Hyponatremia

Question 1

Investigations to do in Hyponatremia

Answer 1

Blood: Na, K, urine, creatinine, osmolality

Urine: Na, creat, osmolality

Monitor urine output

Monitor serum sodium

Depending on history and examination: LFT, TSH, Cortisol, uric acid

Consider neuroimaging if other cause of obtundation/seizures anticipated

South African setting – consider tuberculosis

Question 2

Approach to Hyponatremia in EC

Answer 2

Aggressively treat the following (UpToDate):

Severe symptoms: obtunded, seizures
Acute hyponatremia with symptoms, even if mild
Hyperacute hyponatraemia (primary polydipsia, MDMA intoxication)
With:

100ml Hypertonic Saline 3% over 5-10 minutes (Paeds: 3ml/kg of 3% hypertonic saline)

Can be repeated x 1 if still seizing

Stop hypertonic saline administration thereafter

*note: hypertonic saline can be given safely via peripheral iv

*note: sodium bicarbonate 8.5% can be given in place of hypertonic saline if no hypertonic saline available

Give 1-2 ml of 8.4% NaHCO3 iv.

Question 3

Normal serum osmolality

Answer 3

Normal serum osmolality = 275-295 mOsm/l

Question 4

Calculate osmolality and osmolar gap

Answer 4

Calculated osmolality = 2x Na (mmol/l) + Glucose (mmol/l) + urea (mmol/l) (2 salts, a sugar and bun!)

Osmol gap = Measured osmolality – calculated osmolality. If osmol gap >10 – look for exogenous ?substances!