Dehydration

Dehydration is the unbalanced loss of water from the body, meaning the body loses more water than it takes in. Dehydration is often accompanied by imbalances in the electrolyte balance, especially sodium and potassium.

An adult body is approximately 60% water, which is primarily obtained from food and beverages and is normally eliminated through urine, sweating, and breathing. To maintain water balance, the body has several mechanisms that activate in the absence of fluids:

• Thirst: The brain triggers the sensation of thirst when water is lost.
• Interaction between the pituitary gland and kidneys: If water is lacking, the pituitary gland releases vasopressin (antidiuretic hormone), which stimulates the kidneys to excrete less urine to retain water.
• Osmosis: Water flows from cells to blood vessels to compensate for the loss.

If these mechanisms are not enough to maintain water balance, dehydration occurs.

Depending on the rate of water loss relative to electrolyte loss, dehydration is classified into three types:

• Isotonic dehydration: There is an equal loss of water and minerals.
• Hypertonic dehydration: Water loss is greater than salt loss.
• Hypotonic dehydration: More salts are lost than water.

Symptoms

The symptoms of dehydration worsen as more water is lost and not replenished:

• Mild dehydration: Loss of up to 5% of the body's water volume.
• Thirst.
• Decreased urine production.
• Darker urine color.
• Reduced sweating.
• Dry mouth.
• Moderate dehydration: Loss of between 5% and 9%.
• Low urine production.
• Weakness, fatigue, drowsiness.
• Orthostatic hypotension: dizziness when standing.
• Headache.
• Dry mucous membranes.
• Severe dehydration: Loss greater than 9%.
• Extreme thirst.
• No urine production.
• Lack of skin elasticity.
• Cold, clammy skin.
• Increased heart rate.
• Increased respiratory rate.
• Marked hypotension: dizziness.
• Blurred vision.
• Muscle cramps.
• Altered mental state, confusion.

Dehydration is common in infants. Symptoms of a dehydrated baby include:

• No tears when crying.
• Dry mouth and tongue.
• Dry diapers for several hours.
• Sunken fontanelles (soft spots on the head).
• Sunken eyes and cheeks.
• Irritability.

Causes

The most frequent causes of dehydration include:

• Insufficient fluid intake throughout the day: This may be due to prolonged fasting or a lack of appetite caused by illness.
• Vomiting or diarrhea: These conditions lead to significant loss of water and electrolytes from the gastrointestinal system in a short period.
• Excessive sweating: In hot weather, humidity, or physical activity, the body sweats more, leading to greater water loss.
• Excessive urination: Certain medications, such as diuretics or some antihypertensive drugs, increase the need to urinate, leading to greater fluid loss. Diseases like diabetes, Addison’s disease, or kidney problems also affect urine production.
• Fever: Fever raises body temperature, causing the body to sweat to cool down.
• Burns: Burns cause dehydration because fluid accumulates in the necrotic tissue and is eliminated through the skin.

Risk Factors

The risk of dehydration increases in the following situations:

• Age: Infants, children, and elderly people are more vulnerable to dehydration. In children and infants, the amount of fluid lost during an episode of fever, burns, vomiting, or diarrhea is a larger proportion of their total body volume. Additionally, babies cannot access drinks independently or communicate thirst. Older adults have lower body fluid volume and are at higher risk of taking medications or having diseases that increase urination.
• Hot and humid climates.
• Working or exercising outdoors in hot and humid conditions.
• Infections: These can cause fever, vomiting, and diarrhea.

Complications

In cases of acute hypotonic dehydration, a rapid drop in sodium levels in a short period (hyponatremia) can cause brain swelling due to osmotic water shift into brain cells. This swelling increases intracranial pressure, which may lead to coma or even death.

Additionally, untreated severe dehydration can lead to hypovolemic shock, which is a sudden and severe reduction in circulating blood volume as the body tries to replenish lost fluids from the blood. The decreased blood volume prevents the heart from pumping enough blood to the body, which means organs and tissues do not receive the oxygen and nutrients they need. This can cause permanent damage to vital organs and may be fatal.

Chronic dehydration can affect the excretory system, leading to urinary infections, kidney stones, or kidney failure.

Prevention

The risk of dehydration can be reduced by following these preventive measures:

• Drink enough water: It is recommended to consume between two and three liters of water daily.
• Maintain a diet rich in foods containing water, such as fruits and vegetables.
• Increase water intake during hot or humid conditions.
• Protect yourself from heat: Stay in cool, shaded places, wear light, breathable clothing, and use hats or caps.
• Drink liquids before, during, and after exercise: water or isotonic drinks rich in electrolytes.
• Increase fluid intake when sick, especially with fever or gastrointestinal disorders.
• Reduce alcohol, sugary, or caffeinated beverages.

Which doctor treats dehydration?

Dehydration is diagnosed and treated in internal medicine consultations and emergency services.