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

The Diagnosis of Salt Poisoning Leading to Hypematraemia in Children – September 2009
A study from Vancouver 19 (evidence level 2b) surveyed all breast fed babies less than 28
days presenting to one hospital with a serum sodium exceeding 145mmol/L. They found 19
babies with hypernatraemic dehydration, the highest serum sodium being 207mmol/L. No
denominator information was supplied, so the incidence cannot be calculated. Similarly, an
Italian study 20 (evidence level 1b) of all referrals of healthy term breast fed infants to one
unit over a 6 month period from October 1999 found hypernatraemia in 19 of 53 infants
with postnatal weight loss of over 10%. No denominator information on the population
from which these babies presented was given. A study from Cincinnati (a tertiary centre) 21
(evidence level 4) reported 5 breast fed infants with a serum sodium between 161 and 214
mmol/L over a 5 month period. These appear to be selected cases, and the authors did
not attempt to estimate the incidence. However, in a retrospective review between 1990
and 1994, they found an increasing number of cases. A further case series from Israel 22
(evidence level 4) provided no estimate of incidence.
None of these reported any infants with suspicions of salt poisoning.
No studies were found of the incidence of hypernatraemia in children (excluding lactation
failure) in the UK. One study from Houston, Texas 23 (evidence level 2b) reported 68 children
of all ages admitted to hospital with hypernatraemia (>150mmol/L) over a 2-year period
from January 1992. The hypernatraemia was hospital acquired in 41 (60%), and 60 children
had an associated medical problem before developing hypernatraemia. Gastroenteritis was
a contributing factor in only 14 children. There were no cases due to errors in infant feeds,
pharmacy errors, salt poisoning or breastfeeding malnutrition. The authors did not attempt
to estimate the annual incidence per head of population. The city of Houston had a total
population of just under 2 million in 2000 24 , with 594,000 children under the age of 20
years. This would indicate an approximate annual incidence of between 5 and 6 per 100,000
children with hypernatraemia, or 2 per 100,000 children with hypernatraemia on admission.
A similar study from Pittsburgh in adults in 1993 25 reached similar conclusions about the
range of causes of hypernatraemia.
In summary, there is a paucity of evidence on the incidence of hypernatraemia outside
the neonatal period, where the best estimate of hypernatraemic dehydration in breast fed
infants is 7.1 per 10,000 live births. A very approximate figure of 2 per 100,000 children
per year is suggested by the Texas study.
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