Children most commonly develop dehydration from abnormal fluid losses secondary to vomiting and diarrhea or from inadequate fluid intake. Children who are mildly dehydrated typically demonstrate dry mucous membranes and decreased urination. With progression, reduced skin turgor, sunken eyeballs, hyperpnea, orthostatic hypotension, and tachycardia may be noted in children who are moderately dehydrated (10%). Severe dehydration (15%) is accompanied by decreased alertness, listlessness, and minimal urinary output (Table 1).
Orthostatic vital signs should be obtained in older children. When the patient rises from a lying to a standing (or sitting) position, a decrease in blood pressure of 15 mmHg or an increase in pulse of 20 beats per minute after 2 to 3 minutes is considered significant. Children can usually compensate for fluid losses because of the ability of their peripheral blood vessels to constrict and redistribute the blood flow centrally. With compensated shock, vital organ functions are maintained, associated with decreased central venous pressure, stroke volume, urine output, and increased heart rate and systemic vascular resistance. Perfusion to the periphery (skin and muscles) and to the kidneys and intestine may be compromised. Decreased skin perfusion may produce decreased skin temperature, impaired capillary refill (> 2 sec), and a pale, blue, or mottled appearance. Poor central nervous system perfusion ultimately produces impaired mental activity and poor responsiveness. An acute volume deficit of 10% may produce a minimal pulse increase, but progressive changes occur with further fluid deficit. Gradual volume losses are better tolerated.
With progression of poor fluid intake, shock may evolve with further impairment of perfusion. Ultimately, attempts at circulatory compensation may be overwhelming, leading to decompensation and inadequate tissue perfusion with accompanying ischemia, acidosis, and cell death.
Assessing hydration in younger children is determined both clinically, as described above, and historically. The number and degree of dampness of the diapers used during the preceding 6 to 8 hours is an excellent measure of hydration. Older children may be questioned regarding the frequency of urination and the amount of fluid taken. Determination of the specific gravity of urine is also a useful measure, often supplemented by electrolyte and blood urea nitrogen determinations.
Degree off Dehydration
Types of Dehydration
Although hypotonic and hypertonic dehydration may develop, by far the most common type of dehydration is isotonic, accompanied by sodium level of 130 to 150 mEq/mL. Clinical parameters of the patient with moderate dehydration may vary, reflecting the type of dehydration present,1 as shown in Table 2.
Restoration of vascular volume is essential. Patients who are significantly dehydrated require immediate infusion of fluids, particularly if there are abnormal vital signs or altered mental status.
When administering fluid therapy for the initial management of dehydration, the pediatrician should abide by the following guidelines if the patient has altered vital signs or mental activity or other signs and symptoms of moderate to severe dehydration (10% to 15%):
1 . Give 20 mL/kg of normal saline or lactated Ringer's solution over 20 minutes. If the child is over 8 years of age or has a documented normal glucose (Dextrostik, Chemstrip, or laboratory determination), dextrose may be omitted. Obviously, diabetics should not be given glucose initially.
2. If a poor therapeutic response is noted, the initial infusion should be repeated over 20 to 30 minutes, assuming normal renal and cardiac function.
3. If a poor therapeutic response is noted in the severely dehydrated child following two fluid infusions of a total of 40 mL/kg, or if there are ongoing losses or associated renal, cardiac, or pulmonary disease, monitoring with a central venous or arterial line may need to be initiated.
Following this initial intervention, further fluid management should then begin.
With initial vascular stabilization achieved using fluid boluses, ongoing management combining replacement of deficits with provision of maintenance fluids is essential. It is necessary to replace daily water and electrolyte losses from the skin and the respiratory, urinary, and gastrointestinal tracts. Such water losses may be summarized using the following daily maintenance fluid requirements:
* Children <10 kg- 100 mL/kg/24 hours
* Children 11 to 20 kg- 1000 mL plus 50 mL/kg/24 hours for each kg over 10 kg of weight
* Children >20 kg- 1500 mL plus 20 mL/kg/24 hours for each kg over 20 kg of weight
Electrolyte maintenance requirements primarily include 3 mEq/kg/24 hr of sodium, which predominantly occupies the extracellular fluid space, and 2 mEq/kg/24 hr of potassium, which is predominantly a component of intracellular fluid.
Correction of fluid and electrolyte imbalances is easily achieved in patients with isotonic dehydration with simple administration of appropriate amounts of the proper fluids, followed by close monitoring. Although the following schema provides guidelines for management of dehydration, it is essential to modify the administration of initial fluids to correct abnormalities in clinical and laboratory derangements. The amount of fluid deficit can be calculated by multiplying the percentage of dehydration (eg, 3%, 5%, 10%, etc) by the weight of the child (eg, a 10 kg child who is 10% dehydrated has a total deficit of 1000 mL or 100 mL/kg). The electrolyte composition of this fluid deficit depends on the rapidity of progression of dehydration, which normally consists of 60% extracellular and 40% intracellular fluid losses.
Ongoing abnormal losses will require extended therapy. Table 3 gives the calculations and subsequent management for the patient with isotonic dehydration; these may be modified to reflect the needs and size of a specific child.
In general, following a bolus of normal saline, D5W 0.45% normal saline with 30 mEq KCI/L is the appropriate fluid in the child with isotonic dehydration, infused at a rate reflecting both deficit and maintenance requirements.
Vomiting and Diarrhea - Parental Instruction Sheet
Oral rehydration has been recommended in specific circumstances for children who can tolerate oral fluids and who are under the care of a physician experienced in rehydration techniques. Oral glucose facilitates the absorption of sodium and water across the mucosal cells of the small intestine. Current recommendations in young children distinguish between fluids used for initial oral rehydration under close supervision, Rehydralyte® (similar to WHO oral rehydration solution, but with lower glucose and sodium chloride concentrations), and maintenance solutions, Lytren® or Pedialyte®.2,3
Less commonly, hypotonic dehydration may develop with excessive water intake or excessive salt loss. In children, the most common form of hyponatremia is associated with hypovolemia (decreased total body water) caused by abnormal gastrointestinal losses. Table 4 gives the calculations and subsequent management for the patient with hypotonic dehydration; these may be modified to reflect the needs and size of a specific child.
In the presence of severe hyponatremia with decreased total body water in symptomatic patients, hypertonic 3% saline may be given to raise the serum sodium to 125 mEq/L. Generally, 4 mL/kg are given intravenously over 10 minutes with close monitoring.
Most patients with hypernatremia have a deficit of free water, most often associated with the ingestion of boiled skim milk or excessive salt. Slow rehydration is the rule; rapid rehydration often results in serious neurologic complications, including seizures. The degree of dehydration is difficult to access.
If hypertension exists, 20 mL/kg of normal saline or lactated Ringer's solution should be given over the first hour to expand intravascular volume; otherwise, hypotonic intravenous fluid (D5W 0.20-0.45% normal saline) should be used. The remaining fluid deficit should be replaced over 48 hours, using D5W 0.20-0.45% normal saline with 25 mEq KC1/L. If the serum sodium is 175 mEq/L or more, deficit fluid therapy should be designed to decrease the level by 15 mEq/L/24 hr; if the serum sodium is less than 175 mEq/L, deficit fluid therapy should be designed to decrease the level halfway to normal (145 mEq/L) during the first 24 hours.
Following parenteral hydration, oral fluids should be initiated slowly, with Lytren or Pedialyte. The diet may be advanced slightly in both volume and composition. If the dehydration has followed an episode of acute gastroenteritis, a lactase deficiency may develop. In this instance, lactose-free formula should be used, following severe, prolonged diarrhea, a more elemental formula, such as Alimentum® or Pregestimil®, may be introduced.
Oral hydration is usually adequate in children who are mildly dehydrated (=S 5%), if the patient can tolerate oral intake. If oral fluids are not retained, a parenteral bolus (20 to 40 mL/kg) of D5W 0.9% normal saline or D5W lactated Ringer's solution should be given. Many children will tolerate oral fluid after this initial treatment; often only a short emergency department or inpatient admission is necessary. If vomiting continues, the patient requires hospitalization and parenteral fluid administration. Careful monitoring of fluid intake and output is essential.
Clear liquids should be pushed orally in such children, although slowly in the child who is vomiting. Do not use rice water, tea, or boiled milk, as they may be hypertonic. In infants, it is particularly important to provide adequate electrolytes while minimizing potential errors in formulation of solutions. Fluids such as Rehydralyte may be used initially followed by Lytren or Pedialyte.4
Once ongoing fluid losses have stopped, the diet may be advanced. Milk may be initiated slowly, although a lactose-free formula is better tolerated in recovering children. Applesauce and strained carrots and meat are usually tolerated and provide needed calories and nutrients.
Parental instruction sheets may be useful to provide added emphasis for home management (Table 5).
Dehydration is a potential life-threatening event to the child and requires early recognition and correction. Precise fluid management and follow-up is essential.
1. Barkin RM, Rosen P. Emergency Pediatrics: Guidi lo Ambulmart Care. 3id ed. St Louis, Mo: CV Mosby; 1990.
2. Pirarro D, Castillo B, Posada G, et al. Efficacy comparison of oral tehydration solutions containing eithet 90 ot 75 millimoles of sodium per liter. Pediatrics. I987;79:I90.
3. Tamer AM, Friedman LB. Maxwell SRW, et al. Oral rehydration of infants in a large urban US medical center. ; Pediarr. 1985; 107: 14.
4. Finbere L, Harper PA, Harrison HE, et al. Oral rehydration for diarrhea. ] Pediarr. 1982;l0l:497.
Degree off Dehydration
Types of Dehydration
Vomiting and Diarrhea - Parental Instruction Sheet