuts down these neurons within seconds of administration. The communicating and firing throughout your brain comes to a halt. The frequency of neurons in an awake, healthy brain spike approximately 10 times per second. After the initiation of the anesthetic, those spikes drop to once per second or even less.The fewer electrical spikes throughout the brain means the deeper the anesthesia which is where EEG monitoring comes into play. By viewing real time activity of the brain, the anesthesia dose can be adjusted accordingly per patient.

A study was conducted in Hong Kong in 2013, assessing the outcomes of patients receiving general anesthesia with one group monitored via EEG to keep the brain’s electrical activity as high as possible and the other group monitored via heart rate and blood pressure only. 462 of the patients were in the EEG group and 459 in the other. 16% of the patients who received light anesthesia based on EEG monitoring, displayed confusion postoperatively as compared to 24% of the patients in the standard of care group. Looking at long term outcomes, 15% of patients who received standard of care anesthesia experienced lingering mental setbacks for at least three months compared to 10% in the EEG group.1

It seems EEG monitoring of patients in surgery should become standard of care and could aid in preventing some of these long-lasting, poor outcomes. 

Would regional anesthesia be better for the concussed patient than general?

What if instead of general anesthesia they used a regional block with conscious sedation? Could this potentially protect the brain from the negative effects of general anesthesia?

Regional anesthesia uses local anesthetics to block a nerve of a large area. Conscious sedation is often used with it as a way to offer a comfortable environment for the patient without them completely losing consciousness. The goal of conscious sedation is to make you feel relaxed; you may feel drowsy or loopy. For instance, a patient may undergo hand surgery by having a nerve blocked in the upper arm or wrist in combination with conscious sedation. In theory, this sounds like a better bet for concussed patients. They can perhaps avoid the incapacitation of neuron communication, potential fluctuations in blood pressure and blood flow to the brain. 

The bonus of this is that the patient can undergo a procedure or surgery without losing consciousness and can avoid some of the negatives of general anesthesia. Although, is this always the case?

Anesthesiologist, Frederick Sieber, conducted a study comparing delirium in patients receiving regional versus general anesthesia. All patients were undergoing surgery for hip fractures and were 65 and older. The regional anesthesia group received propofol for conscious sedation and an anesthetic to numb the nerves coming from the spinal cord. The depth of anesthesia achieved was monitored via the standard of care with heart rate and blood pressure. Simultaneously, a computer which Sieber and his team could not see, was monitoring the electrical activity of a patient’s brain using electrodes on the forehead. Sieber was astonished at what he saw. He found that “Eighty-seven percent of patients’ brain activity dipped low enough to qualify as general anesthesia during at least part of the surgery.” Based on this, he suspects it is “common for patients getting regional anesthesia to receive so much sedative drug that they are actually in a state of general anesthesia.”1

Without EEG monitoring of the brain and using the current standard of care monitoring of heart rate and blood pressure, patients may receive so much sedative that they end up in a state of general anesthesia anyway. This is also something to consider in the concussed patient. For me personally, I had thought choosing regional over general would erase all of the concerns but as this shows, the result may just be the same.

Part III

Discussed next are other important factors to consider: the stress of surgery itself, site of surgery, inflammation produced by surgery and if the effects of anesthesia on the brain are completely reversible.


1. The Hidden Dangers of Going Under 
2. This is your brain under anesthesia
3. General Anesthesia Causes Telltale Brain Activity Patterns

Surgery During Concussion Recovery: Is It Worth the Risk?

Prior to my concussion, I was undergoing a work up for a hockey related shoulder injury. I was diagnosed with a torn labrum. I actually received my MRI results the day after my concussion. I saw the orthopedic surgeon who recommended I have surgery to repair it. There was no rush on having the repair; prolonging it just meant I would have to experience the pain and periodic subluxation (partial dislocation) in the shoulder a bit longer. I wasn’t even planning on having the surgery until after that hockey season so then I could rehab it and be ready by the time the next season was due to start. 

Because of my concussion recovery and the prospect of being out of the season for the shoulder injury, I thought I would put this surgery off until I was fully recovered. I thought I would be fully recovered from the concussion fairly quickly and the hockey season would be ending mid-April so I booked the surgery for the first week of May. This way, I could play and finish the season before going forward with the operation. The thought of having this surgery during my concussion recovery didn’t even cross my mind.

I was at an appointment with my concussion specialist and he just happened to see this surgery scheduled in my chart. The doctor said, “Why not have the surgery done now while you are out of work?” I didn’t think through how this might affect my concussion recovery but thought if the concussion specialist is recommending it and doesn’t see an issue with it, I should trust his advice. No potential negative outcomes were discussed regarding the impact it could have on my concussion recovery and I didn’t stop to think about it.

I scheduled the surgery for January of 2019, not even three months after my concussion. Going under (anesthesia) was great – it was the first time I had slept deeply in months. I woke up back to reality and was thinking, can someone just put me back to sleep? Unfortunately, this deep sleep wasn’t worth it and I was in for a brutal awakening.

The shoulder surgery was successful and everything went as planned. I was in a sling for six weeks. About three weeks following the surgery, I started physical therapy. The first step of physical therapy was to increase mobility in the shoulder with passive movements (they moved my arm for me). This seemed to be going okay until we had to start the strengthening phase of physical therapy.

At that point, I had already started to struggle mentally and physically. Prior to the surgery, I had struggled with losing my routine and normal activity level. My quality of life was drifting to the poor category. The surgery added to the physical restrictions I had been dealing with that further challenged my mental bounds. The combination of the concussion recovery and shoulder recovery left me feeling so disabled and I started to feel even more down about it with every day that had passed. My daily headaches worsened and episodic migraines became chronic, daily migraines. My brain fog and neurological fatigue became difficult to manage.

The strengthening phase of physical therapy was disheartening, frustrating and belittling. I was unable to add any weight to the strengthening activities because every time we added a resistance band or even one pound, my neck would flare up so badly causing my headaches to become so debilitating that I had to lie in bed for days at a time. This was the first time I realized just how messed up my neck was and that it wasn’t addressed at all.

I was struggling to understand my body. I was struggling to understand why one pound could cause me to be completely incapacitated. I was losing hope in both recoveries and my spirits began to wither. After trying to strengthen the shoulder in physical therapy for about three months, they decided to abandon that plan and attempt to loosen my neck. This continued through the month of May without any improvement. 

My headaches continued to worsen among other symptoms – neck pain, insomnia, dizziness, dysautonomia, memory, focus, attention, mental clarity. It became so bad that I was collapsing on the floor and experiencing syncopal episodes quite frequently along with chest pain, shortness of breath and extreme fatigue. It seemed like they didn’t really know what to do with me at that point and I didn’t know what to do with me either.

Good rest following a concussion is absolutely necessary for the brain to heal. After any surgery, sleep and rest is hard to come by. It is typically broken sleep and not restorative. And in my case, sleeping with a sling on every night was nearly impossible. Prior to this, I was already struggling with severe insomnia so this was not a good addition to my recovery.   

Physical therapy for my shoulder was abandoned in May of 2019. I persisted to have a lot of pain and stiffness in the shoulder because I never completed the strengthening phase and proper rehab. My shoulder was so weak, my arm felt like a useless, dangling appendage. It seemed like good health was drifting further and further away from me. It wasn’t until starting physical therapy at a new center (The PT Center) the beginning of 2020 where they fully addressed the shoulder and neck. It took about six months to get to a point where we could add weight without wrecking my neck and head.

If you are suffering through a complicated recovery and you are not progressing, you often search to find solutions and learn more about your condition to ultimately achieve relief. This is often how someone becomes knowledgeable in their prospective diagnosis and this is how patients become experts in their diagnoses. Even after all of my education and work as a physician assistant, I did not have the knowledge that I do now about concussions and TBI. I have spent a great deal of time learning more and more in order to find solutions.

I took my doctor’s word for it that going ahead with the surgery would be completely fine at that point in time. In no way am I saying never trust your doctors, but rather, take the time to weigh the options and maybe even get a second opinion before proceeding. I never stopped to truly weigh the risks and benefits and how it might affect my brain recovery which was my top priority. This process has taught me that being your own advocate is so important.

My important takeaway: Avoid surgery unless absolutely necessary while recovering from a brain injury or the aftermath. 

What happens following brain trauma that might make one susceptible to worsened outcomes with surgery? What does the research say?  

The Cascade That Follows Brain Trauma

Immediately following a brain injury, the brain goes into a state of neuro-inflammation propagated by complex changes at the cellular level. This process has been referred to as the neurometabolic cascade. I wanted to touch on this cascade in order to paint you a picture of the vulnerable state of the brain and how surgery might affect it. This is an extremely condensed version of it, not even scratching the surface.


  • Neurons: Basic working units of the brain forming a communication network, connecting every part of the body. Each neuron consists of a cell body and an axon.
  • Axon: electrical signaling tail which I like to call the communication highway. Myelin sheath is the insulation of the axon aiding in communication and speeding up signals
  • Ions: calcium, potassium, sodium, chloride. Flow in and out of the neuronal cell body and travel down the axons as signaling molecules
  • Mitochondria: powerhouse of the cell that produces energy
  • ATP: energy for our cells, made from glucose. Glucose from food -> reaches brain -> enters neurons -> mitochondria turns glucose into ATP for energy
  • Glutamate: excitatory chemical messenger that in excess causes damage and even cell death
  • Free radicals: unstable molecules that contain oxygen and easily react with other molecules (opposite of antioxidants)
  • Blood brain barrier: close knit group of blood vessels and cells that regulate what passes into the brain
  • Glial cells: Support neurons by supplying oxygen, nutrients and insulate axons. Serve as part of the immune system by aiding in removal of cellular debris, dead neurons and toxins.

Let’s break it down:

  • Brain trauma occurs: brain jolts hitting the skull causing tearing or shearing of nerve tissue and axons
  • Axons stretch, becoming porous with holes or break completely, allowing leakage of ions (excess sodium and calcium in, excess potassium out). Broken axons release damaging products and toxins
  • Excess calcium damages the cell and disrupts cellular transmission. Mitochondria is poisoned. Communication highway (axon) severed.
  • Neurons begin to rapid fire = dysfunctional communication
  • Snowball Effect: surrounding cell damage and cell death secondary to toxins
  • Energy Crisis: Ion pump works frantically to attempt to re-establish a balance
  • No energy to clear abnormal proteins and toxins from in and outside the cell. Cells starve
  • Inflammation: Buildup of toxins and inflammatory proteins attacks myelin sheath and cell. Glutamate released causing further damage and excitotoxicity
  • Decreased blood flow = decreased ATP to brain = worsening energy depletion
  • Impaired ability to regulate blood flow, impaired response to changes in blood pressure
  • Free radical accumulation: more inflammation
  • Blood brain barrier permeability: stuff that shouldn’t be allowed in the brain comes in
  • Glial cells and axons damaged…inflammation continues
Photo Credit: Toronto Star Graphic

The pathophysiological changes that occur in the brain following trauma is a very complex cascade. Some of the changes are still not completely understood. I have questioned whether these changes can increase the risk of anesthesia and contribute to worsened concussion symptoms to the already vulnerable brain as I experienced following my surgery. 

Blood Pressure Alterations and Inflammation in Surgery

Sometimes during surgery, you can experience low blood pressure. Even a mild change in blood pressure could affect the blood flow to the brain which has already been compromised by the injury. The brain after such an injury is already under a great deal of stress and has an impaired ability to regulate blood flow as well as an impaired response to changes in blood pressure. If the brain is already experiencing a deficit in oxygen, even a slight drop during surgery could potentially worsen the vulnerable state that the brain is already in. 

Surgery not only has an effect on blood pressure but also glucose regulation and autonomic function. The brain after trauma already experiences impairment in glucose regulation. Autonomic dysfunction is quite common following a head injury and I was already diagnosed with it, so it is not inconceivable that surgery can worsen this process. There have been many cases of patients with a new diagnosis of autonomic dysfunction following a surgery even without head trauma! Sounds like the perfect storm. 

Following any surgery, your body produces an inflammatory response. This response is necessary because it sets the stage for the healing process to occur. Every surgery causes stress to the body. When I had my surgery, my body was already under stress from the high inflammatory state sustained from the TBI which I had not fully recovered from yet. I already likely had inefficient communicating cells and altered blood flow. The surgery was trauma on top of trauma or inflammation on top of inflammation.

I still question if this further inflammation added to my complicated and prolonged recovery. I don’t think it’s a coincidence that my concussion symptoms worsened dramatically after the surgery. It felt like it opened up yet another negative cascade in my body. 

What Does the Research Say?

I have spent some time looking into studies on post-concussion patients undergoing surgery and the outcomes. My concerns are validated in several different published articles. Unfortunately, no randomized, controlled trials on the outcomes of anesthesia and surgery on post-concussion patients exist. Given that it is quite common for patients with concussive symptoms to present for surgery, with estimates ranging from 6-7%, it seems this should be something to consider for these patients.4

Within one year of concussion, typically in the first month, about 8-12% of these patients will present for surgery.4Another study showed 5% of recently concussed patients underwent elective surgeries unrelated to the concussion within one week of injury.1 In reality, these percentages may be higher due to the fact that there are no concussion screening tests implemented preoperatively. With such a prevalence of concussion patients presenting for surgery, the outcomes should be considered.

In a panel session for the International Anesthesia Research Society, it was concluded that future studies are needed for more data but until that is available, the perioperative period of patients with recent concussion should be considered as a potential time period for secondary brain injury. Interestingly, anesthesiologists were surveyed on this matter and most said they would delay elective surgeries until full resolution of concussion symptoms.4

Similarly, in a review published in Current Opinion in Anaesthesiology, the consensus is that both acute and chronic repeated concussion may put the brain at risk for secondary injury due to its already vulnerable state. They go on to suggest further research is needed but that it seems reasonable to delay elective procedures until resolution of clinical symptoms.8

An interesting quote from a published scientific review in the Korean Journal of Anesthesiology: “It is possible that the use of anesthesia may create a neurocognitive exacerbation worsening pre-surgical symptoms such as headache, dizziness, postural instability, sleep disturbances, memory impairment, decreased processing speed, attention deficit, fatigue, depression, and anxiety. This concern again suggests that it may be safest to postpone elective surgery until the patient is ready to return to school or normal daily activities if possible.”This is particularly interesting to me because I experienced worsening of all of these symptoms post-op. 

In an article published in the Journal of Neurosurgical Anesthesiology, patients with pre-op cognitive deficits had an increased risk for worsening post-op cognitive symptoms.10 This study was not dedicated to concussion patients, so is only suggestive of this risk. In another review from Current Opinion in Anaesthesiology, the conclusion is that those suffering post-concussion syndrome may be particularly clinically susceptible to worsening outcomes due to physiologic instability.11

The data from a retrospective study on patients from July 1, 2005, to June 30, 2015, who underwent surgery after concussion suggests clinicians should have an increased awareness for concussion in patients who have recently sustained trauma including those without a formal diagnosis of such because of the vulnerable state of the brain. It is again suggested that clinicians consider postponing elective surgery until resolution of concussion symptoms.2

While there isn’t much research on post-concussion patients and surgical outcomes, it is something that should 100% be considered and something clinicians should have an increased awareness of. At the very least, risk and benefit should be considered. Even the theoretical risk of exacerbating post-concussion symptoms with surgery should be discussed with patients. 

This is definitely something I would consider if discussing elective surgery with my own recently concussed patients. It seems most reasonable to delay elective surgery until concussion symptoms have completely abated, and something I wish I had researched prior to my surgery. 

If I had known what I know now about brain trauma and the cascade that follows, I would have never had this surgery during the recovery of my vulnerable, post-concussed brain.


1. Abcejo, A. and Pasternak, J., 2018. Is a Concussed Brain a Vulnerable Brain? Anesthesia after Concussion – Anesthesia Patient Safety Foundation. 

2. Abcejo, A. S., Savica, R., Lanier, W. L., & Pasternak, J. J. (2017). Exposure to Surgery and Anesthesia After Concussion Due to Mild Traumatic Brain Injury. Mayo Clinic Proceedings, 92(7), 1042–1052.doi:10.1016/j.mayocp.2017.03.012.

3. Büki, A., & Povlishock, J. T. (2005). All roads lead to disconnection? – Traumatic axonal injury revisited. Acta Neurochirurgica, 148(2), 181–194.doi:10.1007/s00701-005-0674-4. 

4. Guay, Christian A., 2018. Concussion in the Perioperative Period: A Common Condition Requiring More Investigation. International Anesthesia Research Society. IARS Annual Meeting.

5. Giza CC, Hovda DA. The new neurometabolic cascade of concussion. Neurosurgery. 2014;75 Suppl 4(0 4):S24-S33. doi:10.1227/NEU.0000000000000505.

6. Katayama, Y., Becker, D. P., Tamura, T., & Hovda, D. A. (1990). Massive increases in extracellular potassium and the indiscriminate release of glutamate following concussive brain injury. Journal of Neurosurgery, 73(6), 889–900.doi:10.3171/jns.1990.73.6.0889.

7. Mele C, Pingue V, Caputo M, Zavattaro M, Pagano L, Prodam F, Nardone A, Aimaretti G, Marzullo P. Neuroinflammation and Hypothalamo-Pituitary Dysfunction: Focus of Traumatic Brain Injury. International Journal of Molecular Sciences. 2021; 22(5):2686. doi:10.3390/ijms22052686.

8. Pasternak, Jeffrey J.; Abcejo, Arnoley S. Anesthesia and the brain after concussion, Current Opinion in Anaesthesiology: October 2020 – Volume 33 – Issue 5 – p 639-645. doi: 10.1097/ACO.0000000000000906.

9. Rasouli MR, Kavin M, Stache S, Mahla ME, Schwenk ES. Anesthesia for the patient with a recently diagnosed concussion: think about the brain!. Korean J Anesthesiol. 2020;73(1):3-7. doi:10.4097/kja.19272.

10. Sheshadri, V., Manninen, P., & Venkatraghavan, L. (2017). Anesthesia in Patients With Postconcussion Syndrome. Journal of Neurosurgical Anesthesiology, 29(2), 185. doi:10.1097/ana.0000000000000269.

11. Tasker, R. C. (2017). Anesthesia and concussion. Current Opinion in Anaesthesiology, 30(3), 343–348.doi:10.1097/aco.0000000000000459.