You are asked to see a 73-year-old female on the ward. She was admitted to the Emergency Department in a dishevelled state.

She has the following vital signs and investigation results:

            Temperature:                         34.5°C

           Blood pressure:                     80/40 mmHg

           Glasgow Coma Score:          11

Parameter

Patient Value

Adult Normal Range

Fi02

0.28

pH

7.26*

7.35 - 7.45

P02

62 mmHg (8.3 kPa)

PC02

37.0 mmHg (4.7 kPa)

35.0 -45.0 (4.6 - 6.0)

sp02

92%

Bicarbonate

16.0 mmol/L*

22.0 - 26.0

Base Excess

-10.0 mmol/L*

_2.0 _ +2.0

Lactate

3.1 mmol/L*

0.5 - 1.6

Sodium

128 mmol/L*

135 - 145

Potassium

3.1 mmol/L*

3.5 -5.0

Chloride

90 mmol/L*

95- 105

Glucose

3.2 mmol/L*

3.5 -6.0

Urea

13.0 mmol/L*

3.0 - 8.0

Creatinine

132 umol/L*

45 — 90

Creatinine Kinase

1500 U/L*

55 - 170

Haemoglobin

80 g/L*

120 - 160

White Cell Count

15.0 x 109/L*

4.0 - 1 1.0

Platelet count

250 x 109/1-

150 - 350

a) Comment on the acid base status and ECG abnormalities 

(ECG show below)

(30% marks) b) List the two most likely differential diagnosis. (20% marks)

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College answer

a) 
Primary metabolic acidosis  
Associated respiratory acidosis, or inadequate compensation 
Increased anion gap. (22) 
Delta ratio 1.2 –pure high anion gap acidosis 
 
ECG: low voltage  
Relative bradycardia 
Prolonged QT 
 
b) 
Myxoedema coma. 
Sepsis 
 

Discussion

Acid base status, in detail:

  1. There is acidaemia
  2. The CO2 is within normal range, which is inappropriate (it should be low)
  3. There is metabolic acidosis, as the SBE is -10
  4. There is also a respiratory acidosis: the expected CO2 is 30 (or 32 by the Boston rules)
  5. The anion gap is 25.1, or 22 sans potassium. Either way, the lactate of 3.1 does not fully explain it. 
  6. The delta ratio is either 1.6 or 1.25, but either way it points to a pure HAGMA.

ECG abnormalities 

  • Bradycardia
  • Long PR interval
  • Long QT interval
  • Borderline widened QRS
  • Low voltage QRS in the limb leads

Overall, the ECG is consistent with hypothermia. Which the patient has. And with ... one other thing.

So... those two most likely differentials? 

Well. One of them HAS to be myxoedema coma. 

How can one be so confident? It's easy, when the college lifted their ECG directly from the LITFL page on ECG changes in hypothyroidism. Which is excellent: as that work is covered by the Creative Commons license, this offers the author a rare opportunity to reproduce the original college image without fear of the CICM intellectual property stormtroopers. 

The other differential could easily be sepsis, MI, acute kidney injury due to prolonged lie and rhabodomyolysis, and so on. 

References