10 Posterior Pituitary

Question 1

Significant neurologic symptoms generally do not occur until serum Na falls below

Answer 1

125 mmol/L

Question 2

Criteria (5) to diagnose SIAD

Answer 2

Decreased effective osmolality <275 mOsm/kg H2O
Inappropriate urinary concentration (less than maximally dilute i.e., >100 mOsm/kg H2O)
Clinical euvolemia
Elevated urinary Na excretion on normal salt and water intake
Absence of other causes of euvolemic hypoosmolality (hypothyroidism, hypocortisolism, diuretic use)

Question 3

Normal response to water loading

Answer 3

Cumulative urine output of at least 90% of the administered water within 4 hours
Suppression of urine osmolality to <100 mOsm/kg H2O

Question 4

Risk factors (5) for ODS

Answer 4

Serum Na <105 mmol/L
Hypokalemia
Advanced liver disease
Malnutrition
Alcoholism

Question 5

Predictors (4) of likely failure of fluid restriction as management of SIAD

Answer 5

Urine osm >500 mOsm/kg H2O
Urine Na + K > serum Na
24 hr urine volume <1500 mL/day
Increase in serum Na <2 mmol/L/day in 24-48 hrs on fluid restriction <=1 L/day

Question 6

Dose of conivaptan

Answer 6

20 mg LD, then 20-40 mg/day

Question 7

Maximum duration of use of conivaptan

Answer 7

4 days

Question 8

Maximal daily rate of change of serum Na during the treatment of hyponatremia

Answer 8

10-12 mmol/L/24 h or 8 mmol/L/24 h for those with risk factors for ODS

Question 9

Dosage of tolvaptan

Answer 9

Starting dose 15 mg on first day, then up to 60 mg

Question 10

Indications to increase tolvaptan dose every 24 h

Answer 10

Serum Na remains <135
Rate of change <5

Question 11

Treatment duration with tolvaptan

Answer 11

30 days or less