Coma in the context of Artificial ventilation

Consciousness, at its simplest, is awareness of states or objects either internal to one's self or in one's external environment. However, its nature has led to millennia of explanations, analyses, and debate among philosophers, scientists, and theologians. Opinions differ about what exactly needs to be studied, or can even be considered consciousness. In some explanations, it is synonymous with mind, and at other times, an aspect of it.

In the past, consciousness meant one's "inner life": the world of introspection, private thought, imagination, and volition. Today, it often includes any kind of cognition, experience, feeling, or perception. It may be awareness, awareness of awareness, metacognition, or self-awareness, either continuously changing or not. There is also a medical definition that helps, for example, to discern "coma" from other states. The disparate range of research, notions, and speculations raises some curiosity about whether the right questions are being asked.

Malaria is a mosquito-borne infectious disease that affects vertebrates and Anopheles mosquitoes. Human malaria causes symptoms that typically include fever, fatigue, vomiting, and headaches. In severe cases, it can cause jaundice, seizures, coma, or death. Symptoms usually begin 10 to 15 days after being bitten by an infected Anopheles mosquito. If not properly treated, people may have recurrences of the disease months later. In those who have recently survived an infection, reinfection usually causes milder symptoms. This partial resistance disappears over months to years if the person has no continuing exposure to malaria. The mosquitoes themselves are harmed by malaria, causing reduced lifespans in those infected by it.

Malaria is caused by single-celled eukaryotes of the genus Plasmodium. In mammals, it is spread through bites of infected female Anopheles mosquitoes. The mosquito bite introduces the parasites from the mosquito's saliva into the blood. The parasites travel to the liver, where they mature and reproduce. Five species of Plasmodium commonly infect humans. The three species associated with more severe cases are P. falciparum (which is responsible for the vast majority of malaria deaths), P. vivax, and P. knowlesi (a simian malaria that spills over into thousands of people a year). P. ovale and P. malariae generally cause a milder form of malaria. Malaria is typically diagnosed by the microscopic examination of blood using blood films, or with antigen-based rapid diagnostic tests. Methods that use the polymerase chain reaction to detect the parasite's DNA have been developed, but they are not widely used in areas where malaria is common, due to their cost and complexity.

On Monday, 21 January 1924, at 18:50 EET, Vladimir Lenin, leader of the October Revolution and the first leader and founder of the Soviet Union, died in Gorki aged 53 after falling into a coma. The official cause of death was recorded as an incurable disease of the blood vessels. Lenin was given a state funeral and then buried in a specially erected mausoleum on 27 January. A commission of the Central Committee of the RCP(b) was in charge of organising the funeral.

An altered level of consciousness is any measure of arousal other than normal. Level of consciousness (LOC) is a measurement of a person's arousability and responsiveness to stimuli from the environment. A mildly depressed level of consciousness or alertness may be classed as lethargy; someone in this state can be aroused with little difficulty. People who are obtunded have a more depressed level of consciousness and cannot be fully aroused. Those who are not able to be aroused from a sleep-like state are said to be stuporous. Coma is the inability to make any purposeful response. Scales such as the Glasgow coma scale have been designed to measure the level of consciousness.

An altered level of consciousness can result from a variety of factors, including alterations in the chemical environment of the brain (e.g. exposure to poisons or intoxicants), insufficient oxygen or blood flow in the brain, and excessive pressure within the skull. Prolonged unconsciousness is understood to be a sign of a medical emergency. A deficit in the level of consciousness suggests that both of the cerebral hemispheres or the reticular activating system have been injured. A decreased level of consciousness correlates to increased morbidity (sickness) and mortality (death). Thus it is a valuable measure of a patient's medical and neurological status. In fact, some sources consider level of consciousness to be one of the vital signs.

The argument from marginal cases (also known as the argument from species overlap) is a philosophical argument within animal rights theory regarding the moral status of non-human animals. Its proponents hold that if human infants, senile people, the comatose, and cognitively disabled people have direct moral status, non-human animals must have a similar status, since there is no known morally relevant characteristic that those marginal-case humans have that animals lack. "Moral status" may refer to a right not to be killed or made to suffer, or to a general moral requirement to be treated in a certain way.

Although various cases are made for it, Raymond Frey has described the argument from marginal cases collectively as 'one of the most common arguments in support of an equal value' of animals' lives.

An induced coma – also known as a medically induced coma (MIC), barbiturate-induced coma, or drug-induced coma – is a temporary coma (a deep state of unconsciousness) brought on by a controlled dose of an anesthetic drug, often a barbiturate such as pentobarbital or thiopental. Other intravenous anesthetic drugs such as midazolam or propofol may be used.

Drug-induced comas are used to protect the brain during major neurosurgery, as a last line of treatment in certain cases of status epilepticus that have not responded to other treatments, and in refractory intracranial hypertension following traumatic brain injury.

Sleep is a state of reduced mental and physical activity in which consciousness is altered and certain sensory activity is inhibited. During sleep, there is a marked decrease in muscle activity and interactions with the surrounding environment. While sleep differs from wakefulness in terms of the ability to react to stimuli, it still involves active brain patterns, making it more reactive than a coma or disorders of consciousness.

Sleep occurs in repeating periods, during which the body alternates between two distinct modes: rapid eye movement sleep (REM) and non-REM sleep. Although REM stands for "rapid eye movement", this mode of sleep has many other aspects, including virtual paralysis of the body. Dreams are a succession of images, ideas, emotions, and sensations that usually occur involuntarily in the mind during certain stages of sleep.

Hyponatremia or hyponatraemia is a low concentration of sodium in the blood. It is generally defined as a sodium concentration of less than 135 mmol/L (135 mEq/L), with severe hyponatremia being below 120 mEq/L. Symptoms can be absent, mild or severe. Mild symptoms include a decreased ability to think, headaches, nausea, and poor balance. Severe symptoms include confusion, seizures, and coma; death can ensue.

The causes of hyponatremia are typically classified by a person's body fluid status into low volume, normal volume, or high volume. Low volume hyponatremia can occur from diarrhea, vomiting, diuretics, and sweating. Normal volume hyponatremia is divided into cases with dilute urine and concentrated urine. Cases in which the urine is dilute include adrenal insufficiency, hypothyroidism, and drinking too much water or too much beer. Cases in which the urine is concentrated include syndrome of inappropriate antidiuretic hormone secretion (SIADH). High volume hyponatremia can occur from heart failure, liver failure, and kidney failure. Conditions that can lead to falsely low sodium measurements include high blood protein levels such as in multiple myeloma, high blood fat levels, and high blood sugar.

Cardiac arrest (also known as sudden cardiac arrest [SCA]) is a condition in which the heart suddenly and unexpectedly stops beating. When the heart stops, blood cannot circulate properly through the body and the blood flow to the brain and other organs is decreased. When the brain does not receive enough blood, this can cause a person to lose consciousness and brain cells begin to die within minutes due to lack of oxygen. Coma and persistent vegetative state may result from cardiac arrest. Cardiac arrest is typically identified by the absence of a central pulse and abnormal or absent breathing.

Cardiac arrest and resultant hemodynamic collapse often occur due to arrhythmias (irregular heart rhythms). Ventricular fibrillation and ventricular tachycardia are most commonly recorded. However, as many incidents of cardiac arrest occur out-of-hospital or when a person is not having their cardiac activity monitored, it is difficult to identify the specific mechanism in each case.

Lead poisoning, also known as plumbism and saturnism, is a type of metal poisoning caused by the presence of lead in the human body. Symptoms of lead poisoning may include abdominal pain, constipation, headaches, irritability, memory problems, infertility, numbness and tingling in the hands and feet. Lead poisoning causes almost 10% of intellectual disability of otherwise unknown cause and can result in behavioral problems. Some of the effects are permanent. In severe cases, anemia, seizures, coma, or death may occur.

Exposure to lead can occur through contaminated air, water, dust, food, or consumer products. Lead poisoning poses a significantly increased risk to children and pets as they are far more likely to ingest lead indirectly by chewing on toys or other objects that are coated in lead paint. Additionally, children absorb greater quantities of lead from ingested sources than adults. Exposure at work is a common cause of lead poisoning in adults, with certain occupations at particular risk. Diagnosis is typically by measurement of the blood lead level. The Centers for Disease Control and Prevention (US) has set the upper limit for blood lead for adults at 10 μg/dL (10 μg/100 g) and for children at 3.5 μg/dL; before October 2021 the limit was 5 μg/dL. Elevated lead may also be detected by changes in red blood cells or dense lines in the bones of children as seen on X-ray.

Involuntary euthanasia, typically regarded as a type of murder, occurs when euthanasia is performed on a person who would be able to provide informed consent, but does not, either because they do not want to die, or because they were not asked.

Involuntary euthanasia is contrasted with voluntary euthanasia (euthanasia performed with the patient's consent) and non-voluntary euthanasia (when the patient is unable to give informed consent, for example when a patient is comatose or a child). Involuntary euthanasia is widely opposed and is regarded as a crime in all legal jurisdictions. Involuntary euthanasia has been practiced in the past, notably in Nazi Germany, where many of the perpetrators were tried, convicted, and executed following World War II. Reference to it or fear of it is sometimes used as a reason for not changing laws relating to voluntary euthanasia.

Obtundation is mild to moderate alertness reduction (altered level of consciousness) with decreased interest in the environment and slower than normal reactivity to stimulation. It is distinguished from the much stronger states of unresponsiveness of stupor and coma. Obtundation typically occurs as a result of a medical condition or trauma.

There is a wide range of potential causes including head injury, interruption of blood circulation, impaired oxygenation or carbon dioxide toxicity (hypercapnia); central nervous system (CNS) infections, drug intoxication or withdrawal, post-seizure state, hypothermia, and metabolic derangements such as hypoglycemia, hyponatremia, and hypercalcaemic crisis.

The Glasgow Coma Scale (GCS) is a clinical diagnostic tool widely used since the 1970s to roughly assess an injured person's level of brain damage. The GCS diagnosis is based on a patient's ability to respond and interact with three kinds of behaviour: eye movements, speech, and other body motions. A GCS score can range from 3 (completely unresponsive) to 15 (responsive). An initial score is used to guide immediate medical care after traumatic brain injury (such as a car accident) and a post-treatment score can monitor hospitalised patients and track their recovery.

Lower GCS scores are correlated with higher risk of death. However, the GCS score alone should not be used on its own to predict the outcome for an individual person with brain injury.

Hepatic encephalopathy (HE) is an altered level of consciousness as a result of liver failure. Its onset may be gradual or sudden. Other symptoms may include movement problems, changes in mood, or changes in personality. In the advanced stages, it can result in a coma.

Hepatic encephalopathy can occur in those with acute or chronic liver disease. Episodes can be triggered by alcoholism, infections, gastrointestinal bleeding, constipation, electrolyte problems, or certain medications. The underlying mechanism is believed to involve the buildup of ammonia in the blood, a substance that is normally removed by the liver. The diagnosis is typically based on symptoms after ruling out other potential causes. It may be supported by blood ammonia levels, an electroencephalogram, or computer tomography (CT scan) of the brain.