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Residency Exam > Sodium Disorders (Panopto Video Link) Background Lecture > Flashcards

Sodium Disorders (Panopto Video Link) Background Lecture Flashcards

1
Q

What is the major cation in the extracellular fluid?

A

Sodium

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2
Q

What is the major determinant of intravesicular volume?

A

Sodium

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3
Q

In what 2 ways may abnormalities of serum sodium be reflected?

A

In changes of total body water, as well as changes in total body sodium

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4
Q

What do we always need to consider when assessing the relevance of sodium results?

A

Total body water

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5
Q

What is the concentration of sodium dependent on?

A

The amount of sodium and the amount of water in the body

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6
Q

What are 3 homeostatic mechanisms to maintain sodium concentration?

A
  1. Renal conservation and excretion
  2. Antidiuretic hormone
  3. Aldosterone
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7
Q

If serum sodium increases, how will this affect osmolality?

A

Increased serum sodium leads to increased osmolality

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8
Q

If serum sodium increases, how will this affect thirst?

A

Increased serum sodium leads to increased thirst

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9
Q

If serum osmolality increases, how will this affect thirst?

A

Increased serum osmolality leads to increased thirst

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10
Q

If serum osmolality increases, how will this affect aldosterone secretion?

A

Increased serum osmolality leads to decreased aldosterone secretion

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11
Q

If aldosterone secretion decreases, how will this affect sodium excretion?

A

Decreased aldosterone secretion leads to increased sodium excretion

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12
Q

How does increased thirst affect antidiuretic hormone release?

A

Increased thirst leads to increased antidiuretic hormone release

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13
Q

How does increased antidiuretic hormone affect water reabsorption?

A

Increased release of antidiuretic hormone increases water reabsorption

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14
Q

What is the role of aldosterone?

A

To increase sodium and water retention

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15
Q

Which is more common: hypernatraemia or hyponatraemia?

A

Hyponatraemia

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16
Q

Why is hypernatraemia relatively uncommon?

A

Because it only occurs in patients who do not respond appropriately to the thirst mechanism

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17
Q

If serum sodium decreases, how will this affect osmolality?

A

Decreased serum sodium leads to decreased osmolality

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18
Q

If serum sodium decreased, how will this affect thirst?

A

Decreased serum sodium leads to decreased thirst

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19
Q

If serum osmolality decreases, how will this affect thirst?

A

Increased serum osmolality leads to decreased thirst

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20
Q

How does decreased thirst affect antidiuretic hormone release?

A

Decreased thirst leads to decreased antidiuretic hormone release

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21
Q

How does decreased antidiuretic hormone affect water reabsorption?

A

Decreased release of antidiuretic hormone decreased water reabsorption

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22
Q

Where is the majority of sodium reabsorbed?

A

In the proximal tubule

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23
Q

Approximately what percentage of sodium is reabsorbed in the loop of Henle?

A

25%

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24
Q

What is hyponatraemia defined as?

A

A sodium concentration < 135 mmol/L

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25
Q

What are the potential mechanisms by which hyponatraemia may occur?

A

It may be a dilutional effect, a depletion of sodium, or a combination of both

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26
Q

What is the first thing you should always look at when assessing hyponatraemia?

A

Fluid status

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27
Q

What are 4 aetiologies of hyponatraemia?

A
  1. Pseudohyponatraemia (i.e. falsely low)
  2. Increased total body sodium/greater increase in body water
  3. Normovolaemic/low sodium
  4. Total body decrease in water/greater than relative decrease in sodium
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28
Q

What are 4 aetiologies of hyponatraemia?

A
  1. Pseudohyponatraemia (i.e. falsely low)
  2. Increased total body sodium/greater increase in body water
  3. Normovolaemic/low sodium
  4. Total body decrease in water/greater than relative decrease in sodium
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29
Q

What are 5 signs of hyponatraemia?

A
  1. Abnormal senses
  2. Cheyne-Stokes respiration
  3. Depressed deep tendon reflexes
  4. Hypothermia
  5. Seizures
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30
Q

What are 7 symptoms of hyponatraemia?

A
  1. Agitation
  2. Anorexia
  3. Apathy
  4. Disorientation
  5. Lethargy
  6. Muscle cramps
  7. Nausea
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31
Q

What are 7 symptoms of hyponatraemia?

A
  1. Agitation
  2. Anorexia
  3. Apathy
  4. Disorientation
  5. Lethargy
  6. Muscle cramps
  7. Nausea
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32
Q

What is moderate hyponatraemia defined as?

A

Sodium < 125 mmol/L

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33
Q

What is severe hyponatraemia defined as?

A

Sodium < 120 mmol/L

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34
Q

What are 8 symptoms of moderate hyponatraemia?

A
  1. Malaise
  2. Lethargy
  3. Fatigue
  4. Muscle cramps
  5. Confusion
  6. Headache
  7. Nausea
  8. Anorexia
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35
Q
  1. Dehydration
  2. Diabetes insipidus
  3. DrugsWhat are 8 symptoms of moderate hyponatraemia?
A
  1. Malaise
  2. Lethargy
  3. Fatigue
  4. Muscle cramps
  5. Confusion
  6. Headache
  7. Nausea
  8. Anorexia
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36
Q

What are 8 symptoms of moderate hyponatraemia?

A
  1. Malaise
  2. Lethargy
  3. Fatigue
  4. Muscle cramps
  5. Confusion
  6. Headache
  7. Nausea
  8. Anorexia
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37
Q

What are 6 symptoms of severe hyponatraemia?

A
  1. Decrease in the deep tendon reflex
  2. Hypothermia
  3. Cheyne-Stokes respiration
  4. Somnolence
  5. Seizures
  6. Coma
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38
Q

Why does severe hyponatraemia lead to central nervous system effects?

A

Due to swelling of the brain

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39
Q

What is the best way for a pharmacist to determine a patient’s volume status?

A

Check the medical notes

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40
Q

What history may be indicative of hypovolaemia?

A

History of fluid losses

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41
Q

What 2 factors in the physical examination may be indicative of hypovolaemia?

A
  1. Low blood pressure
  2. Turgor
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42
Q

What is turgor?

A

The ability of the skin to change shape then return to normal

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43
Q

What are 2 laboratory values which may be indicative of hypovolaemia?

A
  1. Greatly elevated blood urea nitrogen
  2. Elevated creatinine (but increased BUN- Creatinine ratio)
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44
Q

What are 3 medical conditions which may be indicative of hypervolaemia?

A
  1. Congestive heart failure
  2. Cirrhosis
  3. Nephrosis
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45
Q

What is nephrosis?

A

A kidney disorder which causes the kidney to excrete protein in the urine

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46
Q

What is a factor in the physical examination which may be indicative of hypervolaemia?

A

Oedema

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47
Q

What are 2 factors in a physical examination which may be indicative of euvolaemia?

A
  1. Normal blood pressure
  2. No oedema
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48
Q

What are 2 laboratory values which may be indicative of euvolaemia?

A
  1. Normal blood urea nitrogen
  2. Normal or low creatinine
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49
Q

What are the 2 classes of hypovolaemic hyponatraemia?

A
  1. Extrarenal
  2. Renal
50
Q

What laboratory value is indicative of extrarenal hypovolaemic hyponatraemia?

A

Urinary sodium < 10 mmol/L

51
Q

What laboratory value is indicative of renal hypovolaemic hyponatraemia?

A

Urinary sodium > 20 mmol/L

52
Q

What are 3 causes of renal hypovolaemic hyponatraemia?

A
  1. Diuretic use
  2. Glycosuria
  3. Low aldosterone
53
Q

What are two causes of extrarenal hypovolaemic hyponatraemia?

A

Losses of fluid in the gastrointestinal or from sweat

54
Q

What are 3 causes of renal hypovolaemic hyponatraemia?

A
  1. Diuretic use
  2. Glycosuria
  3. Low aldosterone
55
Q

What are 3 causes of renal hypovolaemic hyponatraemia?

A
  1. Diuretic use
  2. Glycosuria
  3. Low aldosterone
56
Q

What is the only cause of hypervolaemic hyponatraemia?

A

Oedema

57
Q

What are the 6 classes of euvolaemic hyponatraemia?

A
  1. Renal failure (C1)
  2. Impaired diuresis (C2)
  3. SIADH (C3)
  4. Endocrine (C4)
  5. Polydipsia (C5)
  6. Essential (C6)
58
Q

What are 3 laboratory values which may be indicative of renal failure euvolaemic hyponatraemia (C1)?

A
  1. High blood urea nitrogen
  2. High creatinine
  3. Urinary sodium > 20 mmol/L
59
Q

What are 3 potential causes of renal failure euvolaemic hyponatraemia (C1)?

A
  1. Renal disease
  2. Oliguria
  3. Water loads
60
Q

What is oliguria?

A

The production of abnormally small amounts of urine.

61
Q

What are 3 potential causes of euvolaemic hyponatraemia due to impaired diuresis (C2)?

A
  1. Impaired diuresis post surgery
  2. Narcotics
  3. Sedatives
62
Q

What are 4 laboratory values which may be indicative of SIADH (C3)?

A
  1. Low blood urea nitrogen
  2. Low creatinine
  3. Urinary sodium > 20 mmol/L
  4. Low uric acid
63
Q

What are 3 potential causes of SIADH?

A
  1. Lung disease/cancer
  2. Central nervous system disease/cancers
  3. Drugs
64
Q

Which subtype of laboratory values are used to diagnose endocrine euvolaemic hyponatraemia (C4)?

A

Endocrine tests

65
Q

What symptoms are suggestive of endocrine euvolaemic hyponatraemia (C4)?

A

Symptoms of endocrine deficiency

66
Q

What are 8 symptoms of endocrine deficiency?

A
  1. Darkened areas of skin.
  2. Extreme loss of body water, also known as dehydration.
  3. Severe fatigue.
  4. Weight loss that doesn’t happen on purpose.
  5. Nausea, vomiting or belly pain.
  6. Lightheadedness or fainting.
  7. Salt cravings.
  8. Muscle or joint pains.
67
Q

What laboratory value is usually seen in polydipsia euvolaemic hyponatraemia (C5)?

A

Urinary osmolality < 80 mmol/L

68
Q

What is a common cause of essential euvolaemic hyponatraemia?

A

Chronic disease

69
Q

What laboratory value is commonly seen in essential euvolaemic hyponatraemia (C6)?

A

Urinary osmolality < 80 mmol/L with water load

70
Q

What is polydipsia?

A

Excessive thirst

71
Q

What are 2 types of pseudohyponatraemia?

A
  1. Osmotic (D1)
  2. Artifactual (D2)
72
Q

What causes osmotic (D1) pseudohyponatraemia?

A

Hyperglycaemia

73
Q

What causes artifactual (D2) pseudohyponatraemia?

A

Laboratory artifact (laboratory error)

74
Q

What is the only way sodium in the urine will be elevated?

A

In renal failure, or nephrotoxicity

75
Q

Which tends to cause more prominent hyponatraemia: congestive heart failure or ascites?

A

Ascites

76
Q

Is SIADH caused by an excess or insufficiency of antidiuretic hormone?

A

Excess

77
Q

What does the excessive antidiuretic hormone in SIADH lead to?

A

Increased body water and subsequent hyponatraemia

78
Q

What investigations are commonly indicative of SIADH?

A
  1. Low plasma osmolality
  2. High urine osmolality
79
Q

What are the 2 mechanisms by which drugs may cause SIADH?

A
  1. Enhanced release of antidiuretic hormone
  2. Potentiation of the renal action of antidiuretic hormone
80
Q

What are 6 drugs known to cause SIADH?

A
  1. CARBAMazepine
  2. Clofibrate
  3. CYCLOPHOSPHamide
  4. Chlorpropamide
  5. vinCRISTine
  6. SSRIs
81
Q

What are 3 potential treatments for SIADH (beyond fluid restriction)?

A
  1. Vaptans
  2. Urea
  3. Demeclocycline
82
Q

What are the Bartter and Schwartz criteria for SIADH?

A
  1. Decreased plasma osmolality (<275 mosm/kg)
  2. Inappropriately concentrated urine (>100 mosm/kg)
  3. Euvolaemic
  4. Elevated urine Na (>20 mEq/L)
  5. Normal thyroid and adrenal function
  6. No diuretic use
83
Q

What are the 3 stages of symptoms of SIADH?

A
  1. Mild-moderate symptoms
  2. Advanced symptoms
  3. Grave symptoms
84
Q

What are 4 mild-moderate symptoms of SIADH?

A
  1. Slowness
  2. Poor concentration
  3. Nausea
  4. Instability of gait/falls
85
Q

What is the mainstay of treatment of SIADH?

A

Fluid restriction

86
Q

What are 3 potential treatments for SIADH (beyond fluid restriction)?

A
  1. Vaptans
  2. Urea
  3. Demeclocycline
87
Q

Why is fluid restriction the mainstay of treatment for SIADH?

A

As SIADH is a disorder of fluid, not of sodium

88
Q

What are 4 advanced symptoms of SIADH?

A
  1. Confusion
  2. Vomiting
  3. Somnolence
  4. Hallucinations
89
Q

What are 2 potential treatments for advanced SIADH?

A
  1. Vaptans
  2. 3% saline
90
Q

What is the usual role for demeclocycline in SIADH?

A

In cancer patients who have recurrent symptomatic hyponatraemia

91
Q

What are 4 grave symptoms of SIADH?

A
  1. Seizures
  2. Hemiplegia
  3. Severe somnolence
  4. Respiratory insufficiency
92
Q

What is the mainstay of treatment for Grave SIADH?

A

3% saline

93
Q

What is the usual role for demeclocycline in SIADH?

A

In cancer patients who have recurrent symptomatic hyponatraemia

94
Q

Describe the time to onset of hyponatraemia with SIADH

A

SIADH tends to cause hyponatraemia quite gradually

95
Q

What may correction of chronic hyponatraemia lead to?

A

A rapid increase in sodium concentration (and thus osmotic demyelination due to dehydration of the brain)

96
Q

What is the risk of a rapid reduction in serum sodium?

A

Cerebral oedema (and thus uncal herniation – a neurological emergency)

97
Q

Describe the effect of chronic hyponatraemia on cell size

A

Initially, hyponatraemia will cause cellular swelling, but over time, adaptions will occur and the cell volume will return to normal. This is why rapid correction of hyponatraemia can cause flaccidity of cells

98
Q

What is the usual fluid restriction used in SIADH?

A

1 to 1.5 L per day

99
Q

What is the second-line management of SIADH if fluid restriction fails?

A

Demeclocycline 600 mg to 1200 mg daily

100
Q

What are three causes of hypernatraemia?

A
  1. Dehydration
  2. Diabetes insipidus
  3. Drugs
101
Q

What are three causes of hypernatraemia?

A
  1. Dehydration
  2. Diabetes insipidus
  3. Drugs
102
Q

What are three causes of hypernatraemia?

A
  1. Dehydration
  2. Diabetes insipidus
  3. Drugs
103
Q

What are 4 drug-induced causes of hypernatraemia?

A
  1. Excessive sodium administration
  2. Corticosteroids
  3. Mineralocorticoids
  4. Anabolic steroids
104
Q

What is hypernatraemia defined as?

A

Sodium > 150 mmol/L

105
Q

Why is hypernatraemia much less common than hyponatraemia?

A

If sodium levels increase, you will respond by becoming thirsty, and drinking water will correct the increasing sodium

106
Q

What are 8 symptoms of hypernatraemia?

A
  1. Thirst
  2. Restlessness
  3. Irritability
  4. Lethargy
  5. Muscle twitching
  6. Hyperreflexia
  7. Seizures
  8. Coma
107
Q

What is the first thing you should always look at when assessing hypernatraemia?

A

Fluid status

108
Q

What occurs in a hypovolaemic hypernatraemia?

A

Total body sodium is reduced, but total body water is reduced more significantly

109
Q

What occurs in a euvolaemic hypernatraemia?

A

Total body water is reduced, but total body sodium is unchanged

110
Q

What occurs in a hypervolaemic hypernatraemia?

A

Total body water is increased, but total body sodium is increased more

111
Q

What are 2 causes of hypovolaemic hypernatraemia?

A
  1. Renal losses
  2. Extrarenal losses
112
Q

What are 3 causes of renal hypovolaemic hypernatraemia?

A
  1. Osmotic or loop diuretics
  2. Postobstruction
  3. Intrinsic renal disease
113
Q

Which laboratory value may be suggestive of renal hypovolaemic hypernatraemia?

A

Urinary sodium > 20 mmol/L

114
Q

What are 4 causes of extrarenal hypovolaemic hypernatraemia?

A
  1. Excessive sweating
  2. Burns
  3. Diarrhoea
  4. Fistulas
115
Q

Which laboratory value may be suggestive of extrarenal hypovolaemic hypernatraemia?

A

Urinary sodium < 20 mmol/L

116
Q

What are 2 renal causes of euvolaemic hypernatraemia?

A
  1. Diabetes insipidus
  2. Hypodipsia
117
Q

What are 3 extrarenal causes of euvolaemic hypernatraemia?

A
  1. Insensible fluid losses
  2. Respiratory fluid loss
  3. Dermal fluid loss
118
Q

Which laboratory value may be indicative of hypervolaemic hypernatraemia?

A

Urinary sodium > 20 mmol/L

119
Q

What are 7 causes of hypervolaemic hypernatraemia?

A
  1. Sodium gains
  2. Primary hypernatraemia
  3. Hyperaldosteronism
  4. Cushing’s syndrome
  5. Hypertonic dialysis
  6. Hypertonic sodium bicarbonate
  7. Sodium chloride tablets
120
Q

What are the 2 main symptoms of diabetes insipidus?

A
  1. Polyuria
  2. Polydipsia
121
Q

How is fluid replaced in hypernatraemia?

A

Slowly, at a rate of reduction no greater than 20 mmol/L 48 hours

122
Q

What are 8 symptoms of moderate hyponatraemia?

A
  1. Malaise
  2. Lethargy
  3. Fatigue
  4. Muscle cramps
  5. Confusion
  6. Headache
  7. Nausea
  8. Anorexia

Residency Exam (22 decks)

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