Hyponatraemia

Question 1

What is the normal range for serum Na+? What values would classify it as moderate and severe?

Answer 1

Normal= 135-145

Moderate= <130

Severe= <120

Question 2

What investigation would you want to order if someone was presenting with signs of hyponatraemia?

Answer 2

VBG/ABG= used to see sodium levels quickly

U+E= need to see baseline renal function and see sodium levels and other electrolyte derrangement

Paired urine and serum osmolality

Urinary sodium

LFTs= liver failure associated with hypervolaemic hyponatraemia

TFTs= severe hypothyroidism

9am cortisol levels = glucocorticoid deficiency

Question 3

What are the 3 broad classifications of hyponatraemia?

Answer 3

Hypovolaemic= sodium and water lost together

Euvolaemic= no change in fluid balance

Hypervolaemic= dilution of serum sodium to give apparent hyponatraemia

Question 4

What can cause hypovolaemic hyponatraemia?

Answer 4

Loss of sodium and water from kidney due to diuretics/renal failure/Addison’s

Loss of sodium and water from burns, D+V, trauma (loss of body fluids which causes subsequent derrangement of electrolytes)

Question 5

How would you investigation hypovolaemic hyponatraemia? What signs might you expect a patient to present with? How might you manage this patient?

Answer 5

Signs:

• tachycardia
• reduced skin turgor
• low BP
• postural drop

Investigations
-urine sodium to distinguish between renal and extra-renal losses

Management:

• stop drugs which might be inducing increased renal loss i.e. diuretics
• 0.9% normal saline for fluid (potential for introducing sodium into infusion)

Question 6

What are the causes of euvolaemic hyponatraemia?

Answer 6

SIADH (syndrome of inappropriate ADH)

Severe hypothyroidism

Glucocorticoid deficiency

Question 7

How would you additional investigation euvolaemic hyponatraemia? How might you manage this patient?

Answer 7

9am cortisol
-used to identify if patient has glucocorticoid deficiency= can cause dilutional hyponatraemia

TFTs
-severe hypothyroidism can lead to hyponatraemia

Managment:
-treat the underling cause i.e. SIADH, glucocorticoid deficiency, hypothyroidism

Question 8

Why can glucocorticoid deficiency lead to hyponatraemia?

Answer 8

Impaired renal water clearance which leads to retention and dilution hyponatraemia

Question 9

What are the causes of hypervolaemic hyponatraemia?

Answer 9

HF

CKD

Liver failure

I.e. fluid overload situations and subsequent dilution of serum sodium

Question 10

What signs might you expect a patient to present with in hypervolaemic hyponatraemia? How might you manage this patient?

Answer 10

peripheral oedema
Raised JVP
Bi-basal crackles
Ascites

Manage:

• fluid restriction
• diuresis= furosemide i.e. proportionally more fluid loss than renal sodium loss

Question 11

What are signs of severe hyponatraemia? How is severe hyponatraemia managed?

Answer 11

Neurological signs= drowsiness + seizures + coma

Management:

• admitted to ITU due to needed more intensive monitoring of sodium levels
• hypertonic saline 3%

Question 12

What is the maximum rate sodium should be replaced? What are the possible complications if it is replaced are a faster rate?

Answer 12

12mEq/day

Central pontine myelinolysis
-Excessive fluid shot between body compartments leading to fluid being drawn from brain which leads to de-myelination of nerve cells in pons

Question 13

How should patient with hyponatraemia be monitored?

Answer 13

VBG

• severe= 2-4hrs
• moderate= 12hrs
• mild= 24hrs

Fluid monitoring

Fluid status exam

Postural BP

Patient symptoms