Lecture 10 - Salt

Question 1

What causes hyponatraemia most commonly

Answer 1

Increases water reabsorption decreasing the Na+ concentration in plasma

Question 2

Test results for hyponatraemia

Answer 2

Decreased serum osmolarity - more water retained
Increased urine osmolarity - less water excreted
Decreased serum Na+ concentration

Question 3

What can cause inappropriate water retention

Answer 3

SIADH

Question 4

Treatment of hyponatraemia

Answer 4

Fluid restriction
Hypotonic saline
Stop drugs that causes ADH release e.g. anti-epileptics

Question 5

Symptoms of hyponatraemia

Answer 5

Agitation
Nausea
Coma
Focal nuerology 
Seizures

Question 6

Investigations for hyponatraemia

Answer 6

FBC - normal
U and E - Low Na+
Mini mental score - confusion 
JVP raised 
oedematous

Question 7

Hypovalaemic hyponatraemia causes- true sodium loss

Answer 7

GI cause:
Diarrhoea
Vomiting
Fistulas

Diureitics - renal failure

Fluid in third space:
Peritonitis
Ascites
Burn - dehydrate

Question 8

What can cause an imbalance of ADH

Answer 8

Heart failure
Liver disease 
Renal disease
Medication - anti epileptics
Tumours - Small cell lung carcinoma

Question 9

What drugs can cause inappropriate ADH release?

Answer 9

Thiazides 
Selective serotonin reuptake inhibitors (SSRIs)
Proton pump inhibitors
ACE inhibitors 
Loop Diuretics

Question 10

What can hypotonic saline casue

Answer 10

Central pontine myelinolysis (osmotic demyelination syndrome)

• correct Na+ too quickly can demyelinate axons and cause permanent cerebral damage
• due to fluid shift and cerebral ability to compensate for low Na+ over chronic periods of time a new set point is made
• By exposing brain to a hypotonic solution, more water is reabsorbed into cells.

Question 11

How to treat central pontine myelinolysis

Answer 11

Hypertonic saline
Furosemide
In symptomatic patients