Question 21.2

Angoff score
4.14
Highest mark
5
Pass rate
57.1%
Other SAQs in this topic:
Other SAQs in this paper:

A patient recently discharged from hospital following a long admission for management of variceal bleeding and decompensated alcoholic cardiomyopathy is referred to the ICU. They have presented to the emergency department with refractory seizures and hypotension.

The biochemistry is as follows:

Parameter

Patient

Reference

Sodium

140 mmol/L

135 – 145

Potassium

5.1 mmol/L *

3.5 – 5.0

Chloride

102 mmol/L

95 – 105

Bicarbonate

20 mmol/L *

22.0 – 26.0

Glucose

5.5 mmol/L

3.5 – 6.0

Urea

9.4 mmol/L *

3.0 – 8.0

Creatinine

145 μmol/L *

45 – 90

Albumin

19 g/L *

35 – 50

Protein

75 g/L *

60 – 80

Total bilirubin

24 μmol/L

< 26

Aspartate transferase (AST)

71 U/L *

< 35

Alanine transferase (ALT)

67 U/L *

< 35

Alkaline phosphatase (ALP)

156 U/L *

30 – 110

Gamma Glutamyl transferase (GGT)      

72 U/L *

< 40

Ionised calcium

0.61 mmol/L *      

1.10– 1.20

a) List five possible causes of these biochemical abnormalities (2.5 marks)

b) List five investigations which would help discriminate between these causes (2.5 marks)

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College comments

Syllabus topic/section: Section 2.1.7 Renal Intensive Care. Topic Acid-base and Electrolyte Disorders

Discussion: 

This question is focused on the understanding of Calcium and Phosphate abnormalities and its relationship with renal and endocrine function in the critically ill.
Many candidates failed to identify severe hypocalaemia and renal dysfunction in Question 21.2. Candidates were awarded marks if they were able to identify the data pattern of hypocalcaemia and renal dysfunction. Candidates who focused on causes of seizure without identifying and corelating it to the biochemical abnormalities were not awarded marks. Examples of investigations acceptable would include Vit D level, PTH and PTH-rp, amylase and lipase.
 

Interpretation

Five possible causes:

  • Acute pancreatitis due to to ongoing alcohol abuse can lead to the depletion of calcium 
  • Rhabdomyolysis due to seizures, causing a raised phosphate and calcium chelation
  • High dose PPI use causing hypomagnesemia, hypomagnesemia causing hypocalcemia by causing PTH resistance
  • Decreased renal function causing decreased Vit D availability
  • Hyperphosphataemia due to, for example, AKI or hyperparathyroisim of chronic renal failure

Five investigations:

  • Vit D level (expected to be low in true deficiency or inefficient synthesis)
  • PTH and PTH-rp
  • Amylase and lipase
  • Magnesium level
  • Phosphate level
  • CK
  • Lactate

References

Cooper, Mark S., and Neil JL Gittoes. "Diagnosis and management of hypocalcaemia." BMJ: British Medical Journal 336.7656 (2008): 1298.

Tohme, J. F., and J. P. Bilezikian. "Hypocalcemic emergencies." Endocrinology and metabolism clinics of North America 22.2 (1993): 363-375.

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