Case #1
1. Define hyponatremia?
Low sodium concentration and can be associated
with a low, normal or high total body sodium.
2. Is hyponatremia synonymous with hypo-osmolality?
No, other compounds
may contribute to the serum osmolality and thereby normalize the osmolality without
increasing the sodium concentration.
3. Calculate the serum osmolality in this patient?
(2 x 120 mmol/L) + 90
+10 = 248.6 mosm/kg
18 2.8
4. What is pseudohyponatremia and what conditions cause it?
Pseudohyponatremia
is hyponatremia associated with normal osmolality such as is seen in
conditions of
increased lipids and proteins. Hyperglycemia is not considered a cause of
pseudohyponatremia because it is associated with the movement of water
from the
intracellular space to the extracellular space.
5. What is the cause of hyponatremia in this patient?
Inappropriate ADH
secretion. The kidney is avidly absorbing water in the presence of decreased serum
osmolality not
associated with volume depletion.
6. Based on what criteria was this diagnosis made?
Elevated urine
osmolality, decreased
serum osmolality, lack of volume depletion or decreased effective
circulatory volume.
7. What is the total body sodium in this patient?
Normal, because patients
with SIADH will maintain normal sodium balance.
8. If furosemide is administered how will it change the urinary composition?
It
will inhibit both normal concentration and dilution because of its effects
on the ascending limb of the loop of Henle. Urine becomes iso-osmolar, the
ratio of water and sodium in the urine is changed and the disproportionate
retention of water is prevented.