Sodium haemostasis and osmolality Flashcards

1
Q

What is normal serum osmolality?

A

282-295mOsm/L

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2
Q

Difference between CSW and SIADH

A

CSW volume depletion with Na loss, SIADH - euvolaemic or hypervolaemic
Note both can have high urinary Na

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3
Q

SIADH seen in particular with which disease?

A

Small cell lung Ca

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4
Q

What percentage of head injuries affected by SIADH?

A

4.6%

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5
Q

Drugs used in neurosurgery that cause SIADH

A

Carbemazepine/oxycarbemazepine
NSAIDS
antipsychotics
DDAVP

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6
Q

What is the risk of over rapid correction of Na?

A

Osmotic demyelination (including cerebral pontine myelinolysis)

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7
Q

2 causes of acute hyponatraemia outside of hospital

A

ecstasy

marathoners

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8
Q

What type of hyponatraemia does mannitol cause?

A

Hypertonic hyponatraemia (pseudohyponatraemia)

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9
Q

Addisons gives what picture of hyponatraemia?

A

same as CSW - Low Na, Low Serum osmo, volume depleted, high urinary Na

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10
Q

What is Schwartz-Bartter syndrome?

A

SIADH first described with small cell lung Ca

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11
Q

Essential features of diagnosing SIADH?

A

Low Na, paired serum (low) and urinary (high) osmos
clinically euvolaemic
Normal thyroid function and no diuretic use

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12
Q

Definitive test for SIADH?

A

Water load test - consume 20ml/kg water up to 1.5L, 65% should be excreted within 4 hours

Note this should not be done in patients with severe or symptomatic hyponatraemia!

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13
Q

What is Conivaptan?

A

Type V1A and V2 vasopressin receptor blocker used in severe hyponatraemia

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14
Q

What is the treatment of CSW?

A

Postive salt balance

fluid replacement

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15
Q

What medications can be used to help treat CSW?

A

Fludrocortisone

Urea can be used in CSW and SIADH

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16
Q

What is the definitive test for DI?

A

Water deprivation test