FIGURE 22.1 Suspected dehydration BSA, body surface area; NS, normal saline; GI, gastrointestinal; CNS, central nervous system; Hx, history; DKA, diabetic ketoacidosis; CAH, congenital adrenal hyperplasia; ATN, acute tubular necrosis; DI, diabetes insipidus; CF, cystic fibrosis TABLE 22.3 OTHER CONSIDERATIONS FOR VOMITING ALONE Diabetic ketoacidosis Increased intracranial pressure Otitis media Heart failure Obstruction (e.g., pyloric stenosis) Urinary tract infection Ingestion Age of the child, nutritional status, and type of dehydration may also affect clinical assessment, which is critical to effective management of the acutely dehydrated child In general, older children show signs of dehydration sooner than babies because of their lower levels of extracellular water Babies with excess subcutaneous fat may look less dehydrated than they really are, whereas severely malnourished babies may appear to be more dehydrated secondary to wasted supporting tissues Signs of dehydration may be less evident or appear later in hypernatremic dehydration Excessive irritability with increased muscle tone, and doughy or smooth and velvety skin, often are noted with this type of dehydration Conversely, signs of dehydration may be more pronounced or appear sooner in hyponatremic dehydration Keeping these observations in mind, particular attention should be paid to the overall appearance, mental status, eyes, and skin on physical examination Patients with obvious burns or diseases that disrupt the integument in the same way (e.g., scalded skin syndrome) are presumed to have become dehydrated through transudation of fluid through the skin Additional considerations are listed in Table 22.1 The mildly dehydrated child usually appears well or may be tired, have decreased tearing, and a slightly dry mouth Dry mucous membranes are an early sign of dehydration, but this finding is affected by rapid breathing and ingestion of fluids Conversely, the severely dehydrated baby classically appears quite ill with lethargy or irritability, a dry mouth, sunken fontanel, and absent tears Moderate states of dehydration, however, require careful evaluation One of the more objective measures of dehydration is assessment of skin perfusion by measuring capillary refill time Although the child’s body temperature does not predictably affect capillary refill time, it may be falsely prolonged when measured on the foot or in a cool room Laboratory In general, laboratory values are not helpful in diagnosing dehydration, rather the history and physical examination should be used However, in children who are judged to have moderate to severe dehydration that requires intravenous (IV) rehydration, laboratory tests of electrolytes, glucose, blood urea nitrogen, and creatinine are usually obtained to determine osmolarity and renal function Approximately one-third of moderately to severely dehydrated children will have hypoglycemia less than 60 mg/dL Based on the initial serum sodium, most children have isonatremic dehydration (also referred to as isotonic dehydration, serum sodium 130 to 150 mEq/L), whereas others have hypernatremic dehydration (hypertonic dehydration, serum sodium greater than 150 mEq/L) or hyponatremic dehydration (hypotonic dehydration, serum sodium less than 130 mEq/L) The acid–base status may be assessed further with an arterial or venous blood gas Urine specific gravity and ketones cannot be reliably used as indicators for dehydration However, a history of polyuria and the presence of glucose and ketones may indicate diabetic ketoacidosis, whereas a history of disorders of the central nervous system (CNS) suggests diabetes insipidus Diagnostic Approach In approaching the patient with presumed dehydration, the initial assessment serves to determine whether compensated or uncompensated shock is present If the child appears to be in shock, resuscitation should begin and a number of lifethreatening disorders need to be considered, as discussed in Chapter 10 Shock A detailed history, including assessment of intake and output, aids in determining the etiology of the patient’s dehydration Together, the physical examination and history usually allow the physician to establish a diagnosis and degree of dehydration Laboratory evaluation is not routinely needed to determine that a patient is dehydrated, but may be collected to assess for suspected electrolyte abnormalities, or to make a diagnosis of a disease at risk for dehydration (i.e., diabetes mellitus) Initial Management The dehydrated child must be examined immediately for the degree of dehydration or state of hypovolemic shock If there is severe dehydration or uncompensated shock, the patient is treated acutely with isotonic fluids to restore intravascular volume regardless of serum osmolarity or cause of the dehydration Normal saline or Ringer lactate is given via an IV or intraosseous line in 20 mL/kg aliquots over approximately 15 to 30 minutes, or as quickly as possible if there is uncompensated shock Reassessment is paramount after each fluid bolus for the patient’s response to treatment Careful reevaluation must be undertaken as rapid infusion of IV fluids in a patient who is actually in heart failure will be detrimental causing worsening of the condition When blood pressure is restored, heart rate returns to normal, distal pulses strengthen, and skin perfusion improves, isotonic fluids may be safely discontinued Careful attention should be paid to ongoing losses Urine output is the most important indicator of restored intravascular volume in patients with intact renal and adrenal function, and without diabetes mellitus or insipidus, and should be a minimum of mL/kg/hr Hypoglycemia can often coexist in severe dehydration Dextrose can be given via IV An initial bolus of mL/kg of D10 can be given via peripheral IV or, if a central line is present, mL/kg of D25 Oral Rehydration Therapy If the child is determined to be mildly or moderately dehydrated, then oral rehydration therapy (ORT) is the therapeutic option of choice ORT is the frequent administration of small volumes of an appropriate rehydration solution, typically with an oral syringe The use of ondansetron, a serotonin 5HT3 selective receptor antagonist, has clearly been shown to improve the success of rehydration with ORT in patients greater than months of age ( Table 22.4 ) A one-time dose has been shown to be sufficient and prescribing for home use has not been shown to reduce return rates to the ED Once given, ORT should be initiated in 15 to 30 minutes An appropriate rehydration solution has the correct balance of glucose and sodium, which enables the body to absorb the water passively via the sodium glucose cotransport mechanism in the small intestine The glucose-tosodium ratio is an important determinant in the acceptability of these solutions Optimal solutions have a 1:1 or a 2:1 glucose:sodium ratio When additional sweetener is added to the rehydration solution, the ratio of glucose to sodium is distorted and may result in osmotic diarrhea or inappropriate absorption of electrolytes There are two categories of rehydration solutions: initial rehydration solutions that contain 60 to 90 mEq/L of sodium (e.g., Rehydralyte, World Health Organization oral rehydration solutions) and maintenance solutions that contain 40 to 60 mEq/L of sodium (e.g., Pedialyte) If the etiology of the dehydration is presumed to be due to cholera, then the higher sodium concentration is appropriate because there is a large sodium loss in the diarrhea stools of cholera patients However, if the etiology of the dehydration is presumed to be viral gastroenteritis, then the lower sodium concentration solutions would be appropriate and are more readily available Both rehydration and maintenance solutions have approximately 20 mEq/L of potassium and a low glucose