Pediatric Dehydration Workup

Updated: Nov 12, 2018
  • Author: Alex Koyfman, MD; Chief Editor: Muhammad Waseem, MBBS, MS, FAAP, FACEP, FAHA  more...
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Approach Considerations

Laboratory studies are of limited use in cases of mild dehydration. However, they should be considered under certain conditions, such as the following:

  • Consider a fingerstick to check serum glucose level in all patients, especially if mental status is not at baseline or hyperglycemia or hypoglycemia are suspected

  • Consider checking serum electrolytes in the moderately dehydrated child if the history or physical examination findings are inconsistent with straightforward gastroenteritis [7]

  • Check serum electrolyte levels in all children with severe dehydration and in those receiving intravenous fluids

  • Pursue appropriate testing when a diagnosis other than gastroenteritis is suspected

For children who are in hypovolemic shock, the following studies are recommended:

  • Comprehensive metabolic panel to include electrolytes, BUN, Cr, glucose, iCa, Phosphate, Magnesium, Albumin.

  • Venous blood gases

  • Serum lactic acid

  • Complete blood cell count (CBC)

  • Urinalysis

Serum electrolyte levels are important to determine sodium concentration, which can guide resuscitation. Bicarbonate and potassium levels also are important to assess the degree of metabolic acidosis from volume depletion and tissue hypoperfusion as well a screen for coexisting hypokalemia. Blood urea nitrogen and creatinine levels measure renal function and intravascular volume. The glucose measurement may reveal hyperglycemia or hypoglycemia.

Serum lactate elevation is indicative of tissue perfusion and oxygenation resulting in anaerobic metabolism. It may be helpful in cases of severe dehydration or sepsis. The CBC may be helpful in cases in which volume depletion is due to sepsis or hemorrhage. On urinalysis, the urine specific gravity indicates the degree of volume depletion. Urinalysis may also reveal an underlying infectious etiology.

Bedside ultrasound has also been used to measure the inferior vena cava and the aorta diameter ratio and has been found to be a marginally accurate measurement of acute weight loss in children with dehydration due to gastroenteritis. [8, 9] A study also reported that ultrasound measured inspiratory inferior vena cava collapse and physician gestalt were poor predictors of the actual level of dehydration. [9]

Jauregui et al designed a study to validate if the ratio of the ultrasound-measured diameter of the inferior vena cava (IVC) to the aorta (Ao) correlates with the level of dehydration in children as previous studies have reported. The study also tested the accuracy of the ultrasound measured inspiratory IVC collapse and physician gestalt to predict significant dehydration in children in the emergency department. The authors concluded that the ultrasound-measured IVC/Ao ratio is a modest predictor of significant dehydration in children. The inspiratory IVC collapse and physician gestalt were poor predictors of the actual level of dehydration in this study. [10]


Obtaining Vascular Access

Prior to vascular access attempts, consider oral rehydration in mild and moderate dehydration. A significant body of evidence indicates that an initial trial of oral rehydration with small, frequent volumes of electrolyte-containing solution (5-10 mL every 5-10 min) for pediatric patients with mild to moderate volume depletion is simple and effective, avoiding the more resource-intensive methods that are noxious to infants and children. [11]

Typical sites for intravenous access include superficial veins in the dorsum of the hand, the antecubital fossa (median cephalic or basilic veins), dorsum of the foot, and scalp veins.

Use intraosseous access if attempts to start percutaneous intravenous lines are unsuccessful. Typical sites are the proximal anterior tibia and the distal femur. [12]

For central venous access, typical sites are as follows:

  • Femoral vein

  • Internal jugular vein

  • Subclavian vein

Bedside ultrasound guidance should be used whenever possible to facilitate direct visualization when placing these lines. In infants and young children, access to the internal jugular vein may be difficult because of the short necks. Umbilical vein catheterization may be difficult and usually is not recommended for neonates who have been discharged from the hospital and are returning to the ED.

Use venous cutdown for emergent access and resuscitation only when intraosseous access is not available or fails. Safe performance depends on the skill of the provider. The typical site is the distal saphenous vein, which is anterior and superior to the medial malleolus.