Dehydration

Dehydration occurs when the body loses more fluid than a person take in. When the normal water content of the body is reduced, it upsets the balance of minerals (salts and sugar) in the body, which affects the way that it functions. Water makes up over two-thirds of the healthy human body. It lubricates the joints and eyes, aids digestion, flushes out waste and toxins and keeps skin healthy.

Some of the early warning signs that a person is dehydrated include:

• feeling thirsty and lightheaded.
• having dark coloured, strong-smelling urine.
• passing urine less often than usual.

A baby may be dehydrated if they have:

• a sunken soft spot (fontanelle) on their head.
• drowsiness.
• few or no tears when they cry.
• fewer wet nappies. 

The body is affected even when a person loses a small amount of fluid. 

Who is at risk from dehydration?

Anyone may become dehydrated, but certain groups are particularly at risk. These include:

• babies and infants, because they have a low body weight and they are sensitive to even small amounts of fluid loss.
• older people, because they may be less aware that they are becoming dehydrated and need to keep drinking fluids.
• people with a long-term condition (e.g. diabetes mellitus or alcoholism).
• athletes, because they lose a large amount of body fluid through sweat.

What to do

If a person is dehydrated, they must drink plenty of fluids. This can be water, semi-skimmed milk and diluted squash or fruit juice, but it is best to avoid fizzy drinks or caffeine if possible. If someone is finding it hard to keep water down because they are vomiting or are having diarrhoea, then they must try drinking small amounts more frequently (perhaps using a teaspoon or syringe for an infant or child).

If a person or their child are dehydrated due to watery diarrhoea or excessive vomiting (hypernatraemic dehydration), then they should try not to drink only water as it is likely to further dilute the minerals in the body and make the problem worse. People should try drinking diluted juice, squash or a rehydration solution (available from pharmacies). If left untreated, severe dehydration may be serious and can cause fits (seizures), brain damage and death.

When should I see my doctor?

Poeple must visit their doctor if their symptoms continue, despite drinking plenty of fluids or if they suspect that their baby or toddler is dehydrated. If the doctor suspects dehydration, patients may be given a blood test or a urine test to check the balance of salts (sodium and potassium) in their body.

Patients must contact their doctor or out-of-hours service, or go to their nearer Emergency department straight away, if they have any of the following symptoms:

• feeling tired (lethargic) or confused.
• rapid pulse (heartbeat) / palpitations.
• dry mouth and eyes that do not produce tears.
• not passing urine for eight hours.
• dry skin which sags slowly into position when pinched up.
• blood in the stools (faeces) or vomit.
• low blood pressure (hypotension).

People should also contact their doctor if they or their child has diarrhoea which lasts longer than 5 days, or vomiting which lasts more than 24 hours in adults or 12 hours in a child.

How does dehydration happen?

Dehydration is usually caused by not drinking enough fluid or by losing fluid and not replacing it. The climate, the amount of physical exercise people are doing and their diet may also contribute to dehydration. Patients can become dehydrated as a result of an illness, such as gastroenteritis, where they have persistent vomiting and diarrhoea, after sweating excessively from a fever, exercising in hot conditions or if they are urinating more frequently (e.g. if they have diabetes). Drinking too much alcohol may also cause dehydration, which is the main symptom of a hangover.

Symptoms of dehydration 

Depending on how much of the body weight is lost through fluids, dehydration can be described as mild, moderate or severe.

Mild to moderate dehydration

The first sign of dehydration is thirst. Other symptoms may include:

• Tiredness.
• Headache.
• Dizziness or light-headedness.
• Dry mouth, lips and eyes.
• Concentrated urine (dark yellow).
• Passing only small amounts of urine infrequently (less than three or four times a day).

Moderate dehydration causes people to lose strength and stamina. It is the primary cause of heat exhaustion. Patients should be able to reverse mild to moderate dehydration by drinking more fluids, without medical attention. If dehydration is ongoing (chronic), it may affect the kidney function, and it can cause kidney stones to develop. It may also cause:

• constipation.
• liver, joint and muscle damage.
• cholesterol problems

Severe dehydration

Untreated mild or moderate dehydration may lead to severe dehydration. Severe dehydration is a medical emergency and requires immediate medical attention. Patients must seek medical attention if they or their child has any of the following symptoms: 

• Irritability.
• Cool hands and feet.
• Sunken eyes.
• Dry, wrinkled skin which sags slowly into position when pinched up.
• An inability to urinate, or not passing urine for 8 hours.
• Low blood pressure (hypotension).
• A weak pulse.
• A rapid heartbeat (pulse) / palpitations.
• Fits (seizures).
• A low level of consciousness.
• Feeling tired (lethargic) or confused.
• Blood in their stools (faeces) or vomit.

If not treated immediately, severe dehydration may lead to complications. Patients may even die from severe dehydration, because the blood stops circulating. If the experience this level of dehydration, people may need to be admitted into hospital and be put on a drip in order to restore the substantial loss of fluids (by having intravenous fluid resuscitation).

When should I see my Doctor?

People must visit their doctor if their symptoms continue, despite drinking plenty of fluids or if they suspect that their baby or toddler is dehydrated. If the doctor suspects dehydration, patients may be given a blood test or a urine test to check the balance of salts (sodium and potassium) in their body. People should contact their doctor or out-of-hours service, or go to their nearest Emergency Department straight away, if they have any of the following symptoms:

• Feeling tired (lethargic) or confused.
• Rapid heartbeat (pulse) / palpitations.
• Dry mouth and eyes which do not produce tears.
• Not passing urine for eight hours.
• Dry skin which sags slowly into position when pinched up.
• Blood in their stools (faeces) or vomit.
• Low blood pressure (hypotension)

Patients should also contact their doctor/ physician, if they or their child has diarrhoea which lasts longer than five days, or vomiting which lasts more than 24 hours in adults or 12 hours in a child.

Causes of dehydration 

Dehydration is caused by not drinking enough fluid or by losing more fluid than people take in.  Fluid is lost through sweat, tears, vomiting, urine or diarrhoea. The severity of dehydration can often depend on a number of factors (e.g. climate, level of physical activity and diet). Dehydration is also linked to a number of other factors, which are described below.

Illness

Dehydration is often the result of an illness, such as gastroenteritis, where fluid is lost through persistent diarrhoea and vomiting.

Sweating

People can also become dehydrated after sweating excessively from a fever, heavy work in hot conditions or exercise and sport. In these situations, it is important that people drink regularly to replace lost fluids. It does not necessarily need to be hot for people to lose a significant amount of fluid from sweating. Children and teenagers are especially at risk, because they may ignore the symptoms of dehydration or not know how to recognise and treat them.

Alcohol

Dehydration can also occur as a result of drinking too much alcohol. Alcohol is a diuretic, which means that it makes you urinate more. The headache associated with a hangover indicates that the body is dehydrated. This is why it is important to drink plenty of water when people have been drinking alcohol.

Diabetes

If a person has diabetes mellitus, then they are at risk of dehydration because they have high levels of glucose in their bloodstream. The kidneys will try to get rid of the glucose by creating more urine, so their body becomes dehydrated from urinating more frequently.

Preventing dehydration 

To avoid becoming dehydrated, people must drink plenty of fluids. The Food Standards Agency (FSA) recommends that if a person lives in the UK (or somewhere with a similar climate), then they should drink six to eight glasses of fluid every day. As well as water, the FSA recommends semi-skimmed milk, diluted fruit juice and diluted squash.

Drinking regularly

If a person is active, or if the weather is particularly hot, there is a greater risk that the person will become dehydrated. To prevent becoming dehydrated, people must increase their fluid intake. When exercising, they should drink up to 1 litre (2 pints) of fluid each hour of exercise on top of their normal daily amount.

This should be increased if they are exercising in warm conditions, because they will sweat more and fluid will be lost from their body more rapidly. Also they need to be aware that drinking more fluid than the body can process may lead to a low amount of sodium in the blood (hyponatremia). This is a serious and potentially fatal condition. If a person starts to feel discomfort and bloating from drinking, then they must allow time to recover.

Illness

If somone, their child or someone they are caring for is ill, it is important to monitor how much fluid they are drinking. If they have a fever, are vomiting or have diarrhoea, it is highly likely that dehydration will occur. Therefore it is important for them to start replacing fluid as soon as possible.

Advice for children

There are no specific recommendations regarding the amount of water or other fluids that children need. However, it is very important for children to replace lost fluid to prevent dehydration. Like adults, children lose more water when they are in hotter climates and when they are physically active. Parents must give their child healthy drinks as part of an overall healthy, balanced diet.

Treating dehydration 

The best way to treat dehydration is to rehydrate the body by drinking plenty of fluids, such as water, diluted squash, diluted fruit juice or semi-skimmed milk. A sweet drink may help to replace lost sugar. A salty snack can help to replace lost salt.

Infants and children who are dehydrated should not be given water as the main replacement fluid because it can further dilute the minerals in their body and make the problem worse. Instead, they should be given diluted squash, diluted fruit juice or a special rehydration solution.

If a person or their child is finding it difficult to hold down fluids because of vomiting or diarrhoea, then they must take smaller amounts more frequently. If necessary, they could use a spoon or a syringe to give their child small amounts of fluids.

Rehydration solutions

If a person is dehydrated, he or she will have lost sugar and salts as well as water. Drinking a rehydration solution will enable them to re-establish the right balance of body fluids. The solution must contain a mixture of potassium and sodium salts, as well as glucose or starch. Several different rehydration products are available from pharmacies or on prescription from the doctor, including solutions which are suitable for infants and children. People should ask their physician or pharmacist for advice.

A typical rehydration solution.

Severe dehydration

If a person suspects that someone is severely dehydrated, then they must seek medical attention immediately. They may need to be admitted to hospital for treatment. In particular, babies, infants and elderly people will need urgent treatment if they become dehydrated.

Fluid may be given up the nose using a nasogastric (NG) tube or via a saline drip into a vein because this provides essential nutrients faster than using solutions that people drink. If someone has had bowel surgery, some rehydration solutions may not contain enough salt. In this case, patients will need a higher-strength solution. The doctor or bowel surgeon (colorectal surgeon) will be able to recommend a suitable rehydration solution for the patient.

Source: NHS Choices.

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