Sodium Homeostasis and Osmolality

Question 1

According to the classification of severity of hyponatremia, severe hyponatremia is sodium level (mEq/L) less than what?
● A. 160
● B. 155
● C. 145
● D. 135
● E. 125

Answer 1

E. 125

Question 2

Which of the following is an etiology for hypotonic hyponatremia?
● A. Mannitol therapy
● B. Renal failure
● C. TURP syndrome
● D. Paraproteinemia
● E. Hypertriglyceridemia

Answer 2

B. Renal failure

Question 3

Hyponatremia is acute if duration documented is less than what?
● A. 48 hours
● B. 56 hours
● C. 72 hours
● D. 5 days
● E. 7 days

Answer 3

A. 48 hours

Question 4

The most important differentiating criterion for differentiation between syndrome of inappropriate ADH (SIAD) and cerebral salt wasting (CSW) is what?
● A. Serum sodium level
● B. Urinary sodium level
● C. Glycemic level
● D. Volume status
● E. Potassium level

Answer 4

D. Volume status

Question 5

Which of the following is not included in the diagnostic criteria for SIAD?
● A. Decreased effective serum osmolality (< 275 mOsm/kg of water)
● B. Urine osmolality > 100 mOsm/kg of water
● C. Clinical euvolemia
● D. Increased thyroid stimulating hormone (TSH) level
● E. No recent diuretic use

Answer 5

D. Increased thyroid stimulating
hormone (TSH) level

Question 6

Solute ratio is defined as (Urinary [Na] + Urinary [K])/Plasma [Na]. For a ratio of 1, what is the recommended fluid intake (mL/d) in SIAD?
● A. < 500
● B. 600
● C. 100
● D. 1500
● E. 2000

Answer 6

B. 600

Question 7

During treatment of SIAD, what is the limit of correction that
should not be exceeded?
● A. 2–4 mEq/L in 24 hours
● B. 6–8 mEq/L in 24 hours
● C. 8–10 mEq/L in 24 hours
● D. 12–14 mEq/L in 48 hours
● E. 14–15 mEq/L in 48 hours

Answer 7

C. 8–10 mEq/L in 24 hours

Question 8

During treatment of SIAD, a patient developed insidious flaccid quadriplegia, mental status changes, and cranial nerve abnormalities with a pseudobulbar palsy appearance. What is the most probable diagnosis?
● A. The diagnosis of SIAD was wrong
● B. Central pontine myelinolysis
● C. Weber syndrome
● D. Transverse myelitis
● E. Hydrocephalus

Answer 8

B. Central pontine myelinolysis

Question 9

Which of the following is avoided during treatment of cerebral salt wasting?
● A. Normal saline
● B. 3% saline
● C. Packed red blood cells
● D. Steroids
● E. Furosemide

Answer 9

E. Furosemide

Question 10

Which of the following drugs is effective in treatment of cerebral salt wasting?
● A. Demeclocycline
● B. Conivaptan
● C. Vasopressin receptor antagonists
● D. Lithium
● E. Fludrocortisone acetate

Answer 10

E. Fludrocortisone acetate

Question 11

Within what time frame should the initial half be replaced?
● A. 10–15 minutes
● B. 30 minutes
● C. 1 hour
● D. 2 hours
● E. 24 hours

Answer 11

E. 24 hours

Question 12

For indeterminate cases, polyuria due to diabetes insipidus can be differentiated from psychogenic polydipsia by the water deprivation test. What is the highest urinary osmolality after Pitressin in water deprivation test that is interpreted as normal?
● A. < 5% increase
● B. 10% increase
● C. 20% increase
● D. 45% increase
● E. > 50% increase

Answer 12

A. < 5% increase

Question 13

Which of the following is not a diagnostic criterion for diabetes insipidus?
● A. Urine osmolality < 300 mOsm/kg
● B. Inability to concentrate urine to > 300 mOsm/kg in the presence of clinical dehydration
● C. Urine output > 50 mL/kg/24 h
● D. Hyponatremia
● E. Normal adrenal function

Answer 13

D. Hyponatremia

Question 14

Intravenous fluid management for diabetes insipidus includes base intravenous fluid: D5 1/2 NS + 20 mEqKCl/L at 75–100 mL/h. In addition to that, the urine output above base intravenous rate should be replaced mL for mL with which of the
following?
● A. Normal saline
● B. ½ Normal saline
● C. Hypertonic saline
● D. Red cell concentrates
● E. No need for this replacement

Answer 14

B. ½ Normal saline

Question 15

Regarding desmopressin in DDAVP® Nasal Spray 100 μg/mL, about how much each spray delivers?
● A. 1 μg
● B. 10 μg
● C. 30 μg
● D. 50 μg
● E. 100 μg

Answer 15

B. 10 μg

Question 16

A patient is presented to emergency with anorexia, headache, difficulty concentrating, and irritability. On investigations, he/she has serum sodium level of 131 mEq/L, serum osmolality of 265 mOsm/kg, and urine osmolality more than 100 mOsm/kg with euvolemia. What is the most probable diagnosis in this patient?
● A. Diabetes insipidus
● B. Cerebral salt wasting
● C. Syndrome of inappropriate antidiuretic hormone secretion (SIADH)
● D. Hyponatremia
● E. Renal failure

Answer 16

C. Syndrome of inappropriate antidiuretic hormone secretion (SIADH)

Question 17

A patient presented with aneurysmal subarachnoid hemorrhage with only symptom of severe headache. After some time he/she developed irritability, difficulty concentrating, and muscle weakness. Her/his plain brain CT showed no new finding. On labs serum osmolality was less than 275 mOsm/kg, urine osmolality was more than 100 mOsm/kg with volume depletion, and urinary sodium more than 20 mEq/L. What is the most probable diagnosis?
● A. Diabetes insipidus
● B. Cerebral salt wasting
● C. SIADH
● D. Hyponatremia
● E. Renal failure

Answer 17

B. Cerebral salt wasting

Question 18

Which of the following is the cause of syndrome of inappropriate antidiuretic hormone secretion?
● A. CNS infection
● B. Head trauma
● C. Brain tumors
● D. Aneurysmal subarachnoid hemorrhage
● E. All of the above

Answer 18

E. All of the above

Question 19

A patient presents with hyponatremia in hospital. On lab investigation urine osmolality is less than 500 mOsm/kg. She/he was given normal saline infusion test with 2 liters of normal saline over 24 to 48 hours. What does correction of hyponatremia suggest?
● A. SIADH
● B. CSW
● C. Extracellular fluid volume depletion
● D. DI
● E. None of the above

Answer 19

C. Extracellular fluid volume depletion

Question 20

A patient being treated for hyponatremia suddenly develops flaccid quadriplegia, mental status changes, and some cranial nerve abnormalities. What is the most probable diagnosis in this case?
● A. Osmotic demyelination syndrome
● B. Severe hyponatremia
● C. Severe hypernatremia
● D. Wernicke’s encephalopathy
● E. All of the above

Answer 20

A. Osmotic demyelination syndrome

Question 21

A patient presents in emergency with severe hyponatremia with syndrome of inappropriate antidiuretic hormone secretion (SIADH). Which of the following are treatment options for
this condition?
● A. Admission in ICU
● B. 3% normal saline at 1 to 2 mL/kg
● C. Furosemide 20 mg
● D. Restriction of water intake
● E. A, B, and C

Answer 21

E. A, B, and C

Question 22

A patient being treated for hyponatremia with normal saline develops decreased renal cortical blood flow, metabolic acidosis, reduced gastric mucosal perfusion, tachypnea, hypocapnia, and increased risk of vasoconstriction in brain. Which of the following is the cause of these symptoms?
● A. Severe hypernatremia
● B. Fluid overload
● C. Hyperchloremic acidosis
● D. Severe hyponatremia
● E. None of the above

Answer 22

C. Hyperchloremic acidosis

Question 23

A patient underwent pituitary surgery. After surgery he developed high urine output. Labs showed urine osmolality less than 300 mOsm/kg and urine specific gravity less than 1.003, with normal or high serum osmolality and high serum sodium.
What is the most probable diagnosis in this case?
● A. SIADH
● B. Cerebral salt wasting
● C. Diabetes insipidus
● D. Dehydration
● E. Hypernatremia

Answer 23

C. Diabetes insipidus

Question 24

Treatment of diabetes insipidus consists of which of the following?
● A. Desmopressin 0.1 mg per oral bd
● B. Nasal spray 2.5 μg by nasal insufflation bd
● C. Clofibrate
● D. Chlorpropamide
● E. All of the above

Answer 24

E. All of the above

Question 25

In nonambulatory comatose patient, treatment of diabetes insipidus consists of what?
● A. Admission in ICU with input–output monitoring every 1 hour, urine specific gravity every 4 hours
● B. Measure serum electrolytes with osmolality every 6 hours
● C. Baseline fluid D5 ½ NS plus 20 mEq/L at 75 to 100 mL/h
● D. Arginine vasopressin
● E. All of the above

Answer 25

E. All of the above