abnormal skin turgor, and abnormal respiratory pattern A combination of examination signs provided the best predictive data In the setting of severe dehydration (greater than or equal to 10% volume loss), evidence of shock may be apparent, with hypotension, poor peripheral perfusion with prolonged capillary refill time, cool or mottled extremities, lethargy, and rapid deep respirations Severe hypovolemia requires immediate attention with aggressive isotonic fluid resuscitation, especially in patients with sepsis (see Chapter 10 Shock ) Though laboratory assessment has been shown to be less useful than physical findings when predicting the degree of volume depletion, laboratory testing can identify associated electrolyte and acid–base abnormalities Classification of the type of hypovolemia based upon the serum sodium may impact subsequent fluid therapy and monitoring Solute is primarily composed of sodium salts in the extracellular fluid (ECF) and potassium salts in the intracellular fluid (ICF) The presenting serum sodium in the child with hypovolemia results from the loss of solute relative to water during the illness Determinants of the serum sodium include the type of fluid lost, the composition of fluid provided prior to presentation, and the ability to excrete water during the illness Hyponatremic hypovolemia (serum sodium less than 135 mEq/L) reflects the net loss of solute in excess of water Isonatremic hypovolemia (serum sodium 135 to 145 mEq/L) results when solute is lost in proportion to water, and hypernatremic hypovolemia (serum sodium greater than 145 mEq/L) reflects net loss of water in excess of solute Other biochemical abnormalities that may develop during hypovolemia include disorders of potassium homeostasis, acid–base abnormalities, and increased blood urea nitrogen (BUN) and creatinine, reflecting a decline in glomerular filtration rate (GFR) Though hyperkalemia may result, hypokalemia is more commonly seen in children with gastroenteritis given the loss of potassium in diarrheal fluid and urine Urine losses of potassium may be significant and driven by aldosterone The effect of aldosterone is to conserve urinary sodium to maintain effective intravascular volume and promote potassium excretion Management Initial management will depend on the severity of hypovolemia and presence of abnormalities of serum sodium, but the aims of treatment are to restore perfusion and maintain adequate volume in the face of ongoing losses Oral therapy, when tolerated, is the preferred treatment of fluid and electrolyte losses in children with mild to moderate dehydration In general, limitations to ORT include severe dehydration, altered mental status, possible surgical pathology that would mandate NPO status, abdominal ileus or disorders that limit intestinal absorption, severe and persistent vomiting, excessive stool losses, and severe electrolyte abnormalities Patients who have moderate or severe hypovolemia will have compromised effective circulating volume, and rapid volume resuscitation is required to restore perfusion and avoid tissue damage Emergent IV fluid therapy should be provided with a rapid infusion of 20 mL/kg of isotonic crystalloid 0.9% sodium chloride (NS) is used most frequently, but lactated Ringer (LR) solution may be appropriate as well Patients with severe hypovolemia should receive their first bolus over 20 minutes by pressure bag or push–pull technique, and may require up to 60 mL/kg in the first hour of resuscitation, especially with sepsis (see Chapter 10 Shock ) There is currently no evidence that addition of dextrose to the crystalloid provides any significant clinical benefit without evidence of hypoglycemia The child should be reassessed during and at completion of the IV bolus in order to determine if additional bolus therapy is indicated and to avoid volume overload Crystalloid boluses should be repeated until adequate perfusion has been restored Intraosseous administration of volume replacement is an appropriate alternative if IV access is not available Currently, there are inadequate data to support the use of colloid-containing solutions during resuscitation in the general population However, if a patient with decreased oncotic pressure due to an illness such as nephrotic syndrome or cirrhosis presents with hypovolemia, he may benefit from infusion of a colloid solution such as 5% albumin when serum albumin level is less than 2.0 to 2.5 g/dL TABLE 100.1 WEIGHT-BASED DAILY MAINTENANCE FLUID FOR CHILDREN Body weight (kg) Daily fluid requirements 3.5–10 11–20 100 mL/kg/day 1,000 mL + 50 mL/kg (for each kg >10), maximum 1,500 mL/day 1,500 mL + 20 mL/kg (for each kg >20), typical maximum 2,400 mL/day >20 Once circulating volume has been adequately restored, the second phase of fluid therapy corrects persistent deficits, replaces ongoing losses, and provides maintenance fluids The maintenance requirements for fluid in children are outlined in Table 100.1 Although common practice has been to provide relatively hypotonic maintenance fluids (D5 ẳ NS or D5 ẵ NS) based upon deficit calculations and maintenance requirements, recent publications have highlighted the potential risks of acquired hyponatremia in some hospitalized patients receiving hypotonic fluids, especially in the setting of substantial ongoing losses In its 2018 Clinical Practice Guideline, the American Academy of Pediatrics recommends that most patients 28 days to 18 years of age requiring maintenance IV fluids should receive isotonic solutions with dextrose (D5NS) and appropriate KCl to decrease the risk of hyponatremia These recommendations apply to children in surgical (postoperative) and medical acute care settings, including critical care and the general inpatient ward Patients with neurosurgical disorders, congenital or acquired cardiac disease, hepatic disease, cancer, renal dysfunction, diabetes insipidus, voluminous watery diarrhea, or severe burns were excluded If isotonic fluid is used for maintenance therapy, the risks of sodium excess, inadequate free water provision during ongoing hypotonic losses, and hypernatremia must be considered Examples of the treatment of isonatremic, hyponatremic, and hypernatremic hypovolemia are provided in Tables 100.2 to 100.4 In all cases, the fluid of choice for the initial emergent phase of volume resuscitation is isotonic saline In most cases, the plan for replacement usually does not need to be exact as the kidneys will correct the electrolytes once well perfused and additionally enteral feeding is often initiated Isonatremic hypovolemia Table 100.2 outlines the estimated deficits and therapeutic approach to a 10-kg child with isotonic hypovolemia In this example, the isotonic deficit is corrected by an initial bolus of isotonic saline followed by ongoing repletion The traditional approach of deficit calculation and therapy is outlined Replacement of ongoing extrarenal losses should be provided if the volume of losses is significant Repeated assessment of the serum sodium may be indicated on the basis of losses and duration of IV therapy ... of substantial ongoing losses In its 2018 Clinical Practice Guideline, the American Academy of Pediatrics recommends that most patients 28 days to 18 years of age requiring maintenance IV fluids