Introduction
A category of drugs known as general anesthetics works by inhibiting the release of excitatory neurotransmitters and enhancing the release of inhibitory neurotransmitters to produce an unconscious state. These drugs affect numerous brain receptors, and they typically have reversible effects. However, there is a higher risk of neurotoxic side effects, such as memory loss and cognitive impairment, in specific patient populations. Some studies show histological evidence of apoptotic neuronal cell death and subsequent learning and memory impairment are two examples of the neurotoxic consequences shown in animals. Several cohort studies in newborns with serious co-morbidities who needed early-life surgery also showed aberrant neurodevelopmental outcomes.
What Is General Anesthesia?
General anesthesia is a reversible state of unconsciousness that cause amnesia and analgesia with or without reversible muscle paralysis. The most frequent uses of general anesthesia are for major operations such as heart surgeries, knee and hip replacements, and other cancer surgical treatments. Anesthesia allows a patient to endure operations that would otherwise cause intense pain, exacerbate severe physiologic chronic conditions, and leave them with unpleasant memories.
How Does General Anesthesia Work?
General anesthesia is administered by an anesthesiologist using a mask or an IV. Meanwhile, the patient's breathing is assisted by inserting the tube into the throat. The anesthesiologist will be monitoring breathing, heart rate, blood pressure, and other vital signs throughout the operation or surgery to make sure you stay asleep and pain-free. Just after the procedure comes to an end, the anesthesiologist will terminate the anesthesia to reverse the consciousness while continuously monitoring the oxygen, breathing, and circulation. Most individuals awaken feeling good, while others have symptoms like nausea, vomiting, or chills.
What Is Neurotoxicity?
The word "neurotoxicity" represents the impairment of the brain or peripheral nervous system brought on by exposure to toxic substances, either naturally occurring or created by humans including anesthetic drugs. These poisons can change the function of the nervous system, which is responsible for the transmission and processing of information in the brain and other parts of the nervous system. Additionally, the neurotoxin can harm specific areas or cellular components of the nervous system depending on its chemical components. The affected neurotransmitter, the stability of the cellular membrane, and the presence of detoxification mechanisms have an impact on the adverse effect of the body on neurotoxins.
What Is Anesthetic Neurotoxicity?
Anesthetic drugs affect numerous brain receptors, and are typically reversible with the adverse effect of neurotoxicity manifested with apoptotic neuronal cell death, subsequent learning, and memory impairment and also includes memory loss and cognitive impairment.
Anaesthetic Neurotoxicity About Pediatric Patients:
The commonly used anesthetic drugs, such as propofol, volatile anesthetics (isoflurane, desflurane, sevoflurane), Ketamine, benzodiazepines (Midazolam, Diazepam), and Phenobarbital, cause apoptosis, which causes the loss of neurons, decreased neurogenesis, and degeneration of neuronal mitochondria in the pediatric population. The anesthetic neurotoxicity is evident in the following research,
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Research of neonatal rat pups exposed to early anesthetics shown that frequent activation of N-methyl-D-aspartate (NMDA) receptors induced neuronal degeneration, which resulted in both the loss of brain cells and long-term impairment of cognitive function, persistent memory, and learning problems when exposed to midazolam, nitrous oxide, and isoflurane.
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When nitrous oxide and isoflurane were administered together, several studies found indications of brain cell death; however, there was no risk when each anesthetic was used alone. According to other studies, using isoflurane alone could make brain cells more susceptible to apoptosis. The risk of brain cell apoptosis appears to be enhanced overall by prolonged anesthetic exposure, the use of several drugs, and repeated dosages of medication.
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Although numerous research on animals has indicated adverse neurological effects following early anesthetic exposure, it has not been proven that this applies to people. Intelligence tests, memory, learning, motor and cognitive speeds, concentration, linguistics, behavior, and visuospatial function were not significantly different in a retrospective study that examined the effects of a single 20 to 240 minute anesthetic exposure in children less than three years of age.
Anaesthetic Neurotoxicity About the Elderly Patients:
Anesthetic drugs have been proven to have negative cognitive effects on the elderly individual. Two distinct syndromes develop after surgery are
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Postoperative Delirium (POD): Acute cognitive impairment known as POD often develops within days to weeks after being exposed to anesthesia. Postoperative delirium further distinguished into
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Mixed.
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Hypoactive.
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Hyperactive.
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In around 50 % of cases of delirium, hypoactive delirium manifested as a lack of responsiveness, slurred speech, and decreased mobility. In about 25 % of instances, hyperactive delirium manifested as hallucinations, illusions, delusions, and anxiety. Delirium may appear as a combination of hyperactive and hypoactive symptoms in the remaining 25 % of cases. Whereas dementia and pre-existing cognitive impairment were often manifested in elderly individuals of 50 years of age and above.
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Postoperative Cognitive Dysfunction (Pocd): POCD is also known as neurocognitive impairments which emerge within weeks to months after being exposed to anesthesia. POCD is also associated with one or more mental states, including focus, executive function, consciousness, ability to focus, cognitive training, and visuospatial power. A study revealed that 10 % to 25 % of patients around 60 experienced memory loss after three months of non-cardiac surgery and 25 % of individuals older than 60 had memory loss.
What Are the Clinical Effects of Anesthetic Neurotoxicity?
Neurotoxicity can have a wide range of effects and may appear immediately, while others develop after months or years. The effects of neurotoxicity depend on several variables, including the properties of the neurotoxin, the dose at which a patient was exposed, and age.
Anaesthetic Neurotoxicity in Pediatric Patients: Despite multiple studies demonstrating there is no significant variation in IQ between children exposed to anesthetics early in life. While at a younger age, the intensity of the postoperative complications, and pre-existing anxiety manifested in the patient or their parents act as the risk factors for these undesirable behavioral changes. The common clinical effect involves,
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Tantrums.
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Sleep disturbance.
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Learning difficulties.
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Cognitive impairments.
Anaesthetic Neurotoxicity in Elderly Patients: Postoperative cognitive dysfunction and postoperative delirium resulting from infection, diabetes (hypoglycemia), thiamine deficiency, unbalanced electrolytes, renal disease, drug interactions, and cardiac ischemia, can affect elderly people's cognitive function. The common clinical symptoms of neurotoxicity involve
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Weakness or paralysis of the limbs.
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Numbness, stinging, and impaired sensation in the limbs.
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Headache.
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Loss of vision.
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Uncontrolled behavior.
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Memory loss and cognitive impairment.
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Depression.
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Circulation deficit.
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Imbalance.
How to prevent Anaesthetic Neurotoxicity?
There are two methods for reducing the incidence of anesthetic neurotoxicity in the juvenile population.
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Postponing of elective procedures.
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Administering xenon or dexmedetomidine infusions is used to reduce exposure to anesthetic drugs, which have been demonstrated to produce anesthetic neurotoxicity.
In the elderly population development of the postoperative cognitive disorder (POCD) and postoperative delirium (POD) is prevented by
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Management of cerebral perfusion.
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Restricted volatile anesthetic administration by employing age-adjusted MAC (monitored anesthesia care).
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Intraoperative EEG (electroencephalogram) monitoring.
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Reorientation techniques involve the use of clocks, calendars, room lighting, and windows.
Conclusion
Patients of all ages, including children and the elderly, are affected by anesthetic neurotoxicity. To reduce anesthetic exposure as much as possible, the healthcare team, which includes the surgeon, anesthesiologist, and nursing staff, is under research to reduce the risk factors. Age less than three or older than 65, previous anesthetic exposures, prolonged anesthetic exposure, baseline cognitive impairment, or dementia are risk factors with an increased chance of neurotoxicity.
