The incidence of anesthesia awareness is higher and has more serious sequelae when muscle relaxants or neuromuscular-blocking drugs are used. This is because without relaxant the patient will move and the anesthesiologist will deepen the anesthesia.

One study has indicated this phenomenon occurs in about 1 or 2 per 1000 patients or 0.13%. There is conflicting data however as another study suggested it is a rare phenomenon, with an incidence of 0.0068% after review of their data from a patient population of 211,842 patients.

Post operative interview by an anesthetist is common practice to elucidate if awareness occurred in the case. If awareness is reported a case review is immediately performed to identify machine, medication, or operator error.

Human errors include repeated attempts at intubation during which the short-acting anesthesic may wear off but the paralysing drug has not, oesophageal intubation, inadequate drug dose, drug given by the wrong route or wrong drug given, drugs given in the wrong sequence, inadequate monitoring, patient abandonment, disconnections and kinks in tubes from the ventilator, and failure to refill the anesthetic machine's vaporizers with volatile anesthetic. Other causes of awareness include unfamiliarity with techniques used, e.g. intravenous anesthetic regimes, or inexperience. Most cases of awareness are caused by inexperience and poor anesthetic technique, which can be any of the above, but also includes techniques that could be described as outside the boundaries of "normal" practice. The American Society of Anesthesiologists recently released a Practice Advisory outlining the steps that anesthesia professionals and hospitals should take to minimize these risks. Other societies have released their own versions of these guidelines, including the Australian and New Zealand College of Anaesthetists.

Machine malfunction or misuse may result in an inadequate delivery of anesthetic. Many Boyle's machines used in many hospitals have the oxygen regulator serving as a slave to the pressure in the nitrous oxide regulator, to enable the nitrous oxide cut-off safety feature. If nitrous oxide delivery suffers due to a leak in its regulator or tubing, an 'inadequate' mixture can be delivered to the patient, causing awareness. Many World War II vintage Boyle 'F' models are still functional and used in UK hospitals. Their emergency oxygen flush valves have a tendency to release oxygen into the breathing system, which when added to the mixture set by the anesthesiologist, can lead to awareness. This may also be caused by an empty vaporizer (or nitrous oxide cylinder) or a malfunctioning intravenous pump or disconnection of its delivery tubing. Patient abandonment, when the anesthesiologist leaves, causes some cases of awareness and death.

To reduce the likelihood of awareness, anesthetists must be adequately trained and supervised while still in training. Equipment that monitors depth of anesthesia, such as bispectral index monitoring, should not be used in isolation.

There is limited evidence that the hypnotic drug zolpidem has an effect. The results of the few scientific studies that have been published so far on the effectiveness of zolpidem have been contradictory.

Currently no treatment for vegetative state exists that would satisfy the efficacy criteria of evidence-based medicine. Several methods have been proposed which can roughly be subdivided into four categories: pharmacological methods, surgery, physical therapy, and various stimulation techniques. Pharmacological therapy mainly uses activating substances such as tricyclic antidepressants or methylphenidate. Mixed results have been reported using dopaminergic drugs such as amantadine and bromocriptine and stimulants such as dextroamphetamine. Surgical methods such as deep brain stimulation are used less frequently due to the invasiveness of the procedures. Stimulation techniques include sensory stimulation, sensory regulation, music and musicokinetic therapy, social-tactile interaction, and cortical stimulation.

The body's inflammatory response to surgery likely plays an important role, at least in elderly patients. Various research initiatives during recent years have evaluated whether actions taken before, during and after surgery can lessen the possible deleterious effects of inflammation. For example, anti-inflammatory agents can be given before surgery. During surgery, inflammation can be modulated by temperature control, use of regional rather than general anesthesia or the use of beta blockers. After surgery, optimal pain management and infection control is important. Several studies have shown variable-significance positive effects when a multidisciplinary, multifactorial approach to elderly patient is followed during pre, peri and post-operative care.

Animal studies indicate that volatile anaesthestics may augment the pathological processes of Alzheimer's Disease by affecting amyloid-beta processing. However, in young healthy mice, the volatile anesthetic isoflurane can also produce long-lasting memory impairment. This adverse effect is preventable by pre-administering the GABA(A)α5 inverse agonist L-655,708.

There is currently no definitive evidence that support altering the course of the recovery of minimally conscious state. There are currently multiple clinical trials underway investigating potential treatments.

In one case study, stimulation of thalamus using deep brain stimulation (DBS) led to some behavioral improvements. The patient was a 38-year-old male who had remained in minimally conscious state following a severe traumatic brain injury. He had been unresponsive to consistent command following or communication ability and had remained non-verbal over two years in inpatient rehabilitation. fMRI scans showed preservation of a large-scale, bi-hemispheric cerebral language network, which indicates that possibility for further recovery may exist. Positron emission tomography showed that the patient's global cerebral metabolism levels were markedly reduced. He had DBS electrodes implanted bilaterally within his central thalamus. More specifically, the DBS electrodes targeted the anterior intralaminar nuclei of thalamus and adjacent paralaminar regions of thalamic association nuclei. Both electrodes were positioned within the central lateral nucleus, the paralaminar regions of the median dorsalis, and the posterior-medial aspect of the centromedian/parafasicularis nucleus complex. This allowed maximum coverage of the thalamic bodies. A DBS stimulation was conducted such that the patient was exposed to various patterns of stimulation to help identify optimal behavioral responses. Approximately 140 days after the stimulation began, qualitative changes in behavior emerged. There were longer periods of eye opening and increased responses to command stimuli as well as higher scores on the JFK coma recovery scale (CRS). Functional object use and intelligible verbalization was also observed. The observed improvements in arousal level, motor control, and consistency of behavior could be a result of direct activation of frontal cortical and basal ganglia systems that were innervated by neurons within the thalamic association nuclei. These neurons act as a key communication relay and form a pathway between the brainstem arousal systems and frontal lobe regions. This pathway is crucial for many executive functions such as working memory, effort regulation, selective attention, and focus.

In another case study of a 50-year-old woman who had symptoms consistent with MCS, administration of zolpidem, a sedative hypnotic drug improved the patient's condition significantly. Without treatment, the patient showed signs of mutism, athetoid movements of the extremities, and complete dependence for all personal care. 45 minutes after 5 to 10 mg of zolpidem was administered, the patient ceased the athetoid movements, regained speaking ability, and was able to self-feed. The effect lasted 3–4 hours from which she returned to the former state. The effects were repeated on a daily basis. PET scans showed that after zolpidem was administered, there was a marked increase in blood flow to areas of the brain adjacent to or distant from damaged tissues. In this case, these areas were the ipsilateral cerebral hemispheres and the cerebellum. These areas are thought to have been inhibited by the site of injury through a GABA-mediated mechanism and the inhibition was modified by zolpidem which is a GABA agonist. The fact that zolpidem is a sedative drug that induces sleep in normal people but causes arousal in a MCS patient is paradoxical. The mechanisms to why this effect occurs is not entirely clear.

There is recent evidence that transcranial direct current stimulation (tDCS), a technique that supplies a small electric current in the brain with non-invasive electrodes, may improve the clinical state of patients with MCS. In one study with 10 patients with disorders of consciousness (7 in VS, 3 in MCS), tDCS was applied for 20 minutes every day for 10 days, and showed clinical improvement in all 3 patients who were in MCS, but not in those with VS. These results remained at 12-month follow-up. Two of the patients in MCS that had their brain insult less that 12 months recovered consciousness in the following months. One of these patients received a second round of tDCS treatment 4 months after his initial treatment, and showed further recovery and emerged into consciousness, with no change of clinical status between the two treatments. Moreover, in a sham-controlled, double-blind crossover study, the immediate effects of a single session of tDCS were shown to transiently improve the clinical status of 13 out of 30 patients with MCS, but not in those with VS

One of the defining characteristics of minimally conscious state is the more continuous improvement and significantly more favorable outcomes post injury when compared with vegetative state. One study looked at 100 patients with severe brain injury. At the beginning of the study, all the patients were unable to follow commands consistently or communicate reliably. These patients were diagnosed with either MCS or vegetative state based on performance on the JFK Coma Recovery Scale and the diagnostic criteria for MCS as recommended by the Aspen Consensus Conference Work-group. Both patient groups were further separated into those that suffered from traumatic brain injury and those that suffered from non-traumatic brain injures (anoxia, tumor, hydrocephalus, infection). The patients were assessed multiple times over a period of 12 months post injury using the Disability Rating Scale (DRS) which ranges from a score of 30=dead to 0=no disabilities. The results show that the DRS scores for the MCS subgroups showed the most improvement and predicted the most favorable outcomes 12 months post injury. Amongst those diagnosed with MCS, DRS scores were significantly lower for those with non-traumatic brain injuries in comparison to the vegetative state patients with traumatic brain injury. DRS scores were also significantly lower for the MCS non-traumatic brain injury group compared to the MCS traumatic brain injury group. Pairwise comparisons showed that DRS scores were significantly higher for those that suffered from non-tramuatic brain injuries than those with traumatic brain injuries. For the patients in vegetative states there were no significant differences between patients with non-traumatic brain injury and those with traumatic brain injuries. Out of the 100 patients studied, 3 patients fully recovered (had a DRS score of 0). These 3 patients were diagnosed with MCS and had suffered from traumatic brain injuries.

In summary, those with minimally conscious state and non-traumatic brain injuries will not progress as well as those with traumatic brain injuries while those in vegetative states have an all around lower to minimal chance of recovery.

Because of the major differences in prognosis described in this study, this makes it crucial that MCS be diagnosed correctly. Incorrectly diagnosing MCS as vegetative state may lead to serious repercussions related to clinical management.

Disorders of consciousness are medical conditions that inhibit consciousness. Some define disorders of consciousness as any change from complete self-awareness to inhibited or absent self-awareness and arousal. This category generally includes minimally conscious state and persistent vegetative state, but sometimes also includes the less severe locked-in syndrome and more severe but rare chronic coma. Differential diagnosis of these disorders is an active area of biomedical research. Finally, brain death results in an irreversible disruption of consciousness. While other conditions may cause a moderate deterioration (e.g., dementia and delirium) or transient interruption (e.g., grand mal and petit mal seizures) of consciousness, they are not included in this category.

POCD is common after cardiac surgery, and recent studies have now verified that POCD also exists after major non-cardiac surgery, although at a lower incidence. The risk of POCD increases with age, and the type of surgery is also important because there is a very low incidence associated with minor surgery. POCD is common in adult patients of all ages at hospital discharge after major noncardiac surgery, but only the elderly (aged 60 years or older) are at significant risk for long-term cognitive problems. Patients with POCD are at an increased risk of death in the first year after surgery. Research interest has increased since early 2000, especially as more elderly patients are able to undergo successful minor and major surgeries.

POCD has been studied through various institutions since the inception of the IPOCDS-I study centred in Eindhoven, Netherlands and Copenhagen, Denmark. This study found no causal relationship between cerebral hypoxia and low blood pressure and POCD. Age, duration of anaesthesia, introperative complications, and postoperative infections were found to be associated with POCD.

- POCD is just as likely to occur after operations under regional anesthesia as under general anesthesia.

- More likely after major operations than minor operations.

- More likely after heart operations than other types of surgery.

- More likely in aged than in younger patients.

- More likely in older patients with high alcohol intake/abuse.

- People with higher preoperative ASA physical status scores are more likely to develop POCD.

- People with lower educational level are more likely to develop POCD than those with a higher educational level.

- People with prior history of a stroke, even though there is complete functional recovery, are more likely to develop POCD.

- More likely in the elderly with pre-existing declining mental functions, termed mild cognitive impairment (MCI). MCI is a transitional zone between normal mental function and evident Alzheimer's disease or other forms of dementia. It is insidious, and seldom recognized, except in retrospect after affected persons are evidently demented.

- Delirium and severe worsening of mental function is very likely in those with clinically evident Alzheimer's disease or other forms of dementia, as well as those with a history of delirium after previous operations.

Many chemical medications have been used for a broad range of neuropathic pain including Dejerine–Roussy syndrome. Symptoms are generally not treatable with ordinary analgesics. Traditional chemicals include opiates and anti-depressants. Newer pharmaceuticals include anti-convulsants and Kampo medicine. Pain treatments are most commonly administered via oral medication or periodic injections. Topical In addition, physical therapy has traditionally been used alongside a medication regimen. More recently, electrical stimulation of the brain and spinal cord and caloric stimulation have been explored as treatments.

The most common treatment plans involve a schedule of physical therapy with a medication regimen. Because the pain is mostly unchanging after development, many patients test different medications and eventually choose the regimen that best adapts to their lifestyle, the most common of which are orally and intravenously administered.

Expensive and invasive, the above treatments are not guaranteed to work, and are not meeting the needs of patients. There is a need for a new, less expensive, less invasive form of treatment, two of which are postulated below.

- Spinal cord stimulation has been studied in the last couple of years. In a long case study, 8 patients were given spinal cord stimulation via insertion of a percutaneous lead at the appropriate level of the cervical or thoracic spine. Between 36 and 149 months after the stimulations, the patients were interviewed. 6 of the 8 had received initial pain relief, and three experienced long-term pain relief. Spinal cord stimulation is cheaper than brain stimulation and less invasive, and is thus a more promising option for pain treatment.

- In 2007, Dr. V. S. Ramachandran and his lab proposed that caloric stimulation might be effective in treating Dejerine–Roussy syndrome. They hypothesized that if cold water was streamed into the ear down the auditory canal, the symptoms associated with Dejerine–Roussy syndrome would be alleviated. Ramachandran stated that he had carried out provisional experiments on two patients and believed that their reactions supported his theory.

One form of treatment that has produced a more integrated body awareness is mirror therapy, in which the individual who denies that the affected limb belongs to their body looks into a mirror at the limb. Patients looking into the mirror state that the limb does belong to them; however body ownership of the limb does not remain after the mirror is taken away.

Metabolic studies are useful, but they are not able identify neural activity within a specific region to specific cognitive processes. Functionality can only be identified at the most general level: Metabolism in cortical and subcortical regions that may contribute to cognitive processes.

At present, there is no established relation between cerebral metabolic rates of glucose or oxygen as measured by PET and patient outcome. The decrease of cerebral metabolism occurs also when patients are treated with anesthetics to the point of unresponsiveness. Lowest value (28% of normal range) have been reported during propofol anesthesia. Also deep sleep represents a phase of decreased metabolism (down to 40% of the normal range)

In general, quantitative PET studies and the assessment of cerebral metabolic rates depends on many assumptions.

PET for example requires a correction factor, the lumped constant, which is stable in healthy brains. There are reports, that a global decrease of this constant emerges after a traumatic brain injury.

But not only the correction factors change due to TBI.

Another issue is the possibility of anaerobic glycolysis that could occur after TBI. In such a case the glucose levels measured by the PET are not tightly connected to the oxygen consumption of the patient's brain.

Third point regarding PET scans is the overall measurement per unit volume of brain tissue. The imaging can be affected by the inclusion of metabolically inactive spaces e.g. cerebrospinal fluidin the case of gross hydrocephalus, which artificially lowers the calculated metabolism.

Also the issue of radiation exposure must be considered in patients with already severely damaged brains and preclude longitudinal or follow-up studies.

Experiences - are characterized by the presence of the following three factors:

- disembodiment, an apparent location of the self outside one's body;

- impression of seeing the world from an elevated and distanced visuo-spatial perspective or extracorporeal, but egocentric visuo-spatial perspective;

- impression of seeing one's own body from this perspective (autoscopy).

Laboratory of Cognitive Neuroscience, École Polytechnique Fédérale de Lausanne, Lausanne, and Department of Neurology, University Hospital, Geneva, Switzerland, have reviewed some of the classical precipitating factors of autoscopy. These are sleep, drug abuse, and general anesthesia as well as neurobiology. They have compared them with recent findings on neurological and neurocognitive mechanisms of the autoscopy. The reviewed data suggest that autoscopic experiences are due to functional disintegration of lower-level multisensory processing and abnormal higher-level self-processing at the temporoparietal junction.

Autoscopy is the experience in which an individual perceives the surrounding environment from a different perspective, from a position outside of his or her own body. Autoscopy comes from the ancient Greek ("self") and ("watcher").

Autoscopy has been of interest to humankind from time immemorial and is abundant in the folklore, mythology, and spiritual narratives of most ancient and modern societies. Cases of autoscopy are commonly encountered in modern psychiatric practice. According to neurological research, autoscopic experiences are hallucinations.

Anaphia, also known as tactile anesthesia, is a medical symptom in which there is a total or partial absence of the sense of touch.

Anaphia is a common symptom of spinal cord injury and neuropathy.

It can reduce the effectiveness of the sodium-channel blocker lidocaine in dental work, so the amide-type local anesthetic. articaine is used on victims instead.

Somatoparaphrenia is a type of monothematic delusion where one denies ownership of a limb or an entire side of one's body. Even if provided with undeniable proof that the limb belongs to and is attached to their own body, the patient produces elaborate confabulations about whose limb it really is, or how the limb ended up on their body. In some cases, delusions become so elaborate that a limb may be treated and cared for as if it were a separate being.

Somatoparaphrenia differs from a similar disorder, asomatognosia, which is characterized as loss of recognition of half of the body or a limb, possibly due to paralysis or unilateral neglect. For example, asomatognosic patients may mistake their arm for the doctor's. However, they can be shown their limb and this error is temporarily corrected.

Somatoparaphrenia has been reported to occur predominately in the left arm of one's body, and it is often accompanied by left-sided paralysis and anosognosia (denial or lack of awareness) of the paralysis. The link between somatoparaphrenia and paralysis has been documented in many clinical cases and while the question arises as to whether paralysis is necessary for somatoparaphrenia to occur, anosognosia is not, as documented by cases with somatoparaphrenia and paralysis with no anosognosia.

The use of oral potassium and avoiding high carbohydrate meals can help treat it according to resent tests. Dr. Jacob O. Levitt, a dermatologist who has hypokalemic periodic paralysis, recently conducted research in to it.

Postanesthetic shivering (PAS) is shivering after anesthesia.

The intensity of PAS may be graded using the scale described by Crossley and Mahajan:

Postanesthetic shivering is one of the leading causes of discomfort in patients recovering from general anesthesia. It usually results due to the anesthetic inhibiting the body's thermoregulatory capability, although cutaneous vasodilation (triggered by post-operative pain) may also be a causative factor. First-line treatment consists of warming the patient; more persistent/severe cases may be treated with medications such as tramadol, pethidine, clonidine and nefopam, which work by reducing the shivering threshold temperature and reducing the patient's level of discomfort. As these medications may react and/or synergize with the anesthetic agents employed during the surgery, their use is generally avoided when possible.

In regard to anosognosia for neurological patients, no long-term treatments exist. As with unilateral neglect, caloric reflex testing (squirting ice cold water into the left ear) is known to temporarily ameliorate unawareness of impairment. It is not entirely clear how this works, although it is thought that the unconscious shift of attention or focus caused by the intense stimulation of the vestibular system temporarily influences awareness. Most cases of anosognosia appear to simply disappear over time, while other cases can last indefinitely. Normally, long-term cases are treated with cognitive therapy to train patients to adjust for their inoperable limbs (though it is believed that these patients still are not "aware" of their disability). Another commonly used method is the use of feedback – comparing clients' self-predicted performance with their actual performance on a task in an attempt to improve insight.

Neurorehabilitation is difficult because, as anosognosia impairs the patient's desire to seek medical aid, it may also impair their ability to seek rehabilitation. A lack of awareness of the deficit makes cooperative, mindful work with a therapist difficult. In the acute phase, very little can be done to improve their awareness, but during this time, it is important for the therapist to build a therapeutic alliance with patients by entering their phenomenological field and reducing their frustration and confusion. Since severity changes over time, no single method of treatment or rehabilitation has emerged or will likely emerge.

In regard to psychiatric patients, empirical studies verify that, for individuals with severe mental illnesses, lack of awareness of illness is significantly associated with both medication non-compliance and re-hospitalization. Fifteen percent of individuals with severe mental illnesses who refuse to take medication voluntarily under any circumstances may require some form of coercion to remain compliant because of anosognosia. Coercive psychiatric treatment is a delicate and complex legal and ethical issue.

One study of voluntary and involuntary inpatients confirmed that committed patients require coercive treatment because they fail to recognize their need for care. The patients committed to the hospital had significantly lower measures of insight than the voluntary patients.

Anosognosia is also closely related to other cognitive dysfunctions that may impair the capacity of an individual to continuously participate in treatment. Other research has suggested that attitudes toward treatment can improve after involuntary treatment and that previously committed patients tend later to seek voluntary treatment.

Tardive Dysmentia is a rarely used term introduced in a 1983 paper to describe "changes in affect, activation level, and interpersonal interaction", and hypothesized to be caused by long-term exposure to neuroleptic drugs in the same way as the much better known syndrome of tardive dyskinesia. Several papers in the following years discussed the validity of the concept, and this small literature was reviewed in a 1993 publication by M. S. Myslobodsky, who drew attention to the "possibility that the syndrome of dysmentia is occasional excessive emotional reactivity, enhanced responsiveness to environmental stimuli, and indifference to or reduced awareness of the patient's abnormal involuntary movements", but concluded that the pathophysiology is uncertain. Since then, the term has fallen into disuse, receiving at most only passing mentions in the literature.

Asomatognosia is a neurological disorder characterized as loss of recognition or awareness of part of the body. The failure to acknowledge, for example, a limb, may be expressed verbally or as a pattern of neglect. The limb may also be attributed to another person, a delusion known as somatoparaphrenia. However, they can be shown their limb and this error is temporarily corrected. Some authors have focused on the prevalence of hemispatial neglect in such patients.

Pharmacological techniques are often continued in conjunction with other treatment options. Doses of pain medications needed often drop substantially when combined with other techniques, but rarely are discontinued completely. Tricyclic antidepressants, such as amitriptyline, and sodium channel blockers, mainly carbamazepine, are often used to relieve chronic pain, and recently have been used in an attempt to reduce phantom pains. Pain relief may also be achieved through use of opioids, ketamine, calcitonin, and lidocaine.

Postoperative residual curarization (PORC) is a residual paresis after emergence from general anesthesia with neuromuscular-blocking drugs.