Anesthesia 101

We are back with another episode of the show. As always, this is not medical advice and is not intended as medical advice, just for educational purposes only. I am very excited about this episode. Our guest works in one of the most critical and least understood roles in modern medicine. While surgeons often take center stage, it is the anesthesiologists who ensure patients are safe, stable, and pain-free before, during, and after surgery. Joining us is Dr. McCarthy, my dad, who has years of experience. I am so excited about this episode, so welcome.

Thank you for that nice introduction. I appreciate being here, and I know we've got a lot of information we are going to go through here. 

To start with, let us actually go into what exactly an anesthesiologist is.

Most people think an anesthesiologist is the person who puts you to sleep for surgery. That is the primary function of most anesthesiologists. That is what they are doing day in, day out. An anesthesiologist has gone through medical school and then done residency training, which currently is four years after graduating from medical school. You do four years of training to be an anesthesiologist. 

Some anesthesiologists go on and do fellowship training after four years of training. They may do critical care medicine, pain medicine, cardiac anesthesia, obstetric anesthesia, and pediatric anesthesia. There are a lot. Those are subspecialties that focus on that particular area. Frequently, the people who do those fellowship training, additional training, continue to do general anesthesia for regular adult-type surgery.

Lots of different types. 

What the anesthesiologist does is keep you asleep during surgery, which helps you get through it safely. 

Yes, because I mean, I think everybody would agree you want to be sleeping during your surgery, you do not really want to be awake. It’s very important. You spent decades putting people to sleep. Do you ever feel like you have the most trusted job in the hospital?

You definitely had to have trust because an anesthesiologist is a consultant, which means the other doctors are like a surgeon and be like, "You're going to anesthetize my patients." If they did not trust you, they would not want you anesthetizing their patients. You had to earn that trust. The same thing with the other medical specialists in the hospital, the cardiologists, pulmonologists, etc., the internists. With the patients, a lot of them trust that their surgeon trusts their anesthesiologist. They can trust them. That is when you meet the patient, you really have to establish that rapport and be able to quickly gain their trust that you are going to take good care of them.

I am sure you get it all the time. People are asking what you do, and you say you are an anesthesiologist. When someone finds out that you are an anesthesiologist, what is the first thing that they say?

A lot of times, they say, "I'm an anesthesiologist." "You put people to sleep?" I will say, "Yes, that's pretty much what I do." I am not that excited. I joked with the pastor, saying, "You and I have a lot in common." He said, "What are you talking about?" "We both put people to sleep." 

Except you want to put people to sleep, and you want to then wake them up. What do you think? I am sure you have so many stories, but what is one of the funniest things a patient has ever said right before going under?

One that is fairly common is that some patients worry that they are going to be incontinent under anesthesia.

Yes, they do not want to wet the bed.

It is a rare thing.

You do not have to worry about it.

You do not worry about that. 

I am sure there are quite a few stories you have because we have all seen the videos of people waking up under anesthesia and all sorts of stuff. I am sure it is entertaining. Probably something else that we should get into is what exactly anesthesia is. When we say someone is asleep, we are putting somebody to sleep. What is actually happening in the brain?

For us, we define a general anesthetic is going to be, they are asleep so they are not going to respond to the surgical stimulation. They are not going to move. They are going to have amnesia. They will have no recall of the events. They are going to have pain control. Other things are also important. Basically, the brain is shut off, not connected. You could go into what the EEG looks like. 

Which is like an electrical picture of your brain.

They call it an electroencephalograph. That is the one where you have probably seen on TV where they hook up all the wires to that, and they are looking at the brain waves. That is a typical brain wave pattern when you're awake. Typical brainwave patterns during normal sleep. There are brainwave patterns for anesthesia, which is different from being awake or normal sleep. 

We call it sleep, but it seems like it is something a little different.

It is different. Normal sleep, you are going to have rapid eye movement sleep. Call REM sleep, which is the time while you're sleeping that you normally have your dreams during REM sleep. There is deep sleep, and anesthesia is different from that. Those are higher frequency, lower amplitude brain waves, and anesthesia has low frequency, higher amplitude brain waves, so it is a totally different pattern. Also, think that part of anesthesia is that the different areas of the brain do not communicate with each other anymore. You're not forming any memories. You do not wake up and say, “That surgery went great. I could hear you saying it was going so well. “

Ideally, we do not want that to happen, right? Everybody says they do not want to remember anything. You just want to wake up.

Also, with regular sleep, I can come along and say, "Wake up," and you can wake someone up. With a general anesthetic, with someone to sleep, you do not wake them up. They are operating on them.

You do not want to be woken up.

My job is to put them to sleep, and then the surgeon is operating, using the scalpel and things like that. That is pretty stimulating. 

It is.

They do not wake up despite that stimulation. They have to be, really.

They are asleep, but it is a different type of sleep. Does that make sense? A lot of people probably do not understand the different types of anesthesia. When you're going in for surgery, there are a lot of different types of anesthesia that you can use. It would be interesting to go over the differences between general anesthesia, twilight, like how people always say, "You're just going to be in a twilight state," or like a nerve block, just like a block.

General anesthesia is what we were already discussing. That is, you are completely asleep. One of the things with our anesthetics when you put someone under general anesthesia. For certain operations, it is mandatory, like when someone may have colon cancer, and they are getting part of their intestines taken out. They are opening up their abdominal cavity. There are a lot of muscles there. We give muscle relaxants so the muscles are relaxed and the surgeon does not have to pull on them. It actually causes less trauma to the tissues. It also means the other muscles in the body are relaxed, like your respiratory muscles, so you would not be breathing on your own.

You would be paralyzed basically.

We give them a medicine that we call a paralytic. It paralyzes them while the medicine is working. There are medicines you can give to reverse the effects of the paralytic medicine, or you can just wait for it to wear off. Typically, you are going to give a reversal agent. If someone is getting part of their colon taken out, you are going to give them a muscle relaxant, and you are going to help them breathe with what we call an endotracheal tube. That is the breathing tube that goes in the windpipe. 

That is probably what most people think of when they think of anesthesia.

You can give a general anesthetic for an operation where they do not need muscle relaxation, but you still want the patient all the way under. If it is a very short operation, you might just help them breathe with a face mask, or there is another device called the laryngeal mask airway, which just goes in the back of the throat. It does not have to go all the way into the windpipe. You might help them breathe with that. Your anesthetic medications are causing respiratory depression, so typically, we're helping them breathe during the general anesthetic.

That is like when you talk about people being on a ventilator for anesthesia and for a big surgery. This would be the scenario where they are on a ventilator.

There are, you could debate whether, when someone is having a procedure. It goes into the next one, sedation. There are different degrees of sedation. A common term, as you said, is the twilight. "You're just going to be under twilight." That would be a lot of operations where maybe you're getting some skin thing taken off, a lipoma, which is just a little fatty, typically benign little fatty thing, where it is okay, maybe it is under the skin, and it would be uncomfortable to have it done completely awake or without any sedation. You might just give them twilight.

Endoscopies like for people who are going to be looking at the stomach or colon.

For colonoscopy, it is pretty common that we give them a medication called propofol, which will just make you go to sleep. Patients can breathe on their own and go through the colonoscopy. You can have them deep enough under the colonoscopy where they're not responding at all. That is a general anesthetic, but they're breathing on their own. With sedation, there are different levels of sedation. As I said, you could be all the way sedated or twilight. What is twilight? I had a patient who was getting a procedure that the surgeon wanted to do under local conditions, which is some sedation. 

I told him, "We're just going to give you, as people call it, twilight." The patient said, "I do not want twilight. I want midnight." He did not want to know anything. There are different degrees with people. I had a patient who was having a procedure on his finger. We were going to numb up his finger. I said, "I'll give you a little sedation because that's a little uncomfortable," and the patient's like, "What do I need sedation for? Just numb up the finger. I'll be fine." Everyone is different. Some do not want to know anything, and some do not mind knowing something. You could have a twilight where the patient knows what's going on, but you've given them sedation to help them be relaxed. 

What about nerve blocks? 

Nerve blocks, you can do an operation just with a nerve block, like a peripheral nerve block. One operation you might think of is a bunionectomy. You can do a bunionectomy just by numbing up the foot and not giving them anything else.

They just do not feel the feet? Is it that you just do not feel that part of the foot?

You can do it in different ways. Some are just part of the foot, some are the whole foot. An ankle block would be much of the whole foot.

If you cannot feel it, can you also not use it?

Afterwards, yes, you would have a protective boot on it, whatever. Most patients having a bunion operation, they do not want to know anything. They want to be sedated enough so that they do not know anything. Sometimes even to the point of a general anesthetic. I had a patient who I told, "I'm going to give you this medicine to make you sleepy and will numb your foot," and she said, "No, I do not want to be sleepy." She read a book during surgery.

Everyone is different.

That is an outlier. 

I bet.

The majority of people are like, "I do not want to know anything. I do not want to hear anything. I want to be out." It varies a lot. Another difference. A nerve block, as I mentioned on the foot, but a common one people think about is shoulder surgery, when people are getting shoulder arthroscopy or things like that. They will do injections where the nerves are coming out of the neck, and that is called a brachial plexus block. 

There are different techniques for getting those nerves, but it will numb up the shoulder and arm. A lot of those patients having an arthroscopy find it is hard to get it 100% perfectly numb. A lot of those patients will get the nerve block plus a general anesthetic. A lot of times, it would be with the laryngeal mask airway, not with the endotracheal tube.

For those blocks, how long would they usually last?

For shoulder surgery, the longer the better. Some of them will last twelve hours. There are some procedures where an anesthesiologist may put in a catheter that will connect to a little infusion pump, which is disposable. It might look like a little tennis ball type of thing, and it contracts and pumps the medicine in at a specific rate to keep the medicine going in and prolong the block to keep the local anesthetic going in.

That is cool. You would still have the pain control even after the surgery, after you're out of it for a little longer.

They can go home with that pain pump, and it just gets thrown out. It is disposable. 

For people who are going to be going under for a shoulder repair or knee replacement, maybe something to ask. 

There are additives besides the local anesthetic that they add to their block medication that help prolong the duration of the block.

How would that differ from an epidural, like what people have when they are delivering?

We call those blocks, and then, like an epidural or spinal anesthetic, we typically call regional because it numbs up a whole region of the body. As a spinal anesthetic, you can have a total knee replacement or even a total hip replacement under a spinal anesthetic. 

That would be the same thing that people get when they're delivering an epidural.

The difference between a spinal and an epidural, they have a lot of similarities, but they do have differences. The needle is different. A spinal needle is very thin and goes right into where the spinal fluid is. You inject the local anesthetic into the spinal fluid so that it will numb up all the big nerves. It is numbing up the nerves going to the lower part of the body. You do not want it to go too high and get the respiratory muscles. The spinal cord is for the lower part of the body. Typically, as an epidural. 

They do use epidurals for post-operative pain control, in which case they might put in an epidural higher up in the thoracic area. That is a thoracic epidural. They use those for some thoracic surgery post-op pain control. For a labor epidural, they will put it in a lumbar, which is in the lower back region, and put a catheter in and put a lower dose of local anesthetic so it is more dilute. The goal is to numb up the sensory nerves, which are more sensitive to the local anesthetic than are the motor nerves. The idea is to provide analgesia, pain relief, without motor blockade, so the patient can still move.

That makes sense and also pushes, right? That would be very different than if you're trying to completely block.

It is not 100%, so you get a little bit of motor even with the lower dose, the lower concentration. Which is why, typically, once the patient gets a labor epidural, they are not allowed to get up and walk around, which is one of the reasons a lot of women want to walk around in early labor. That is why they might wait until a little further along in labor before they get their epidural. People worry about headaches with epidurals. I do not know how many people worry about it, but some people will ask about it, or a spinal anesthetic.

The chance of a headache is pretty low. The epidural is a bigger needle than the spinal because you have to pass a catheter through it. It goes above the sac where the spinal fluid is, which is where the name came from. Epi is above. Accidentally, sometimes the needle does not stop above the outside of the sac and goes inside the sac where the spinal fluid is, so that it makes a hole, and it is felt as a headache. The headache is caused by the spinal fluid leaking out through that hole later. Typically, the headache does not show up until even 48 hours later. 

It takes a couple of days.

It is not typically immediate. You might get a, we call it a wet tap, where it goes into where the spinal fluid is. A lot of studies have said that, for most anesthesiologists, the incidence of a wet tap would be somewhere in the 1% range, 2%.

Probably a big fear for some people is paralysis. How likely is it that you could, from an epidural or something, that you could walk away and then just not be able to use your legs ever again?

It is very uncommon. It is not an impossibility. It is very uncommon. For one thing, the spinal cord, which is where the bodies of the nerves are, ends up higher in the back. It usually ends around the first or second lumbar vertebra. The nerves keep coming down and going out. 

In school, they used to call it a horse tail. 

Cauda equina is the technical term, but it means horse's tail. That is where all the nerves are coming down. If you go into the sac there, the nerves just cannot move out of the way, and you are not hitting the spinal cord itself. Even if you get into where the spinal fluid is, it typically does not cause a problem. The way people get paralyzed is if you hit a blood vessel, which can happen, and they do not clot normally, and it keeps bleeding, and it puts pressure on everything.

If it puts too much pressure, it can reduce the blood flow into the spinal cord, and that can cause problems. That is why we do not do a spinal or epidural on people who are on active blood thinners. If you came in and said, "I just took my Eliquis yesterday," which is one of the blood thinners, you would be like, "You're not getting a spinal or epidural."

That makes sense. What about baby aspirin? Same thing or not as much?

Baby aspirin has not been shown to be an issue.

Low risk, lower dose. Another fun question would be, you have retired, and congratulations.

Thank you.

Has anesthesia changed a lot from when you started practicing to when you retired?

There have been a lot of changes. Particularly, I started my anesthesia training in the 80s, the number of medications that are out, the techniques, like even all this ultrasound stuff, they were not doing any of that when I was in training and first coming out. In terms of now, they do. It is very common for people to use ultrasound-guided regional anesthesia. Those blocks in the neck now, when I started out, we had been using a nerve stimulator. You have a special needle that is insulated except for the tip of the needle. 

It has a wire that hooks to this little gadget called a nerve stimulator that puts some electric current out. It stimulates the nerve with the electric current, and you see the muscles move. You turn down your electric current until at a very low current, you are still getting a little twitch, and you know you are right near the nerve. You inject your local anesthetic. Now people can see the nerve with their ultrasound. They can watch the medicine spread around the nerves, which enables, in some cases, to reduce the amount of local anesthetic you need to inject because you see, “The nerves are surrounded.”

You can see exactly where you're going and how much is there and everything.

It has made some of the blocks a lot safer because there are some blocks up in the neck area, like supraclavicular, infraclavicular, where the lung lives in that area too. The top of the lung comes up there, and if you hit the lung, then you can get a complication, so it is nice to be able to see, “I am over here, and this is a safe area.”

Not to mention all the blood vessels, too. 

The blood vessels also.

Yes, so it makes sense. 

Even the medications, like some of the inhalation agents that we use routinely now, the anesthetic gases. They were not out when I started. Even propofol did not come out until after I finished residency training. 

Really?

Yes. Okay, yes, so a lot has changed. 

Yes, that is cool. I guess we will get into our next section. What do you think people should ask before surgery? One of the questions is, your anesthesiologist pops in for the pre-op chat, you know they will pop in and out, and for that pre-op chat, what should patients actually be asking?

A lot of patients, actually, I would say the majority of patients, do not actually have any questions. Part of that is probably nerves, but they should ask anything that is on their mind, like "What kind of anesthesia are you recommending for this operation?" If they are having a knee replacement or having this done, operations that have more than one choice. If you are coming in and getting part of your colon taken out, you are getting a general anesthetic.

There is not much choice.

You might ask, "What are my options for anesthesia?" It might be an operation where you can have, we talked about the twilight, the different types of sedation with local anesthetic versus just a straight-up general anesthetic. You could ask about what are the advantages and disadvantages of the different options. What kind of complications would be more likely with one versus the other? 

Some good things to remember there. What do patients forget to tell you that actually matters?

One of the important ones is alcohol and drug use, particularly if they have done it recently. I did have a patient come in and say he had a six-pack in the morning.

You appreciated his honesty, but did you think it was just a six-pack when he said that?

Yes, I mean his operation was at like noon. It was not a big operation. He was getting a carpal tunnel, and we were just going to numb up his arm so he did not have to go under general anesthesia. It was long. A beer is a clear liquid. It is out of the stomach, so you do not worry about aspiration. We went ahead and did the procedure. Depending on the operation, you might have said, "Come back tomorrow." 

It’s very important.

Alcohol is a tough one because this guy probably was an alcoholic, drinking all the time. If you’re drinking all the time, you may go into withdrawal if you do not drink. Alcohol withdrawal can be very bad.

They can. Something that people probably do not realize is how alcohol can change your seizure threshold. Everybody has heard of seizures. It is all those electrical patterns in your brain that basically make it easier for you to have a seizure, especially if you are a heavy drinker and then you are withdrawing from it. That can be very dangerous with anesthesia. Something very important for people who are drinking is to be very honest about that. For supplements, recreation, I am sure that those have effects too. 

Like marijuana, it is not just the effects of the THC. It is also the effects of like, if someone had smoked in the morning before coming in, they have just put something in their lungs that is going to irritate their lungs, and they are more likely to have some bronchospasm under anesthesia because the airways are already irritated. It can affect the amount of anesthesia you need.

It’s very important. 

The alcoholic may need more anesthesia. They have built up tolerance to this. Alcohol depresses your central nervous system, which can put you to sleep. Their bodies have gotten to tolerate that. Under anesthesia, they may actually need more anesthesia.

It has big effects in terms of anesthesia. It's very important to be honest in that aspect. Let us see, if someone is terrified of anesthesia, what would you say to them?

You do not have to be terrified. People hear the worst-case scenarios, and it frightens them. I have had people who are really nervous and like, "What if I don't wake up?" Part of our job is we have to explain to them what we are going to do and explain the risks involved. 

Even if the risks are very low.

All of our consent forms said you might die from anesthesia. The patients would be really nervous. I would say it is like, “Imagine if you were getting on a plane and they made you sign a consent form, ‘I know this plane can crash and I might die.’" You would be a little more nervous getting on that plane than you would have otherwise. We have to tell patients all of this right before. I would tell them how unlikely it is for that to happen. 

You cannot say it is impossible, but it is very unlikely. You asked about one of the things that has changed over the years with anesthesia. When I was starting out, they talked about how anesthesia was already getting safer. In the 60s, the risk of dying just as a complication from anesthesia, like "You died from anesthesia," was probably about one out of 10,000 people. That is a small number. Now they say it is probably closer to one out of 200,000 people. That is a very low number.

It is, yes. It’s very reassuring.

Patients would still be nervous. I would say, “It is normal to be nervous.” One way I would explain it, I would say, "When I get off from work today, I'm going to drive home. Can you guarantee I'm going to make it there alive?" “No.” I said, "I know that, but I'm not going to be nervous when I get in my car because the odds of me not making it home are very low. The odds of you not waking up from anesthesia today are lower than that."

Yes, statistically, driving a car, that is 100% true. 

We are not playing Russian roulette here. Part of the reason people are nervous is that they do not really know the odds. It is one out of 200,000. Now that is for the healthy person who is coming in.

Is there a bad candidate for anesthesia? That's a good question. 

There are bad candidates. One of the things that, when we are asking patients pre-op, we try to get an idea of their risk, we talk about their metabolic equivalents, like how much exercise can you do? It gives you an idea of their cardiac reserve and things like that. Someone who can walk up, when you're just lying down at rest, that is one metabolic equivalent. That is how much energy your body is consuming, how much oxygen you're consuming. 

Your heart would have to pump around to meet that need. That is one. Walking up a flight of steps is about four metabolic equivalents. A lot of people say, “If you can do four, you're okay.” It is not a magic number. If someone is frail and gets short of breath walking to the refrigerator, those people are at very high risk. If they were coming in to get a total knee replacement, "Yes, it hurts my knee when I get up and go into the refrigerator." 

You just keep going along with your knee hurting a little bit because your risk of having this operation is very high. Perhaps they can do some things to get in better shape. If they do not, and some people, there is nothing they can do. They may already have had heart attacks, things like that. There is nothing they can do about it. 

Definitely, then some different risk factors and some candidates that you would say, “If this is a non-emergent procedure, then maybe we do not do it just because of the risk.” That makes sense. 

Another category would be someone with very bad lung disease. We would have patients where even their pulmonologist would say, "No, because you have to be on the ventilator for surgery, and you may never get off the ventilator." We talk about reserves, so part of the thing with metabolic equivalents is your heart is going to have to work harder after surgery because you are healing, you've got to pump nutrients around, you've got to have an inflammatory process from the operation itself. The amount of blood your heart pumps is going to have to go up. Call that cardiac output, how much blood your heart pumps every minute. That is going to have to increase post-operatively. If you are not able to do that, there is more risk.

Which is why those pre-op appointments exist and why you go and see your doctors a lot of times beforehand, make sure that you're optimized and everything. 

It's also why, like a bad car accident, someone who is twenty is more likely to survive it than someone who is 80. They have more reserves. They have a better ability to overcome that. They can increase their cardiac output to a greater extent than can the 80-year-old.

It’s very interesting. Our next section can be all the stuff I feel like people wonder about. The biggest question that probably a lot of people have is, why can't we eat after midnight? I feel like that is always the biggest complaint. Everybody is like, "I'm starving." 

Occasionally, you will get someone who cheats and does not want to tell you about it. That is one of those things where what do they not tell you?

That is very important.

Do not do that. That's not what they forgot. That is, they are not telling you on purpose. We had mentioned that, for a lot of operations, we do a general anesthetic, and you put a breathing tube in. The patient comes into the operating room, they get on the table, you hook them up to their monitors, and you start giving them oxygen to breathe through a mask. That is another thing people wonder about. "Why are you giving me this mask?" It is because we want extra oxygen in the lungs when we go to sleep. 

If you looked at the normal adult, their total lung capacity, when I breathe in, how much air is in my lungs? It is about five liters. When I am just at rest, so you're not actively exhaling the last bit, you've got about two and a half liters of air in there. Room air is whatever, 21% oxygen. If you've got two and a half liters at rest, when we give you the medicine, you stop breathing, and your lungs are in that rest state. Two and a half liters if you're on room air, 21% oxygen, that's about 500 ccs of oxygen. 

A normal body is burning up almost 250 ccs of oxygen per minute at rest. If we give you medication and you cannot breathe right away, you do not have a whole lot of time. If we fill that up with oxygen, now instead of having 500 ccs of oxygen, you have almost 2.5 liters of oxygen. It gives you a lot more time to get the breathing tube. They're going to come in, they're going to be breathing the oxygen. We give them medicine to go to sleep. Most people can help them breathe with the anesthetic mask. Some people find it difficult to breathe. Those are the ones we're having. 

Giving them extra oxygen ahead of time is going to be extremely helpful. It is going to be extremely helpful. They go to sleep. You've got them all the way to sleep with your anesthetic medications, and now you're going to put the breathing tube in the windpipe. Once the breathing tube is in the windpipe, it has a little balloon on the end so that you can push gas in and out of the lungs. It goes in the trachea of the windpipe. Once you inflate that balloon, it seals the windpipe. This is a long way from answering your question.

No, but this is good. A lot of people probably do not know this.

If the patient has eaten, we call that a full stomach. They got a bunch of stuff in their stomach. If they stopped at Burger King or McDonald's or whatever on their way, that is all still sitting in the stomach. When you put them to sleep, that can come up, regurgitate, we call that, come up the esophagus, and it can go into the windpipe. You do not want your hamburger in your windpipe. We call that aspiration. Aspiration can kill you. That is why we want you not to eat, and that is it is very important to follow those directions. The majority of people do not know. I would ask people, "Do you know why we make you not eat?" The vast majority would say, "Yes, I do not get nauseous." I would say, "No, it's a lot more important than that."

A lot of people just do not think about when you're breathing in the beginning, before it separates from the esophagus and the trachea, that it is sharing that space. Until you actually have that blocked off, anything from the esophagus, if it does go up high enough, it can go to those lungs. As you said, aspiration pneumonia, it can be deadly. You can also just have aspiration pneumonitis, where you get all that inflammation. You just think about your stomach contents, you have acid to help break down all the food, and you have whatever food was there. You do not want that going to the lungs.

If you had just water that went into your lungs, that is not going to be as big a problem as if you had all those small particles and the acid and all of that. When people say, "Why would just locals be safer?" It would be because everybody's gotten sick and vomited. They have what we call protective reflexes. I am going to get dirty on the floor, but I am not going to aspirate because I know, “Here it comes, or a mild regurgitation. People like, "Yes, I just tasted last night's dinner again." That is a mild regurgitation. It wasn't even so much that you had to spit it out. You swallowed it. When they have been given the anesthetic agents, they cannot protect themselves, so then they're at risk of aspiration. 

You went over obviously like a hamburger, but what about it when somebody is sneaking coffee?

For a typical person, the current guidelines for anesthesia say not to eat solids for at least eight hours. Now, if you had a cracker or slice of toast, that's more like six hours. Clear liquids are allowed for two hours. The reason for there being different categories is that it takes a different amount of time for that stuff to get out of your stomach. 

If someone has a cup of black coffee, that's real, even though you cannot see through it. It functions like a clear liquid because it's just liquid. It goes through the stomach quickly. If someone came in and said, “I had a cup of coffee this morning, say it's like 8:00,” and they said, “I had a cup of coffee at 5:30 when I got up this morning.” I'll be like, “That's okay.” I'll ask them, “How much cream did you put in it?” If you had gone to Starbucks and gotten a café latte, that's mostly milk.

It is, yeah.

That's going to be eight hours.

It's going to go through, your stomach isn't going to clear it as fast because it's higher fat and higher protein. 

It's got all the particles that are going to be bad for your lungs if it went into your lungs. If someone said, “Can I have my coffee in the morning?” “Black coffee, here's what time your surgery is scheduled.” Usually, we put a little wiggle room in. They're saying you're the second patient for the day, and you're scheduled for 10:00, and the first patient canceled. Now you show up, and they want to get you an operating room at 9:00 instead of 10:00. If it's me, “Start at 9:00.” If I had my cup of coffee at 8:00, they might make me wait. 

Anyway, so you would check with your physician, but my advice would be if you're someone who drinks coffee regularly and you're going to miss that morning cup of coffee, check with your anesthesiologist. What time can I have my black coffee? If someone put just like a pinch of coffee in cream or milk or whatever in their coffee, that did not bother me. Some people are more concerned about that, so it's good to check with your anesthesiologist. 

I feel like another question that you guys always ask is about your teeth. Why do loose teeth matter?

We talked about putting in the breathing tube, and for most people, it's not a problem putting it in, but sometimes it's difficult, and the instrument we use can put some pressure on your teeth. Normal teeth normally can withstand some pressure, but a loose tooth might come out with a little bit of pressure. I can push on my teeth, and they stay where they are. Remember when you were a kid, or you've seen a six-year-old recently, and they're like, “Look at my loose tooth.” It's just wiggling around. The problem would be if that comes out, it goes into the lungs. 

That makes sense. 

Patients who have loose teeth, I'll say something to them. “That might get damaged.” They'll be like, “That's fine. I'm not worried about it.” “If it went to the lungs, you'd be worried about it.” You've got to be really careful. It's good for us to know, too, that over there, you've got to really watch out for.

What about nail polish? feel like gel nails, manicures, everybody has that now for girls who waste a lot of people.

One of the things that has made anesthesia a lot safer, and pretty much everybody's heard about a pulse oximeter, but most of the time clip it on the finger and it has to transmit the light through the finger and the light is comes out on one side and it's measured on the other side because it's looking at how the hemoglobin is absorbing the light that's being transmitted. Now, a nail polish will inhibit the normal transmission of that light. 

You just cannot see what their oxygen level is.

It makes it so that it doesn't work. There are other oxybarians you can put on the ear. A lot of times, if you turn the pulse oximeter sideways, it'll still work on the finger. A lot of times, they'll say just take the nail polish off one finger. 

Let's see, I think another one that would kind of be big is all these GLP-1s, Ozempic. I feel like maybe it's not quite half the population, but it feels like half the population is on Ozempic right now. 

There are a lot of people on it.

Why would that matter with anesthesia?

I just read recently that about one in eight US adults is on some type of GLP-1 antagonist.

I believe it. 

The GLP-1 agonists have a lot of different names. You might be on one of those.

Ozempic, Wegovy, those I feel like are the ones everybody knows.

Might be, some you take once a day, some you take once a week. The problem that anesthesiologists worry about is that one of its effects is it delays gastric emptying. Your stomach doesn't get the food and liquids out as quickly as it normally would. That's a problem, as we had already discussed that if you have stuff in your stomach, you worry about aspiration. 

You do not want all that food to come back up.

You do not want it to come up and go into the lungs. That's why anesthesiologists are concerned about patients taking those medications. 

If you're on those drugs, how would that really change in terms of surgery planning?

This is in a state of flux in terms of these, which have only recently started to be used. There are no good, there are no good studies that have said this is what the percentage of patients who aspirate. Aspiration, even when you have some stuff in the stomach, is still relatively rare and does not happen all that often. The incidence of aspiration is relatively low. 

Since it can have such severe consequences, you want it to be zero. Anesthesiologists do not want to put their patients at any unnecessary risk. The Anesthesia Society came out with guidelines saying if you are taking the GLP-1 drugs daily, hold the dose. If you are taking it weekly, hold it a week before to help the stomach empty. The problem is that there are still some high-risk patients. 

That is what I was reading about. It is interesting, and it is good to do something called risk stratification in medicine, where you look at different patients and populations that would maybe be at a higher risk. There are some people I found interesting, and it makes sense when you're first starting the medication, you're titrating up. You're going up on higher doses, trying to get to that effect. In that up-titration in the beginning, it seems like a higher risk, right?

That’s true. Higher risk would be up-titration and also during that titrating up, and also patients who are on a very high dose tend to be at higher risk. If you were in that up-titration phase and you were having an elective procedure, like say you're getting your knee replaced, no emergency. We are talking about elective procedures. Emergency procedures are a separate category. We take care of people who have eaten prior to, think it has gotten into a car accident, yes, gotten into a car accident pulling out of the fast food place. 

It's like, “You still need the surgery, and so we just accept those risks.”

There are procedures that we do to minimize the risk. You quickly put the patient to sleep and get the breathing tube in. There are things you do to minimize the risk. The risk would be even lower if your stomach is empty. That is why, if you were having an elective procedure that could be delayed and you're in that dose escalation phase, let us wait until a little bit after your dose escalation phase. Other patients who are at increased risk would be those with diabetes, maybe you're on high-dose narcotics, which will also slow down your gastric emptying, people with Parkinson's disease, or other reasons why they may have slowed gastric emptying.

There is a guideline that came out after the anesthesiologist guideline that was signed on by the anesthesiologist, also, it was also the gastroenterologists, the endocrinologists, there were a bunch of societies that said, "Let us look at this.” A lot of this is based on expert medical opinion, not studies. The expert medical opinion was that if the patient is in the low-risk category, the other one would be. If the patient comes in on the day of the surgery and they're feeling bloated, they're nauseous, they've been vomiting.

They probably just are in a little higher risk category, even though they might not have been there on paper. 

Their guidelines say, “Delay the surgery,” or depending on the situation, you can discuss it with the patient, with whoever is doing the procedure, the surgeon, the gastroenterologist, whoever, about the risk of aspiration, and we can do what is called a rapid. Those patients would get the endotracheal tube, whereas maybe it is a procedure where you might not have used an endotracheal tube. One example might be a knee arthroscopy. We do not use an endotracheal tube. Typically, we're using a laryngeal mask airway, which does not protect you from aspiration. We can go ahead and do the procedure, but now you are getting an endotracheal tube, and discuss that with the patient, and why. 

Risk benefits. 

Probably a lot of anesthesiologists are still going to hold your dose for a day if it is once daily or for a week for weekly medication.

That is another reason why always talk to your anesthesiologist and your provider, because these will probably continue to change. I feel like we're just finding more and more about them. As you said, there are no big studies, and this is currently based on expert advice, which can change based on what you see in the population.

It is best to check with them about it.

It is interesting because so many people are on them now. It is a big topic for anesthesia for sure.  The other thing that people, we touched base on it earlier, but the big fear is waking up during surgery. You do not want to wake up during surgery. Can you actually wake up during surgery? Is that something that people are so scared of, but is that possible?

It is possible, but it is unlikely. It is a rare event. Some patients are at increased risk for it. One category in particular would be a trauma patient. An example would be someone who fractured their leg. It was an open fracture, and they were bleeding a lot. Anybody with a type of injury, such as a gunshot wound, would be another large category. They have had a lot of blood loss. All our anesthetics tend to drop your blood pressure a little bit. 

They're what we call vasodilators. They dilate your blood vessels. Also, a little bit of what we describe as myocardial depression. They make your heart not pump quite as strongly. It is fairly common that the blood pressure will go down a little bit when we give anesthesia. We were talking before about people having a reserve. A normal person can compensate. It is not an issue. Someone whose blood volume is low can experience issues. Those people, you cannot give them quite as much anesthesia. 

If I had someone with bad trauma coming in, and a lot of times they're pretty much unconscious from the trauma and injury, but you still want to make sure they do not remember anything. You tend to give them a benzodiazepine, which would be a Versed or midazolam. I do not know if people have heard of that or another common class.

As Valium, I think a lot of people have probably heard of Valium in the same category as that.

This tends not to drop your blood pressure as much. There are other medications we would give in that situation that tend not to drop the blood pressure as much. Their risk would be, so they're probably not going to remember, because if you're unconscious from low blood pressure, your brain is already shut off. We give you some medicines, and your brain shuts off. We give you some medicine, so it is still not common.

What about? I'm just curious, because that makes me think of, like, if somebody did lose a lot of blood in surgery and they're getting new blood. They're getting blood transfusions. That blood does not have the medicine that you put in it. Does that have any effect on anesthesia, and maybe waking up or not really?

Typically, those patients are getting medications continuously. You would be replacing that medication.

Would it not have a huge effect on them waking up or anything like that?

Not typically.

Interesting. How are you actually monitoring that patients are okay while they're under?

A routine anesthetic, so someone just having the example we used previously, like a knee arthroscopy or something like that, we're monitoring their blood pressure, their EKG, their electrocardiogram, and their pulse oximeter. We're monitoring that there is enough oxygen in their blood. We're also monitoring end-tidal CO2. What does that mean? That is the CO2 at the end of your respiration that you're breathing out. 

If someone has an endotracheal tube or the laryngeal mask airway, which is another type of airway device, or even just we can put a nasal cannula on and sample the gas that you're breathing out to make sure you're breathing out CO2. With an endotracheal tube, it's fairly accurate that we're ventilating you enough, you're getting enough oxygen in your blood, the pulse oximeter. Pretty much every anesthesia monitor now samples gas to look at the end-tidal CO2. 

Pretty much every anesthetic monitor now also measures how much oxygen you're breathing in and out. We have an oxygen analyzer, make sure we're giving you enough oxygen before the pulse oximeter. Also, it measures how much of the anesthetic gas you're breathing in and breathing out. One thing that an anesthetic gas monitor allows is for you to know how much of the anesthetic gas you are breathing out. That gives you a measure of how much is in the body, which is the gas.

The CO2 monitor, if that was really low, what would you change?

If the CO2 monitor is low, we'll go with just low. Maybe you're ventilating the patient too frequently. Let us slow down the ventilation.

It would be the equivalent of somebody hyperventilating.

If your CO2 has been great, it has been straight, it has been normal, and all of a sudden it drops off, if it went to zero, probably your anesthesia machine and tube got disconnected, and you're not ventilating the patient anymore.

That is not good.

That is an early warning system. That is not good. You will not know about that right away. You're like, "That tube fell off. Let me hook it back up." You know right away. Those things do not cause problems. Another reason for your CO2 to drop to a lower number might be a pulmonary embolism. There are certain operations where pulmonary embolism is a risk, like people who have fractured their femur frequently get blood clots in their legs, in the deep veins. We call that deep vein thrombosis, DVT. If one of those blood clots breaks off and goes to the lungs, that's a pulmonary embolism.

It’s because that's basically a blood clot that goes to the lungs. Pulmonary embolism again, the blood clot.

That would block the blood from going into the lungs. The blood cannot get there for you to breathe out the CO2. We're measuring the CO2 you breathe out with the end-tidal CO2. That would be the reason. 

That is very helpful.

In the old days, it would be, "Their blood pressure went down. Why didn't their blood pressure go down?" You wouldn't have an end-tidal CO2 monitor, and you might not be thinking of pulmonary embolism. Now you have an end-tidal CO2. When I started in residency, the pulse oximeter was not universally used.

Really?

Yes.

That's wild to think.

Nor was the end-tidal CO2. 

Again, for those just tuning in, the pulse ox, if you're not in medicine. Again, we talked about it, but that's what shows you what your oxygen level is at.

It is important to have enough oxygen.

Especially for anesthesia. It just seems wild that they didn't even have pulse ox in all patients back then. It has come a long way.

Before I started, it was called the finger on the pulse. They did not have a pulse oximeter, and they'd be feeling the pulse. The surgeon might say, "You do not have a pulse oximeter." They'd be like, "The blood's looking a little darker." For your blood to be, we call that cyanosis. For you to be cyanotic and have some cyanosis and look a little blue, you need to have like 5 grams of hemoglobin without oxygen on it.

That's a lot. Definitely not ideal.

It's definitely a whole lot safer. In terms of what people worry about with waking up, I tell them it's very uncommon. There is even another monitor, which I didn't mention, which is a brand name, the BIS monitor. It is a sticker that goes on the head. We use that for some operations, and that looks at the brain waves. If the number is low, you know they're asleep. 

There's a lot more. In all your years, what do you think has scared patients the most, and what should not scare them? We touched on this a bit earlier. 

That's not the waking-up part. There's the waking up and not waking up. Yes. Two sides of the same coin. I think the not waking up, "Am I going to wake up after surgery?" The other thing, and we did not touch on this, it was pretty common that patients would come in and they're not having a huge operation, and the thing they worried most about was nausea.

It may be someone who has had a previous anesthetic where nausea was a big issue. There are ways of tailoring the anesthetic to reduce the risk of nausea. If you are someone who has had a previous anesthetic where you were really nauseous, that would be another thing that is important to tell your anesthesiologist preoperatively, because they can tailor the anesthetic to reduce your chance of nausea.

That makes sense. That is probably why a common question you guys ask is, “Have you ever had anesthesia before? Any issues with it?” It would bring that up if you've been nauseous before. 

There are risk factors for nausea. Women are more likely to be nauseous than men. You can thank your hormones for that. Another risk factor is nausea with a previous anesthetic. You had nausea before, you might have it again.

What is something the public does not realize anesthesiologists do during surgery?

They do not realize how much we're continuing to monitor them and make sure that the blood pressure stays good. You mentioned, "What if your CO2 went down?" That you're breathing the right amount. That your cardiac rhythm stays normal. Those kinds of things, and continuing to administer anesthetic medications. Make sure you're still asleep. You know that thing about not waking up during surgery. 

It’s important. You're focused on that too. Did you ever have to think fast in a critical moment?

The one critical moment, a lot of times, would be when we talked about the airway. The patient was doing fine. It was just a procedure, not a really long procedure, and they were breathing the anesthetic gas by mask. All of a sudden, they just got an airway obstruction where they weren't breathing. We talked about how you do not have a whole lot of time to help them breathe again. 

That is where one of the advances, like the laryngeal mask airway, I mentioned previously, that did not come out until well after I had finished my anesthesia training. That has really been a big safety advance, because that really helps the vast majority of patients, where maybe you start having a little difficulty helping them breathe with the mask, the laryngeal mask airway will solve that. 

That is cool.

The other one would be unexpected bleeding. I remember one patient I had who we did not know how much he drank.

Again, it is important to tell your anesthesiologist.

We did not know how much he drank, and he was getting his gallbladder out. We knew he had some lung problems and some medical issues. The operation is over, and now when they do the gallstones are under laparoscopic gallbladder. They just do the little incisions, put their scopes in, and do it with the camera.

With a little video camera. They blow up your belly with a little bit of air, and then they go in just a couple of small incisions. It is actually very cool.

They recover so much faster.

You’re not having to go through the muscles in just those small spots instead of a big area. 

A lot of people go home the same day. On this guy, the tube they pulled out is probably about as thick as that pen. They pulled that out of the abdominal wall, and this guy just started bleeding. They still had the camera inside, and it turned out that he had such bad cirrhosis. The liver processes and detoxes a lot of your blood, and most of your blood returns from the veins from your intestines, going through the liver.

It is very vascular, and then on top of that, it also helps with clotting factors. It basically also helps make things that can stop you from bleeding. When it is not working well, plus all this blood flow that is supposed to be going through it, then it can.

The blood is supposed to go through the liver, but when the liver gets all scarred up, it has to find another way to get around to get back to the heart. This guy, one of the ways of getting back to the heart was through the veins on his abdominal wall. He had this abnormally large vein on his abdominal wall, which you really could not see from the surface. It was like under the skin. When they pulled that, it happened to go through that vein, and this guy started losing blood. His blood pressure got low. We had to transfuse him. We were not expecting to have to transfuse him. That would be another example.

You have to be thinking on your toes and reacting very quickly because it's something that you wouldn't expect, but that's why. 

You do not have time to say, "Let me go look this up. How do we handle this problem?"

That's where it's important to have all the experience and everything and be ready for all of the variables that can happen. After all those years, because we talked about how long you've been practicing for, what part of the job are you the most proud of?

You asked about being respected. I think I was. I am proud of that. It is about the patients. I am happy that I was able to get people through that stressful time well. When I went and met patients preoperatively, I tended to have a calming effect. 

Which is what you want. You want to feel a little bit more relaxed after you meet your anesthesiologist. 

You do not want them to come in and be all, "I hope you make it today." You want them to be, "You're going to be fine. Here's what we're going to do. Here's the plan. Here's what you can expect after surgery." That is one of the things patients will ask, "How long am I going to sleep? How long is it going to take me to wake up? How long do I have to be in the recovery room?" Which are all good questions. I would go through all of that.

What is one moment that stayed with you?

There are so many, but one would be that I was covering the obstetric unit.

That is the OB unit, where people are going to deliver basically.

This patient had come in, and she was fairly far along in her pregnancy. I do not know if she was 34, 36 weeks, or something like that, and she had a previous c-section, and she had come in just for prenatal testing, let us check the baby's heartbeat and all that stuff. She was in her street clothes, about ready to go home, and then she had some abdominal pain, and they laid her down and saw that the scar on her uterus had come undone, and the baby was coming out intra-abdominal. This is a true emergency. We rushed her back into the operating room. She did not even have an IV yet. We rushed her back into the operating room, got an intravenous in, and even gave her pre-op antibiotics. I think within five minutes, that baby was born. 

That is two lives saved.

They both did well.

That is very cool. If you could tell every future surgery patient one thing, what would it be?

Not to be that worried about it. A good night's sleep the night before surgery. I know it is easier said than done, but a good night's sleep actually helps you be rested. There was another thing we had talked about, alcohol before, but I would also mention not drinking alcohol the night before, because alcohol acts as a diuretic, and you also do not get normal sleep. It interferes with your REM sleep, your deep sleep, so you're not going to be as well rested. If you're a cigarette smoker, even one day of not smoking will reduce the amount of carbon monoxide in your blood. 

Just one day. That is impressive.

Even one day will reduce the amount of carbon monoxide in your blood, which will help you heal. It will also help for even one day.

Do not drink the night before. Get some good sleep.

As for eating, I would probably stay away from the big fatty foods and eat some extra protein. Carbs are okay.

Probably, you do not need to carb load like you would before a race.

You do not need to carb load. 

This has been great. Thank you so much. I really enjoyed this and learned so much. Hopefully, you guys learned something, too. This was really an exciting topic to talk about.

It is something a lot of people do not know, so that is a good topic.

I look forward to another episode of more anesthesia-related topics.

Thank you for having me. It was fun. 

Thanks for being on the show. Bye, you all.

Bye-bye.

Dr. Dennis McCarthy on LinkedIn

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