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

The Diagnosis of Salt Poisoning Leading to Hypematraemia in Children – September 2009
The last publication, from France in 1990 225 , describes a 2 year 11 month old child with an
initial sodium of 186 mmol/L, in whom there was suspicion of chronic water deprivation.
The child was reported by her parents always to be demanding something to drink. She
had been observed at preschool to be licking drops of water from windowpanes and from
puddles. She improved after removal from her parents. Both peer reviewers agreed (one
beyond reasonable doubt, one on the balance of probability) with the authors’ conclusions
that the child had been abused. However, they pointed out that the physiology was not
well worked out, and considered that the authors had failed to distinguish between water
deprivation and salt poisoning.
In the adult literature there is a case report of a prisoner who went on a “thirst strike” 242 ,
with a resulting plasma sodium of 164 mmol/L, a fractional urinary excretion of sodium of
0.21% (suggesting a normal sodium intake and renal function 27 ), and approaching a 20%
increase in weight after restoration of hydration. The resulting sodium concentration was
not nearly as high as in some of the children described above. It is therefore possible that
the children reported as hypernatraemic secondary to water deprivation may also have
been administered excessive salt.
Evidence statement
Although there are credible case reports of significant hypernatraemia in children
secondary to water deprivation, at least some of these children may have been
administered salt as well [Grade C].
Evidence statement
Careful measurement of weight at the time of admission and before restoration of full
hydration provides a reliable estimate of the degree of dehydration [Grade B].
This should be undertaken if possible in children presenting with hypernatraemia of
uncertain cause [Grade D].
Evidence statement
A urine sample for calculation of fractional urinary sodium excretion (for which
plasma and urine sodium and creatinine measurements taken at a similar time are
required) in the presence of normal renal function should help to ascertain whether the
hypernatraemia is secondary to excessive sodium ingestion [Grade D].
Regular urine samples for fractional urinary sodium excretion are recommended in
children presenting with hypernatraemia of uncertain cause [Grade D].
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