The syndrome of inappropriate ADH secretion.
This arises when there is
excess ADH release.
ADH causes excess water retention
by the kidneys
and can lead to
a dilutional hyponatremia.
What you will notice when checking
the electrolytes on these patients
is that their sodium levels
are decreased below normal,
you know, usually well below
the normal 140 range.
Causes of ADH release
Central nervous system disorders
which can include brain metastases,
or brain infections like meningitis,
as well as strokes and cerebral infarcts,
and head trauma can all cause
excess ADH release from the posterior pituitary.
Another cause of ectopic ADH release
is pulmonary disease.
Patients who present with
lung cancer or even pneumonias
can manifest hyponatremia
based on the fact that ADH is released.
And then finally, pituitary surgery,
usually three to seven days post-op,
excess ADH, inappropriate ADH release
can be noted.
The diagnosis is usually made
when measured plasma and urine osmolarity
give you an indication of what
the patient's volume status is.
ADH will usually cause a dilutional hyponatremia
because of excess water retention,
and this will be manifest by differences
in urine osmolarity and plasma osmolarity.
The treatment of these patients
consists of fluid restriction,
which will improve
If patients are symptomatic
or if the sodium is less than 110,
hypertonic saline should be given.
But please remember,
this should be done very slowly.
Excessively rapid correction
of low serum sodium
can relead to irreversible
central pontine myelinolysis.