The differential diagnosis of hypernatraemia in children, with ...

The Diagnosis of Salt Poisoning Leading to Hypematraemia in Children – September 2009
This study is important in the recognition of excessive sodium intake as it is
children with hypernatraemic dehydration who are the most likely to be confused
with them. However, none of these infants received intravenous 0.9% saline, and
the effects of this treatment on the FE Na is unknown.
In conclusion, there are a small number of case series which report normal values
for FE Na, and one study from which can be deduced the expected range of FE Na
values in young children presenting with gastroenteritis and dehydration.
Evidence statement
In the absence of renal failure, a raised calculated urinary fractional sodium
excretion is indicative of increased sodium excretion by the kidneys. The
fractional sodium excretion values reported in the 3 severely hypernatraemic
individuals were all 9.5% or above, well above the upper reported limits in
healthy children and in those presenting with gastroenteritis and dehydration.
[Grade D]
Further research into fractional excretion of sodium in normal infants
and children and those with other causes of hypernatraemia including
hypernatraemic dehydration is needed.
6.2.3 24 hour urinary sodium and chloride excretion
It is often not possible to obtain a 24-hour urine sample started at the time of the
presentation with hypernatraemia, and this will be impossible in patients who die soon
after admission. However, the following cases demonstrate that urine sample collection is
of value even after several days.
One case in which there is information on the urinary volume as well as the urinary sodium
concentration was of a 5 week old baby who had seizures and an admission sodium of 211
mmol/L 161 . No peritoneal dialysis was undertaken. His urinary sodium was measured on
arrival and then 12 and 20 hours later and on the subsequent 3 days, together with urine
outputs in mls/kg/hour at these times. Assuming that these values are representative of the
whole 24 hour periods, the following 24 hour urinary sodium outputs were seen:
1 st 24 hours: 11.3 mmol/kg
2 nd 24 hours: 10.7 mmol/kg
3 rd 24 hours: 10.1 mmol/kg
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