So in the last entry, I got into what exactly happens in the time between leaving the preoperative area holding room and the time you go to sleep, with the monitors and oxygen being applied, but usually not remembered by the patient due to the amnesia properties of midazolam...
It is at this point that general anesthesia begins. I get asked all the time, not unreasonably, about what kinds of drugs I will use. Being that most patients don't know or care much about pharmacology, I don't bore the crap out of them with details. Most want to know if I will give them "gas." Most are surprised by my reply, which is that the actual drug that initially puts them to sleep is given through the IV. That drug, which is used in 98 to 99 percent of anesthetics in the United States, is propofol, which has unfortunately gained quite a notorious reputation due to its link to the death of Michael Jackson.
Propofol, in the right hands, i.e. those of a trained and skilled anesthesiologist or nurse anesthetist, is a very safe drug. It has been used millions of times in operating rooms in the last twenty years and has a great track record of success. But it does two important things. It makes the blood pressure go down significantly, and when given in the quantities needed to induce general anesthesia, it slows and even stops breathing. Now these are the qualities that can make it dangerous when not given in the proper setting. That's why the monitors are put on the patient before they go to sleep, so that if the blood pressure goes down and/or the breathing stops, we can do something about it right away.
Fortunately, when I give propofol to a patient to put them to sleep for anesthesia, I'm not walking out of the room or standing in another room while other people give it. I, like every other anesthesiologist who does the same thing, am right there, standing at the head of the patient's bed, waiting for them to fall asleep. Once they are asleep, I use the mask, which is attached to an anesthesia machine, to help them breathe.
Propofol also hurts when it's injected. We try to give a little bit of local anesthetic through the IV with the propofol, to try to diminish that discomfort. Usually it works; sometimes it doesn't. Fortunately, because of the midazolam the patient has received before, they don't remember the displeasure of that experience.
Once the propofol has been given to put the patient initially to sleep, then that is the point where we turn on the anesthetic gas, and that keeps the patient asleep during the duration of the surgery. The problem is that we need a way to give that gas, and if the initial medicine has made the patient stop breathing, then we need to breathe for them. So some sort of tube is inserted into the patient's mouth and is hooked up to a breathing machine from there.
Often, especially in shorter surgeries, the tube that is placed in the patient's mouth is a soft, plastic or rubber tube called a laryngeal mask airway, or LMA. The LMA has a large, teardrop shaped cuff at one end, which when placed correctly, sits on top of the opening to the esophagus and vocal cords. It's usually fairly straightforward to put in; the patient's mouth is opened and the LMA is just gently inserted. It's the other kind of tube that is put in, an endotracheal tube, that is what most people associate when they think of a "breathing tube."
An intubation, as it is called, is the process of placing one of these endotracheal tubes into the patient's mouth and through their vocal cords, where the tip of the tube sits inside the trachea. From this point, the other end of the tube can be attached to an anesthesia machine, and the anesthetic gases that keep the patient asleep can be given.
An intubation, to a layperson who has never seen one before, is kind of a wild procedure. It always amazes me when I'm intubating a patient and can see out of the corner of my eye, some medical student or nursing student and the shocked look on their face. They're fascinated and horrified at the same time.
I remember the first time I saw an intubation as a medical student. The anesthesiologist tilted the patient's head back a little bit, opened the mouth, and stuck this...big, metal thing...into the patient's mouth, and then after some maneuvering, grabbed the breathing tube and shoved it into the patient's mouth for what seemed like forever. I thought he would shove it in so far that it'd get lost. And as he pushed the tube in, I could see the patient's Adam's apple sort of bounce up. I swallowed hard, and I think I felt a little twinge of sympathy pain in my own throat at that point.
I found later on that the big metal thing was a laryngoscope, a metal flashlight of sorts with a straight, dull metal blade attached to it. When held in the right position, a little light shines down the length of the blade. The blade is placed into the patient's mouth to move the tongue out of the way and visualize the epiglottis and vocal cords. Once the vocal cords are in view, it is just a matter of guiding, gently, the tube through them. It's not nearly as violent a procedure as I witnessed that day, but it can be a challenging one that takes some getting used to. But again, as general anesthesia slows or even stops the patient's breathing, it is up to the anesthesiologist to maintain an airway and use that airway to breathe for the patient during the duration of the surgery. That's where the intubation comes in. There is method to the madness...
Thursday, December 1, 2011
Wheeling on back
So you're having surgery...you get to the operating room area, where the nurses greet you, ask you to take off all of your clothes and put on this skimpy little gown, and ask you a bunch of questions. Then a couple more people ask you all of the same questions, and you're thinking, Didn't any of you guys read my chart? And that's where your anesthesiologist comes in, promising you amnesia and the absence of pain, hopefully reassuring you that all will be OK.
The role of the anesthesiologist before the operation starts is one of reassurance. Once they have checked over your medical records and history and determine that it is indeed safe for you to receive anesthesia, they want to ease whatever (understandable) anxiety you might have about the surgery. Of course, a large part of that is done through verbal reassurance, but, yes, drugs do play a major part in the process.
Somewhere between the holding area where you get dressed for surgery and the actual operating room, the anesthesiologist slips you a little medication through your IV. There are a few ones that can be used, but these days, by far the most common drug used for this purpose is midazolam, also known by the trade name of Versed. For those who want to know, it is a class of drug known as a benzodiazepine, which potentiates an inhibitory neurotransmitter in the nervous system known as GABA. The great thing about midazolam in the context of preparing patients for surgery is that it causes amnesia. It probably doesn't take longer than 30 seconds to work, and it only lasts about 30 minutes, but in that time, it's enough for people to forget completely about the entire process of leaving the surgery holding area and going into the operating room.
So most of the time, by the time the patient gets to the operating room, they have had midazolam, and though they may look and act normally to the casual observer, they in fact will have amnesia of the events in question. Patients move themselves onto the operating table and make small talk with the OR staff and the anesthesiologist, and usually don't remember a second of it. Midazolam can make some people a little bit disinhibited as well, so occasionally we'll get the patient who suddenly gets into confessional mode when the drugs are on board. I actually know people who worked in the OR with me who, when they needed elective surgery, decided to have it done somewhere else because they were so afraid of what they might say when they were given midazolam.
The good thing, though, is that midazolam calms the anxious patient and that is good for everyone. Once the patient is in the room, they are monitored with several things, just like in the holding area - a blood pressure cuff, EKG pads for the heart, and a small probe on the finger. This is a pulse oximeter, which measures a value known as the oxygen saturation, a measure of how much oxygen is in the blood. It also makes a distinctive high-pitched beeping sound in concert with the patient's heartbeat and is a useful tool in that regard.
Usually, while the anesthesiologist is placing these monitors, the OR nurses, and whoever else may be in the room (surgeons, medical students, etc.) are doing other stuff to the patient. One particularly important thing is the placement of these funny compression devices around the legs - they make the legs look like they're wrapped in large white inflatable tortillas. They inflate and deflate periodically during the surgery, squeezing the legs in the process. This device is called an SCD, or Sequential Compression Device. It is important because the leg squeezing that it does promotes the continuous flow of blood in the legs.
During anesthesia, and especially during the beginning of anesthesia, the blood in the patient's legs tends to slow down as sleep sets in and the blood pressure goes down. The problem with slowed blood is that it increases the risk of forming a blood clot in the leg, which can then travel up to the lung. When this happens, it is called a pulmonary embolism, and it can be fatal. These squeezing devices, funny though they look, are very effective and have greatly decreased the incidence of what used to be a rare but all-too-common complication of even routine general anesthetics.
But I digress. Once all of these monitors and sequential devices are placed, the patient is then ready to go off to sleep. But it's not as simple as slapping a gas mask on them or slamming drugs through the IV. First, the patient is given oxygen to breathe through a mask. Often, when people are not sedated until they actually come into the room, this is the last thing they remember, lying on the bed, looking up at the ceiling, with a mask on top of their nose and mouth.
As a medical student, I never understood, watching the anesthesiologists put patients to sleep, why in the world they did this. Why didn't they just go right to the gas? What's the point? Well, the normal air we breathe is about 21% oxygen; most of the rest of it is nitrogen. Right before going to sleep, when the patient breathes 100% oxygen, it fills their lungs with oxygen and removes the nitrogen. Nitrogen is nice, but it doesn't help human cells metabolize and thrive like oxygen does. All that oxygen serves as a safety net of sorts; if for some reason the breathing slows or stops as the patient goes to sleep, there is enough oxygen in the blood that a few seconds of not breathing won't be a disaster. So the oxygen mask is a nice thing to do for patients, allowing them to relax with the deep breaths we ask them to take, but it serves this safety purpose as well.
So at this point, with the monitors on and the oxygen in place being breathed by the patient, the induction of anesthesia - the "going to sleep" part - can begin...
The role of the anesthesiologist before the operation starts is one of reassurance. Once they have checked over your medical records and history and determine that it is indeed safe for you to receive anesthesia, they want to ease whatever (understandable) anxiety you might have about the surgery. Of course, a large part of that is done through verbal reassurance, but, yes, drugs do play a major part in the process.
Somewhere between the holding area where you get dressed for surgery and the actual operating room, the anesthesiologist slips you a little medication through your IV. There are a few ones that can be used, but these days, by far the most common drug used for this purpose is midazolam, also known by the trade name of Versed. For those who want to know, it is a class of drug known as a benzodiazepine, which potentiates an inhibitory neurotransmitter in the nervous system known as GABA. The great thing about midazolam in the context of preparing patients for surgery is that it causes amnesia. It probably doesn't take longer than 30 seconds to work, and it only lasts about 30 minutes, but in that time, it's enough for people to forget completely about the entire process of leaving the surgery holding area and going into the operating room.
So most of the time, by the time the patient gets to the operating room, they have had midazolam, and though they may look and act normally to the casual observer, they in fact will have amnesia of the events in question. Patients move themselves onto the operating table and make small talk with the OR staff and the anesthesiologist, and usually don't remember a second of it. Midazolam can make some people a little bit disinhibited as well, so occasionally we'll get the patient who suddenly gets into confessional mode when the drugs are on board. I actually know people who worked in the OR with me who, when they needed elective surgery, decided to have it done somewhere else because they were so afraid of what they might say when they were given midazolam.
The good thing, though, is that midazolam calms the anxious patient and that is good for everyone. Once the patient is in the room, they are monitored with several things, just like in the holding area - a blood pressure cuff, EKG pads for the heart, and a small probe on the finger. This is a pulse oximeter, which measures a value known as the oxygen saturation, a measure of how much oxygen is in the blood. It also makes a distinctive high-pitched beeping sound in concert with the patient's heartbeat and is a useful tool in that regard.
Usually, while the anesthesiologist is placing these monitors, the OR nurses, and whoever else may be in the room (surgeons, medical students, etc.) are doing other stuff to the patient. One particularly important thing is the placement of these funny compression devices around the legs - they make the legs look like they're wrapped in large white inflatable tortillas. They inflate and deflate periodically during the surgery, squeezing the legs in the process. This device is called an SCD, or Sequential Compression Device. It is important because the leg squeezing that it does promotes the continuous flow of blood in the legs.
During anesthesia, and especially during the beginning of anesthesia, the blood in the patient's legs tends to slow down as sleep sets in and the blood pressure goes down. The problem with slowed blood is that it increases the risk of forming a blood clot in the leg, which can then travel up to the lung. When this happens, it is called a pulmonary embolism, and it can be fatal. These squeezing devices, funny though they look, are very effective and have greatly decreased the incidence of what used to be a rare but all-too-common complication of even routine general anesthetics.
But I digress. Once all of these monitors and sequential devices are placed, the patient is then ready to go off to sleep. But it's not as simple as slapping a gas mask on them or slamming drugs through the IV. First, the patient is given oxygen to breathe through a mask. Often, when people are not sedated until they actually come into the room, this is the last thing they remember, lying on the bed, looking up at the ceiling, with a mask on top of their nose and mouth.
As a medical student, I never understood, watching the anesthesiologists put patients to sleep, why in the world they did this. Why didn't they just go right to the gas? What's the point? Well, the normal air we breathe is about 21% oxygen; most of the rest of it is nitrogen. Right before going to sleep, when the patient breathes 100% oxygen, it fills their lungs with oxygen and removes the nitrogen. Nitrogen is nice, but it doesn't help human cells metabolize and thrive like oxygen does. All that oxygen serves as a safety net of sorts; if for some reason the breathing slows or stops as the patient goes to sleep, there is enough oxygen in the blood that a few seconds of not breathing won't be a disaster. So the oxygen mask is a nice thing to do for patients, allowing them to relax with the deep breaths we ask them to take, but it serves this safety purpose as well.
So at this point, with the monitors on and the oxygen in place being breathed by the patient, the induction of anesthesia - the "going to sleep" part - can begin...
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