Post by natalie on Oct 10, 2014 15:59:05 GMT -5
Laura Tedesco
Oct 10, 2014
A new study reveals how often anesthesia wears off when a patient is still on the table.
It’s not just the fear of dying on the table that makes patients leery of going under anesthesia. It’s also the fear of waking up much sooner than intended — a paranoia perhaps made greater by the 2007 movie Awake, when a man found himself totally conscious, yet paralyzed, during heart surgery.
Terrifying, yes. But likely? Probably not. Still, it does happen. In September, the journal Anesthesia published the largest-ever study of awareness under general anesthesia, the NAP5 report, which found that the incidence rate is about 1 in every 19,000 cases (lower than previously reported).
“We’ve had the opportunity to study more episodes of anesthesia awareness than any other study has by an enormous amount,” said study author Dr. Tim Cook, a consultant in anesthesia at the Royal United Hospital in the U.K. “Previously, there were around 350 reports of awareness in the literature . We’ve studied another 300.” Those 300 incidences were drawn from an analysis of 3 million cases of general anesthesia, reported by every public hospital in the UK and Ireland.
WHAT GOES WRONG—AND WHEN
In addition to analyzing the frequency of anesthesia awareness, the study delved into the actual nature of such events. “People think that you are awake and paralyzed, trapped — that it’s like being locked in for hours,” said Dr. Alex Evers, head of the department of anesthesiology at Washington University in St. Louis. “But the average episode of anesthesia awareness is relatively brief. And it’s not always crystal clear.” In the new study, most episodes lasted less than five minutes; in 34 percent of cases, the duration was estimated to be less than one minute.
And despite patient fears of waking up to the sensation of a scalpel, anesthesia awareness doesn’t typically happen during the procedure itself. “Two-thirds of the episodes occurred either before surgery had started or after surgery had finished,” Cook told Yahoo Health.
For starters, the moment when the patient passes out is not always clear, making awareness early on more likely. Plus, shortly after the anesthesia is administered, a tube is inserted into the patient’s airway. When somebody yanks open your mouth, “that is very stimulating,” said Dr. Tong Joo “TJ” Gan, chairman of the department of anesthesiology at Stony Brook Medicine in New York. If the patient didn’t receive enough anesthetic or the doctor inserts the tube prematurely, that may trigger awareness, he said. In the study, for example, one patient recalled his doctors struggling to insert the tube — and thanking them for their care. Toward the end of surgery, it may take longer to wrap things up than anticipated, allowing the anesthesia to wear off prematurely, he added.
WAKING UP ON THE OPERATING TABLE
So what exactly does an unintentionally conscious patient perceive? In 42 percent of cases, patients reported being unable to move, a side effect of muscle relaxants administered to keep them from squirming on the table; 41 percent couldn’t communicate; 37 percent said they could hear noise or voices; 21 percent perceived touch (without pain); and 18 percent reported feeling pain.
Only 3 percent said they actually had visual awareness, despite the common fear of watching yourself being operated on. “For the most part, your eyes are closed,” Dr. Marc Bloom, an associate professor of anesthesiology at New York University, told Yahoo Health. “The one thing that gets preserved most is your hearing.” (Hearing is the last sense to go, and the first to come back.)
As Sandra, a woman interviewed for the study, recalled, “Suddenly, I was aware something had gone very wrong. I could hear what was going on around me, and I realized with horror that I had woken up in the middle of the operation, but couldn’t move a muscle….While they fiddled, I lay there, frantically trying to decide whether I was about to die, and what options were open to me.”
The cocktail of drugs that make up anesthesia is the likely explanation for this variability of experience. “Years ago, it was plausible that you might get a single-agent anesthetic,” Bloom said. But, now, patients typically receive a handful of meds designed to tackle different issues, including pain, consciousness, and movement. So if the drug that knocks you out quits working, you may experience awareness — but if your painkiller is still doing its job, you may not feel any actual discomfort.
Of all the symptoms reported, paralysis was considered the most distressing — even more so than pain. “You know you’re awake, but you can’t indicate to anybody that you are,” Bloom said. About half of all cases were associated with distress, with incidences involving both paralysis and pain being considered most traumatic. “Some patients described it as being locked in a crypt or feeling like they were dying,” Cook said.
Even when the incident is brief, this terror can result in longer-term psychological problems, such as insomnia, flashbacks, nightmares, and even PTSD. One patient, interviewed for the study, developed symptoms of PTSD — including seeing the anesthesiologist’s face when asleep — after waking up, trying to cry to notify the doctors, and then feeling pain as surgery commenced.
It’s impossible to predict exactly who will be unfortunate enough to experience anesthesia awareness, although certain factors, like being female or obese, are associated with increased risk. “Women — in particular redheads — need a little more drug,” Bloom told Yahoo Health. “It’s mainly genetic factors.” In fact, in the study, patients who reported awareness were female the majority of the time.
Overweight and obese people also seem to face a higher risk of waking up on the table, probably because it’s tough to estimate exactly how much anesthesia to give to a larger-than-average individual. “If you have a 400-pound person, he needs more. But he doesn’t need three times more than the average patient,” Bloom said. “So I have to guesstimate somewhere in between.”
Fat doesn’t have as large a blood supply as other types of tissue, so less anesthesia is necessary than you might expect when much of a person’s body weight is fat. “We have these discussions about whether the calculations of your dose should use your actual body weight, your ideal body weight, or your lean body weight,” he said. “The answers aren’t there yet.”
The type of procedure performed also plays a strong role in the likelihood of anesthesia awareness, with C-sections (1 in 670 cases) and cardio-thoracic procedures (1 in 8,600 cases) posing an especially high risk. Generally, patients are given about 30 percent more anesthesia than they’re expected to require. “But there are certain conditions where we can’t just blindly give more,” Bloom said.
During C-sections, for example, doctors worry about the unborn baby’s exposure to anesthesia, so a smaller dose is typically administered, raising the odds of awareness. “Similarly, some cardiac patients’ hearts are so weak that they don’t tolerate a lot of drug, so we tend to give them less,” said Bloom. “And then there’s trauma, when you’re already unstable since you’ve been bleeding or injured. Your vital signs aren’t good, and because anesthetics tend to depress your vital signs, we tend to be lighter-handed in those situations.”
And some people may simply be less sensitive to anesthesia — or altogether resistant, said Dr. Norman Cohen, an anesthesiologist at Oregon Health & Science University. This may explain why, in about a quarter of cases, the researchers concluded that even though awareness occurred, the anesthesia had been administered perfectly. “There was no evidence that too little drug has been given, and there were no technical problems,” Cook said. “It may be that patients were intrinsically resistant.”
Still, Cook thinks anesthesia awareness is highly avoidable. In the study, “the majority [of cases] would be regarded as preventable,” he said. “There is no doubt that human error was a significant factor in a number of these cases.” The most common reason for awareness is drug-delivery problems — for example, the pump for the anesthesia IV stops working, said Cohen. In fact, in 74 percent of during-surgery episodes, there was evidence of inadequate care, including equipment malfunction or a too-low dose being administered. (Undetected machine malfunction is usually to blame when episodes of awareness are prolonged.)
“In simple terms, all cases are preventable by giving more drug,” Cook said. “But that’s oversimplifying it, because if we give too much drug, then the patient will come to harm.” Potential complications range from minor — for example, excessive sleepiness — to serious or even fatal, such as chest infections, heart attacks, and stroke. “We have to tread a careful line between giving too much drug and giving too little drug,” he said. That’s made infinitely trickier because the maximum effective dose can be 10 times higher than the minimum effective dose, said Dr. Bloom. “With a range that wide, it’s possibly for any individual to be outside of what we’d expect. This has become a Goldilocks story of not too much and not too little.”
Technological advancements now allow doctors to track more than your blood pressure or heart rate during surgery, which are indicators of your level of consciousness. If you’re feeling pain, your vitals will spike, alerting doctors in to the fact that you may be awake, even if you can’t move, Bloom said. These numbers, however, aren’t always reliable because medications such as beta blockers can prevent your BP from rising, Cohen noted. That’s why devices that measure your brain waves when you’re under anesthesia, such as the bispectral index (BIS) monitor, can be especially useful. These tell doctors how out of it the patient is, although, Cohen cautioned, they haven’t been proven to actually prevent awareness.
Even if you do wake up, the study suggests that simply being acknowledged by your doctor can mitigate the amount of distress you experience. “As soon as you hear someone say, ‘You’re OK. We’re going to give you some more drug now,’ then that awareness panic goes away,” Bloom said. That’s why the researchers recommend doctors speak to patients when awareness is suspected, reassuring them that they’re aware of their predicament. (They also remind practitioners to keep chit-chat professional during surgery, just in case the patient is, in fact, awake.)
CAN PREVENT AWARENESS UNDER ANESTHESIA?
What can you do to decrease your odds of waking up when you’re supposed to be conked out? Bloom suggests inquiring about the type of anesthetic you’re going to be given — and if it’s an IV anesthetic, asking whether a brain-function monitor will be used.
Another question to consider: Are muscle relaxers totally necessary? When patients had received a neuromuscular blocking agent, which, again, is the cause of panic-inducing paralysis, the incidence of awareness was approximately 1 in 8,000 cases. “Obviously, if there isn’t a muscle relaxant being used, you just start moving or clinching your fist to indicate that you’re awake,” Bloom said. During complicated procedures — such as abdominal, thoracic, and orthopedic surgeries — the meds are often necessary. But you may not need them for more superficial surgeries, such as those involving the skin or breasts, he said.
Even if you require a muscle relaxant, the experts overwhelmingly agree that anesthesia is safe — and awareness is unlikely. “Most important is that it really is very rare,” Bloom said. “So it’s not something to be terribly feared. The incidence is low enough that people shouldn’t be afraid to have surgery.”
Oct 10, 2014
A new study reveals how often anesthesia wears off when a patient is still on the table.
It’s not just the fear of dying on the table that makes patients leery of going under anesthesia. It’s also the fear of waking up much sooner than intended — a paranoia perhaps made greater by the 2007 movie Awake, when a man found himself totally conscious, yet paralyzed, during heart surgery.
Terrifying, yes. But likely? Probably not. Still, it does happen. In September, the journal Anesthesia published the largest-ever study of awareness under general anesthesia, the NAP5 report, which found that the incidence rate is about 1 in every 19,000 cases (lower than previously reported).
“We’ve had the opportunity to study more episodes of anesthesia awareness than any other study has by an enormous amount,” said study author Dr. Tim Cook, a consultant in anesthesia at the Royal United Hospital in the U.K. “Previously, there were around 350 reports of awareness in the literature . We’ve studied another 300.” Those 300 incidences were drawn from an analysis of 3 million cases of general anesthesia, reported by every public hospital in the UK and Ireland.
WHAT GOES WRONG—AND WHEN
In addition to analyzing the frequency of anesthesia awareness, the study delved into the actual nature of such events. “People think that you are awake and paralyzed, trapped — that it’s like being locked in for hours,” said Dr. Alex Evers, head of the department of anesthesiology at Washington University in St. Louis. “But the average episode of anesthesia awareness is relatively brief. And it’s not always crystal clear.” In the new study, most episodes lasted less than five minutes; in 34 percent of cases, the duration was estimated to be less than one minute.
And despite patient fears of waking up to the sensation of a scalpel, anesthesia awareness doesn’t typically happen during the procedure itself. “Two-thirds of the episodes occurred either before surgery had started or after surgery had finished,” Cook told Yahoo Health.
For starters, the moment when the patient passes out is not always clear, making awareness early on more likely. Plus, shortly after the anesthesia is administered, a tube is inserted into the patient’s airway. When somebody yanks open your mouth, “that is very stimulating,” said Dr. Tong Joo “TJ” Gan, chairman of the department of anesthesiology at Stony Brook Medicine in New York. If the patient didn’t receive enough anesthetic or the doctor inserts the tube prematurely, that may trigger awareness, he said. In the study, for example, one patient recalled his doctors struggling to insert the tube — and thanking them for their care. Toward the end of surgery, it may take longer to wrap things up than anticipated, allowing the anesthesia to wear off prematurely, he added.
WAKING UP ON THE OPERATING TABLE
So what exactly does an unintentionally conscious patient perceive? In 42 percent of cases, patients reported being unable to move, a side effect of muscle relaxants administered to keep them from squirming on the table; 41 percent couldn’t communicate; 37 percent said they could hear noise or voices; 21 percent perceived touch (without pain); and 18 percent reported feeling pain.
Only 3 percent said they actually had visual awareness, despite the common fear of watching yourself being operated on. “For the most part, your eyes are closed,” Dr. Marc Bloom, an associate professor of anesthesiology at New York University, told Yahoo Health. “The one thing that gets preserved most is your hearing.” (Hearing is the last sense to go, and the first to come back.)
As Sandra, a woman interviewed for the study, recalled, “Suddenly, I was aware something had gone very wrong. I could hear what was going on around me, and I realized with horror that I had woken up in the middle of the operation, but couldn’t move a muscle….While they fiddled, I lay there, frantically trying to decide whether I was about to die, and what options were open to me.”
The cocktail of drugs that make up anesthesia is the likely explanation for this variability of experience. “Years ago, it was plausible that you might get a single-agent anesthetic,” Bloom said. But, now, patients typically receive a handful of meds designed to tackle different issues, including pain, consciousness, and movement. So if the drug that knocks you out quits working, you may experience awareness — but if your painkiller is still doing its job, you may not feel any actual discomfort.
Of all the symptoms reported, paralysis was considered the most distressing — even more so than pain. “You know you’re awake, but you can’t indicate to anybody that you are,” Bloom said. About half of all cases were associated with distress, with incidences involving both paralysis and pain being considered most traumatic. “Some patients described it as being locked in a crypt or feeling like they were dying,” Cook said.
Even when the incident is brief, this terror can result in longer-term psychological problems, such as insomnia, flashbacks, nightmares, and even PTSD. One patient, interviewed for the study, developed symptoms of PTSD — including seeing the anesthesiologist’s face when asleep — after waking up, trying to cry to notify the doctors, and then feeling pain as surgery commenced.
It’s impossible to predict exactly who will be unfortunate enough to experience anesthesia awareness, although certain factors, like being female or obese, are associated with increased risk. “Women — in particular redheads — need a little more drug,” Bloom told Yahoo Health. “It’s mainly genetic factors.” In fact, in the study, patients who reported awareness were female the majority of the time.
Overweight and obese people also seem to face a higher risk of waking up on the table, probably because it’s tough to estimate exactly how much anesthesia to give to a larger-than-average individual. “If you have a 400-pound person, he needs more. But he doesn’t need three times more than the average patient,” Bloom said. “So I have to guesstimate somewhere in between.”
Fat doesn’t have as large a blood supply as other types of tissue, so less anesthesia is necessary than you might expect when much of a person’s body weight is fat. “We have these discussions about whether the calculations of your dose should use your actual body weight, your ideal body weight, or your lean body weight,” he said. “The answers aren’t there yet.”
The type of procedure performed also plays a strong role in the likelihood of anesthesia awareness, with C-sections (1 in 670 cases) and cardio-thoracic procedures (1 in 8,600 cases) posing an especially high risk. Generally, patients are given about 30 percent more anesthesia than they’re expected to require. “But there are certain conditions where we can’t just blindly give more,” Bloom said.
During C-sections, for example, doctors worry about the unborn baby’s exposure to anesthesia, so a smaller dose is typically administered, raising the odds of awareness. “Similarly, some cardiac patients’ hearts are so weak that they don’t tolerate a lot of drug, so we tend to give them less,” said Bloom. “And then there’s trauma, when you’re already unstable since you’ve been bleeding or injured. Your vital signs aren’t good, and because anesthetics tend to depress your vital signs, we tend to be lighter-handed in those situations.”
And some people may simply be less sensitive to anesthesia — or altogether resistant, said Dr. Norman Cohen, an anesthesiologist at Oregon Health & Science University. This may explain why, in about a quarter of cases, the researchers concluded that even though awareness occurred, the anesthesia had been administered perfectly. “There was no evidence that too little drug has been given, and there were no technical problems,” Cook said. “It may be that patients were intrinsically resistant.”
Still, Cook thinks anesthesia awareness is highly avoidable. In the study, “the majority [of cases] would be regarded as preventable,” he said. “There is no doubt that human error was a significant factor in a number of these cases.” The most common reason for awareness is drug-delivery problems — for example, the pump for the anesthesia IV stops working, said Cohen. In fact, in 74 percent of during-surgery episodes, there was evidence of inadequate care, including equipment malfunction or a too-low dose being administered. (Undetected machine malfunction is usually to blame when episodes of awareness are prolonged.)
“In simple terms, all cases are preventable by giving more drug,” Cook said. “But that’s oversimplifying it, because if we give too much drug, then the patient will come to harm.” Potential complications range from minor — for example, excessive sleepiness — to serious or even fatal, such as chest infections, heart attacks, and stroke. “We have to tread a careful line between giving too much drug and giving too little drug,” he said. That’s made infinitely trickier because the maximum effective dose can be 10 times higher than the minimum effective dose, said Dr. Bloom. “With a range that wide, it’s possibly for any individual to be outside of what we’d expect. This has become a Goldilocks story of not too much and not too little.”
Technological advancements now allow doctors to track more than your blood pressure or heart rate during surgery, which are indicators of your level of consciousness. If you’re feeling pain, your vitals will spike, alerting doctors in to the fact that you may be awake, even if you can’t move, Bloom said. These numbers, however, aren’t always reliable because medications such as beta blockers can prevent your BP from rising, Cohen noted. That’s why devices that measure your brain waves when you’re under anesthesia, such as the bispectral index (BIS) monitor, can be especially useful. These tell doctors how out of it the patient is, although, Cohen cautioned, they haven’t been proven to actually prevent awareness.
Even if you do wake up, the study suggests that simply being acknowledged by your doctor can mitigate the amount of distress you experience. “As soon as you hear someone say, ‘You’re OK. We’re going to give you some more drug now,’ then that awareness panic goes away,” Bloom said. That’s why the researchers recommend doctors speak to patients when awareness is suspected, reassuring them that they’re aware of their predicament. (They also remind practitioners to keep chit-chat professional during surgery, just in case the patient is, in fact, awake.)
CAN PREVENT AWARENESS UNDER ANESTHESIA?
What can you do to decrease your odds of waking up when you’re supposed to be conked out? Bloom suggests inquiring about the type of anesthetic you’re going to be given — and if it’s an IV anesthetic, asking whether a brain-function monitor will be used.
Another question to consider: Are muscle relaxers totally necessary? When patients had received a neuromuscular blocking agent, which, again, is the cause of panic-inducing paralysis, the incidence of awareness was approximately 1 in 8,000 cases. “Obviously, if there isn’t a muscle relaxant being used, you just start moving or clinching your fist to indicate that you’re awake,” Bloom said. During complicated procedures — such as abdominal, thoracic, and orthopedic surgeries — the meds are often necessary. But you may not need them for more superficial surgeries, such as those involving the skin or breasts, he said.
Even if you require a muscle relaxant, the experts overwhelmingly agree that anesthesia is safe — and awareness is unlikely. “Most important is that it really is very rare,” Bloom said. “So it’s not something to be terribly feared. The incidence is low enough that people shouldn’t be afraid to have surgery.”
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