Anesthesia Awareness During Surgery - A Rare But Potentially Horrifying Occurrence
The thought of being wide awake, unable to speak or move a muscle, while having major surgery performed is terrifying, more so because it has happened before an almost certainly will happen to someone again.
The fact that its occurrence is less than 0.
5% doesn't help the psyche much, especially if you are a patient in the pre-op holding area contemplating their day ahead.
When given a general anesthesia a patient is administered a 'cocktail' of drugs most often including a mixture of: an induction agent such as propofol or sodium pentathol (the initial drug that puts you to sleep), an opiate such as fentanyl or sufentanyl, which provides analgesia (blunts the pain) as well as having a synergistic effect on the induction agent, a benzodiazepine, most commonly midazolam, which reduces anxiety and also has a synergistic effect on both the induction agent and the opiate, and finally a neuromuscular blocking agent such as succinycholine, vecuronium, rocuronium, and others.
Once asleep, the patient is most often kept asleep by breathing a vaporized liquid anesthetic such as isoflurane or desflurane mixed with oxygen, room air and sometimes nitrous oxide.
Total Intravenous Anesthesia is also a valid and effective technique where the patient is kept asleep using an infusion of IV drugs (propofol or sufentanyl for example).
Most often, perhaps >95% of the time, general anesthesia is maintained by a mixture of an inhalation anesthetic and intermittent doses of an opiate (the Balanced Anesthesia Technique).
The neuromuscular blocking agent does not affect consciousness, but does completely paralyze the patient.
The paralysis is the desired affect and the only reason these drugs are used.
It facilitates the insertion of a breathing tube and control of the patient's respiration (all of the previously mentioned anesthesia agents cause breathing to slow or cease at anesthetic doses).
Now that you know all about the anesthesia process, it is easy to immediately identify at least one obvious situation where a patient would be awake, unable to move or speak, while still being able to feel all the pain of surgery: the neuromuscular blocking agent is working, while the anesthetic is insufficient (has worn off and the current doses are inadequate to maintain the anesthetic state, whether due to an unusual patient tolerance or human or mechanical error such as an empty or malfunctioning inhalation anesthesia vaporizer).
All general anesthesia patients have specific continuous, standard monitoring of physiologic systems such as blood pressure, heart rate, respiratory rate, expired carbon dioxide and blood oxygen saturation.
When anesthesia 'lightens' most patients will exhibit an increase in blood pressure and heart rate well before they become conscious and the anesthetic is adjusted appropriately.
Expired inhalation anesthetic is also measured confirming adequate dosing.
Also widely available but not as yet standard is the use of a Bispectral Index Monitoring (BIS) where sticky pads are applied to the forehead and attached to a monitor which applies a novel algorithmic analysis of the patients EEG and then produces a quantitative wave form which allows determination of level of consciousness.
The theory is that the BIS will identify patients whose anesthetic is inadequate before they would wake up, thus preventing Anesthesia Awareness as well as refining the 'art' of anesthesia to a more exacting process.
Unfortunately some large patient studies have not shown that using BIS lowers the incidence of memory of events during anesthesia.
Certain subsets of patients are more prone to Anesthesia Awareness because of their current medical condition.
Trauma patients and other patients with dangerously low blood pressures cannot tolerate usual doses of anesthesia, yet require emergency life saving surgery.
Alternative IV drugs which have less effect on blood pressure such as ketamine and etomidate, can be employed as alternatives in some of these patients to produce unconsciousness without killing them...
which a typical general anesthetic would do.
Female patients requiring emergency c-section cannot be given usual doses of general anesthesia since the drugs readily cross into the blood stream of the fetus until the umbilical cord is clamped.
A balance must always be struck between patient safety and anesthetic administered.
Anesthesia Awareness is relatively rare, but has tremendous lingering psychological effects of many who experience it.
Severity depends on level and length of awareness combined with amount of pain and discomfort felt.
"If anesthesia awareness does occur about 42% feel the pain of the operation, 94% experience panic/anxiety and 70% experience lasting psychological symptoms".
N.
Moerman et al.
,Anesthesiology;79:454-464, 1993 Anesthesia Awareness is not necessarily predictive of malpractice as it occurs absent avoidable error.
The 2007 movie "Awake" centered on a man who had Anesthesia Awareness during surgery when he heard a plot to murder him being hatched.
Then award winning horror flick "Anesthesia", whose entire plot was based on a woman experiencing Anesthesia Awareness during heart surgery, was made in 2006.
The fact that its occurrence is less than 0.
5% doesn't help the psyche much, especially if you are a patient in the pre-op holding area contemplating their day ahead.
When given a general anesthesia a patient is administered a 'cocktail' of drugs most often including a mixture of: an induction agent such as propofol or sodium pentathol (the initial drug that puts you to sleep), an opiate such as fentanyl or sufentanyl, which provides analgesia (blunts the pain) as well as having a synergistic effect on the induction agent, a benzodiazepine, most commonly midazolam, which reduces anxiety and also has a synergistic effect on both the induction agent and the opiate, and finally a neuromuscular blocking agent such as succinycholine, vecuronium, rocuronium, and others.
Once asleep, the patient is most often kept asleep by breathing a vaporized liquid anesthetic such as isoflurane or desflurane mixed with oxygen, room air and sometimes nitrous oxide.
Total Intravenous Anesthesia is also a valid and effective technique where the patient is kept asleep using an infusion of IV drugs (propofol or sufentanyl for example).
Most often, perhaps >95% of the time, general anesthesia is maintained by a mixture of an inhalation anesthetic and intermittent doses of an opiate (the Balanced Anesthesia Technique).
The neuromuscular blocking agent does not affect consciousness, but does completely paralyze the patient.
The paralysis is the desired affect and the only reason these drugs are used.
It facilitates the insertion of a breathing tube and control of the patient's respiration (all of the previously mentioned anesthesia agents cause breathing to slow or cease at anesthetic doses).
Now that you know all about the anesthesia process, it is easy to immediately identify at least one obvious situation where a patient would be awake, unable to move or speak, while still being able to feel all the pain of surgery: the neuromuscular blocking agent is working, while the anesthetic is insufficient (has worn off and the current doses are inadequate to maintain the anesthetic state, whether due to an unusual patient tolerance or human or mechanical error such as an empty or malfunctioning inhalation anesthesia vaporizer).
All general anesthesia patients have specific continuous, standard monitoring of physiologic systems such as blood pressure, heart rate, respiratory rate, expired carbon dioxide and blood oxygen saturation.
When anesthesia 'lightens' most patients will exhibit an increase in blood pressure and heart rate well before they become conscious and the anesthetic is adjusted appropriately.
Expired inhalation anesthetic is also measured confirming adequate dosing.
Also widely available but not as yet standard is the use of a Bispectral Index Monitoring (BIS) where sticky pads are applied to the forehead and attached to a monitor which applies a novel algorithmic analysis of the patients EEG and then produces a quantitative wave form which allows determination of level of consciousness.
The theory is that the BIS will identify patients whose anesthetic is inadequate before they would wake up, thus preventing Anesthesia Awareness as well as refining the 'art' of anesthesia to a more exacting process.
Unfortunately some large patient studies have not shown that using BIS lowers the incidence of memory of events during anesthesia.
Certain subsets of patients are more prone to Anesthesia Awareness because of their current medical condition.
Trauma patients and other patients with dangerously low blood pressures cannot tolerate usual doses of anesthesia, yet require emergency life saving surgery.
Alternative IV drugs which have less effect on blood pressure such as ketamine and etomidate, can be employed as alternatives in some of these patients to produce unconsciousness without killing them...
which a typical general anesthetic would do.
Female patients requiring emergency c-section cannot be given usual doses of general anesthesia since the drugs readily cross into the blood stream of the fetus until the umbilical cord is clamped.
A balance must always be struck between patient safety and anesthetic administered.
Anesthesia Awareness is relatively rare, but has tremendous lingering psychological effects of many who experience it.
Severity depends on level and length of awareness combined with amount of pain and discomfort felt.
"If anesthesia awareness does occur about 42% feel the pain of the operation, 94% experience panic/anxiety and 70% experience lasting psychological symptoms".
N.
Moerman et al.
,Anesthesiology;79:454-464, 1993 Anesthesia Awareness is not necessarily predictive of malpractice as it occurs absent avoidable error.
The 2007 movie "Awake" centered on a man who had Anesthesia Awareness during surgery when he heard a plot to murder him being hatched.
Then award winning horror flick "Anesthesia", whose entire plot was based on a woman experiencing Anesthesia Awareness during heart surgery, was made in 2006.
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