Assessment of Dehydration Percentage
This 6-month-old child has moderate dehydration, representing approximately 5-9% fluid deficit, most likely around 5-6%.
Clinical Assessment Framework
The presence of depressed fontanelle and sunken eyes are classic signs of moderate dehydration in infants, while the normal vital signs and alert/oriented mental status argue against severe dehydration (≥10%) 1, 2. The child's eagerness to drink indicates preserved thirst mechanism and consciousness, further supporting a moderate rather than severe classification 3.
Key Clinical Indicators Present
- Sunken eyes: This finding has a likelihood ratio of 2.5-4.0 for predicting dehydration ≥5% and is one of the most valid clinical signs 3, 4
- Depressed fontanelle: Associated with hospital admission (positive LR 3.4) and indicates clinically significant dehydration 5, 6
- Alert and oriented: Rules out severe dehydration, which typically presents with altered mental status or severe lethargy 1, 2
- Normal vital signs: Severe dehydration (≥10%) would typically show signs of shock, decreased perfusion, or abnormal respiratory pattern 4, 6
Dehydration Classification by Percentage
The clinical presentation fits moderate dehydration (6-9% fluid deficit) based on established guidelines 1, 2:
- Mild dehydration (3-5%): Increased thirst, slightly dry mucous membranes only 1
- Moderate dehydration (6-9%): Loss of skin turgor, dry mucous membranes, sunken eyes, depressed fontanelle 1, 2
- Severe dehydration (≥10%): Severe lethargy/altered consciousness, prolonged skin tenting, signs of shock 1, 2
Clinical Validation
Research demonstrates that children with sunken eyes and depressed fontanelle typically have fluid deficits of 4.9-5.3% when classified as moderate dehydration 3. The presence of two or more clinical signs (sunken eyes + depressed fontanelle) has 87% sensitivity and 82% specificity for detecting deficits ≥5% 6.
Treatment Implications
This child requires oral rehydration solution (ORS) at 100 mL/kg over 2-4 hours as first-line therapy for moderate dehydration 2, 7. The preserved alertness and normal vital signs indicate ORS therapy is appropriate without immediate need for intravenous access 7, 2.
Common Pitfall to Avoid
Do not underestimate dehydration severity based solely on normal vital signs in infants—compensatory mechanisms can maintain blood pressure and heart rate until severe dehydration develops 4. The combination of physical findings (sunken eyes + depressed fontanelle) is more reliable than vital signs alone for estimating fluid deficit 6.