Hyponatremia and Hypernatremia (chemical pathology) Flashcards

1
Q

What is the normal range of sodium ECF concentration?

A

135-145 mmol/L

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2
Q

What are the symptoms of hyponatremia?(4)

A

Weakness, dizziness, confusion and coma.

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3
Q

What are the signs of hyponatremia? (6)

A
  • Oliguria, tachycardia, weight loss, peripheral circulatory failure, hypotension, decreased skin turgor.
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4
Q

Symptoms of acute hyponatremia.

A

Severe cerebral oedema, coma, seizures and respiratory distress.

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5
Q

True or false:
Chronic hyponatremia is a medical emergency.

A

False, it is acute hyponatremia that is a medical emergency.

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6
Q

What are the symptoms of chronic hyponatremia (5)

A

Headache, restlessness, muscle cramps, vomiting, lethargy.

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7
Q

What are the three causes of hyponatremia and their examples?

A

Decreased ECF volume-Thiazide diuretics, addison’s disease.
Increased ECF volume- Cirrhosis, impaired renal water excretion, heart failure.
Normal ECF volume- SIADH, hypothyroidism, Excessive water intake, psychogenic polydipsia.

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8
Q

Three circumstances in which hyponatremia can occur

A
  • Sodium depletion (Hypovolemic hyponatremia)
    -Water excess, sodium normal (euvolemic hyponatremia)
    -Both water and sodium excess- Hypervolemic hyponatremia
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9
Q

How do we calculate osmolal GAP

A

Osmolal GAP = Osmolality - Osmolarity

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10
Q

Three things a clinician should do when assessing a patient with hypoNa

A
  • History- time frame to development of hyponatremia.
    -Establish fluid status (water retention/fluid loss)
  • Establish true hyponatremia
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11
Q

What is true hyponatremia?

A

Hypotonic hyponatremia

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12
Q

What causes isotonic hyponatremia? (2)

A
  • Hyperlipidemia
    Hyperproteinemia
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13
Q

What causes hypertonic hyponatremia? (2)

A

Hyperglycemia
Mannitol

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14
Q

What’s the next step to take in case of a hypotonic hyponatremia?

A

Assess volume status

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15
Q

What can be the causes of hypovolaemic hypotonic hyponatraemia ? (7)

A

Renal losses (urine sodium is high >40)
-Addison’s disease
-Diuretics
-Osmotic diuretics
Ketonuria

Extra-renal losses
-Diarrhoea
-Burns
-3rd space losses

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16
Q

What causes euvolaemic hypotonic hyponatraemia? (4)

A

-Psychogenic polydipsia
-SIADH
-Hypothyroidism
-Secondary adrenal insufficiency

17
Q

What causes hypervolaemic hypotonic hyponatraemia? (5)

A

Urine sodium levels are high
-Renal failure
Low urine sodium levels
-Nephrotic syndrome
-Liver cirrhosis
Hypoalbuminaemia
-CCF

18
Q

What are the symptoms of hypernatremia? (6)

A

Thirst, nausea and vomiting, diarrhoea, muscle twitching, confusion.

19
Q

What are the signs of hypernatremia?

A

Irritability, hypovolemia, decreased skin turgor, dehydration.

20
Q

What causes persistent hypernatremia?

A

Defect in thirst mechanism.

21
Q

What is the first step in assessing hypernatremia?

A

Assess volume status

22
Q

What can cause hypovolaemic hypernatraemia?

A

Renal losses(urine sodium is high)
-Osmotic diuretics
-ATN polyuric phase

Extra-renal losses (urine sodium is low)
-Diarrhoea
-Burns
-Sweating

23
Q

What can cause euvolemic hypernatremia?

A

Renal losses (urine osmolality is low)
-Diabetes insipidus

Extra-renal losses (urine osmol is high)
-Insensible losses

24
Q

What causes hypervolaemic hypernatraemia? (4)

A

-Ingestion of sea water
- Overconcentrated formula milk
- Hypertonic saline IV of NaHCO3
- Hypertonic dialysis

25
Q

How does the brain adapt to:
A. Hypernatraemia
B. Hyponatraemia

A

A. Accumulating intracellular idiogenic molecules.
B. Secreting idiogenic molecules out of brain cells to ECF.

26
Q

What are the effects of hyponatraemia on the brain? (5)

A

-Low sodium levels on the ECF causes water to move into the brain, which can cause cerebral oedema.
- Adaptation (1) rapid loss of water and salts, tonicity remain low.
- Adaptation (2) slow loss of osmolytes and water to eliminate the oedema.

Note: Rapid correction can lead to brain shrinkage.

27
Q

Effect of hypernatremia on brain (5)

A
  • Extracellular hypertonicity causes water to move out of the brain.
  • This causes cerebral shrinkage.
  • Adaptation (1) rapid gain of water and salts from ECF, tonicity remains high.
  • Adaptation (2) slow gain of osmolytes and water to correct the shrinkage.

Note: Rapid correction may lead to cerebral oedema.