pediatrics
Dehydration in Children
Treatment of Dehydration in Children
Fluid replacement (oral if possible) Treatment of dehydration is best approached by considering the following separately: Fluid resuscitation requirements Current deficit Ongoing losses Maintenance requirements The volume (eg, amount of fluid), composition, and rate of replacement differ for each. Formulas and estimates used to determine treatment parameters provide a starting place, but treatment requires ongoing monitoring of vital signs, clinical appearance, urine output, weight, and sometimes serum electrolyte levels. The American Academy of Pediatrics and the World Health Organization (WHO) both recommend Oral Rehydration for mild and moderate dehydration. Children with severe dehydration (eg, evidence of circulatory compromise) should receive fluids IV. Children who are unable or unwilling to drink or who have repetitive vomiting can receive fluid replacement orally through frequently repeated small amounts, through an IV, or through a nasogastric tube (see Patients with signs of hypoperfusion should receive fluid resuscitation with boluses of isotonic fluid (eg, 0.9% saline or Ringer's lactate). The goal is to restore adequate circulating volume to restore blood pressure and perfusion. The resuscitation phase should reduce moderate or severe dehydration to a deficit of about 6 to 8% body weight. If dehydration is moderate, 20 mL/kg (2% body weight) is given IV over 20 to 30 minutes, reducing a 10% deficit to 8%. If dehydration is severe, 3 boluses of 20 mL/kg (6% body weight) may be required. The end point of the fluid resuscitation phase is reached when peripheral perfusion and blood pressure are restored and the heart rate is returned to normal (in an afebrile child). Total deficit volume is estimated clinically as described previously. Sodium deficits are usually about 60 mEq/L (60 mmol/L) of fluid deficit, and potassium deficits are usually about 30 mEq/L (30 mmol/L) of fluid deficit. The resuscitation phase should have reduced moderate or severe dehydration to a deficit of about 6 to 8% body weight; this remaining deficit is typically replaced over the next 24 hours. Because 0.45% saline has 77 mEq sodium per liter (77 mmol/L), it is usually an appropriate fluid choice, particularly in children with diarrhea, because the electrolyte content of diarrhea is typically 50 to 100 mEq/L (50 to 100 mmol/L) (see table); 0.9% saline may be used as well. Potassium replacement (usually by adding 20 to 40 mEq potassium per liter [20 to 40 mmol/L] of replacement fluid) should not begin until adequate urine output is established. Dehydration in neonates, particularly with significant Neonatal Hypernatremia (eg, serum sodium Volume of ongoing losses should be measured directly (eg, nasogastric tube, catheter, stool measurements) or estimated (eg, 10 mL/kg per diarrheal stool). Replacement should be milliliter for milliliter in time intervals appropriate for the rapidity and extent of the loss. Ongoing electrolyte losses can be estimated by source or cause (see table). Urinary electrolyte losses vary with intake and disease process but can be measured if electrolyte abnormalities fail to respond to replacement therapy. (See also the American Academy of Pediatrics'clinical practice guideline (2018)for maintenance IV fluids in children.) Fluid and electrolyte needs from basal metabolism must also be accounted for. Maintenance requirements are related to metabolic rate and affected by body temperature. Insensible losses (evaporative free water losses from the skin and respiratory tract) account for about one third of total maintenance water (slightly more in infants and less in adolescents and adults). Volume rarely must be exactly determined but generally should aim to provide an amount of water that does not require the kidney to significantly concentrate or dilute the urine. The most common estimate is the Holliday-Segar formula, which uses patient weight to calculate metabolic expenditure in kcal/24 hours, which approximates fluid needs in mL/24 hours (see table). More complex calculations (eg, those using body surface area) are rarely required. Maintenance fluid volumes can be given as a separate simultaneous infusion, so that the infusion rate for replacing deficits and ongoing losses can be set and adjusted independently of the maintenance infusion rate. Baseline estimates are affected by fever (increasing by 12% for each degree>37.8°C), hypothermia, and activity (eg, increased for hyperthyroidism or status epilepticus, decreased for coma). The traditional approach to calculating the composition of maintenance fluids was also based on the Holliday-Segar formula. According to that formula, patients require Sodium: 3 mEq/100 kcal/24 hours (3 mEq/100 mL/24 hours) Potassium: 2 mEq/100 kcal/24 hours (2 mEq/100 mL/24 hours) (NOTE: 2 to 3 mEq/100 mL is equivalent to 20 to 30 mEq/L [20 to 30 mmol/L].) solution. Other electrolytes (eg, magnesium, calcium) are not routinely added. Normally, serum osmolarity controls moment-to-moment antidiuretic hormone (ADH) release. ADH release can also occur in response to vascular volume and not osmolarity (nonosmotic ADH release). Recent literature suggests that hospitalized dehydrated children receiving 0.2% saline for maintenance fluid sometimes develop Neonatal Hyponatremia . This development is likely due to volume-related ADH release as well as to significant amounts of stimuli-related ADH release (eg, from stress, vomiting, dehydration, or hypoglycemia). The ADH causes increased free water retention. Iatrogenic hyponatremia may be a greater problem for more seriously ill children and those who are hospitalized after surgery where stress plays a bigger role. Because of this possibility of iatrogenic hyponatremia, many centers are now using a more isotonic fluid such as 0.45% or 0.9% saline for maintenance in dehydrated children. The American Academy of Pediatrics'clinical practice guideline (2018)recommends all patients 28 days to 18 years of age receive isotonic solutions with appropriatepotassium chlorideanddextroseas maintenance IV fluids. This change also has the benefit of allowing use of the same fluid to replace ongoing losses and supply maintenance needs, which simplifies management. Although practice variation still exists in choosing appropriate maintenance IV fluids, all clinicians agree the important point is to closely monitor dehydrated patients receiving IV fluids, which includes monitoring of serum electrolyte levels. 