1: Hyponatraemia

Question 1

What is hypotonic hyponatraemia

Answer 1

• Hypernatraemia

- Low serum osmolality

Question 2

How can causes of hypotonic hyponatraemia be divided

Answer 2

• Hypovolaemia
• Euvolaemia
• Hypervolaemia

Question 3

What is hypovolaemic hyponatraemia

Answer 3

There is large loss of sodium with associated small loss of water

Question 4

What are the renal causes of hypovolaemic hypontraemia

Answer 4

• Diuretics

- Osmotic Diuresis

Question 5

What are the extra-renal causes of hypovolaemic hyponatraemia

Answer 5

Diarrhoea
Vomitting
Burns
Cerebral salt-wasting

Question 6

What is cerebral salt wasting syndrome

Answer 6

Low sodium and dehydration in response to head trauma or tumour

Question 7

What is euvolaemic hyponatraemia

Answer 7

When serum sodium remains the same, however there is an increase in total body water. However, as water is increased in vascular and not interstitial space, it does not cause oedema

Question 8

How can euvolaemic hyponatraemia be divided

Answer 8

• Increase urine osmolality (concentration)

- Decrease urine osmolality (concentration)

Question 9

What causes euvolaemic hyponatraemia with concentrated urine (high urine osmolality)

Answer 9

• SIADH

= increase water reabsorption leaves concentrated urine and dilute plasma

Question 10

What causes euvolaemic hyponatraemia with dilute urine (low urine osmolality)

Answer 10

• Psychogenic polydipsia
• Pottomania
• Hypothyroidism

Question 11

What is potomania

Answer 11

Excess beer intake

Question 12

What is hypervolaemia hyponatraemia

Answer 12

Excess water, with relatively small increase in sodium

Question 13

What causes hypervolaemic hyponatraemia

Answer 13

CHF
Liver cirrhosis
Nephrotic syndrome

Question 14

What is isotonic hyponatraemia

Answer 14

Same serum osmolality

Question 15

What causes isotonic hyponatraemia

Answer 15

Pseudohyponatraemia

Paraproteinaemia

Question 16

What is Pseudohyponatrarmia

Answer 16

Increase in lipids and proteins - interferes with measurement of sodium

Question 17

What causes paraproteinaemia

Answer 17

Myeloma

Question 18

What is hypertonic hyponatraemia

Answer 18

Increase serum osmolality

Question 19

What causes hypertonic hyponatraemia

Answer 19

Hyperglycaemia

Cushing’s Disease

Question 20

What are the symptoms of hyponatraemia

Answer 20

N+V

Weakness

Question 21

What does severe hyponatraemia cause

Answer 21

Cerebral Oedema

Question 22

How does cerebral oedema present

Answer 22

Confusion
Seizures
Death

Question 23

What are the two mechanisms of hyponatraemia

Answer 23

1. Loose more sodium than water

2. Gain more water than sodium

Question 24

What is first-line investigation for hyponatraemia

Answer 24

U+E

Question 25

How will U+Es present in hyponatraemia

Answer 25

Low sodium

Question 26

What is second-line for investigating hyponatraemia

Answer 26

Serum osmolality

Question 27

How is serum osmolality calculated

Answer 27

2Na + Glucose + Urea

Question 28

If serum osmolality is low, what does it indicate

Answer 28

True hyponatraemia. = Loss of sodium will cause a low serum osmolality

Question 29

what is a 'true' hyponatraemia also known as and why

Answer 29

Hypotonic hyponatraemia | = Low sodium causes reduction in serum osmolality and therefore hypotonic

Question 30

what does a normal serum osmolality indicate and why

Answer 30

Pseudohyponatraemia. There is no loss of osmotic particles which contribute to serum osmolality measurement. However there is a gain of lipids and protein which disrupt sodium measurement in U+E

Question 31

what does a high serum osmolality indicate and why

Answer 31

Raised glucose

Question 32

after working out serum osmolality, what is calculated

Answer 32

urine osmolality

Question 33

what urine osmolality indicates concentrated urine

Answer 33

>500

Question 34

what does a high urine osmolality and hyponatraemia indicate and why

Answer 34

SIADH - Increase ADH causing water reabsorption. This means more concentrated urine (high osmolality). - Increase water dilutes sodium causing hyponatraemia

Question 35

how is hyponatraemia managed

Answer 35

- Treat cause | - Hypertonic saline

Question 36

explain correction of hyponatraemia

Answer 36

Needs to be corrected slowly at a rate of 4-6mmol/L in 24h

Question 37

why is hyponatraemia corrected at 4-6mmol/L in 24h

Answer 37

Too rapid correction causes cerebral pontine myelinolysis

Question 38

when do symptoms of hyponatraemia present

Answer 38

Days-after

Question 39

what are symptoms of cerebral pontine myelinolysis

Answer 39

Presents as 'locked-in' syndrome patients are awake but: - Quadraplegia - Paraparesis - Dysarthria - Dysphagia - Seizures

Question 40

is cerebral pontine myelinolysis reversible

Answer 40

Yes