Question 10.1

The following results were obtained from a 62-year-old female one week following a subarachnoid haemorrhage with increasing confusion:

Parameter

Patient Value

Adult Normal Range

Sodium

130 mmol/L*

135 – 145

Potassium

4.0 mmol/L

3.5 – 5.0

Chloride

96 mmol/L

95 – 105

Bicarbonate

26.5 mmol/L*

22.0 – 26.0

Glucose

5.5 mmol/L

3.5 – 6.0

Urea

2.5 mmol/L*

3.0 – 8.0

Creatinine

37 μmol/L*

45 – 90

Magnesium

0.87 mmol/L

0.75 – 0.95

Albumin

33 g/L*

35 – 50

Protein

74 g/L

60 – 80

Total bilirubin

10 μmol/L

< 26

Alanine transferase          

26 U/L

< 35

Serum Osmolality

274 mosm/kg*        

285 – 295

Ionised calcium

1.19 mmol/L

1.10 – 1.35

Calcium corrected

2.34 mmol/L

2.12 – 2.62

Phosphate

0.97 mmol/L

0.80 – 1.50

a) What are the two most likely causes for this biochemical profile? (10% marks)

b) How would you distinguish between the two biochemically and clinically? (30% marks)

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College answer

Not available.

Discussion

What we are seeing here is a patient with recent CNS pathology who has now developed

  • Hypoosmolar hyponatremia
  • Mild metabolic alkalosis
  • A low urea (suggestive of low protein metabolism or protein intake)
  • New confusion

The two most likely causes of this bicohemical profile would surely have to be endocrine, and related to the SAH.

  • SIADH
  • Hypoadrenalism (due to pituitary dysfunction)

One could also make the argument that any pituitary injury from SAH that is bad enough to cause hypoadrenalism would probably also cause hypothyroidism.

References