Hyponatraemia (SIADH) + Diabetes Insipidus

Question 1

What is the difference between osmolality and osmolarity?

Answer 1

• osmolality = solute concentration is osmoles of solute/kg of solution
• osmolarity = solute concentration in osmoles of solute per litre of solution

Question 2

If there is an increased extracellular (outside the cell) osmolality (high solutes around the cell) which of the following will occur?

1 - H2O enters the cell and cell becomes swollen
2 - H2O leaves the cell and cell becomes dehydrated
3 - H2O moves between intra and extracellular space, but no change to the cell
4 - no change

Answer 2

2 - H2O leaves the cell and cell becomes dehydrated
- H2O leaves to dilute high extracellular solutes
- the cell loses H2O and becomes dehydrated

Question 3

If there is an increased intracellular (inside the cell) osmolality (high solutes inside the cell) which of the following will occur?

1 - H2O enters the cell and cell becomes swollen
1 - H2O leaves the cell and cell becomes dehydrated
1 - H2O moves between intra and extracellular space, but no change to the cell
4 - no change

Answer 3

1 - H2O enters the cell and cell becomes swollen
- H2O enters the cell to dilute the high intracellular (inside the cell) osmolality
- the cell becomes swollen and oedema occurs

Question 4

How does the body detect when there is change in the osmolality in the plasma?

1 - juxtaglomerular cells
2 - V2 receptors in collecting tubules
3 - baroreceptors
4 - osmoreceptors in hypothalamus

Answer 4

4 - osmoreceptors in hypothalamus
- located in the anterior hypothalamus on the wall of the 3rd ventricle

Question 5

If we lose H2O due to sweat or we eat a really salty meal, the extracellular (outside the cell) osmolality (ECO) will increase, stimulating the osmoreceptors located in the anterior wall of the 3rd ventricle and the the anterior hypothalamus. This cluster of nuclei in the hypothalamus is called the supraoptic nuclei. When they detect the increased ECO what happens?

1 - anterior pituitary reduces anti-diuretic hormone secretion to reduce H2O retention
2 - anterior pituitary increase anti-diuretic hormone secretion to increase H2O retention
3 - posterior pituitary reduces anti-diuretic hormone secretion to reduce H2O retention
4 - posterior pituitary increases anti-diuretic hormone secretion to increase H2O retention

Answer 5

4 - posterior pituitary increases anti-diuretic hormone secretion to increase H2O retention

• hypothalamus stimulates the posterior pituitary gland
• posterior pituitary gland releases anti-diuretic hormone (ADH) aka vasopressin
• ADH retains H2O through kidneys and vasoconstricts blood vessels
• the body also instigates thirst to consume more H2O

Question 6

One of the key functions of anti-diuretic hormone is to retain H2O in the collecting tubules. How is it able to do this?

1 - reabsorbs Na+ and H2O follows
2 - binds AVPR2 in distal convoluted tubules increasing aquaporin-2
3 - increases Na+/Cl-/K+ channels in thick ascending loop of Henley thus increasing their reabsorption
4 - reduces eGFR and therefore less H2O is lost in urine

Answer 6

2 - binds AVPR2 in distal convoluted tubules increasing aquaporin-2

• aquaporin-2 are responsible for reabsorbing just H2O

Question 7

One of the key functions of anti-diuretic hormone (ADH), aka vasopressin is to retain water in the kidneys. What is one other key function of ADH?

1 - induce vasoconstriction and increase BP
2 - reduce cardia workload
3 - induce vasodilation and reduce BP
4 - retain K+ and Na+ in collecting tubules

Answer 7

1 - induce vasoconstriction and increase BP

Question 8

What is the normal plasma osmolality range?

1 - 100-200 mosmol/kg
2 - 185-195 mosmol/kg
3 - 275-295 mosmol/kg
4 - 355-395 mosmol/kg

Answer 8

3 - 275-295 mosmol/kg

Formula =
2 x (Na+ K+) + Glucose + Urea
Example using normal values:
- 2 x (Na+ add K+ = 135) = 278 mmol/L
- glucose = 5.5 mmol/L
- urea = 3 mmol/L
- 278 + 8 + 5.5 + 3 = 294.5 mosmol/kg

Question 9

When extracellular osmolality increases, due to fluid loss, the sensation of thirst is stimulated and there is a release of anti-diuretic hormone (ADH). What 2 parts of the brain are involved in this response?

1 - thalamus
2 - pituitary gland
3 - hypothalamus
4 - cerebral cortex

Answer 9

3 - hypothalamus = ADH
4 - cerebral cortex = thirst

Question 10

What happens to thirst and anti-diuretic hormone release in the presence of:

• high plasma osmolality (lots of solutes in blood)
• low plasma osmolality (fewer solutes in blood)

Answer 10

• high plasma osmolality = thirst and ADH release
• low plasma osmolality = no thirst and no ADH release

Question 11

What cation is required for the release of packed anti-diuretic hormone in vesicles to be released into the posterior pituitary gland and then into the blood?

1 - Na+
2 - Ca2+
3 - K+
4 - Mg2+

Answer 11

2 - Ca2+

Question 12

Which of the following does anti-diuretic hormone NOT have an effect and increase H2O retention? Label the image with the labels below:

1 - proximal tubule
2 - distal tubule
3 - collecting tubule
4 - collecting duct epithelia

Answer 12

1 - proximal tubule

Question 13

Anti-diuretic hormone (ADH) able to increase water retention in the kidneys. ADH is able to bind with vasopressin receptor 2 (AVPR2). What type of membrane receptor is this and what does this trigger intracellularly?

1 - receptor tyrosine kinase
2 - ion channel receptor
3 - GPCR
4 - enzyme linked receptor

Answer 13

3 - GPCR
- specifically Gas
- increases synthesis of aquaporin 2 (AQP-2)
- vesicles containing AQP-2 bind with the cell membrane
- more AQP-2 increases water retention

Question 14

What does polyuria mean?

1 - increased urine output
2 - pain when urinating
3 - lack of urine
4 - all of the above

Answer 14

1 - increased urine output
- poly = lots of
- uria = urine
- production of lots of urine

Question 15

What does polydipsia mean?

1 - increased urine output
2 - pain when urinating
3 - reduced thirst
4 - increased thirst

Answer 15

4 - increased thirst
- poly = lots of
- dipsia = greek for thirst-

Question 16

What effect does polyuria (high urine output) have on plasma osmolality?

1 - increases plasma osmolality
2 - decreases plasma osmolality
3 - no effect on plasma osmolality

Answer 16

1 - increases plasma osmolality
- less fluid means an increase of solutes in plasma and an increased osmolality
- polydipsia = excessive thirst and water consumption = decrease of plasma osmolality

Question 17

What effect does polydipsia (high thirst) and increased fluid intake have on plasma osmolality?

1 - increases plasma osmolality
2 - decreases plasma osmolality
3 - no effect on plasma osmolality

Answer 17

2 - decreases plasma osmolality
- more fluid means solutes are diluted, and thus a reduced plasma osmolality

Question 18

If a patient presents with polyuria and/or polydipsia, what is the first disease that must be ruled out?

1 - CKD
2 - diabetes
3 - liver disease
4 - HF

Answer 18

2 - diabetes
- high solutes (hyperglycaemia or hypercalcaemia) means the body increases ADH and thirst to dilute solutes and reduce osmolality

Question 19

Diabetes insipidus relates to polyuria, that is tasteless as no sugar like in diabetes mellitus. There are different types of diabetes insipidus. One of these is central diabetes insipidus (CDI), a rare disorder cause polydipsia and polyuria. In CDI, the problem is located centrally. Typically what is the issue in CDI?

1 - increased ADH and larger volumes of H2O retained
2 - increased ADH and less H2O retained
3 - decreased ADH and less H2O retained
4 - decreased ADH and more H2O retained

Answer 19

3 - decreased ADH and less H2O retained
- central problem is in hypothalamus menaing less ADH is released
- less ADH means less retention of H2O and polyuria
- polyuria means higher osmolality and therefore polydipsia to dilute higher osmolality

Question 20

Central diabetes insipidus (CDI) is a rare disorder that can cause polydipsia and polyuria. Which of the following is NOT typically a cause of CDI?

1 - idiopathic = 27%
2 - head trauma or neurosurgery
3 - genetic (5%)
4 - pituitary tumour (no ADH released)
5 - schizophrenia

Answer 20

5 - schizophrenia
- associated with Dipsogenic diabetes insipidus

• idiopathic is most common = 27%

Question 21

Central diabetes insipidus (CDI) is a rare disorder that can cause polydipsia and polyuria. This is due to a problem is located centrally in the hypothalamus or pituitary gland reducing anti-diuretic hormone (ADH) release, meaning reduced ADH reduces vasoconstriction of blood vessels and reduced H2O retention in kidneys. How can this be treated?

1 - synthetic ADH called desmopressin is administered
2 - administer spirolactone
3 - provide psychoeducation and CBT
4 - all of the above

Answer 21

1 - synthetic ADH called desmopressin is administered
- can cause hyponatraemia (low Na+) IF the polydipsia is not treated (stop excessive fluid intake)

Question 22

Nephrogenic diabetes insipidus (NDI) is a rare disorder that can cause polydipsia and polyuria. Typically what is the issue in NDI?

1 - nephrons are inflamed and become blocked so H2O is retained
2 - nephrons are damaged and unresponsive to ADH so more H2O is retained
3 - nephrons are damaged and unresponsive to ADH so H2O is not retained

Answer 22

3 - nephrons are damaged and unresponsive to ADH so H2O is not retained
- less response to ADH means polyuria, causing increased osmolality
- increased osmolality triggers polydipsia to dilute high osmolality

Question 23

Nephrogenic diabetes insipidus (NDI) is a rare disorder that can cause polydipsia and polyuria as the renal tubules are damaged and become less responsive to ADH. Which of the following is NOT a cause of NDI?

1 - genetic disorder (receptor dysfunction)
2 - medications (lithium)
3 - polycystic kidney disease
4 - increased vassopressinase
5 - persistant hypercalcaemia (Ca2+) and hypokalaemia (K+)

Answer 23

4 - increased vassopressinase

Question 24

Nephrogenic diabetes insipidus (DI) is a rare disorder that can cause polydipsia and polyuria. Caused by damage to the nephron in the kidneys, which are unresponsive to anti-diuretic hormone (ADH). The most common causes include genetic disorder, medications (lithium) and kidney disease. How can this be treated?

1 - synthetic ADH called desmopressin is administered
2 - administer spirolactone
3 - provide psychoeducation and CBT
4 - address cause of nephron damage

Answer 24

4 - address cause of nephron damage
- correct metabolic or drug cause damaging nephrons
- likely to be due to thiazide diuretics (help clear fluid from the body) / NSAIDs

Question 25

Dipsogenic diabetes insipidus (DDI) is a rare disorder that can cause polydipsia and polyuria. What is this and what causes this?

1 - mutated ADH that is not effective upon acting on the kidneys
2 - psychological condition causing patient to consume excessive water
3 - nephrons are damaged and unresponsive to ADH
4 - hypothalamus secretes less ADH

Answer 25

2 - psychological condition causing patient to consume excessive water
- high water intake causes reduced osmolality
- patient has less ADH and polyuria in an attempt to increase plasma osmolality

• common in patients with mental disorders such as psychosis

Question 26

Dipsogenic diabetes insipidus (DI) is a rare disorder that can cause polydipsia and polyuria. It is caused by drinking excessive amounts of H2O and is common in patients with mental disorders such as psychosis. How can this be treated?

1 - synthetic ADH called desmopressin is administered
2 - administer spirolactone
3 - provide psychoeducation and CBT
4 - address cause of nephron damage

Answer 26

3 - provide psychoeducation and CBT

Question 27

To be diagnosed with any form of diabetes insipidus, how much fluid must a patient pass in 1 day?

1 - >6L
2 - >4L
3 - >3L
4 - >1L

Answer 27

3 - >3L
- patients need to document fluid intake

Question 28

A water deprivation test is a test which measures how your kidneys respond when you don’t have anything to drink. What are the 2 methods that can be used in this test?

1 - patient given a specific amount of fluid over a specific period of time
2 - patients are dehydrated for a specific period of time
3 - patients are given ADH called desmopressin
4 - patients ADH is supressed

Answer 28

2 - patients are dehydrated for a specific period of time
3 - patients are given ADH called desmopressin

Question 29

A water deprivation test is a test which measures how your kidneys respond when you don’t have anything to drink. There are 2 methods that can be used in this test:

• period of dehydration with the patient
• administer synthetic vasopressin (ADH) called desmopressin

What must be measured in the patient prior to and following the test?

1 - plasma and urine osmolality
2 - U&Es
3 - FBC
4 - LFTs

Answer 29

1 - plasma and urine osmolality

Question 30

A water deprivation test is a test which measures how your kidneys respond when you don’t have anything to drink. There are 2 methods that can be used in this test:

• period of dehydration with the patient
• administer synthetic vasopressin (ADH) called desmopressin

Plasma and urine osmolality must be measured in the patient prior to and following the test. In the results, what does normal plasma osmolality and high urine osmolality indicate?

1 - a normal response
2 - central diabetes insipidus
3 - nephrogenic diabetes insipidus
4 - dipsogenic diabetes insipidus

Answer 30

1 - a normal response

Question 31

A water deprivation test is a test which measures how your kidneys respond when you don’t have anything to drink. There are 2 methods that can be used in this test:

• period of dehydration with the patient
• administer synthetic vasopressin (ADH) called desmopressin

Plasma and urine osmolality must be measured in the patient prior to and following the test. In the results, what would be the diagnosis if the patient has:

• low urine osmolality prior to and following dehydration due to polyuria
• following desmopressin administration, urine osmolality increases

1 - a normal response
2 - central diabetes insipidus
3 - nephrogenic diabetes insipidus
4 - dipsogenic diabetes insipidus

Answer 31

2 - central diabetes insipidus
- low/no ADH means H2O is not retained causing dilute low urine osmolality

• synthetic ADH (desmopressin) is administered and the kidneys respond normally and retain some H2O and thus increase urine osmolality

Question 32

A water deprivation test is a test which measures how your kidneys respond when you don’t have anything to drink. There are 2 methods that can be used in this test:

• period of dehydration with the patient
• administer synthetic vasopressin (ADH) called desmopressin

Plasma and urine osmolality must be measured in the patient prior to and following the test. In the results, what would be the diagnosis if a patient has:

• low urine osmolality prior to and following dehydration
• following desmopressin administration, urine osmolality does not increase, or only marginally

1 - a normal response
2 - central diabetes insipidus
3 - nephrogenic diabetes insipidus
4 - dipsogenic diabetes insipidus

Answer 32

3 - nephrogenic diabetes insipidus
- damaged kidneys mean they do not respond to synthetic ADH
- urine osmolality remains low

Question 33

A water deprivation test is a test which measures how your kidneys respond when you don’t have anything to drink. There are 2 methods that can be used in this test:

• period of dehydration with the patient
• administer synthetic vasopressin (ADH) called desmopressin

Plasma and urine osmolality must be measured in the patient prior to and following the test. What would the diagnosis be if the patient has:

• a high urine osmolality following dehydration due to low urine output
• no need to administer vasopressin

1 - a normal response
2 - central diabetes insipidus
3 - nephrogenic diabetes insipidus
4 - dipsogenic diabetes insipidus

Answer 33

4 - dipsogenic diabetes insipidus
- dehydration means the patients returns to normal levels

Question 34

What is the diagnosis of hyponatraemia?

1 - <140mmol/L of Na+
2 - <150mmol/L of Na+
3 - <165mmol/L of Na+
4 - <135mmol/L of Na+

Answer 34

4 - <135mmol/L of Na+
- normal = 133-146 mmol/L

Question 35

Which of the following is NOT an acute non-emergency symptom of hyponatraemia?

1 - headache and confusion
2 - nausea
3 - constipation
4 - mood change
5 - cramps
6 - lethargy

Answer 35

3 - constipation
- severe = confusion, drowsiness, seizures, coma

Question 36

Which of the following is NOT an chronic non-emergency symptom of hyponatraemia?

1 - Headache and Irritability
2 - Nausea / vomiting
3 - Cachexia
4 - Mental slowing
5 - Unstable gait / falls
6 - Confusion / delirium
7 - Disorientation
8 - Depression

Answer 36

3 - Cachexia

Question 37

Which of the following is NOT an acute emergency symptom of hyponatraemia?

1 - Stupor (unconscious) / coma
2 - Convulsions
3 - Respiratory arrest
4 - Cardiac Arrest

Answer 37

4 - Cardiac Arrest
- could occur, but not common
- acute symptoms could occur rapidly <48h

Question 38

Hypotonic relates to the low solute concentration extracellularly when compared to intracellular solute concentration. There are 3 types of hyponatraemia based hyponatraemia. What is hypervolemic hyponatraemia. What happens here?

1 - large increase in H2O and Na+
2 - large increase in H2O but small Na+ change
3 - large increase in Na+ but a small change in H2O
4 - reduction in H2O and Na+

Answer 38

2 - large increase in H2O but small Na+ change
- pathology causes increased fluid retention that leaks into interstitial space
- this causes reduces circulating volume
- momentarily increases plasma osmolality and ADH is released
- ADH increases H2O only retention
- therefore we have increased fluid that dilutes Na+ causing hyponatraemia
- decreased plasma osmolality

Question 39

Hypervolemic hyponatraemia is due to a large increase in H2O but small Na+ change. The following causes fluid retention:
- pathology causes increased fluid retention that leaks into interstitial space
- this causes reduces circulating volume
- momentarily increases plasma osmolality and ADH is released
- ADH increases H2O only retention
- therefore we have increased fluid that dilutes Na+ causing hyponatraemia

What is the cause for the small rise in Na+?

1 - ADH simulates the release of aldosterone
2 - ADH stimulates the number of Na+/Cl-/K+ channels to retain more Na+
3 - Na+ follows the retained water
4 - all of the above

Answer 39

1 - ADH simulates the release of aldosterone

• aldosterone retains Na+ and water follows Na+
• so we retain a little Na+ this way, but we retain even more water

Question 40

Hypervolemic hyponatraemia is when there is an increased H2O retention causing a dilution in Na+ causing hyponatraemia. Which of the following is NOT a cause of hypervolemic hyponatraemia?

1 - congestive heart failure
2 - diarrhea and vomiting
3 - liver fibrosis
4 - nephrotic syndrome

Answer 40

2 - diarrhea and vomiting

Question 41

What happen in hypovolemic hyponatraemia?

1 - small decrease in H2O and Na+
2 - small decrease in H2O but large reduction in Na+
3 - large decrease in Na+ and H2O
4 - large reduction in H2O but an increase in Na+

Answer 41

2 - small decrease in H2O but large reduction in Na+
- small volumes of H2O lost with large reductions in Na+ causes a reduced plasma osmolality and hyponatraemia

Question 42

In hypovolemic hyponatraemia there is a large reduction in Na+, but only a small reduction in H2O. Which of the following does NOT typically cause hypovolemic hyponatraemia?

1 - congestive heart failure
2 - diarrhea and vomiting
3 - inappropriate ADH secretion
4 - medications (diuretics)
5 - meningitis
6 - primary adrenal insufficiency

Answer 42

1 - congestive heart failure

• meningitis impairs sympathetic nervous system that leads to disproportionate loss of Na+ in the renal tubules, further diluting plasma osmolality, specifically Na+
• primary adrenal insufficiency where steroids such as cortisol and aldosterone which help retain Na+ are deficient

Question 43

What happen in euvolaemic hyponatraemia?

1 - small decrease in H2O and Na+
2 - large decrease in Na+ and H2O
3 - large reduction in H2O but an increase in Na+
4 - increase in H2O but no change in Na+

Answer 43

4 - increase in H2O but no change in Na+
- there is no overloading the interstitial space so there is no oedema

Question 44

In euvolaemic hyponatraemia there is a normal level of Na+, but there is an increase in H2O retention, but this is not visible as oedema. All of the following are causes of euvolaemic hyponatraemia, but which is the most common?

1 - Medications (diuretics)
2 - Syndrome of inappropriate antidiuretic hormone (SIADH)
3 - Addison’s disease.
4 - Hypothyroidism

Answer 44

2 - Syndrome of inappropriate antidiuretic hormone (SIADH)

Question 45

Which of the following is NOT a cause of Syndrome of inappropriate antidiuretic hormone (SIADH)?

1 - stroke
2 - haemorrhage/head trauma
3 - anti-epileptics
4 - anti-psychotics
5 - surgery
6 - tumours (small cell lung cancer)
7 - all of the above

Answer 45

7 - all of the above

Question 46

Syndrome of inappropriate antidiuretic hormone secretion (SIADH) is a condition in which the body makes too much antidiuretic hormone (ADH). How can patients present in relation to plasma volumes?

1 - Hypovolaemia
2 - Normovolaemia (euvolaemia)
3 - Hypervolaemia

Answer 46

2 - Normovolaemia (euvolaemia)
- Na+ levels are normal BUT there is an increase in fluid retention, BUT no oedema

Question 47

Syndrome of inappropriate antidiuretic hormone (SIADH) is the most common cause of euvolaemic hyponatraemia. Raised ADH causes excessive H2O to be retained, which dilutes the Na+ but also increases intravascular volume. This then inhibits the release of which hormone which is involved in Na+ management?

1 - cortisol
2 - aldosterone
3 - dehydroepiandrosterone
4 - leutenising hormone

Answer 47

2 - aldosterone
- aldosterone normally retains Na+, but with increased intravascular fluid aldosterone is inhibited

Question 48

In syndrome of inappropriate antidiuretic hormone (SIADH) which cause of euvolaemic hyponatraemia there is an increase in fluid retention, increased intravascular fluid and a dilution of Na+. This also inhibits aldosterone release. What happens to Na+ and H2O levels if aldosterone is inhibited?

1 - Na+ is excreted and H2O is retained
2 - Na+ and H2O are retained
3 - Na+ and H2O are excreted
4 - Na+ is retained and H2O is excreted

Answer 48

3 - Na+ and H2O are excreted
- H2O follows Na+ due to osmosis
- this normalised the fluid in the blood

Question 49

Which of the following is not part of the essential diagnostic criteria for Syndrome of inappropriate antidiuretic hormone secretion (SIADH)?

1 - Hyponatraemia <135 mmol/L
2 - Plasma hypo-osmolality >275 mOsm/kg
3 - Urine osmolality >100 mOsm/kg
4 - clinically euvolaemia
5 - increased urinary sodium excretion >30 mmol/L with normal salt and water intake
6 - absence of other potential causes of SIADH

Answer 49

2 - Plasma hypo-osmolality >275 mOsm/kg

• it should be low osmolality <275 mOsm/kg as we are losing Na+ in the urine
• urine osmolality is slightly high as Na+ is being excreted

Question 50

Which of the following medications can increase the release of ADH?

1 - Opioids
2 - SSRIs and Tricyclic antidepressants 3 3 - Carbamazepine
4 - Antipsychotics
5 -NSAIDs
6 - all of the above

Answer 50

6 - all of the above

Question 51

Syndrome of inappropriate antidiuretic hormone secretion (SIADH) is a condition in which the body secretes inappropriate amounts of antidiuretic hormone (ADH). Patients present with normovolaemia (euvolaemia), BUT patients have a low plasma Na+, and low plasma osmolality. What should be tested in these patients?

1 - Paired serum and urine osmolalities
2 - Urinary sodium
3 - Renal function
4 - TFTs
5 - Random plasma glucose
6 - LFTs
7 - 9 a.m. cortisol >300nmol/L usually enough to exclude cortisol deficiency.
8 - all of the above

Answer 51

8 - all of the above

• renal = can cause poor Na+ reabsorption
• adrenal = aldosterone is important in Na+ and fluid management
• thyroid function = hypothyroidism can result in hyponatraemia

Question 52

In Syndrome of inappropriate antidiuretic hormone secretion (SIADH) would the urine Na+ and osmolality be high or low?

Answer 52

• urine osmolality = high
• urine Na+ = high
• BIG RED FLAGS FOR SIADH

Question 53

In Syndrome of inappropriate antidiuretic hormone secretion (SIADH) would the plasma Na+ and osmolality be high or low?

Answer 53

• plasma osmolality = low
• plasma Na+ = low
• BIG RED FLAGS FOR SIADH

Question 54

Syndrome of inappropriate antidiuretic hormone secretion (SIADH) is a condition in which the body makes too much antidiuretic hormone (ADH) causing euvolaemic hyponatraemia. Which of the following is NOT an aspect of patients with SIADH management?

1 - fluid restriction (induce negative fluid balance)
2 - demeclocycline (induces nephrogenic diabetes insipidus (non responsive to ADH)
3 - vasopressin (ADH) antagonist
4 - reduce or stop any medications associated with SIADH
5 - aldosterone administration

Answer 54

5 - aldosterone administration
- we do not want to retain more fluid which is what will have with this

• fluid restriction is 1st line treatment, BUT it is hard for patients to adhere to

Question 55

Fluid restriction is 1st line treatment for patients with Syndrome of inappropriate antidiuretic hormone secretion (SIADH), although adherence can be difficult. How much should fluid be reduced by each day?

1 - 500ml/day
2 - 1000ml/day
3 - 1500ml/day
4 - 2000ml/day

Answer 55

1 - 500ml/day
- Furst formula can be used to help determine fluid restrictions

• DO NOT RESTRICT Na+

Question 56

Fluid restriction is 1st line treatment for patients with Syndrome of inappropriate antidiuretic hormone secretion (SIADH), although adherence can be difficult. 500ml/day should be the aim, but how much does this correct hyponatreamia each day?

1 - 10-20 mmol/day
2 - 10-15 mmol/day
3 - 5-10 mmol/day
4 - 1-2 mmol/day

Answer 56

4 - 1-2 mmol/day
- it is a slow process, but can resolve SIADH spontaneously
- CAN TAKE DAYS TO SEE RESULTS
- DO NOT RESTRICT NA+

Question 57

Which medication is the first and only pharmacotherapyfor treating hyponatraemia secondary to SIADH to be approved by the European Medicines Association (EMA)?

1 - Tolvaptan
2 - Demeclocycline
3 - Spriolcatone
4 - Haloperidol

Answer 57

1 - Tolvaptan
- ADH/vasopressin receptor antagonist

Inhibits anti-diuretic hormone activity

• associated with polyuria and liver damage

Question 58

In the acute management of a patient with Syndrome of inappropriate antidiuretic hormone secretion (SIADH), what fluid should be given over 20 minutes within the first hour to patients presenting with severe symptoms?

1 - 150ml Na+ chloride 0.18% with 4% dextrose
2 - 150ml 3% hypertonic saline (NaCl)
3 - 150ml 5% glucose
4 - 150ml 0.9% NaCl

Answer 58

2 - 150ml 3% hypertonic saline (NaCl)
- high Na+

• REPEAT TWICE OR UNTIL 5MMOL/L INCREASE IN Na+
• after this reduce to 0.9% saline

Question 59

When giving patients with severe symptoms of hyponatraemia fluids, we must be very careful about how much we increase their Na+ levels. What should the Na+ increase be limited to in the 1st 24h?

1 - 5 mmol/L
2 - 10 mmol/L
3 - 15 mmol/L
4 - 20 mmol/L

Answer 59

2 - 10 mmol/L
- BUT do not exceed 6 mmol/L in 1st 6h
- then aim for 4-8mmol/L for each 24h following the first 24h

Question 60

It is crucial that Na+ does not rise too quickly in patients with hyponatraemia. If the Na+ is rising too quickly, which of the following can be implemented to stop the rise?

1 - 5% dextrose (3ml/kg per 1 hour)
2 - Desmopressin 2-4mcg S/C / IV every 8hrs
3 - more frequent monitoring
4 - stop Tolvaptan
5 - stop saline solutions
6 - all of the above

Answer 60

6 - all of the above

Question 61

If we raise the Na+ levels too quickly what can this cause?

1 - cardiac arrhythmia and sudden death
2 - central pontine myelinolysis
3 - increased intracranial pressure/haemorrhage
4 - cerebellum oedema

Answer 61

2 - central pontine myelinolysis
- also called osmotic demyelination syndrome

Question 62

Prior to any diagnosis being made in hyponatraemia, what must be determined?

1 - if patient has other comorbidities
2 - if patient is frail
3 - if the hyponatraemia is real
4 - all of the above

Answer 62

3 - if the hyponatraemia is real
- is it a pseudohyponatraemia

Question 63

Assessing if a patient has genuine hyponatraemia must be assessed 1st to rule out pseudohyponatraemia. Which of the following is NOT an example of pseudohyponatraemia?

1 - vomiting and diarrhoea
2 - hyperglycaemia
3 - medication (mannitol)
4 - hyperlipid and proteinaemia
5 - transurethral resection of the prostate (TURP)

Answer 63

1 - vomiting and diarrhoea

• mannitol = cannot enter cells and remains in intravascular space. So mannitol draws fluid into intravascular space and appears to dilute Na+. Used to reduce intracranial pressure, but increases plasma osmolality
• hyperlipid and proteinaemia = impair measurement of osmolality so Na+ appears low
• TURP = high sugars used that are absorbed by the body into the intravascular compartment and draw in H2O, thus diluting Na+

Question 64

Hyperglycaemia is a cause of a false hyponatraemia, called pseudohyponatraemia. Why does hyperglycaemia cause this?

1 - glucose forces H2O into interstial space triggering an increase in ADH and H2O retention
2 - glucose binds Na+ and Na+ appears lower than normal
3 - glucose increases pH of blood causing Na+ to bind to albumin
4 - glucose draws fluid from intracellular to intravascular space

Answer 64

4 - glucose draws fluid from intracellular to intravascular space
- more H2O in intravascular space makes Na+ appear low
- BUT if you correct hyperglycaemia then Na+ returns to normal as well
- plasma osmolality would be high due to excessive glucose

• similar mechanism to mannitol which is used to reduce intracranial pressure