Fontanel depression

Depression of the anterior fontanel below the surrounding bony ridges of the skull is a sign of dehydration. A common disorder of infancy and early childhood, dehydration can result from insufficient fluid intake, but typically reflects excessive fluid loss from severe vomiting or diarrhea. It may also reflect insensible water loss, pyloric stenosis, or tracheoesophageal fistula. It’s best to assess the fontanel when the infant is in an upright position and isn’t crying.

Emergency interventions

If you detect a markedly depressed fontanel, take the infant’s vital signs, weigh him, and check for signs of shock — tachycardia, tachypnea, and cool, clammy skin. If these signs are present, insert an I.V. line and administer fluids. Have size-appropriate emergency equipment on hand. Anticipate oxygen administration. Monitor urine output by weighing wet diapers.

History and physical examination

Obtain a thorough patient history from a parent or caretaker, focusing on recent fever, vomiting, diarrhea, and behavioral changes. Monitor the infant’s fluid intake and urine output over the past 24 hours, including the number of wet diapers during that time. Ask about the child’s preillness weight, and compare it to his current weight; weight loss in an infant reflects water loss.

Medical causes

Dehydration

With mild dehydration (5% weight loss), the anterior fontanel appears slightly depressed. The infant has pale, dry skin and mucous membranes; decreased urine output; a normal or slightly elevated pulse rate; and, possibly, irritability

Moderate dehydration (10% weight loss) causes slightly more pronounced fontanel depression, along with gray skin with poor turgor, dry mucous membranes, decreased tears, and decreased urine output. The infant has normal or decreased blood pressure, an increased pulse rate and, possibly, lethargy.

Severe dehydration (15%or greater weight loss) may result in a markedly sunken fontanel, along with extremely poor skin turgor, parched mucous membranes, marked oliguria or anuria, lethargy, and signs of shock, such as a rapid, thready pulse; very low blood pressure; and obtundation.

Special considerations

Continue to monitor the infant’s vital signs and intake and output, and watch for signs of worsening dehydration. Obtain serum electrolyte values to check for an increased or decreased sodium, chloride, or potassium level. If the patient has mild dehydration, provide small amounts of clear fluids frequently or provide an oral rehydration solution. If the infant can’t ingest sufficient fluid, begin I.V. parenteral nutrition.

If the patient has moderate to severe dehydration, your first priority is rapid restoration of extracellular fluid volume to treat or prevent shock. Continue to administer I.V. solution with sodium bicarbonate added to combat acidosis. As renal function improves, administer I.V. potassium replacements. When the infant’s fluid status stabilizes, begin to replace depleted fat and protein stores through diet.

Tests to evaluate dehydration include urinalysis for specific gravity and, possibly, blood tests to determine blood urea nitrogen and serum creatinine levels, osmolality, and acid-base status.

Book Source Details

• Book Title: Handbook of Signs & Symptoms (Third Edition)
• Author(s): Springhouse
• Year of Publication: 2006
• Copyright Details: Handbook of Signs & Symptoms (Third Edition), Copyright © 2006 Lippincott Williams & Wilkins.

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More About This Book: Title: Handbook of Signs & Symptoms (Third Edition) Authors: Springhouse Publisher: Lippincott Williams & Wilkins Copyright: 2006 ISBN: 1-58255-402-1

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