Case #2
1. Calculate the serum osmolality in this patient?
(2 x 127 mm/L) + 105
+ 35 = 272.3 mosm/kg
18 2.8
2. What is the cause of hyponatremia in this patient?
Water overload in
excess of sodium overload.
3. Based on what criteria was this diagnosis made?
Clinical exam and urine
and serum osmolality and sodium concentration.
4. What is the total body sodium in this patient?
Increased- this patient
is sodium and water overloaded with a greater increase in water as compared
to sodium.
5. What are the physiologic conditions which stimulate ADH secretion?
Increased
osmolality and decreased volume. ADH secretion is much more sensitive to
changes in serum osmolality requiring ~1-2% increase whereas volume
stimulation will require a decrease of 5-10%. However, once effective volume
depletion does occur it will override a decrease in serum osmolality as a
stimulus to inhibit its release.
6. What is the clinical condition responsible for ADH secretion in this patient ?
The decrease in effective circulating arterial volume due to this
patient’s liver disease.
7. If furosemide is administered to this patient how will it change the urinary composition?
It will disproportionately increase water excretion as
compared to sodium.
8. What are the major categories of hyponatremia and their pathogenesis?
Conditions associated with a decrease in total body sodium, normal sodium and excess
sodium.
Integrative Questions
9. What accounts for the differences in total body sodium in these two cases?
In the first case the patient maintains normal sodium handling by the kidney
but retains excess water. In the second case the patient is both sodium and
water avid due to the decrease in effective circulating arterial volume.
10. Why are there differences in the urinary sodium between the two cases?