question: If being dehydrated gives you a headache, why don’t we always wake up with a headache after 8 hours without water?
comment: To add to the above comments, our bodies aren’t running at full capacity when asleep. A lot of brain functions and therefore bodily functions shut down or perform at a percentage of their day time capacity, so less calories and water are consumed by the body. In contract, 8 hours at work without water would leave plenty of people feeling parched to say the least.
passages: Treatment for a current tension headache is to drink water and confirm that there is no dehydration. If symptoms do not resolve within an hour for a person who has had water, then stress reduction might resolve the issue.
  
  Section::::Treatment.:Medications.
  
  Section::::Treatment.:Medications.:Treatment of ETTH.
   The term dehydration has sometimes been used incorrectly as a proxy for the separate, related condition hypovolemia, which specifically refers to a decrease in volume of blood plasma. The two are regulated through independent mechanisms in humans; the distinction is important in guiding treatment.
  
  Section::::Prevention.
   For severe cases of dehydration where fainting, unconsciousness, or other severely inhibiting symptom is present (the patient is incapable of standing or thinking clearly), emergency attention is required. Fluids containing a proper balance of replacement electrolytes are given orally or intravenously with continuing assessment of electrolyte status; complete resolution is the norm in all but the most extreme cases.
  
  Section::::See also.
  
  BULLET::::- Hydrational fluids
  
  BULLET::::- Terminal dehydration
  
  BULLET::::- Dryness (medical)
  
  BULLET::::- Oral Rehydration Therapy
  
  Section::::External links.
  
  BULLET::::- Definition of dehydration by the U.S. National Institutes of Health's MedlinePlus medical encyclopedia
   BULLET::::- DDAVP (desmopressin) tablets are a synthetic replacement for antidiuretic hormone, the hormone that reduces urine production during sleep. Desmopressin is usually used in the form of desmopressin acetate, DDAVP. Patients taking DDAVP are 4.5 times more likely to stay dry than those taking a placebo. The drug replaces the hormone for that night with no cumulative effect. US drug regulators have banned using desmopressin nasal sprays for treating bedwetting since the oral form is considered safer.
   Early hydrocephalus can also cause severe excessive daytime sleepiness. Additionally, head trauma can be associated with a primary/central hypersomnia, and symptoms similar to those of idiopathic hypersomnia can be seen within 6–18 months following the trauma. However, the associated symptoms of headaches, memory loss, and lack of concentration may be more frequent in head trauma than in idiopathic hypersomnia. "The possibility of secondary narcolepsy following head injury in previously asymptomatic individuals has also been reported."
  
  Section::::Diagnosis.:Differential diagnosis.:Secondary hypersomnias.
  
  Secondary hypersomnias are extremely numerous.
   People had fled from civil war in Mozambique to southern Malawi. In November 1990, cholera broke out in a refugee camp in southern Malawi where approximately 74,000 persons were temporarily living. David Swerdlow of the U.S.'s CDC Epidemic Intelligence Service (EIS) wrote about the situation. He recommended setting up a tent just for children who would be assisted by some of the best nurses. He recommended against over-reliance on IV tubes, which often were left attached to persons for a week or more and which could lead to infections and septic shock. And he noticed that sick persons were not drinking enough rehydration solution. He assigned so-called "ORS officers" whose job was to encourage persons to drink more solution.
   In some cases, correction of a dehydrated state is accomplished by the replenishment of necessary water and electrolytes (through oral rehydration therapy or fluid replacement by intravenous therapy). As oral rehydration is less painful, less invasive, less expensive, and easier to provide, it is the treatment of choice for mild dehydration. Solutions used for intravenous rehydration must be isotonic or hypertonic. Pure water injected into the veins will cause the breakdown (lysis) of red blood cells (erythrocytes).
   Section::::Causes.:Vitamin and electrolyte loss.
  
  The metabolic processes required for alcohol elimination deplete essential vitamins and electrolytes. Furthermore, alcohol is a diuretic, causing excretion of electrolytes through urination. After a night of drinking, the resulting lack of key B and C vitamins, as well as potassium, magnesium, and zinc may cause fatigue, aching and other hangover-like symptoms.
  
  Section::::Causes.:Dehydration.
   Section::::Diagnosis.
  
  Section::::Diagnosis.:Definition.
  
  Dehydration occurs when water intake is not enough to replace free water lost due to normal physiologic processes, including breathing, urination, and perspiration, or other causes, including diarrhea and vomiting. Dehydration can be life-threatening when severe and lead to seizures or respiratory arrest, and also carries the risk of osmotic cerebral edema if rehydration is overly rapid.
   Most people can tolerate a three to four percent decrease in total body water without difficulty or adverse health effects. A five to eight percent decrease can cause fatigue and dizziness. Loss of over ten percent of total body water can cause physical and mental deterioration, accompanied by severe thirst. Death occurs at a loss of between fifteen and twenty-five percent of the body water. Mild dehydration is characterized by thirst and general discomfort and is usually resolved with oral rehydration.
   Antibiotic treatments for one to three days shorten the course of the disease and reduce the severity of the symptoms. Use of antibiotics also reduces fluid requirements. People will recover without them, however, if sufficient hydration is maintained. The WHO only recommends antibiotics in those with severe dehydration.
   Dehydration
  
  In physiology, dehydration is a deficit of total body water, with an accompanying disruption of metabolic processes. It occurs when free water loss exceeds free water intake, usually due to exercise, disease, or high environmental temperature. Mild dehydration can also be caused by immersion diuresis, which may increase risk of decompression sickness in divers.
   In warm or humid weather or during heavy exertion, water loss can increase markedly, because humans have a large and widely variable capacity for the active secretion of sweat. Whole-body sweat losses in men can exceed 2 L/h during competitive sport, with rates of 3–4 L/h observed during short-duration, high-intensity exercise in the heat. When such large amounts of water are being lost through perspiration, electrolytes, especially sodium, are also being lost.
   Section::::Cause.
  
  Risk factors for dehydration include but are not limited to: exerting oneself in hot and humid weather, habitation at high altitudes, endurance athletics, elderly adults, infants, children and people living with chronic illnesses.
  
  Dehydration can also come as a side effect from many different types of drugs and medications.
   MOH is common and can be treated. The overused medications must be stopped for the patient's headache to resolve. Clinical data shows that the treatment of election is abrupt drugs withdrawal, followed by starting prophylactic therapy. However, the discontinuation of overused drugs usually leads to the worsening of headache and the appearance of drug withdrawal symptoms (that greatly depend on the previously overused drugs and typically last from two to ten days and that are relieved by the further intake of the overused medication), which might reinforce the continuation of overuse. Where physical dependence or a rebound effect such as rebound headache is possible, gradual reduction of medication may be necessary. It is important that the patient's physician be consulted before abruptly discontinuing certain medications as such a course of action has the potential to induce medically significant physical withdrawal symptoms. Abruptly discontinuing butalbital, for example, can actually induce seizures in some patients, although simple over the counter analgesics can safely be stopped by the patient without medical supervision. A long-acting analgesic/anti-inflammatory, such as naproxen (500 mg twice a day), can be used to ease headache during the withdrawal period. Two months after the completion of a medication withdrawal, patients suffering from MOH typically notice a marked reduction in headache frequency and intensity.
   When an unconscious person is being fed intravenously (for example, total parenteral nutrition) or via a nasogastric tube, the fluids given must be carefully balanced in composition to match fluids and electrolytes lost. These fluids are typically hypertonic, and so water is often co-administered. If the electrolytes are not monitored (even in an ambulatory patient), either hypernatremia or hyponatremia may result.
  
  Some neurological/psychiatric medications (Oxcarbazepine, among others) have been found to cause hyponatremia in some patients. Patients with diabetes insipidus are particularly vulnerable due to rapid fluid processing.
  
  Section::::Pathophysiology.
   Section::::Aquatic organisms.
  
  Water is a critical issue for the survival of all living organisms. Some can use salt water but many organisms including the great majority of higher plants and most mammals must have access to fresh water to live. Some terrestrial mammals, especially desert rodents, appear to survive without drinking, but they do generate water through the metabolism of cereal seeds, and they also have mechanisms to conserve water to the maximum degree.
   Significant scientific evidence, first reported by the Associated Press, and later the "New York Times", "Al Jazeera", and ABC News has shown that Nepalese Peacekeeping troops stationed at a remote base in Mirebalais, Haiti, triggered a deadly cholera epidemic that has ravaged the country since October 2010. Cholera is a waterborne disease that causes diarrhoea and vomiting, and it can kill in a matter of hours if patients do not receive rehydration intervention. As of July 2012, Haiti's cholera epidemic was the worst in the world: about 7,500 had died and about 585,000 Haitians (about 1 in every 20 Haitians) had become ill with the disease.
   Appropriate amounts of supplemental zinc and potassium should be added if available. But the availability of these should not delay rehydration. As WHO points out, the most important thing is to begin preventing dehydration as early as possible. In another example of prompt ORS hopefully preventing dehydration, CDC recommends for the treatment of cholera continuing to give Oral Rehydration Solution during travel to medical treatment.
   According to Maxwell Stamp PLC, those who received a piped water supply in 2003 in the nation's capital Kampala were "usually" supplied continuously for 24 hours per day. NWSC, however, acknowledged that parts of Kampala such as Kyaliwajala, Kulambiro, and most places on hilltops suffered from chronic water shortages. In addition, some areas went without water for a week when repairs were undertaken. In other towns, Maxwell Stamp PLC found in 2003 that most customers were supplied more than five days per week.
   Psychologists may use a definition from the DSM-IV, defining nocturnal enuresis as repeated urination into bed or clothes, occurring twice per week or more for at least three consecutive months in a child of at least 5 years of age and not due to either a drug side effect or a medical condition. Even if the case does not meet these criteria, the DSM-IV definition allows psychologists to diagnose nocturnal enuresis if the wetting causes the patient clinically significant distress.
  
  Section::::Treatment.
   In the elderly, blunted response to thirst and/or inadequate ability to access free water in the face of excess free water losses (especially hyperglycemia related) seem to be the main causes of dehydration. Excess free water or hypotonic water can leave the body in two ways - "sensible" loss such as osmotic diuresis, sweating, vomiting and diarrhea, and "insensible" water loss, occurring mainly through the skin and respiratory tract. In humans, dehydration can be caused by a wide range of diseases and states that impair water homeostasis in the body. These occur primarily through either impaired thirst/water access or sodium excess.
   When fresh water is unavailable (e.g. at sea or in a desert), seawater and ethanol will worsen the condition. Urine contains a lower solute concentration than seawater, and numerous guides advise against its consumption in survival situations. If somebody is dehydrated and is taken to a hospital, IVs are also used.
   In January 2015 the Greater Accra Region and Volta region still reported cases of Cholera while in the rest of Ghana the outbreak was declared over. As of January 11 the Democratic Republic of the Congo, Ghana and Nigeria are the countries with highest number of new cases of the disease in 2015.
   The large-scale inflammation that occurs in the subarachnoid space during meningitis is not a direct result of bacterial infection but can rather largely be attributed to the response of the immune system to the entry of bacteria into the central nervous system. When components of the bacterial cell membrane are identified by the immune cells of the brain (astrocytes and microglia), they respond by releasing large amounts of cytokines, hormone-like mediators that recruit other immune cells and stimulate other tissues to participate in an immune response. The blood–brain barrier becomes more permeable, leading to "vasogenic" cerebral edema (swelling of the brain due to fluid leakage from blood vessels). Large numbers of white blood cells enter the CSF, causing inflammation of the meninges and leading to "interstitial" edema (swelling due to fluid between the cells). In addition, the walls of the blood vessels themselves become inflamed (cerebral vasculitis), which leads to decreased blood flow and a third type of edema, "cytotoxic" edema. The three forms of cerebral edema all lead to increased intracranial pressure; together with the lowered blood pressure often encountered in acute infection, this means that it is harder for blood to enter the brain, consequently brain cells are deprived of oxygen and undergo apoptosis (programmed cell death).
  
presuppositions: Humans should face symptoms of dehydration after waking from 8 hours of sleep.  The body requires the same amount of water when asleep as the body does when it is awake.
corrections: As brain and bodily functions do not operate at full capacity while one is asleep, less water is required by the body when one sleeps. Brain and bodily functions perform at a percentage of capacity during sleep, which requires less water .
raw_presuppositions: Humans should face symptoms of dehydration after waking from 8 hours of sleep.  The body requires the same amount of water when asleep as the body does when it is awake. The body requires the same amount of water when asleep as the body does when it is awake.
raw_corrections: As brain and bodily functions do not operate at full capacity while one is asleep, less water is required by the body when one sleeps. Brain and bodily functions perform at a percentage of capacity during sleep, which requires less water . As brain and bodily functions do not operate at full capacity while one is asleep, less water is required by the body when one sleeps.