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AIP: Acute confusional state > Hyper/hyponatraemia > Flashcards

Hyper/hyponatraemia Flashcards

1
Q

What is the definition of hypernatraemia?

A

serum sodium concentration >145 mmol/L

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2
Q

What are 6 clinical features of hypernatraemia?

A
  1. Lethargy
  2. Weakness
  3. Confusion
  4. Agitation
  5. Seizures
  6. Coma
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3
Q

What are 3 groups of causes of hypernatraemia?

A
  1. Excess water loss
  2. Excessive hypertonic fluid
  3. Decreased thirst
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4
Q

What are 7 causes of excess water loss that can lead to hypernatraemia?

A
  1. Diabetes insipidus
  2. Diretics
  3. Osmtic diuresis (E.g. DKA and HHS)
  4. Diarrhoea
  5. Vomiting and NG suction
  6. Sweating
  7. Burns
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5
Q

What are 3 causes of excessive hypertonic fluid that can lead to hypernatraemia?

A
  1. IV infusions
  2. Total parental nutrition
  3. Enteral feeds
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6
Q

What are 2 causes of excessive decreased thirst that can lead to hypernatraemia?

A
  1. acute illness
  2. old age
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7
Q

What is the most common cause of hypernatraemia in the elderly?

A

dehydration - either due to decreased intake or increased GI loss (nausea or vomiting)

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8
Q

What are the 4 commonest causes of hypernatraemia?

A
  1. Dehydration
  2. Osmotic diuresis - HHS, DKA
  3. Diabetic insipidus
  4. Excess IV saline
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9
Q

Why must hypernatraemia be corrected with great caution?

A

although brain tissue can lose sodium and potassium rapidly, lowering of other osmolytes, and importantly water, occurs at a slower rate, predispoing to cerebral oedema, resulting in seizures, coma and death

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10
Q

What is the generally accepted rate of correction of sodium in hypernatraemia?

A

no greater than 0.5 mmol/hour

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11
Q

What does correction of hypernatraemia involve?

A

fluids - oral or IV (if IV be careful of overcorrection and cerebral oedema)

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12
Q

What is the definition of hyponatraemia?

A

serum sodium concentration <135 mmol/L

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13
Q

What are 2 ways that hyponatraemia can be categorised?

A
  1. Based on urinary sodium: > or < 20mmol/L
  2. Based on fluid status: hypovolaemic, euvolaemic or hypervolaemic hyponatraemia
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14
Q

What are 2 causes of pseudohyponatraemia?

A
  1. Hyperlipidaemia (increase in serum volume)
  2. Taking blood from a drip arm
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15
Q

Whatare 5 examples of causes of hyponatraemia when urinary sodium is >20 mmol/L?

A
  1. Diuretics: thiazides, loop diuretics
  2. Addison’s disease
  3. Diuretic stage of renal failure
  4. SIADH (urine osmolality > 500 mmol/kg)
  5. Hypothyroidism
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16
Q

What are 6 causes of hyponatraemia when urinary sodium is <20 mmol/L?

A
  1. diarrhoea, vomiting, swaetig
  2. burns, adenoma of rectum
  3. secondary hyperaldosteronism: heart failure, liver cirrhosis
  4. nephrotic syndrome
  5. IV dextrose
  6. psychogenic polydipsia
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17
Q

What are 6 causes of hypovolaemic hyponatraemia?

A
  1. Burns
  2. Sweating
  3. Diarrhoea
  4. Vomiting
  5. Fistulae
  6. Addison’s disease
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18
Q

What are 2 causes of euvolaemic hyponatraemia?

A
  1. Syndrome of Inappropriate ADH release (SIADH)
  2. Hypothyroidism
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19
Q

What are 4 hypervolaemic hyponatraemia?

A
  1. Renal failure
  2. Heart failure
  3. Liver failure
  4. Nephrotic syndrome
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20
Q

What determines which tests are performed in hyponatraemia?

A

if clear cause of hyponatraemia may not be necessary; when cause is not well-defined a number of tests required to confirm/exclude SIADH

21
Q

What are 5 investigations to perform in hyponatraemia?

A
  1. U+Es to confirm
  2. Urine and plasma paired osmolalities
  3. Urine sodium
  4. Urine dip
  5. TSH and cortisol
22
Q

Why is it important to measure urea and electrolytes and what condition should be met, when investigating hyponatraemia?

A
  • to confirm hyponatraemia and exclude mixed electrolyte abnormalities which are not seen in SIADH
  • patient should not be on diuretics
23
Q

Why should urine and plasma paired osmolalities be measured in hyponatraemia?

A

to demonstrate the inappropriate concentration of the urine - occurs in SIADH

24
Q

Why should urine sodium be measured in hyponatraemia and under what condition?

A
  • to demonstrate sodium wasting in the kidneys
  • while not on diuretics
25
Q

Why should a urine dip be performed in hyponatraemia?

A

to screen for infection and glomerular pathology

26
Q

Why should TSH and cortisol be measured in hyponatraemia?

A

to exclude hypothyroidism (rare caus eof euvolaemia hyponatraemia) and Addison’s disease

27
Q

What type of hyponatraemia can be caused by hypothyroidism?

A

euvolaemic hyponatraemia

28
Q

What are 4 parameters that must be considered when deciding how to treat hyponatraemia?

A
  1. Duration of hyponatraemia: acute or chronic
  2. Severity of hyponatraemia: what is the sodium level
  3. Symptoms: is the patient symptomatic
  4. hypovolaemia, euvolaemia, hypervolaemia
29
Q

What is the difference in duration between acute and chronic hyponatraemia?

A

acute hyponatraemia is < 48h, chronic is >48h

30
Q

What usually causes acute hyponatraemia?

A

excessive fluid intake, parenteral or oral e.g. post-op parenteral fluids and athletes

31
Q

What is the difference in severity of acute vs chronic hyponatraemia?

A

acute more likely to be severe

32
Q

What is the serum Na+ for mild vs moderate vs severe hyponatraemia?

A
  • mild: 130-134 mmol/L
  • moderate: 120-129 mmol/L
  • severe: <120 mmolL
33
Q

What are the symptoms of mild, moderate and severe hyponatraemia?

A
  • mild: non-specific symptoms such as headache, lethargy, nausea, vomiting, dizziness, confusion and muscle cramps
  • moderate: same as mild
  • severe: seizures, coma and respiratory arrest
34
Q

What is the management of mild hyponatraemia? 2 aspects

A
  • fluid restriction: <800 ml/day
  • loop diuretics (furosemide/ bumetanide)
35
Q

What is the management of moderate hyponatraemia? 3 aspects

A
  1. Hypertonic saline in first 3-4 hours to increase sodium >120 mmol/L
  2. Fluid restriction <800 ml/day
  3. Loop diuretics
36
Q

What are 2 aspects of management of severe hyponatraemia?

A
  1. bolus of hypertonic saline until symptom resolution
  2. with or without conivaptan (vasporessin/ADH receptor antagonist)
37
Q

What are 4 patients in whom fluid intake should be less than urine output in the following patients?

A
  1. Oedematous states like heart failure and cirrhosis
  2. SIADH
  3. Renal failure
  4. Psychogenic polydipsia
38
Q

What is the mechanism of action of conivaptan?

A
  • vasopressin/ ADH receptor antagonist
  • acts on V1 and V2 receptors
  • V1 receptors cause vasoconstriction while V2 receptors reult in selective water diuresis, sparing the electrolytes
39
Q

In which patients should vasopressin antagonists such as conivaptan be avoided? 2 key groups

A
  1. patients with hypovolaemia hyponatraemia (burns, sweating, diarrhoea, vomiting etc.)
  2. can be hepatotoxic in patients with underlying liver disease
40
Q

What is a key side effect of vasopressin/ADH receptor antagonists such as conivaptan?

A

can stimulate the thirst receptors leading to the desire to drink free water

41
Q

What are 3 aspects of the management of SIADH?

A
  1. fluid restriction
  2. ADH receptor antagonists (conivaptan, tolvaptan, deomeclocycline)
  3. Oral sodium and furosemide
  4. Hypothyroidism
  5. Levothyroxine
42
Q

How does the treatment of hypovolaemic vs hypervolaemic hyponatraemia differ?

A

fluid restriction if hypervolaemic vs IV normal saline if hypovolaemic

43
Q

What fluids can be given in patients who are unwell with hyponatraemia e.g. having seizures or comatose?

A

3% saline (but with great care - central pontine myelinosis)

44
Q

In what setting should 3% NaCl be given for severe hyponatraemia?

A

critical care

45
Q

What is the key risk when correcting hyponatraemia?

A

central pontine myelinosis due to over-correction of severe hyponatraemia

46
Q

At what rate should hyponatraemia be corrected to avoid central pontine myelinosis?

A

raise by 4-6 mmol/L in 24hrs (maximum 12 mmol/L)

47
Q

When do symptoms of central pontine myelinosis occur?

A

after 2 days, usually irreversible

48
Q

What are 7 features of central pontine myelinosis?

A
  1. Dysarthria
  2. Dysphagia
  3. Paraparesis or quadriparesis
  4. Seizures
  5. Confusion
  6. Coma
  7. Locked-in syndrome

AIP: Acute confusional state (14 decks)

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