Hyponaetremia

Question 1

What is Hyponatremia?

Answer 1

Serum Sodium < 136mmol/l

Question 2

What are the symptoms of Hyponatremia?

Answer 2

They are caused my decreased ECF osmolality so water does intracellular - this causes cerebral oedema and:

• Lethargy
• Confusion
• Coma
• Convulsions

Question 3

What are the causes of hyponaetremia?

Answer 3

Question 4

What is the role of ADH/Vasopressin in hyponatremia?

What does it do?

Answer 4

It is released in times of stress or dehydration and causes the following things:

V1 - Vasoconstriction

V2 - Increased water uptake via aquaporins

Net effect of retaining fluid and keeping BP up

Question 5

How can true volume depletion and high ADH lead to hyponatremia?

Answer 5

Vomiting and diarrhoea causes volume depletion and release of ADH - can lead to hyponatremia

Question 6

What is hypervolemic hyponaetremia?

Answer 6

Question 7

How does ecstasy lead to high ADH and hyponatremia?

Answer 7

It directly increases ADH and increases thirst which leads to hyponatremia

Question 8

How does SIADH lead to high ADH and hyponatremia?

Answer 8

Related to lung diseases and increased ADH levels causes relative hyponaetremia

Question 9

How does marathon running lead to increased ADH and hyponatremia

Answer 9

Exercise stimulated ADH despite loss of salt in sweat.

This plus increased water uptake causes hyponaetremia

Question 10

What could be the causes hyponatremia and low ADH?

Answer 10

Polydypsia eg alcohol

Renal failure - not responding to ADH so it stops being produced

Question 11

What physical signs may suggest hyponatremia?

Answer 11

Nausea

Confusion

Lethargy

Postural hypotension (due to fluid in cells)

Reduced skin turgor (loss of free water)

Oedema/ascites (if SIADH or LF, HF N.B less barorecptor activation despite high fluid levels)

Question 12

What would urine osmolality be in hyponatremia?

Answer 12

High if trying to get rid of water eg SIADH

Low in may be low in polydypsia or volume depletion

Question 13

What would the blood results be for SIADH?

Answer 13

LOW serum oslomality

LOW serum sodium

LOW blood urea (it is diluted)

HIGH urine osmolality (no water)

HIGH urine sodium (not reabsorped)

Question 14

How do you treat hyponatremia?

Answer 14

Treat underlying cause

Fluid restriction if needed

Fluid if volume depleted

Salt replacement

Loop diurtic in SIADH to reduce medullary osmolality

Question 15

What do you do in severe hyponatremia

Answer 15

Hypertonic solution and ADH receptor antagonist

Question 16

What would urinary sodium be like in hyponatremia caused by SIADH?

Answer 16

High as water absorbed

Question 17

How do you treat SIADH?

Answer 17

Loop diuretic to decrease medullary osmalility

Question 18

What is the difference between loop and thiazide diuretics?

Answer 18