Dehydration in children

Causes and mechanisms of development

Exicosis in children does not occur on its own. It is always a consequence of acute pathological conditions leading to abnormal fluid losses:

• Through the gastrointestinal tract: diarrhea and vomiting (the main mechanisms in intestinal infections). Vomiting is particularly dangerous because it not only removes fluid rich in ions (sodium, potassium, chloride, bicarbonates) but also makes oral rehydration impossible.
• Through the respiratory tract: rapid breathing (tachypnea) in respiratory infections leads to insensible water losses (perspiration).
• Through the skin: fever and profuse sweating.

A distinct category is acetonemic vomiting. In this condition, metabolic acidosis (due to the accumulation of ketone bodies) acts as a trigger for vomiting. This condition frequently occurs in children with a neuro-arthritic diathesis due to dietary errors, stress, or infections.

Pathogenetic classification (by osmolarity)

Depending on whether the body loses more water or electrolytes, three types of dehydration are distinguished:

1. Water-deficit (hypertonic). More water is lost. The blood becomes hemoconcentrated, and its osmolarity increases. Cells release fluid and "shrivel." It manifests with severe thirst, central nervous system excitation, and high fever. The skin is warm, mucous membranes are dry, but tissue turgor is initially preserved. Blood pressure (BP) does not drop immediately.
2. Salt-deficit (hypotonic). More electrolytes are lost. Blood osmolarity decreases, and fluid rushes into the cells, causing them to swell. This is the most severe variant for the brain (seizures, coma). Temperature is normal or decreased, skin is cold, and tissue turgor drops sharply ("cooling wax" sign). Blood pressure drops early, tachycardia is pronounced, and the pulse is weak.
3. Isotonic. Water and sodium are lost in proportion. Blood osmolarity is normal. The child is lethargic, the skin is cold with reduced turgor, and mucous membranes are moderately dry. Blood pressure is decreased, and tachycardia is present.

Clinical grades of severity

The severity of exicosis is assessed using three blocks: body weight deficit, local tissue signs, and systemic disorders.

• Grade I (mild). Weight loss up to 5%. This is the stage of initial manifestations: thirst is present, but local signs of dehydration (reduced turgor, sunken fontanelle) are absent. Systemic functions (diuresis, hemodynamics) are normal.
• Grade II (moderate). Weight loss of 6–9%. Full-blown clinical picture. Thirst is replaced by restlessness. Tissue signs appear: the skin loses elasticity, the mouth is dry, eyes are soft, and the large fontanelle is sunken. Systemic signs include oliguria, a moderate drop in blood pressure, and tachycardia. Compensated acidosis develops.
• Grade III (severe). Weight loss of 10% or more. Stage of decompensation (shock). The child is lethargic, there is no thirst. Tissue signs are critical (skin fold does not flatten). Sharp drop in blood pressure, bradycardia (a poor prognostic sign), oliguria progresses to anuria. Acidosis is decompensated.

Principles of treatment: rehydration

Treatment is based on eliminating the cause (e.g., correcting acidosis in acetonemic vomiting) and replenishing losses. The fluid volume always consists of the physiological requirement, current deficit, and ongoing losses.

Oral rehydration The method of choice for Grade I–II dehydration without signs of shock. Low-osmolarity glucose-electrolyte solutions are used. Glucose in their composition is essential for the active absorption of sodium and water in the intestine. Rules: in children under 3 years of age, electrolyte solutions are alternated with electrolyte-free fluids (tea, rice water). For diarrhea, the ratio is 1:1; for vomiting, 2:1 (electrolyte to electrolyte-free solutions). Administer fractionally (5–15 ml every 5–10 minutes).

Parenteral rehydration Indicated for severe dehydration (loss >7–10%), shock, uncontrollable vomiting, or failure of the oral method. Crystalloids (Ringer's solution, dextrose) are used. In hypovolemic shock, colloids (albumin, dextrans) must be added, but not exceeding 1/3 of the total infusion volume. Vasopressors (dopamine) are used if necessary.

Class and exam questions

What else to study on this topic

• Formulas and step-by-step method for calculating physiological fluid requirements based on the child's weight
• Calculation of the volume to compensate for ongoing losses (in fever, tachypnea, diarrhea)
• Calculation of volume deficit during the initial stage of oral rehydration
• Management tactics and pharmacological support in hypovolemic shock
• Features of water-electrolyte balance in acetonemic syndrome

Other topics in "Chapter 13. Main syndromes requiring emergency care"

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.