Hyponatraemia

Question 1

What are normal Na levels?

Answer 1

135-145 mmol/L

Question 2

What is mild hypoNa?

What sx?

Answer 2

130-135 mmol/L

ASX or subtle changes

Question 3

What is moderate hypoNa?

What sx?

Answer 3

125-130 mmol/L

Non-specific e.g. nausea and malaise

Question 4

What is severe hypoNa?

What sx?

Answer 4

<125 mmol/L

Confusion, coma, death

Question 5

Which drugs can cause hypoNa?

Answer 5

• Omeprazole
• Anticonvulsants: sodium valproate, carbazmaepine
• Anti-deps: SSRIs, MAOI
• Diuretics
• Ecstasy

Question 6

How can hypoNa be classified?

Answer 6

Hypovolaemic hypoNa

Euvolaemic hypoNa

Hypervolaemic hypoNa

Question 7

What is significant about Na being an extracellular electrolyte?

Answer 7

Means Na is linked to fluid levels

Question 8

What are the causes of hypovolaemic hypoNa?

Answer 8

Renal: diuretics, addisons, osmotic diuresis (hypoglcaemia), nephropathy

GI: V, D

Other: burns, rhabdomyolysis, pancreatitis, peritonitis

Question 9

What are the causes of euvolaemic hypoNa?

Answer 9

SIADH
Diuretics
Water retention
Low dietary Na
Addison's
Hypothyroid 
Pregnancy

Question 10

What are the causes of hypervolaemic hypoNa?

Answer 10

HF
Renal failure
Liver failure
Hyperglycaemia

Question 11

What are the SX?

Answer 11

Headache 
Lethargy 
N/V
Dizziness
Confusion 
Muscle cramps 
Seizures
Coma 
Resp arrest

Question 12

What IX should you do?

Answer 12

HX - fluid loss, xs water intake, PMH

Exam - oedema

Serum osmolality
Urine osmolality
Urine Na

Question 13

How do you RX mild hypoNa?

Answer 13

Fluid restriction <800 mL/day

Loop diuretics

Question 14

How do you RX moderate hypoNa?

Answer 14

Hypertonic saline in first 3-4h to increase Na to >120mmol/L

Question 15

How do you RX severe?

Answer 15

Bolus of hypertonic saline until SX resolution

+/- conivaptan

Question 16

What caution must you consider when RX hypoNa with Na?

Answer 16

AVOID RAID CORRECTION 
Only raise Na levels by 4-6mmol/L
   - NEVER go >10mmol/L in a 24h period 
Can lead to central pontine myelinolysis 
SX occur after 2d and are irreversible 

Dysarthria, paraparesis, quadriparesis, seziures, confusion, coma = locked-in syndrome