ENDOCRINE

Question 1

Hyponatremia Severity

Answer 1

Biochemical severity

• when [Na+] measured by an ion specific electrode
• Na+ 130 -135 mmol/L - mild
• Na+ 125 -129 mmol/L - moderate
• Na+ < 125 mmol/L - severe

Na+ > 125 mmol/L

• usually asymptomatic
• mild GIT symptoms may be present

Na+ < 125 > 115 mmol/L

•subtle changes in mental status, lethargy, and confusion

Na+ < 115 mmol/L

• depressed mental state
• neuromuscular hyper excitability
• seizures
• initial improvement may be followed by delayed neurologic symptoms

Question 2

Hyponatremia - Flowchart

Answer 2

Question 3

Hyponatremia - IX - urine and serum osmolatiry

Answer 3

Serum osmolality

• initial investigation of choice
• if > 280 mosm/kg indicates spurious causes
• hyperproteinaemia / hyperlipidaemia
• hyperglycaemia / methanol / mannitol

Urine osmolality

• if hypo-osmolality confirmed by direct measurement
• measure as close as possible to the time of measurement of the serum osmolality

< 100 mosm/kg

• indicates complete and appropriate suppression of ADH
• causes
• primary polydipsia
• reset osmostat syndrome

> 100 mosm/kg

• indicates impaired water excretion
• causes
• hypothyroidism
• adrenocortical insufficiency
• hypovolaemia
• renal /hepatic / cardiac failure
• SIAD

Urinary Na+ or