Xenon (Xe) has been found to have anesthetic effect for more than 50 years. Xenon is highly valued in medical treatment. Xenon can dissolve in the oil of cells, causing anesthesia and expansion of cells, thus temporarily stopping the effect of nerve endings. A mixture of 80% xenon and 20% oxygen by volume fraction has been used as an anesthetic without side effects.
However, its clinical application is limited due to its rare content in the atmosphere and high production cost. In recent years, a series of clinical studies have confirmed that xenon inhalation anesthesia is safe and effective, with excellent pharmacokinetics, analgesic effect, high safety performance, and good cardio cerebral vascular protection. It has broad clinical application prospects. Xenon is absolutely the most ideal anesthetic at present.
When used for anesthesia, its blood gas partition coefficient is 0.14, oil gas partition coefficient is 1.9, and MAC value (human) is 0.71. Xenon is difficult to obtain or lose electrons to form covalent bonds, and xenon halides, such as XeF2 and XeF4, can be formed only under extreme non biological conditions. In conclusion, xenon has the following physicochemical and pharmacological characteristics:
*Chemical properties are highly stable;
*Will not burn or explode;
*Low solubility in blood tissue;
*No reaction with various surgical materials;
*No metabolites are produced in the body;
*The toxicity of tissues and organs is low.
Characteristics of xenon anesthesia
Induce quick awakening:
During xenon inhalation anesthesia, its blood gas partition coefficient was 0.14, which was lower than other inhalation anesthetics, such as desflurane 0.42, isoflurane 1.4, nitrous oxide 0.47. Its induction time was very short, only 71 seconds. The recovery time of xenon anesthesia is about 2/3 shorter than that of nitrous oxide/isoflurane or nitrous oxide/7halothane with the same MAC concentration. Even if it is used for long operation, the recovery time of anesthesia will not be prolonged. The recovery time of xenon anesthesia was significantly shorter than that of propofol at the same anesthesia depth. Therefore, the rapid induction and recovery of xenon inhalation anesthesia can be safely applied not only to LC and other short operations, but also to outpatient operations. At the same time, because of its good analgesic and organ protective effects, it is also conducive to the "fast track" cardiac surgery anesthesia and the stability of cardiovascular function.
Myocardial protection:
Xenon has little effect on cardiovascular system. Under inhalation anesthesia, hemodynamics is stable, and ECG, cardiac index, blood pressure, etc. have no significant changes. The isolated guinea pig heart experiment showed that 40-80% xenon did not change heart rate, atrioventricular conduction time, left ventricular pressure, coronary blood flow, oxygen supply and oxygen consumption significantly. Xenon has myocardial protective effect: in the rabbit model of local myocardial ischemia/reperfusion, xenon can reduce the myocardial infarction area during reperfusion. Xenon can produce myocardial protection through preconditioning mechanism (that is, the application of stimulators or emergency agents in advance can protect against later damage), and ischemic preconditioning can protect myocardial tissue from forming infarct focus in the short-term non fatal ischemic stage. The experimental results show that PKC and p38 MAPK are the key media for xenon preconditioning; Other experiments have shown that xenon can also produce delayed myocardial protection similar to delayed adaptation after ischemia. The molecular mechanism of xenon is still unknown, and further research is needed.
It has analgesic effect:
Xenon has analgesic effect. Under xenon anesthesia, the amount of fentanyl required for analgesia is greatly reduced compared with nitrous oxide anesthesia. In the rat model of spinal cord transection injury, xenon can directly inhibit the nociceptive response of the dorsal horn of the spinal cord. Ohara et al. reported that the analgesic effect of xenon does not depend on opioid or adrenergic receptors. At the same time, xenon can activate the mesencephalic reticular system, which may mean that it may also have analgesic effect at the level above the spinal cord. The current research shows that xenon has different analgesic mechanism from other inhalation anesthetics, which may be produced by inhibiting NMDA receptor.
Neuroprotective effect:
NMDA receptor plays an important role in the occurrence and development of acute nerve injury. Therefore, many scholars believe that NMDA receptor antagonists can block the pathophysiological process of acute nerve injury. A series of in vitro and in vivo animal model tests showed that xenon is a powerful neuroprotective drug. When the concentration is lower than the anesthetic concentration, xenon IC50 in some animal models is even only 10-20% of 1 atmosphere, which has obvious anti injury protection effect. Xenon can alleviate the acute injury of the combined neuroglial cell culture system after exogenous neurotoxin or oxygen glucose deprivation. Xenon can prevent the morphological and functional changes of acute nerve injury caused by ischemia (middle cerebral artery occlusion method), cardiopulmonary bypass and neurotoxin.
Low toxic and side effects:
As an inert gas, xenon hardly participates in any chemical reaction. It does not undergo biotransformation in the body, and it still exhales through the lung in the original form after inhalation anesthesia. Froeba G and other studies have shown that xenon does not trigger malignant hyperthermia. Burov N and others reported that xenon had no evidence of toxic reaction; Animal experiments showed that xenon had no mutagenicity or carcinogenicity. Xenon does not destroy the ozone layer, produce greenhouse effect, burn or explode after being discharged into the atmosphere, and has little impact on the ecological environment.
Xenon is not irritating to respiratory tract, and 70% xenon+30% oxygen can be used for anesthesia maintenance. Xenon inhalation does not affect lung compliance, so it can be applied to elderly patients with chronic lung diseases. Xenon inhalation anesthesia should be prohibited for patients with intestinal obstruction because xenon can be trapped in visceral hollow organs, intestinal cavity and adipose tissue.
Xenon can erase part of brain memory
According to the Daily Science website, researchers at McLean Hospital reported the latest scientific research results that xenon may be able to treat post-traumatic stress disorder (PTSD) and other diseases.
Edward G. Meloni, assistant professor of psychiatry at Harvard Medical School and assistant psychologist at McLean Hospital, said: "In the study, we found that xenon has the ability to reduce the memory of traumatic events. This is an exciting breakthrough, because it may become a new treatment for post-traumatic stress disorder."
This research was published in the latest issue of PLoS One. Meloni and Dr. Marc J. Kaufman, the director of the transformation imaging laboratory of McLean Hospital, studied whether low concentration xenon would interfere with the process of "reconsolidation" - reactivating memory and making it easier to modify. Meloni explained: "From previous studies, we know that every time an emotional memory is aroused, the brain will actually restore it as a new memory. Based on these conditions, we decided whether to test whether the process could be adjusted by introducing xenon immediately after the fear memory was reactivated.
The researchers used an animal model of PTSD in a state of fear to train mice to fear environmental factors, and at the same time, they used a simple plantar electric shock. Then, the mice were placed again in the same environmental factors to awaken fear memories, and their frozen feedback was measured to measure the degree of fear.
Dr Meloni said: "We found that exposure to xenon can block NMDA receptors from participating in brain memory formation, which can significantly reduce memory for up to two weeks, as if frightened animals no longer remember these." Meloni pointed out that the inherent properties of xenon and other gases are ideal therapeutic materials. Because xenon can quickly enter and exit the brain, accurately intervene the time when the brain evokes memories, and accurately control the dosage.
Xenon "lights up" the lungs
"Light up" the corners of the lungs, not only "understand" the information of gas and gas exchange in the lungs, but also "capture" the information of gas and blood exchange, so as to early discover and comprehensively evaluate the lung function. Absorb xenon and wear the vest. At present, there is no clinical imaging equipment that can visually detect the pulmonary gas exchange function without invasion and radiation, which hinders the early diagnosis and treatment of pulmonary diseases.
The detection process of "bright lung" is fast, and the patient will be comfortable without injection and intervention. The hyperpolarized xenon (xenon-129) is prepared and sealed in a bag. Just like drinking milk, the patient needs to inhale xenon and hold his breath. Then put on a 'little vest', and after a few seconds of scanning, you can obtain the magnetic resonance image. Faster than X-rays! The "vest" is equivalent to a mobile phone, helping to receive signals from the lungs. The hyperpolarized gas signal is very strong, and 8 magnetic resonance images of different sections of the lung can be obtained in about 6 seconds; Single image time is shorter. Hyperpolarization, commonly understood, is to enhance the strength of the gas signal. This technology is called hyperpolarized gas magnetic resonance technology of human lung. The magnetic resonance signal can be enhanced 44000 times through "two steps", so as to "light up" the lung. This technology is for the diagnosis of lung diseases and the relief of patients' pain. The gas contrast agent must be non-toxic and harmless. Xenon is an inert gas, similar to nitrogen in air. People normally breathe oxygen and nitrogen. In the detection, it is equivalent to replacing nitrogen with xenon, non-toxic and harmless, and there is no biological background noise.
Xenon (Xe) has been found to have anesthetic effect for more than 50 years. Xenon is highly valued in medical treatment. Xenon can dissolve in the oil of cells, causing anesthesia and expansion of cells, thus temporarily stopping the effect of nerve endings. A mixture of 80% xenon and 20% oxygen by volume fraction has been used as an anesthetic without side effects.
However, its clinical application is limited due to its rare content in the atmosphere and high production cost. In recent years, a series of clinical studies have confirmed that xenon inhalation anesthesia is safe and effective, with excellent pharmacokinetics, analgesic effect, high safety performance, and good cardio cerebral vascular protection. It has broad clinical application prospects. Xenon is absolutely the most ideal anesthetic at present.
When used for anesthesia, its blood gas partition coefficient is 0.14, oil gas partition coefficient is 1.9, and MAC value (human) is 0.71. Xenon is difficult to obtain or lose electrons to form covalent bonds, and xenon halides, such as XeF2 and XeF4, can be formed only under extreme non biological conditions. In conclusion, xenon has the following physicochemical and pharmacological characteristics:
*Chemical properties are highly stable;
*Will not burn or explode;
*Low solubility in blood tissue;
*No reaction with various surgical materials;
*No metabolites are produced in the body;
*The toxicity of tissues and organs is low.
Characteristics of xenon anesthesia
Induce quick awakening:
During xenon inhalation anesthesia, its blood gas partition coefficient was 0.14, which was lower than other inhalation anesthetics, such as desflurane 0.42, isoflurane 1.4, nitrous oxide 0.47. Its induction time was very short, only 71 seconds. The recovery time of xenon anesthesia is about 2/3 shorter than that of nitrous oxide/isoflurane or nitrous oxide/7halothane with the same MAC concentration. Even if it is used for long operation, the recovery time of anesthesia will not be prolonged. The recovery time of xenon anesthesia was significantly shorter than that of propofol at the same anesthesia depth. Therefore, the rapid induction and recovery of xenon inhalation anesthesia can be safely applied not only to LC and other short operations, but also to outpatient operations. At the same time, because of its good analgesic and organ protective effects, it is also conducive to the "fast track" cardiac surgery anesthesia and the stability of cardiovascular function.
Myocardial protection:
Xenon has little effect on cardiovascular system. Under inhalation anesthesia, hemodynamics is stable, and ECG, cardiac index, blood pressure, etc. have no significant changes. The isolated guinea pig heart experiment showed that 40-80% xenon did not change heart rate, atrioventricular conduction time, left ventricular pressure, coronary blood flow, oxygen supply and oxygen consumption significantly. Xenon has myocardial protective effect: in the rabbit model of local myocardial ischemia/reperfusion, xenon can reduce the myocardial infarction area during reperfusion. Xenon can produce myocardial protection through preconditioning mechanism (that is, the application of stimulators or emergency agents in advance can protect against later damage), and ischemic preconditioning can protect myocardial tissue from forming infarct focus in the short-term non fatal ischemic stage. The experimental results show that PKC and p38 MAPK are the key media for xenon preconditioning; Other experiments have shown that xenon can also produce delayed myocardial protection similar to delayed adaptation after ischemia. The molecular mechanism of xenon is still unknown, and further research is needed.
It has analgesic effect:
Xenon has analgesic effect. Under xenon anesthesia, the amount of fentanyl required for analgesia is greatly reduced compared with nitrous oxide anesthesia. In the rat model of spinal cord transection injury, xenon can directly inhibit the nociceptive response of the dorsal horn of the spinal cord. Ohara et al. reported that the analgesic effect of xenon does not depend on opioid or adrenergic receptors. At the same time, xenon can activate the mesencephalic reticular system, which may mean that it may also have analgesic effect at the level above the spinal cord. The current research shows that xenon has different analgesic mechanism from other inhalation anesthetics, which may be produced by inhibiting NMDA receptor.
Neuroprotective effect:
NMDA receptor plays an important role in the occurrence and development of acute nerve injury. Therefore, many scholars believe that NMDA receptor antagonists can block the pathophysiological process of acute nerve injury. A series of in vitro and in vivo animal model tests showed that xenon is a powerful neuroprotective drug. When the concentration is lower than the anesthetic concentration, xenon IC50 in some animal models is even only 10-20% of 1 atmosphere, which has obvious anti injury protection effect. Xenon can alleviate the acute injury of the combined neuroglial cell culture system after exogenous neurotoxin or oxygen glucose deprivation. Xenon can prevent the morphological and functional changes of acute nerve injury caused by ischemia (middle cerebral artery occlusion method), cardiopulmonary bypass and neurotoxin.
Low toxic and side effects:
As an inert gas, xenon hardly participates in any chemical reaction. It does not undergo biotransformation in the body, and it still exhales through the lung in the original form after inhalation anesthesia. Froeba G and other studies have shown that xenon does not trigger malignant hyperthermia. Burov N and others reported that xenon had no evidence of toxic reaction; Animal experiments showed that xenon had no mutagenicity or carcinogenicity. Xenon does not destroy the ozone layer, produce greenhouse effect, burn or explode after being discharged into the atmosphere, and has little impact on the ecological environment.
Xenon is not irritating to respiratory tract, and 70% xenon+30% oxygen can be used for anesthesia maintenance. Xenon inhalation does not affect lung compliance, so it can be applied to elderly patients with chronic lung diseases. Xenon inhalation anesthesia should be prohibited for patients with intestinal obstruction because xenon can be trapped in visceral hollow organs, intestinal cavity and adipose tissue.
Xenon can erase part of brain memory
According to the Daily Science website, researchers at McLean Hospital reported the latest scientific research results that xenon may be able to treat post-traumatic stress disorder (PTSD) and other diseases.
Edward G. Meloni, assistant professor of psychiatry at Harvard Medical School and assistant psychologist at McLean Hospital, said: "In the study, we found that xenon has the ability to reduce the memory of traumatic events. This is an exciting breakthrough, because it may become a new treatment for post-traumatic stress disorder."
This research was published in the latest issue of PLoS One. Meloni and Dr. Marc J. Kaufman, the director of the transformation imaging laboratory of McLean Hospital, studied whether low concentration xenon would interfere with the process of "reconsolidation" - reactivating memory and making it easier to modify. Meloni explained: "From previous studies, we know that every time an emotional memory is aroused, the brain will actually restore it as a new memory. Based on these conditions, we decided whether to test whether the process could be adjusted by introducing xenon immediately after the fear memory was reactivated.
The researchers used an animal model of PTSD in a state of fear to train mice to fear environmental factors, and at the same time, they used a simple plantar electric shock. Then, the mice were placed again in the same environmental factors to awaken fear memories, and their frozen feedback was measured to measure the degree of fear.
Dr Meloni said: "We found that exposure to xenon can block NMDA receptors from participating in brain memory formation, which can significantly reduce memory for up to two weeks, as if frightened animals no longer remember these." Meloni pointed out that the inherent properties of xenon and other gases are ideal therapeutic materials. Because xenon can quickly enter and exit the brain, accurately intervene the time when the brain evokes memories, and accurately control the dosage.
Xenon "lights up" the lungs
"Light up" the corners of the lungs, not only "understand" the information of gas and gas exchange in the lungs, but also "capture" the information of gas and blood exchange, so as to early discover and comprehensively evaluate the lung function. Absorb xenon and wear the vest. At present, there is no clinical imaging equipment that can visually detect the pulmonary gas exchange function without invasion and radiation, which hinders the early diagnosis and treatment of pulmonary diseases.
The detection process of "bright lung" is fast, and the patient will be comfortable without injection and intervention. The hyperpolarized xenon (xenon-129) is prepared and sealed in a bag. Just like drinking milk, the patient needs to inhale xenon and hold his breath. Then put on a 'little vest', and after a few seconds of scanning, you can obtain the magnetic resonance image. Faster than X-rays! The "vest" is equivalent to a mobile phone, helping to receive signals from the lungs. The hyperpolarized gas signal is very strong, and 8 magnetic resonance images of different sections of the lung can be obtained in about 6 seconds; Single image time is shorter. Hyperpolarization, commonly understood, is to enhance the strength of the gas signal. This technology is called hyperpolarized gas magnetic resonance technology of human lung. The magnetic resonance signal can be enhanced 44000 times through "two steps", so as to "light up" the lung. This technology is for the diagnosis of lung diseases and the relief of patients' pain. The gas contrast agent must be non-toxic and harmless. Xenon is an inert gas, similar to nitrogen in air. People normally breathe oxygen and nitrogen. In the detection, it is equivalent to replacing nitrogen with xenon, non-toxic and harmless, and there is no biological background noise.
