4.4 Hyponatraemia in TBI

Question 1

List 2 common causes ↓Na in TBI

Answer 1

SIADH

CSWS

Question 2

Clinical and biochemical features

SIADH

biochem features

Answer 2

Serum Na
↓ (both)

Urine Na ↑
both

Serum osmolality
↓

Urine osmolality
↑
(both)

Serum urea and creat
↓ or <->

Plasma Vol
↑

Question 3

CSWS

biochem features

Answer 3

Serum Na
↓ (both)

Urine Na ↑
(both)

Serum osmolality
<-> / ↑

Urine osmolality
↑
(both)

Urea and creat
↑

Plasma Vol
↓

Question 4

SIADH

Clin features

Answer 4

Urine
↓ volume / conc

Na balance
equal

Volaemic status:
euvolemic

CVP
<-> / ↑

No postural hypotension

Hct ↑

Question 5

CSWS

Answer 5

Urine
High volume

Na bal:
Negative

Hypovolaemic

CVP ↓

Postural hypotension

HCT low

Question 6

Rx SIAD

Answer 6

Only if symptomatic
Severe hypoNa
Rapid decrease Na

Fluid restrict:
Aim serum rise Na 1-1.5mmol/L/day

Hypertonic 3% via CVC if very low or symptoms

Demecycline
inhibit renal response to AD

Consider ADH Receptor antagonists

Question 7

Rx CSWS

Answer 7

Restore plasma volume + Na Conc
Initially 0.9%

Consider hypertonic saline via CVC line

Fludrocortisone 0.1-0.4 mg/day
standard Rx resistant cases
Caution HyperK