Pediatric Dehydration Workup

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 hyperglycemia or hypoglycemia is suspected
• Consider checking serum electrolytes in the moderately dehydrated child if the history or physical examination findings are inconsistent with straightforward gastroenteritis^[4]
• Check serum electrolyte levels in all children with severe dehydration and in those receiving intravenous fluids
• Pursue appropriate testing when a diagnosis other than straightforward gastroenteritis is suspected

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

• Basic metabolic panel
• Venous blood gases
• Serum lactic acid
• Complete blood cell count (CBC)
• Urinalysis

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

Venous blood gas measurements are indicated in patients with severe volume depletion. Serum pH provides a more direct measure of acidosis than the calculated bicarbonate level.

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.

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.^[5]

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.^[6]

For central venous access, typical sites are as follows:

• Femoral vein
• Internal jugular vein
• Subclavian vein
• Antecubital veins

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 emergency department.

Use venous cutdown for emergent access and resuscitation only. 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.