Affiliations: Department of Pediatrics, College of Medicine and
Health Sciences, United Arab Emirates University, Al Ain, United Arab
Emirates
Note: [] Corresponding author: Hassib Narchi, Department of Pediatrics,
College of Medicine and Health Sciences, United Arab Emirates University, Al
Ain, P.O. Box 17666, United Arab Emirates. Tel.: +971 37137 414; Fax: +971
37672 022; E-mail: hassib.narchi@uaeu.ac.ae
Abstract: Hypernatremia results from a deficit of total body water in relation
to the total body's sodium stores. This is caused by two main
mechanisms: 1) net water depletion exceeding sodium losses or 2) increased
sodium gain exceeding water gain. Net water depletion occurs when increased
water loss exceeds sodium loss, either due to extrarenal losses (increased
evaporative water losses, hypernatremic dehydration caused by diarrhea) or to
renal losses (central and nephrogenic diabetes insipidus, intrinsic renal
disease). Insufficient water intake occurs with neonatal hypernatremic
dehydration secondary to lactation failure, essential hypernatremia or
osmoreceptor dysfunction. Increased sodium gain can be caused by iatrogenic
hypernatremia, administration of concentrated infant formula, deliberate
abusive water restriction and deliberate or non-accidental salt poisoning.
Hypernatremia results in a movement of water across cell membranes from the
intracellular to the extracellular space, resulting in cellular dehydration,
which, in cells of the central nervous system results in brain shrinkage
leading to tearing of cerebral blood vessels and neurological complications. As
a protective mechanism, idiogenic osmoles accumulate inside the brain cells to
help them retain water intracellularly. However this may lead to cerebral edema
during rapid rehydration as these idiogenic osmoles attract water inside the
neurons. As the appropriate management of hypernatremia invariably depends on
the underlying mechanism and cause, a methodical history taking and clinical
examination, with the judicious use of laboratory tests will lead to a precise
etiological diagnosis to enable appropriate and timely therapy.
