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Make the Diagnosis: Hypovolemia, Child

Prior Probability

Dehydration develops progressively, depending on the underlying condition, and therefore, a consistent prior probability of dehydration cannot be established for most general conditions. For infants and children whose parents bring them for emergency care for diarrhea, vomiting, or poor oral intake, the prevalence of at least 5% dehydration is approximately 25% (95% CI, 14%-39%).

Population for Whom Childhood Dehydration Should Be Considered

In our initial article, we were unable to identify published parental historical elements that made dehydration more likely. However, vomiting, diarrhea, change in oral intake, decreased urine output, fever, change in mental status, or the presence of potentially dehydrating underlying conditions (eg, diabetes insipidus) prompts an evaluation for dehydration.6

Detecting the Likelihood of Childhood Dehydration

Accurately identifying the presence of dehydration requires the use of combinations of signs. Combinations of findings can include results being either present or absent or graded on an ordinal scale (eg, 0, 1, 2) and then summed across findings. Each scale must be assessed in comparison with the reference standard. See Table 25-7.

Table 25-7.Likelihood Ratio of Combinations of Findings for Greater Than or Equal to 5% Dehydration

Reference Standard Tests

The difference between the “well” weight and the acute weight divided by the well weight represents the standard for the percentage of volume lost because of dehydration.

Original Article: Is This Child Dehydrated?

Clinical Scenarios

Case 1

A 20-month-old girl is brought to the emergency department (ED) after 2 days of vomiting and diarrhea. Her father reports that she has not eaten normally since the illness began and now will not drink. She has had 8 stools so far today, but he does not think there were any diapers with urine in them. The child appears mildly ill but does make tears while crying. Her respiratory rate and quality are normal, along with her other vital signs. Her mouth is somewhat dry, capillary refill time is 1.5 seconds, and skin turgor is normal. Her serum (blood) urea nitrogen concentration (BUN) is 12 mg/dL, and bicarbonate concentration is 19 mEq/L.

Case 2


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