Background: Due to the lack of a reliable way of clinically measuring
dehydration, laboratory tests are usually used to improve the accuracy of clinical
assessment of dehydration in children. The purpose of this study was to compare the
relationship between clinical and laboratory parameters in the assessment of
dehydration and to evaluate the improvement of those parameters over time.
Methods: We conducted a retrospective study to assess the relationship
between clinical assessment of dehydration and laboratory findings.
Results: Three hundred children were eligible for the study. Twenty-six
per cent of those with mild dehydration had serum urea concentrations greater than
14.3 mmol/L, compared with 38% and 5% of those with moderate or no dehydration,
respectively. Urea concentration showed a good specificity, 95%. Creatinine
concentrations and mean pH were similar whether or not dehydration was present.
Bicarbonate and base excess concentrations decreased with the increasing severity of
dehydration and were significantly greater in subjects with moderate dehydration than
in those without. The sensitivity (71%) and specificity (74%) of both tests were
rather poor. All groups had an abnormal anion gap, which was significantly greater in
those with mild or moderate dehydration.
Conclusion: This study confirms that there is a discrepancy between
clinical assessment and laboratory parameters of dehydration. Urea showed good
specificity, and anion gap was the most sensitive laboratory parameter for assessment
of dehydration. These findings need further validation.
