A child with dehydration has lost water; there is usually a concurrent loss of sodium and potassium. The fluid deficit is the percentage of dehydration multiplied by the patient’s weight (for a 10-kg child, 10% of 10 kg =1 L deficit).
Approach to Dehydration
The child with dehydration requires acute intervention to ensure that there is adequate tissue perfusion (see Chapter 40). This resuscitation phase requires rapid restoration of the circulating intravascular volume, which should be done with an isotonic solution, such as normal saline (NS) or Ringer’s lactate. Blood is an appropriate fluid choice for a child with acute blood loss. The child is given a fluid bolus, usually 20 mL/kg of the isotonic solution, over about 20 minutes. A child with severe dehydration may require multiple fluid boluses and may need to receive fluid at a faster rate. The initial resuscitation and rehydration is complete when signs of intravascular volume depletion resolve. The child typically becomes more alert and has a lower heart rate, normal blood pressure, and improved perfusion.
With adequate intravascular volume, it is now appropriate to plan the fluid therapy for the next 24 hours (Table 33-6). To
Restore intravascular volume Normal saline: 20 mL/kg over 20 minutes Repeat as needed
Rapid volume repletion: 20 mL/kg normal saline (maximum = 1 L) over 2 hours
Calculate 24-hour fluid needs: maintenance + deficit volume Subtract isotonic fluid already administered from 24-hour fluid needs
Administer remaining volume over 24 hours using D5 ½ normal saline + 20 mEq/L KCl Replace ongoing losses as they occur ensure that the intravascular volume is restored, the patient receives an additional 20 mL/kg bolus of isotonic fluid over 2 hours. The child’s total fluid needs are added together (maintenance + deficit). The volume of isotonic fluids the patient has received as acute resuscitation is subtracted from this total. The remaining fluid volume is then administered over 24 hours. Potassium usually is not included in the IV fluids until the patient voids, unless significant hypokalemia is present. Children with significant ongoing losses need to receive an appropriate replacement solution.
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All calculations in fluid therapy are only approximations. Thus,the patient needs to be monitored during treatment with therapymodifications based on the clinical situation (Table 33-7).
Hyponatremic dehydration occurs in children who have diarrhea and consume a hypotonic fluid (water or diluted formula). Volume depletion stimulates secretion of antidiuretic hormone, preventing the water excretion that should correct the hyponatremia. Some patients develop symptoms, predominantly neurologic, from the hyponatremia (see Chapter 35). Most patients with hyponatremic dehydration do well with the same general approach outlined in Table 33-6. Overly rapid correction of hyponatremia (>12 mEq/L/24 hr) should be avoided because of the remote risk of central pontine myelinolysis.
Hypernatremic dehydration is usually a consequenceof an inability to take in fluid, because of a lack of access, apoor thirst mechanism (neurologic impairment), intractableemesis, or anorexia. The movement of water from the intracellular space to the extracellular space during hypernatremic dehydration partially protects the intravascular volume.Urine output may be preserved longer, and there may be lesstachycardia. Children with hypernatremic dehydration areoften lethargic and irritable. Hypernatremia may cause fever,
Clinical signs of depletion or overload Electrolytes hypertonicity, hyperreflexia, and seizures. More severe neurologic symptoms may develop if cerebral bleeding or thrombosis occurs.