OVERVIEW

What is dehydration?

In medical terms, dehydration refers to a metabolic disorder characterized by weakness and fatigue caused by significant fluid loss in the body that cannot be replenished in time. Severe cases can be life-threatening and require fluid replacement.

Who is prone to dehydration?

Comatose individuals unable to eat, patients with high fever, those experiencing prolonged vomiting or diarrhea, esophageal cancer patients, the elderly, people working in high-temperature environments, diabetes insipidus patients, burn victims, diabetics, children, etc.

Why can severe dehydration become dangerous?

Water constitutes about 50%–80% of the human body, with significant individual variations depending on age, gender, and body weight. Newborns have the highest total body water, accounting for about 80% of their weight, followed by infants at around 70%. Water in the body is mainly distributed in intracellular and extracellular fluids, as well as solid supporting tissues.

One-third of total body water is in extracellular fluids, including blood, cerebrospinal fluid, and joint fluid, while two-thirds are in intracellular fluids. During dehydration, intracellular and extracellular fluids compensate for each other to ensure blood supply to vital organs and maintain cell function and morphology.

Severe water deficiency causes cells to shrink, impairing their function. In extreme cases, cells may necrotize and rupture. Increasing cell damage leads to organ failure, while reduced extracellular fluid volume may cause insufficient blood supply to vital organs, potentially endangering life.

Which department should you visit for dehydration?

Adults should see internal medicine or emergency care, while children should visit pediatrics.

SYMPTOMS

What are the common manifestations of dehydration?

Clinically, dehydration is classified into mild, moderate, and severe based on its degree:

• Mild dehydration: Symptoms include dizziness, headache, fatigue, reduced skin elasticity upon examination, and thirst. Fluid loss accounts for 2%–3% of body weight.

• Moderate dehydration: May present with decreased blood pressure and circulatory dysfunction. Fluid loss accounts for 3%–6% of body weight.

• Severe dehydration: Can lead to shock, coma, and other critical symptoms. Fluid loss exceeds 6% of body weight.

What are the main types of dehydration?

Dehydration is categorized by osmotic pressure into hypertonic, isotonic, and hypotonic:

• Hypertonic dehydration / Hypernatremic dehydration: Water loss exceeds sodium loss, with serum sodium >150 mmol/L and plasma osmolality >310 mOsm/L. Common causes include excessive sweating in high-temperature environments or fever, respiratory distress, tracheostomy, diabetes insipidus, diabetic ketoacidosis, and osmotic diuresis.

• Isotonic dehydration / Normonatremic dehydration: Water and sodium are lost proportionally, maintaining extracellular isotonicity. Serum sodium remains 130–145 mmol/L, and plasma osmolality stays at 280–310 mOsm/L. Occurs in acute diarrhea, severe vomiting, gastrointestinal drainage/fistula, extensive burns, or repeated drainage of pleural/ascitic fluid.

• Hypotonic dehydration / Hyponatremic dehydration: Sodium loss exceeds water loss, with serum sodium <130 mmol/L and plasma osmolality <280 mOsm/L. Seen in polyuric phase of acute renal failure, overuse of natriuretic diuretics, or inadequate sodium replacement during rehydration (e.g., vomiting, diarrhea, gastric decompression, or burns treated with water-only replenishment).

Is dehydration the same as blood loss?

No:

Blood loss often involves significant plasma colloid loss, leading to early decompensation and high-risk hemorrhagic shock with slower recovery.

Dehydration primarily involves water loss, triggering compensatory mechanisms. Shock develops later, and early rehydration ensures faster recovery.

How do dehydration symptoms differ between adults and children?

Adults have relatively lower body water content but greater reserves and resilience, resulting in milder and prolonged dehydration symptoms.

Children, with higher water content and limited reserves, show early fatigue, poor appetite, and rapid consciousness impairment or shock. Their inability to articulate symptoms may delay treatment, warranting urgent attention.

CAUSES

What Causes Dehydration?

• Insufficient Intake: For example, lack of timely water replenishment in deserts often leads to dehydration; unconscious patients unable to consume food or water, or esophageal cancer patients who cannot ingest fluids.

• Increased Demand: Patients with high fever or individuals working in high-temperature environments may experience dehydration.

• Excessive Loss: Conditions such as intestinal fistulas, diarrhea, burns, diabetes insipidus; procedures like large-volume drainage of ascites or pleural effusion; diuretic use; osmotic diuresis (e.g., oral mannitol, diabetic ketoacidosis); long-distance runners or soccer players sweating excessively in hot environments without timely hydration.

DIAGNOSIS

How to Identify Dehydration Early?

• Early dehydration assessment should be based on a history of fluid loss;

• Symptoms such as dry mouth, fatigue, dizziness, reduced urine output, dark urine, along with physical findings like a dry tongue and poor skin elasticity, should be considered for a comprehensive evaluation;

• In infants, the absence of tears while crying is also a sign;

• Disappearance of symptoms like dry mouth after rehydration is another way to confirm dehydration.

TREATMENT

Is hospital treatment necessary in the early stages of dehydration?

• In the early stages of dehydration, oral rehydration can quickly restore fluid balance, such as with Oral Rehydration Salts III. For workers in high-temperature environments, timely replenishment of water and electrolytes is sufficient, and hospitalization is not required. However, those who have difficulty drinking orally must go to the hospital for nasogastric or intravenous rehydration.

• Children have a higher water content but poor compensatory ability, making them more prone to dehydration. If vomiting or diarrhea prevents them from eating or drinking, early medical intervention is necessary.

• Patients with conditions like intestinal fistula or diabetes insipidus require identifying the underlying cause for targeted treatment, which should not be overlooked.

• Diabetic patients are at higher risk of severe consequences if dehydration occurs, so vigilance is essential.

Why are dehydrated patients often overlooked?

Dehydration is often masked by other symptoms. For example, in children with vomiting and diarrhea, fluid loss is hard to estimate, and parents may avoid giving them food or water, assuming rest will suffice. Fatigue may be mistaken for lack of food, leading to underestimation of dehydration.

Similarly, bedridden or comatose elderly patients may be thought to have cerebrovascular disease or early-stage dehydration from diuretics. Experienced doctors will thoroughly assess fluid volume and correct dehydration early during treatment.

What are the treatment principles for dehydrated patients?

• Determine the rehydration volume based on the severity of dehydration and select fluid composition according to osmotic pressure.

• Oral rehydration is safest, so it should be attempted first. If oral intake is impossible, nasogastric feeding is an option, followed by intravenous rehydration, with attention to electrolyte replenishment.

• Adjust the rehydration rate based on cardiac and renal function.

• For diabetes insipidus, identifying and addressing the root cause is more critical than rehydration.

• For the elderly and children, control the rehydration speed to avoid heart failure.

• Monitor blood glucose levels in diabetic patients while replenishing fluids and electrolytes.

• Weigh the pros and cons of rehydration for patients on diuretics.

How should patients with cardiac or renal insufficiency rehydrate?

For dehydrated patients with cardiac or renal insufficiency, carefully control the speed and volume of rehydration. Assess heart rate, blood pressure, urine output, and peripheral circulation, adhering to the principle of "better less than more."

What adverse effects can severe dehydration cause if untreated?

Severe dehydration can lead to impaired consciousness, low blood pressure, cardiac arrest, and life-threatening conditions. Insufficient blood supply to organs may cause ischemia and hypoxia, resulting in multiple organ failure.

What is the prognosis for dehydrated patients?

With timely fluid replenishment, most dehydrated patients recover well. Even those in shock can improve with active treatment. Doctors should continuously evaluate symptoms like dry mouth, urine output, skin elasticity, and peripheral circulation to adjust treatment. The vast majority of dehydration cases are curable.

DIET & LIFESTYLE

What should be paid attention to in terms of diet for dehydration?

The primary treatment for dehydration is oral or intravenous rehydration, with no specific dietary restrictions.

During dehydration, in addition to standard rehydration, you can choose to consume liquid or semi-liquid foods to replenish energy and fluids.

What should be paid attention to in daily life for dehydration?

There are no special precautions in daily life; maintaining a healthy lifestyle is sufficient.

Replenish fluids promptly after excessive sweating or fluid loss;

Ensure adequate sleep daily, regardless of early or late bedtime;

Learn to self-regulate when experiencing high stress or emotional tension.

PREVENTION

How to Prevent Dehydration?

• In daily life, dehydration often occurs due to hot weather, loss of body fluids and electrolytes, and failure to replenish them in time. With the recent scorching heat across the country, it's especially important to stay hydrated in such extreme temperatures.

• Additionally, people with chronic illnesses or athletes are more prone to dehydration. They should drink more water, replenish fluids, or take oral rehydration salts to prevent electrolyte imbalances.

• As older adults lose muscle mass, their body fluid levels also decrease, making them more susceptible to dehydration. Their sense of thirst may also become less sensitive.

• It is recommended to hydrate before and after sleep, bathing, and exercise.

• In hot summers, if you sweat excessively or experience dehydration due to diarrhea, remember to replenish electrolytes along with fluids. Vegetable soup, fruits, sports drinks, or oral rehydration salts are good options.

• If symptoms are severe, seek medical attention promptly.